Re: [DISCUSS] KIP-712: Shallow Mirroring
Hi, Henry,
Thanks for the reply.
3. Regarding EOS, supporting read_committed makes sense.
1. Regarding re-implementing 30 methods. Could we structure the code such
that the implementation of most of the methods could be shared?
Thanks,
Jun
On Thu, Apr 1, 2021 at 11:18 PM Henry Cai
wrote:
> Tom,
>
> I don't think we need to refactor the Consumer/Producer class hierarchy for
> this KIP. If we introduce a separate class for BatchConsumer, there are
> more than 30 methods in Consumer interface this new class needs to
> implement and the implementation would be exactly the same as
> KafkaConsumer.
>
> If we just introduce a new method 'ConsumerBatchRecord pollBatch(duration)'
> on the Consumer class, there is no need to make this method to handle
> generic type since the return type is a concrete class. The worry you have
> that later the user can tweak the content so they can send
> ProducerRecord can be avoided if we make the class
> ConsumerBatchRecord final and only define one method
> 'toProducerBatchRecord()' on the class, and makes the constructor on
> ProducerBatchRecord package private as well to make people not able to
> create a ProducerBatchRecord with arbitrary content.
>
> The other design is just have one class BatchRecord (instead of having two
> classes: ConsumerBatchRecord and ProducerBatchRecord),
> Consumer.pollBatch(duration) will return BatchRecord,
> Producer.sendBatch(BatchRecord) will send the batch. BatchRecord class is
> final and the constructor is hidden, so it's unmodifiable by the user code.
>
> On Thu, Apr 1, 2021 at 6:27 AM Tom Bentley wrote:
>
> > Hi Henry, Jun and Ismael,
> >
> > A few things make me wonder if building this into the existing Producer
> and
> > Consumer APIs is really the right thing to do:
> >
> > 1. Type safety. The existing Producer and Consumer are both generic in K
> > and V, but those type parameters are meaningless in the batch case. For
> > example, the apparent type safety of a Producer would be
> violated
> > by using the batch method to actually send a . Another
> example:
> > What happens if I pass a producer configured for records to someone that
> > requires one configured for batches (and vice versa)?
> >
> > 2. The existing Producer and Consumer would both accept a number of
> configs
> > which didn't apply in the batch case.
> >
> > In the discussion for KIP-706 Jason was imagining a more abstracted set
> of
> > client APIs which separated the data from the topic destination/origin,
> and
> > he mentioned basically this exact use case. This got me thinking, and
> > although I don't want to derail this conversion, I thought I'd sketch
> what
> > I came up with.
> >
> >
> > On the Consumer side:
> >
> > ```java
> > // Abstraction over where messages come from
> > interface ReceiveSource;
> > class TopicPartition implements SendTarget, ReceiveSource;
> > class Topic implements SendTarget, ReceiveSource;
> > class TopicId implements SendTarget, ReceiveSource;
> > class TopicPattern implements ReceiveSource;
> >
> > // New abstraction for consumer-like things
> > interface Receiver {
> > assign(ReceiveSource source);
> > subscribe(ReceiveSource source);
> > // etc
> > X poll(Duration);
> > }
> >
> > // Consumer doesn't change, except for the implements clause
> > interface Consumer implements Receiver> {
> > assign(ReceiveSource source);
> > subscribe(ReceiveSource source);
> > ConsumerRecords poll(Duration);
> > }
> >
> > // KafkaConsumer doesn't change at all
> > class KafkaConsumer implements Consumer {
> > }
> >
> > // Specialise Receiver for batch-based consumption.
> > interface BatchConsumer implements Receiver {
> >
> > }
> >
> > // Implementation
> > class KafkaBatchConsumer implements BatchConsumer {
> >
> > }
> >
> > class ConsumerBatch {
> > // For KIP-712, a way to convert batches without exposing low level
> > details like ByteBuffer
> > ProducerBatchPayload toProducerBatch();
> > }
> > ```
> >
> > On the producer side:
> > ```java
> > // Abstraction over targets (see the ReceiveSource for the impls)
> > interface SendTarget;
> >
> > // Abstraction over data that can be send to a target
> > interface Payload;
> > class ProducerRecordPayload implements Payload {
> > // Like ProducerRecord, but without the topic and partition
> > }
> > class ProducerBatchPayload implements Payload {
> > // For the KIP-712 case
> > }
> >
> > // A new abstraction over producer-like things
> > interface Transmitter {
> > CompletionStage send(SendTarget target, P payload);
> > }
> >
> > // Producer gains an extends clause
> > interface Producer extends Transmitter> {
> > }
> >
> > class KafkaProducer implements Producer {
> > // Unchanged, included for completeness
> > }
> >
> > interface BatchProducer extends Transmitter {
> > CompletionStage send(SendTarget target, ProducerBatch)
> > }
> >
> > class KafkaBatchProducer extends BatchProducer {
> > // New. In practice a lot of common code between this and
Re: [DISCUSS] KIP-712: Shallow Mirroring
Tom,
I don't think we need to refactor the Consumer/Producer class hierarchy for
this KIP. If we introduce a separate class for BatchConsumer, there are
more than 30 methods in Consumer interface this new class needs to
implement and the implementation would be exactly the same as KafkaConsumer.
If we just introduce a new method 'ConsumerBatchRecord pollBatch(duration)'
on the Consumer class, there is no need to make this method to handle
generic type since the return type is a concrete class. The worry you have
that later the user can tweak the content so they can send
ProducerRecord can be avoided if we make the class
ConsumerBatchRecord final and only define one method
'toProducerBatchRecord()' on the class, and makes the constructor on
ProducerBatchRecord package private as well to make people not able to
create a ProducerBatchRecord with arbitrary content.
The other design is just have one class BatchRecord (instead of having two
classes: ConsumerBatchRecord and ProducerBatchRecord),
Consumer.pollBatch(duration) will return BatchRecord,
Producer.sendBatch(BatchRecord) will send the batch. BatchRecord class is
final and the constructor is hidden, so it's unmodifiable by the user code.
On Thu, Apr 1, 2021 at 6:27 AM Tom Bentley wrote:
> Hi Henry, Jun and Ismael,
>
> A few things make me wonder if building this into the existing Producer and
> Consumer APIs is really the right thing to do:
>
> 1. Type safety. The existing Producer and Consumer are both generic in K
> and V, but those type parameters are meaningless in the batch case. For
> example, the apparent type safety of a Producer would be violated
> by using the batch method to actually send a . Another example:
> What happens if I pass a producer configured for records to someone that
> requires one configured for batches (and vice versa)?
>
> 2. The existing Producer and Consumer would both accept a number of configs
> which didn't apply in the batch case.
>
> In the discussion for KIP-706 Jason was imagining a more abstracted set of
> client APIs which separated the data from the topic destination/origin, and
> he mentioned basically this exact use case. This got me thinking, and
> although I don't want to derail this conversion, I thought I'd sketch what
> I came up with.
>
>
> On the Consumer side:
>
> ```java
> // Abstraction over where messages come from
> interface ReceiveSource;
> class TopicPartition implements SendTarget, ReceiveSource;
> class Topic implements SendTarget, ReceiveSource;
> class TopicId implements SendTarget, ReceiveSource;
> class TopicPattern implements ReceiveSource;
>
> // New abstraction for consumer-like things
> interface Receiver {
> assign(ReceiveSource source);
> subscribe(ReceiveSource source);
> // etc
> X poll(Duration);
> }
>
> // Consumer doesn't change, except for the implements clause
> interface Consumer implements Receiver> {
> assign(ReceiveSource source);
> subscribe(ReceiveSource source);
> ConsumerRecords poll(Duration);
> }
>
> // KafkaConsumer doesn't change at all
> class KafkaConsumer implements Consumer {
> }
>
> // Specialise Receiver for batch-based consumption.
> interface BatchConsumer implements Receiver {
>
> }
>
> // Implementation
> class KafkaBatchConsumer implements BatchConsumer {
>
> }
>
> class ConsumerBatch {
> // For KIP-712, a way to convert batches without exposing low level
> details like ByteBuffer
> ProducerBatchPayload toProducerBatch();
> }
> ```
>
> On the producer side:
> ```java
> // Abstraction over targets (see the ReceiveSource for the impls)
> interface SendTarget;
>
> // Abstraction over data that can be send to a target
> interface Payload;
> class ProducerRecordPayload implements Payload {
> // Like ProducerRecord, but without the topic and partition
> }
> class ProducerBatchPayload implements Payload {
> // For the KIP-712 case
> }
>
> // A new abstraction over producer-like things
> interface Transmitter {
> CompletionStage send(SendTarget target, P payload);
> }
>
> // Producer gains an extends clause
> interface Producer extends Transmitter> {
> }
>
> class KafkaProducer implements Producer {
> // Unchanged, included for completeness
> }
>
> interface BatchProducer extends Transmitter {
> CompletionStage send(SendTarget target, ProducerBatch)
> }
>
> class KafkaBatchProducer extends BatchProducer {
> // New. In practice a lot of common code between this and KafkaProducer
> could be factored into an abstract class.
> }
> ```
>
> Really I'm just re-stating Jason's KIP-706 idea in the context of this KIP,
> but it would address the type safety issue and also enable a batch consumer
> to have its own set of configs. It also allows the new Producer.send return
> type to be CompletionStage, which is KIP-706's objective. And, of course
> it's compatible with possible future work around produce to/consume from
> topic id.
>
> Kind regards,
>
> Tom
>
>
>
> On Thu, Apr 1, 2021 at 9:11 AM Henry Cai
> wrote:
>
> > Jun,
> >
> >
Re: [DISCUSS] KIP-712: Shallow Mirroring
Jun, On the EOS support, I looked at KIP-98 and it seems to me all the control is specified in the RecordBatch header fields: 1. Whether the batch is a control batch which contains commit or abort marker 2. Whether the batch is transactional which contains PID In read_committed isolation level mode (I think that's the mode makes sense for mirroring), in the existing code in Fetcher.nextFetchRecord(), the code decides to skip the control batch or the aborted batch based on the abortedTransactions from FetchResponse. This logic would also work in the shallow iterator mode, we would just skip to the next batch. On Thu, Apr 1, 2021 at 9:46 AM Jun Rao wrote: > Hi, Henry, > > Thanks for the response. > > 1. I agree with Tom that it's worth thinking about a separate class for > shallow iteration instead of trying to add more complexity into the > existing producer/consumer API. We could potentially make the new class an > internal API if it's only useful for MM. > > 3. I am not sure that we could ignore transactional messages in the first > phase. The usage of EOS is increasing. Also, one can't tell from the > metadata of a topic whether it has EOS data or not. So, there is no easy > way to skip EOS data from the source. > > Jun > > On Thu, Apr 1, 2021 at 1:07 AM Henry Cai > wrote: > > > Jun, > > > > Thanks for your insight looking into this KIP, we do believe the shallow > > iteration will give quite a significant performance boost. > > > > On your concerns: > > > > 1. Cleaner API. One alternative is to create new batch APIs. On > consumer, > > it would become Consumer.pollBatch returns a ConsumerBatch object which > > contains topic/partition/firstOffsetOfBatch/pointerToByteBuffer, > similarly > > Producer.sendBatch(ProducerBatch). Both ConsumerBatch and ProducerBatch > > objects are fixed types (no generics), serializer is gone, interceptors > are > > probably not needed initially (unless people see the need to intercept on > > the batch level). On MM2 side, the current flow is ConsumerRecord -> > > Connect's SourceRecord -> ProducerRecord, we would need to enhance > Connect > > framework to add SourceTask.pollBatch() method which returns a > SourceBatch > > object, so the object conversion flow becomes ConsumerBatch -> > SourceBatch > > -> ProducerBatch, we probably won't support any transformers on Batch > > objects. > > 2. PID/ProducerEpoch/SeqNo passing through RecordBatch. I think those > > transaction fields are only meaningful in the original source kafka > > cluster, producer id/seqNo are not the same for the target kafka cluster. > > So if MM is not going to support transactions at the moment, we can clear > > those fields when they are going through MM. Once MM starts to support > > transactions in the future, it probably will start its own PID/SeqNo etc. > > 3. For EOS and read_committed/read_uncommitted support, we can do phased > > support. Phase 1, don't support transactional messages in the source > > cluster (i.e. abort if it sees control batch records). Phase 2: applying > > commit/abort on the batch boundary level. I am not too familiar with the > > isolation level and abort transaction code path, but it seems the control > > unit is currently on the batch boundary (commit/abort the whole batch), > if > > so, this should also be doable. > > 4. MessageHandler in MM1 or SMT in MM2, initially we don't need to > support > > them. Since now the object is a ConsumerBatch and the existing handler > is > > written for the individual object. Deserialize the batch into individual > > objects would defeat the purpose of performance optimization. > > 5. Multiple batch performances, will do some testing on this. > > > > On Wed, Mar 31, 2021 at 10:14 AM Jun Rao > wrote: > > > > > Hi, Henry, > > > > > > Thanks for the KIP. Sorry for the late reply. A few comments below. > > > > > > 1. The 'shallow' feature is potentially useful. I do agree with Tom > that > > > the proposed API changes seem unclean. Quite a few existing stuff don't > > > really work together with this (e.g., generics, serializer, > interceptors, > > > configs like max.poll.records, etc). It's also hard to explain this > > change > > > to the common users of the consumer/producer API. I think it would be > > > useful to explore if there is another cleaner way of adding this. For > > > example, you mentioned that creating a new set of APIs doesn't work for > > > MM2. However, we could potentially change the connect interface to > allow > > > MM2 to use the new API. If this doesn't work, it would be useful to > > explain > > > that in the rejected alternative section. > > > > > > 2. I am not sure that we could pass through all fields in RecordBatch. > > For > > > example, a MM instance could be receiving RecordBatch from different > > source > > > partitions. Mixing the PID/ProducerEpoch/FirstSequence fields across > them > > > in a single producer will be weird. So, it would be useful to document > > this > > > part
Re: [DISCUSS] KIP-712: Shallow Mirroring
Henry, a suggestion: instead of introducing a new configuration property which enables the proposed behavior in the existing clients, we could expose this behavior only thru package-private classes (RecordBatchConsumer/Producer or something) which wrap or extend the existing clients. In other words, the KIP remains as proposed except client code must instantiate a different class. Then, ofc, MM could use these internal clients without exposing a new public API. This would allay many of the concerns raised so far, re exposing unsafe APIs, weird generics, etc, and would require no significant changes to Connect or MM. I'm not familiar enough with the EOS implementation to know, but I hope there is a way forward there. Very often the sort of topic that gets replicated is not transactional anyway. Ryanne On Thu, Apr 1, 2021, 3:06 AM Henry Cai wrote: > Jun, > > Thanks for your insight looking into this KIP, we do believe the shallow > iteration will give quite a significant performance boost. > > On your concerns: > > 1. Cleaner API. One alternative is to create new batch APIs. On consumer, > it would become Consumer.pollBatch returns a ConsumerBatch object which > contains topic/partition/firstOffsetOfBatch/pointerToByteBuffer, similarly > Producer.sendBatch(ProducerBatch). Both ConsumerBatch and ProducerBatch > objects are fixed types (no generics), serializer is gone, interceptors are > probably not needed initially (unless people see the need to intercept on > the batch level). On MM2 side, the current flow is ConsumerRecord -> > Connect's SourceRecord -> ProducerRecord, we would need to enhance Connect > framework to add SourceTask.pollBatch() method which returns a SourceBatch > object, so the object conversion flow becomes ConsumerBatch -> SourceBatch > -> ProducerBatch, we probably won't support any transformers on Batch > objects. > 2. PID/ProducerEpoch/SeqNo passing through RecordBatch. I think those > transaction fields are only meaningful in the original source kafka > cluster, producer id/seqNo are not the same for the target kafka cluster. > So if MM is not going to support transactions at the moment, we can clear > those fields when they are going through MM. Once MM starts to support > transactions in the future, it probably will start its own PID/SeqNo etc. > 3. For EOS and read_committed/read_uncommitted support, we can do phased > support. Phase 1, don't support transactional messages in the source > cluster (i.e. abort if it sees control batch records). Phase 2: applying > commit/abort on the batch boundary level. I am not too familiar with the > isolation level and abort transaction code path, but it seems the control > unit is currently on the batch boundary (commit/abort the whole batch), if > so, this should also be doable. > 4. MessageHandler in MM1 or SMT in MM2, initially we don't need to support > them. Since now the object is a ConsumerBatch and the existing handler is > written for the individual object. Deserialize the batch into individual > objects would defeat the purpose of performance optimization. > 5. Multiple batch performances, will do some testing on this. > > On Wed, Mar 31, 2021 at 10:14 AM Jun Rao wrote: > > > Hi, Henry, > > > > Thanks for the KIP. Sorry for the late reply. A few comments below. > > > > 1. The 'shallow' feature is potentially useful. I do agree with Tom that > > the proposed API changes seem unclean. Quite a few existing stuff don't > > really work together with this (e.g., generics, serializer, interceptors, > > configs like max.poll.records, etc). It's also hard to explain this > change > > to the common users of the consumer/producer API. I think it would be > > useful to explore if there is another cleaner way of adding this. For > > example, you mentioned that creating a new set of APIs doesn't work for > > MM2. However, we could potentially change the connect interface to allow > > MM2 to use the new API. If this doesn't work, it would be useful to > explain > > that in the rejected alternative section. > > > > 2. I am not sure that we could pass through all fields in RecordBatch. > For > > example, a MM instance could be receiving RecordBatch from different > source > > partitions. Mixing the PID/ProducerEpoch/FirstSequence fields across them > > in a single producer will be weird. So, it would be useful to document > this > > part clearer. > > > > 3. EOS. While MM itself doesn't support mirroring data in an > > exactly-once way, it needs to support reading from a topic with EOS data. > > So, it would be useful to document whether both read_committed and > > read_uncommitted mode are supported and what kind of RecordBatch the > > consumer returns in each case. > > > > 4. With the 'shallow' feature, it seems that some existing features in MM > > won't work. For example, I am not sure if SMT works in MM2 > > and MirrorMakerMessageHandler works in MM1. It would be useful to > document > > this kind of impact in the KIP. > > > >
Re: [DISCUSS] KIP-712: Shallow Mirroring
On Thu, Apr 1, 2021, at 09:45, Jun Rao wrote: > Hi, Henry, > > Thanks for the response. > > 1. I agree with Tom that it's worth thinking about a separate class for > shallow iteration instead of trying to add more complexity into the > existing producer/consumer API. We could potentially make the new class an > internal API if it's only useful for MM. > Yes, I think a separate API that just allowed sending / receiving record bytes might be the best way to go. > 3. I am not sure that we could ignore transactional messages in the first > phase. The usage of EOS is increasing. Also, one can't tell from the > metadata of a topic whether it has EOS data or not. So, there is no easy > way to skip EOS data from the source. I also agree... we should not create more technical debt here. Colin > > Jun > > On Thu, Apr 1, 2021 at 1:07 AM Henry Cai wrote: > > > Jun, > > > > Thanks for your insight looking into this KIP, we do believe the shallow > > iteration will give quite a significant performance boost. > > > > On your concerns: > > > > 1. Cleaner API. One alternative is to create new batch APIs. On consumer, > > it would become Consumer.pollBatch returns a ConsumerBatch object which > > contains topic/partition/firstOffsetOfBatch/pointerToByteBuffer, similarly > > Producer.sendBatch(ProducerBatch). Both ConsumerBatch and ProducerBatch > > objects are fixed types (no generics), serializer is gone, interceptors are > > probably not needed initially (unless people see the need to intercept on > > the batch level). On MM2 side, the current flow is ConsumerRecord -> > > Connect's SourceRecord -> ProducerRecord, we would need to enhance Connect > > framework to add SourceTask.pollBatch() method which returns a SourceBatch > > object, so the object conversion flow becomes ConsumerBatch -> SourceBatch > > -> ProducerBatch, we probably won't support any transformers on Batch > > objects. > > 2. PID/ProducerEpoch/SeqNo passing through RecordBatch. I think those > > transaction fields are only meaningful in the original source kafka > > cluster, producer id/seqNo are not the same for the target kafka cluster. > > So if MM is not going to support transactions at the moment, we can clear > > those fields when they are going through MM. Once MM starts to support > > transactions in the future, it probably will start its own PID/SeqNo etc. > > 3. For EOS and read_committed/read_uncommitted support, we can do phased > > support. Phase 1, don't support transactional messages in the source > > cluster (i.e. abort if it sees control batch records). Phase 2: applying > > commit/abort on the batch boundary level. I am not too familiar with the > > isolation level and abort transaction code path, but it seems the control > > unit is currently on the batch boundary (commit/abort the whole batch), if > > so, this should also be doable. > > 4. MessageHandler in MM1 or SMT in MM2, initially we don't need to support > > them. Since now the object is a ConsumerBatch and the existing handler is > > written for the individual object. Deserialize the batch into individual > > objects would defeat the purpose of performance optimization. > > 5. Multiple batch performances, will do some testing on this. > > > > On Wed, Mar 31, 2021 at 10:14 AM Jun Rao wrote: > > > > > Hi, Henry, > > > > > > Thanks for the KIP. Sorry for the late reply. A few comments below. > > > > > > 1. The 'shallow' feature is potentially useful. I do agree with Tom that > > > the proposed API changes seem unclean. Quite a few existing stuff don't > > > really work together with this (e.g., generics, serializer, interceptors, > > > configs like max.poll.records, etc). It's also hard to explain this > > change > > > to the common users of the consumer/producer API. I think it would be > > > useful to explore if there is another cleaner way of adding this. For > > > example, you mentioned that creating a new set of APIs doesn't work for > > > MM2. However, we could potentially change the connect interface to allow > > > MM2 to use the new API. If this doesn't work, it would be useful to > > explain > > > that in the rejected alternative section. > > > > > > 2. I am not sure that we could pass through all fields in RecordBatch. > > For > > > example, a MM instance could be receiving RecordBatch from different > > source > > > partitions. Mixing the PID/ProducerEpoch/FirstSequence fields across them > > > in a single producer will be weird. So, it would be useful to document > > this > > > part clearer. > > > > > > 3. EOS. While MM itself doesn't support mirroring data in an > > > exactly-once way, it needs to support reading from a topic with EOS data. > > > So, it would be useful to document whether both read_committed and > > > read_uncommitted mode are supported and what kind of RecordBatch the > > > consumer returns in each case. > > > > > > 4. With the 'shallow' feature, it seems that some existing features in MM > > > won't work. For example, I am
Re: [DISCUSS] KIP-712: Shallow Mirroring
Hi, Henry, Thanks for the response. 1. I agree with Tom that it's worth thinking about a separate class for shallow iteration instead of trying to add more complexity into the existing producer/consumer API. We could potentially make the new class an internal API if it's only useful for MM. 3. I am not sure that we could ignore transactional messages in the first phase. The usage of EOS is increasing. Also, one can't tell from the metadata of a topic whether it has EOS data or not. So, there is no easy way to skip EOS data from the source. Jun On Thu, Apr 1, 2021 at 1:07 AM Henry Cai wrote: > Jun, > > Thanks for your insight looking into this KIP, we do believe the shallow > iteration will give quite a significant performance boost. > > On your concerns: > > 1. Cleaner API. One alternative is to create new batch APIs. On consumer, > it would become Consumer.pollBatch returns a ConsumerBatch object which > contains topic/partition/firstOffsetOfBatch/pointerToByteBuffer, similarly > Producer.sendBatch(ProducerBatch). Both ConsumerBatch and ProducerBatch > objects are fixed types (no generics), serializer is gone, interceptors are > probably not needed initially (unless people see the need to intercept on > the batch level). On MM2 side, the current flow is ConsumerRecord -> > Connect's SourceRecord -> ProducerRecord, we would need to enhance Connect > framework to add SourceTask.pollBatch() method which returns a SourceBatch > object, so the object conversion flow becomes ConsumerBatch -> SourceBatch > -> ProducerBatch, we probably won't support any transformers on Batch > objects. > 2. PID/ProducerEpoch/SeqNo passing through RecordBatch. I think those > transaction fields are only meaningful in the original source kafka > cluster, producer id/seqNo are not the same for the target kafka cluster. > So if MM is not going to support transactions at the moment, we can clear > those fields when they are going through MM. Once MM starts to support > transactions in the future, it probably will start its own PID/SeqNo etc. > 3. For EOS and read_committed/read_uncommitted support, we can do phased > support. Phase 1, don't support transactional messages in the source > cluster (i.e. abort if it sees control batch records). Phase 2: applying > commit/abort on the batch boundary level. I am not too familiar with the > isolation level and abort transaction code path, but it seems the control > unit is currently on the batch boundary (commit/abort the whole batch), if > so, this should also be doable. > 4. MessageHandler in MM1 or SMT in MM2, initially we don't need to support > them. Since now the object is a ConsumerBatch and the existing handler is > written for the individual object. Deserialize the batch into individual > objects would defeat the purpose of performance optimization. > 5. Multiple batch performances, will do some testing on this. > > On Wed, Mar 31, 2021 at 10:14 AM Jun Rao wrote: > > > Hi, Henry, > > > > Thanks for the KIP. Sorry for the late reply. A few comments below. > > > > 1. The 'shallow' feature is potentially useful. I do agree with Tom that > > the proposed API changes seem unclean. Quite a few existing stuff don't > > really work together with this (e.g., generics, serializer, interceptors, > > configs like max.poll.records, etc). It's also hard to explain this > change > > to the common users of the consumer/producer API. I think it would be > > useful to explore if there is another cleaner way of adding this. For > > example, you mentioned that creating a new set of APIs doesn't work for > > MM2. However, we could potentially change the connect interface to allow > > MM2 to use the new API. If this doesn't work, it would be useful to > explain > > that in the rejected alternative section. > > > > 2. I am not sure that we could pass through all fields in RecordBatch. > For > > example, a MM instance could be receiving RecordBatch from different > source > > partitions. Mixing the PID/ProducerEpoch/FirstSequence fields across them > > in a single producer will be weird. So, it would be useful to document > this > > part clearer. > > > > 3. EOS. While MM itself doesn't support mirroring data in an > > exactly-once way, it needs to support reading from a topic with EOS data. > > So, it would be useful to document whether both read_committed and > > read_uncommitted mode are supported and what kind of RecordBatch the > > consumer returns in each case. > > > > 4. With the 'shallow' feature, it seems that some existing features in MM > > won't work. For example, I am not sure if SMT works in MM2 > > and MirrorMakerMessageHandler works in MM1. It would be useful to > document > > this kind of impact in the KIP. > > > > 5. Multiple batches per partition in the produce request. This seems not > > strictly required in KIP-98. However, changing this will probably add a > bit > > more complexity in the producer. So, it would be useful to understand its > > benefits, especially
Re: [DISCUSS] KIP-712: Shallow Mirroring
Hi Henry, Jun and Ismael,
A few things make me wonder if building this into the existing Producer and
Consumer APIs is really the right thing to do:
1. Type safety. The existing Producer and Consumer are both generic in K
and V, but those type parameters are meaningless in the batch case. For
example, the apparent type safety of a Producer would be violated
by using the batch method to actually send a . Another example:
What happens if I pass a producer configured for records to someone that
requires one configured for batches (and vice versa)?
2. The existing Producer and Consumer would both accept a number of configs
which didn't apply in the batch case.
In the discussion for KIP-706 Jason was imagining a more abstracted set of
client APIs which separated the data from the topic destination/origin, and
he mentioned basically this exact use case. This got me thinking, and
although I don't want to derail this conversion, I thought I'd sketch what
I came up with.
On the Consumer side:
```java
// Abstraction over where messages come from
interface ReceiveSource;
class TopicPartition implements SendTarget, ReceiveSource;
class Topic implements SendTarget, ReceiveSource;
class TopicId implements SendTarget, ReceiveSource;
class TopicPattern implements ReceiveSource;
// New abstraction for consumer-like things
interface Receiver {
assign(ReceiveSource source);
subscribe(ReceiveSource source);
// etc
X poll(Duration);
}
// Consumer doesn't change, except for the implements clause
interface Consumer implements Receiver> {
assign(ReceiveSource source);
subscribe(ReceiveSource source);
ConsumerRecords poll(Duration);
}
// KafkaConsumer doesn't change at all
class KafkaConsumer implements Consumer {
}
// Specialise Receiver for batch-based consumption.
interface BatchConsumer implements Receiver {
}
// Implementation
class KafkaBatchConsumer implements BatchConsumer {
}
class ConsumerBatch {
// For KIP-712, a way to convert batches without exposing low level
details like ByteBuffer
ProducerBatchPayload toProducerBatch();
}
```
On the producer side:
```java
// Abstraction over targets (see the ReceiveSource for the impls)
interface SendTarget;
// Abstraction over data that can be send to a target
interface Payload;
class ProducerRecordPayload implements Payload {
// Like ProducerRecord, but without the topic and partition
}
class ProducerBatchPayload implements Payload {
// For the KIP-712 case
}
// A new abstraction over producer-like things
interface Transmitter {
CompletionStage send(SendTarget target, P payload);
}
// Producer gains an extends clause
interface Producer extends Transmitter> {
}
class KafkaProducer implements Producer {
// Unchanged, included for completeness
}
interface BatchProducer extends Transmitter {
CompletionStage send(SendTarget target, ProducerBatch)
}
class KafkaBatchProducer extends BatchProducer {
// New. In practice a lot of common code between this and KafkaProducer
could be factored into an abstract class.
}
```
Really I'm just re-stating Jason's KIP-706 idea in the context of this KIP,
but it would address the type safety issue and also enable a batch consumer
to have its own set of configs. It also allows the new Producer.send return
type to be CompletionStage, which is KIP-706's objective. And, of course
it's compatible with possible future work around produce to/consume from
topic id.
Kind regards,
Tom
On Thu, Apr 1, 2021 at 9:11 AM Henry Cai wrote:
> Jun,
>
> Thanks for your insight looking into this KIP, we do believe the shallow
> iteration will give quite a significant performance boost.
>
> On your concerns:
>
> 1. Cleaner API. One alternative is to create new batch APIs. On consumer,
> it would become Consumer.pollBatch returns a ConsumerBatch object which
> contains topic/partition/firstOffsetOfBatch/pointerToByteBuffer, similarly
> Producer.sendBatch(ProducerBatch). Both ConsumerBatch and ProducerBatch
> objects are fixed types (no generics), serializer is gone, interceptors are
> probably not needed initially (unless people see the need to intercept on
> the batch level). On MM2 side, the current flow is ConsumerRecord ->
> Connect's SourceRecord -> ProducerRecord, we would need to enhance Connect
> framework to add SourceTask.pollBatch() method which returns a SourceBatch
> object, so the object conversion flow becomes ConsumerBatch -> SourceBatch
> -> ProducerBatch, we probably won't support any transformers on Batch
> objects.
> 2. PID/ProducerEpoch/SeqNo passing through RecordBatch. I think those
> transaction fields are only meaningful in the original source kafka
> cluster, producer id/seqNo are not the same for the target kafka cluster.
> So if MM is not going to support transactions at the moment, we can clear
> those fields when they are going through MM. Once MM starts to support
> transactions in the future, it probably will start its own PID/SeqNo etc.
> 3. For EOS and
Re: [DISCUSS] KIP-712: Shallow Mirroring
Jun, Thanks for your insight looking into this KIP, we do believe the shallow iteration will give quite a significant performance boost. On your concerns: 1. Cleaner API. One alternative is to create new batch APIs. On consumer, it would become Consumer.pollBatch returns a ConsumerBatch object which contains topic/partition/firstOffsetOfBatch/pointerToByteBuffer, similarly Producer.sendBatch(ProducerBatch). Both ConsumerBatch and ProducerBatch objects are fixed types (no generics), serializer is gone, interceptors are probably not needed initially (unless people see the need to intercept on the batch level). On MM2 side, the current flow is ConsumerRecord -> Connect's SourceRecord -> ProducerRecord, we would need to enhance Connect framework to add SourceTask.pollBatch() method which returns a SourceBatch object, so the object conversion flow becomes ConsumerBatch -> SourceBatch -> ProducerBatch, we probably won't support any transformers on Batch objects. 2. PID/ProducerEpoch/SeqNo passing through RecordBatch. I think those transaction fields are only meaningful in the original source kafka cluster, producer id/seqNo are not the same for the target kafka cluster. So if MM is not going to support transactions at the moment, we can clear those fields when they are going through MM. Once MM starts to support transactions in the future, it probably will start its own PID/SeqNo etc. 3. For EOS and read_committed/read_uncommitted support, we can do phased support. Phase 1, don't support transactional messages in the source cluster (i.e. abort if it sees control batch records). Phase 2: applying commit/abort on the batch boundary level. I am not too familiar with the isolation level and abort transaction code path, but it seems the control unit is currently on the batch boundary (commit/abort the whole batch), if so, this should also be doable. 4. MessageHandler in MM1 or SMT in MM2, initially we don't need to support them. Since now the object is a ConsumerBatch and the existing handler is written for the individual object. Deserialize the batch into individual objects would defeat the purpose of performance optimization. 5. Multiple batch performances, will do some testing on this. On Wed, Mar 31, 2021 at 10:14 AM Jun Rao wrote: > Hi, Henry, > > Thanks for the KIP. Sorry for the late reply. A few comments below. > > 1. The 'shallow' feature is potentially useful. I do agree with Tom that > the proposed API changes seem unclean. Quite a few existing stuff don't > really work together with this (e.g., generics, serializer, interceptors, > configs like max.poll.records, etc). It's also hard to explain this change > to the common users of the consumer/producer API. I think it would be > useful to explore if there is another cleaner way of adding this. For > example, you mentioned that creating a new set of APIs doesn't work for > MM2. However, we could potentially change the connect interface to allow > MM2 to use the new API. If this doesn't work, it would be useful to explain > that in the rejected alternative section. > > 2. I am not sure that we could pass through all fields in RecordBatch. For > example, a MM instance could be receiving RecordBatch from different source > partitions. Mixing the PID/ProducerEpoch/FirstSequence fields across them > in a single producer will be weird. So, it would be useful to document this > part clearer. > > 3. EOS. While MM itself doesn't support mirroring data in an > exactly-once way, it needs to support reading from a topic with EOS data. > So, it would be useful to document whether both read_committed and > read_uncommitted mode are supported and what kind of RecordBatch the > consumer returns in each case. > > 4. With the 'shallow' feature, it seems that some existing features in MM > won't work. For example, I am not sure if SMT works in MM2 > and MirrorMakerMessageHandler works in MM1. It would be useful to document > this kind of impact in the KIP. > > 5. Multiple batches per partition in the produce request. This seems not > strictly required in KIP-98. However, changing this will probably add a bit > more complexity in the producer. So, it would be useful to understand its > benefits, especially since it doesn't seem to directly help reduce the CPU > cost in MM. For example, do you have performance numbers with and without > this enabled in your MM tests? > > Thanks, > > Jun > > On Tue, Mar 30, 2021 at 1:27 PM Henry Cai > wrote: > > > Tom, > > > > Thanks for your comments. Yes it's a bit clumsy to use the existing > > consumer and producer API to carry the underlying record batch, but > > creating a new set of API would also mean other use cases (e.g. MM2) > > wouldn't be able to use that feature easily. We can throw exceptions if > we > > see clients are setting serializer/compression in the consumer config > > option. > > > > The consumer is essentially getting back a collection of > > RecordBatchByteBuffer records and passing them to the
Re: [DISCUSS] KIP-712: Shallow Mirroring
Hi, Henry, Thanks for the KIP. Sorry for the late reply. A few comments below. 1. The 'shallow' feature is potentially useful. I do agree with Tom that the proposed API changes seem unclean. Quite a few existing stuff don't really work together with this (e.g., generics, serializer, interceptors, configs like max.poll.records, etc). It's also hard to explain this change to the common users of the consumer/producer API. I think it would be useful to explore if there is another cleaner way of adding this. For example, you mentioned that creating a new set of APIs doesn't work for MM2. However, we could potentially change the connect interface to allow MM2 to use the new API. If this doesn't work, it would be useful to explain that in the rejected alternative section. 2. I am not sure that we could pass through all fields in RecordBatch. For example, a MM instance could be receiving RecordBatch from different source partitions. Mixing the PID/ProducerEpoch/FirstSequence fields across them in a single producer will be weird. So, it would be useful to document this part clearer. 3. EOS. While MM itself doesn't support mirroring data in an exactly-once way, it needs to support reading from a topic with EOS data. So, it would be useful to document whether both read_committed and read_uncommitted mode are supported and what kind of RecordBatch the consumer returns in each case. 4. With the 'shallow' feature, it seems that some existing features in MM won't work. For example, I am not sure if SMT works in MM2 and MirrorMakerMessageHandler works in MM1. It would be useful to document this kind of impact in the KIP. 5. Multiple batches per partition in the produce request. This seems not strictly required in KIP-98. However, changing this will probably add a bit more complexity in the producer. So, it would be useful to understand its benefits, especially since it doesn't seem to directly help reduce the CPU cost in MM. For example, do you have performance numbers with and without this enabled in your MM tests? Thanks, Jun On Tue, Mar 30, 2021 at 1:27 PM Henry Cai wrote: > Tom, > > Thanks for your comments. Yes it's a bit clumsy to use the existing > consumer and producer API to carry the underlying record batch, but > creating a new set of API would also mean other use cases (e.g. MM2) > wouldn't be able to use that feature easily. We can throw exceptions if we > see clients are setting serializer/compression in the consumer config > option. > > The consumer is essentially getting back a collection of > RecordBatchByteBuffer records and passing them to the producer. Most of > the internal APIs inside consumer and producer code paths are actually > taking on ByteBuffer as the argument so it's not too much work to get the > byte buffer through. > > For the worry that the client might see the inside of that byte buffer, we > can create a RecordBatchByteBufferRecord class to wrap the underlying byte > buffer so hopefully they will not drill too deep into that object. Java's > ByteBuffer does have a asReadOnlyBuffer() method to return a read-only > buffer, that can be explored as well. > > On Tue, Mar 30, 2021 at 4:24 AM Tom Bentley wrote: > > > Hi Henry and Ryanne, > > > > Related to Ismael's point about the producer & consumer configs being > > dangerous, I can see two parts to this: > > > > 2a. Both the proposed configs seem to be fundamentally incompatible with > > the Producer's existing key.serializer, value.serializer and > > compression.type configs, likewise the consumers key.deserializer and > > value.deserializer. I don't see a way to avoid this, since those existing > > configs are already separate things. (I did consider whether using > > special-case Deserializer and Serializer could be used instead, but that > > doesn't work nicely; in this use case they're necessarily all configured > > together). I think all we could do would be to reject configs which tried > > to set those existing client configs in conjunction with fetch.raw.bytes > > and send.raw.bytes. > > > > 2b. That still leaves a public Java API which would allow access to the > raw > > byte buffers. AFAICS we don't actually need user code to have access to > the > > raw buffers. It would be enough to get an opaque object that wrapped the > > ByteBuffer from the consumer and pass it to the producer. It's only the > > consumer and producer code which needs to be able to obtain the wrapped > > buffer. > > > > Kind regards, > > > > Tom > > > > On Tue, Mar 30, 2021 at 8:41 AM Ismael Juma wrote: > > > > > Hi Henry, > > > > > > Can you clarify why this "network performance" issue is only related to > > > shallow mirroring? Generally, we want the protocol to be generic and > not > > > have a number of special cases. The more special cases you have, the > > > tougher it becomes to test all the edge cases. > > > > > > Ismael > > > > > > On Mon, Mar 29, 2021 at 9:51 PM Henry Cai > > > wrote: > > > > > > > It's interesting this VOTE
Re: [DISCUSS] KIP-712: Shallow Mirroring
Tom, Thanks for your comments. Yes it's a bit clumsy to use the existing consumer and producer API to carry the underlying record batch, but creating a new set of API would also mean other use cases (e.g. MM2) wouldn't be able to use that feature easily. We can throw exceptions if we see clients are setting serializer/compression in the consumer config option. The consumer is essentially getting back a collection of RecordBatchByteBuffer records and passing them to the producer. Most of the internal APIs inside consumer and producer code paths are actually taking on ByteBuffer as the argument so it's not too much work to get the byte buffer through. For the worry that the client might see the inside of that byte buffer, we can create a RecordBatchByteBufferRecord class to wrap the underlying byte buffer so hopefully they will not drill too deep into that object. Java's ByteBuffer does have a asReadOnlyBuffer() method to return a read-only buffer, that can be explored as well. On Tue, Mar 30, 2021 at 4:24 AM Tom Bentley wrote: > Hi Henry and Ryanne, > > Related to Ismael's point about the producer & consumer configs being > dangerous, I can see two parts to this: > > 2a. Both the proposed configs seem to be fundamentally incompatible with > the Producer's existing key.serializer, value.serializer and > compression.type configs, likewise the consumers key.deserializer and > value.deserializer. I don't see a way to avoid this, since those existing > configs are already separate things. (I did consider whether using > special-case Deserializer and Serializer could be used instead, but that > doesn't work nicely; in this use case they're necessarily all configured > together). I think all we could do would be to reject configs which tried > to set those existing client configs in conjunction with fetch.raw.bytes > and send.raw.bytes. > > 2b. That still leaves a public Java API which would allow access to the raw > byte buffers. AFAICS we don't actually need user code to have access to the > raw buffers. It would be enough to get an opaque object that wrapped the > ByteBuffer from the consumer and pass it to the producer. It's only the > consumer and producer code which needs to be able to obtain the wrapped > buffer. > > Kind regards, > > Tom > > On Tue, Mar 30, 2021 at 8:41 AM Ismael Juma wrote: > > > Hi Henry, > > > > Can you clarify why this "network performance" issue is only related to > > shallow mirroring? Generally, we want the protocol to be generic and not > > have a number of special cases. The more special cases you have, the > > tougher it becomes to test all the edge cases. > > > > Ismael > > > > On Mon, Mar 29, 2021 at 9:51 PM Henry Cai > > wrote: > > > > > It's interesting this VOTE thread finally becomes a DISCUSS thread. > > > > > > For MM2 concern, I will take a look to see whether I can add the > support > > > for MM2. > > > > > > For Ismael's concern on multiple batches in the ProduceRequest > > (conflicting > > > with KIP-98), here is my take: > > > > > > 1. We do need to group multiple batches in the same request otherwise > the > > > network performance will suffer. > > > 2. For the concern on transactional message support as in KIP-98, since > > MM1 > > > and MM2 currently don't support transactional messages, KIP-712 will > not > > > attempt to support transactions either. I will add a config option on > > > producer config: allowMultipleBatches. By default this option will be > > off > > > and the user needs to explicitly turn on this option to use the shallow > > > mirror feature. And if we detect both this option and transaction is > > > turned on we will throw an exception to protect current transaction > > > processing. > > > 3. In the future, when MM2 starts to support exact-once and > transactional > > > messages (is that KIP-656?), we can revisit this code. The current > > > transactional message already makes the compromise that the messages in > > the > > > same RecordBatch (MessageSet) are sharing the same > > > sequence-id/transaction-id, so those messages need to be committed all > > > together. I think when we support the shallow mirror with > transactional > > > semantics, we will group all batches in the same ProduceRequest in the > > same > > > transaction boundary, they need to be committed all together. On the > > > broker side, all batches coming from ProduceRequest (or FetchResponse) > > are > > > committed in the same log segment file as one unit (current behavior). > > > > > > On Mon, Mar 29, 2021 at 8:46 AM Ryanne Dolan > > > wrote: > > > > > > > Ah, I see, thanks Ismael. Now I understand your concern. > > > > > > > > From KIP-98, re this change in v3: > > > > > > > > "This allows us to remove the message set size since each message set > > > > already contains a field for the size. More importantly, since there > is > > > > only one message set to be written to the log, partial produce > failures > > > are > > > > no longer possible. The
Re: [DISCUSS] KIP-712: Shallow Mirroring
Ismael, On the network performance side, the issue is on the throughput. For networking purposes, you gain throughout by combining data into bigger batch otherwise you pay higher overhead on network handshaking/roudtrip-delay and wastage on the underlying network packet buffer. On mirrormaker, it fetches data inbound through FetchResponse from source broker which can return data in MBytes (comprised of multiple batches in the same response), however the outbound ProduceRequest to target broker are in KByte batch size range if we don't optimize. (The reason those batches are in KBytes is because when the application client originally produced to the 1st broker, they tended to select smaller batch sizes to achieve low latency). The outbound throughput is not going to be able to match with the inbound throughput. In order to match the networking parity between inbound FetchResponse (which allows packing multiple batches) and outbound ProduceRequest, we ask to restore the multiple batch packing capability of ProduceRequest. I think KIP-98 did a shortcut to remove the multiple batch packing capability to save the extra work they need to do to support transactions across multiple batches. For our use case, we view MM as a mere replication pipe to get the data from one data center into another data center, the remote broker is almost like a follower to the broker in the source cluster. For broker to broker replication, it's using FetchRequest/FetchResponse which does use multiple batch packing to achieve the optimal network throughput. On the broker code path, FetchResponse and ProduceRequest went to the same handling code and the broker will just append the MemoryRecords (which contains multiple batches) into the same log segment file as one unit. So it's not particularly hard to restore the multiple batch packing feature back for ProduceRequest. On Tue, Mar 30, 2021 at 12:34 AM Ismael Juma wrote: > Hi Henry, > > Can you clarify why this "network performance" issue is only related to > shallow mirroring? Generally, we want the protocol to be generic and not > have a number of special cases. The more special cases you have, the > tougher it becomes to test all the edge cases. > > Ismael > > On Mon, Mar 29, 2021 at 9:51 PM Henry Cai > wrote: > > > It's interesting this VOTE thread finally becomes a DISCUSS thread. > > > > For MM2 concern, I will take a look to see whether I can add the support > > for MM2. > > > > For Ismael's concern on multiple batches in the ProduceRequest > (conflicting > > with KIP-98), here is my take: > > > > 1. We do need to group multiple batches in the same request otherwise the > > network performance will suffer. > > 2. For the concern on transactional message support as in KIP-98, since > MM1 > > and MM2 currently don't support transactional messages, KIP-712 will not > > attempt to support transactions either. I will add a config option on > > producer config: allowMultipleBatches. By default this option will be > off > > and the user needs to explicitly turn on this option to use the shallow > > mirror feature. And if we detect both this option and transaction is > > turned on we will throw an exception to protect current transaction > > processing. > > 3. In the future, when MM2 starts to support exact-once and transactional > > messages (is that KIP-656?), we can revisit this code. The current > > transactional message already makes the compromise that the messages in > the > > same RecordBatch (MessageSet) are sharing the same > > sequence-id/transaction-id, so those messages need to be committed all > > together. I think when we support the shallow mirror with transactional > > semantics, we will group all batches in the same ProduceRequest in the > same > > transaction boundary, they need to be committed all together. On the > > broker side, all batches coming from ProduceRequest (or FetchResponse) > are > > committed in the same log segment file as one unit (current behavior). > > > > On Mon, Mar 29, 2021 at 8:46 AM Ryanne Dolan > > wrote: > > > > > Ah, I see, thanks Ismael. Now I understand your concern. > > > > > > From KIP-98, re this change in v3: > > > > > > "This allows us to remove the message set size since each message set > > > already contains a field for the size. More importantly, since there is > > > only one message set to be written to the log, partial produce failures > > are > > > no longer possible. The full message set is either successfully written > > to > > > the log (and replicated) or it is not." > > > > > > The schema and size field don't seem to be an issue, as KIP-712 already > > > addresses. > > > > > > The partial produce failure issue is something I don't understand. I > > can't > > > tell if this was done out of convenience at the time or if there is > > > something incompatible with partial produce success/failure and EOS. > Does > > > anyone know? > > > > > > Ryanne > > > > > > On Mon, Mar 29, 2021, 1:41 AM Ismael Juma
Re: [DISCUSS] KIP-712: Shallow Mirroring
Hi Henry and Ryanne, Related to Ismael's point about the producer & consumer configs being dangerous, I can see two parts to this: 2a. Both the proposed configs seem to be fundamentally incompatible with the Producer's existing key.serializer, value.serializer and compression.type configs, likewise the consumers key.deserializer and value.deserializer. I don't see a way to avoid this, since those existing configs are already separate things. (I did consider whether using special-case Deserializer and Serializer could be used instead, but that doesn't work nicely; in this use case they're necessarily all configured together). I think all we could do would be to reject configs which tried to set those existing client configs in conjunction with fetch.raw.bytes and send.raw.bytes. 2b. That still leaves a public Java API which would allow access to the raw byte buffers. AFAICS we don't actually need user code to have access to the raw buffers. It would be enough to get an opaque object that wrapped the ByteBuffer from the consumer and pass it to the producer. It's only the consumer and producer code which needs to be able to obtain the wrapped buffer. Kind regards, Tom On Tue, Mar 30, 2021 at 8:41 AM Ismael Juma wrote: > Hi Henry, > > Can you clarify why this "network performance" issue is only related to > shallow mirroring? Generally, we want the protocol to be generic and not > have a number of special cases. The more special cases you have, the > tougher it becomes to test all the edge cases. > > Ismael > > On Mon, Mar 29, 2021 at 9:51 PM Henry Cai > wrote: > > > It's interesting this VOTE thread finally becomes a DISCUSS thread. > > > > For MM2 concern, I will take a look to see whether I can add the support > > for MM2. > > > > For Ismael's concern on multiple batches in the ProduceRequest > (conflicting > > with KIP-98), here is my take: > > > > 1. We do need to group multiple batches in the same request otherwise the > > network performance will suffer. > > 2. For the concern on transactional message support as in KIP-98, since > MM1 > > and MM2 currently don't support transactional messages, KIP-712 will not > > attempt to support transactions either. I will add a config option on > > producer config: allowMultipleBatches. By default this option will be > off > > and the user needs to explicitly turn on this option to use the shallow > > mirror feature. And if we detect both this option and transaction is > > turned on we will throw an exception to protect current transaction > > processing. > > 3. In the future, when MM2 starts to support exact-once and transactional > > messages (is that KIP-656?), we can revisit this code. The current > > transactional message already makes the compromise that the messages in > the > > same RecordBatch (MessageSet) are sharing the same > > sequence-id/transaction-id, so those messages need to be committed all > > together. I think when we support the shallow mirror with transactional > > semantics, we will group all batches in the same ProduceRequest in the > same > > transaction boundary, they need to be committed all together. On the > > broker side, all batches coming from ProduceRequest (or FetchResponse) > are > > committed in the same log segment file as one unit (current behavior). > > > > On Mon, Mar 29, 2021 at 8:46 AM Ryanne Dolan > > wrote: > > > > > Ah, I see, thanks Ismael. Now I understand your concern. > > > > > > From KIP-98, re this change in v3: > > > > > > "This allows us to remove the message set size since each message set > > > already contains a field for the size. More importantly, since there is > > > only one message set to be written to the log, partial produce failures > > are > > > no longer possible. The full message set is either successfully written > > to > > > the log (and replicated) or it is not." > > > > > > The schema and size field don't seem to be an issue, as KIP-712 already > > > addresses. > > > > > > The partial produce failure issue is something I don't understand. I > > can't > > > tell if this was done out of convenience at the time or if there is > > > something incompatible with partial produce success/failure and EOS. > Does > > > anyone know? > > > > > > Ryanne > > > > > > On Mon, Mar 29, 2021, 1:41 AM Ismael Juma wrote: > > > > > > > Ryanne, > > > > > > > > You misunderstood the referenced comment. It is about the produce > > request > > > > change to have multiple batches: > > > > > > > > "Up to ProduceRequest V2, a ProduceRequest can contain multiple > batches > > > of > > > > messages stored in the record_set field, but this was disabled in V3. > > We > > > > are proposing to bring the multiple batches feature back to improve > the > > > > network throughput of the mirror maker producer when the original > batch > > > > size from source broker is too small." > > > > > > > > This is unrelated to shallow iteration. > > > > > > > > Ismael > > > > > > > > On Sun, Mar 28, 2021, 10:15 PM Ryanne
Re: [DISCUSS] KIP-712: Shallow Mirroring
Hi Henry, Can you clarify why this "network performance" issue is only related to shallow mirroring? Generally, we want the protocol to be generic and not have a number of special cases. The more special cases you have, the tougher it becomes to test all the edge cases. Ismael On Mon, Mar 29, 2021 at 9:51 PM Henry Cai wrote: > It's interesting this VOTE thread finally becomes a DISCUSS thread. > > For MM2 concern, I will take a look to see whether I can add the support > for MM2. > > For Ismael's concern on multiple batches in the ProduceRequest (conflicting > with KIP-98), here is my take: > > 1. We do need to group multiple batches in the same request otherwise the > network performance will suffer. > 2. For the concern on transactional message support as in KIP-98, since MM1 > and MM2 currently don't support transactional messages, KIP-712 will not > attempt to support transactions either. I will add a config option on > producer config: allowMultipleBatches. By default this option will be off > and the user needs to explicitly turn on this option to use the shallow > mirror feature. And if we detect both this option and transaction is > turned on we will throw an exception to protect current transaction > processing. > 3. In the future, when MM2 starts to support exact-once and transactional > messages (is that KIP-656?), we can revisit this code. The current > transactional message already makes the compromise that the messages in the > same RecordBatch (MessageSet) are sharing the same > sequence-id/transaction-id, so those messages need to be committed all > together. I think when we support the shallow mirror with transactional > semantics, we will group all batches in the same ProduceRequest in the same > transaction boundary, they need to be committed all together. On the > broker side, all batches coming from ProduceRequest (or FetchResponse) are > committed in the same log segment file as one unit (current behavior). > > On Mon, Mar 29, 2021 at 8:46 AM Ryanne Dolan > wrote: > > > Ah, I see, thanks Ismael. Now I understand your concern. > > > > From KIP-98, re this change in v3: > > > > "This allows us to remove the message set size since each message set > > already contains a field for the size. More importantly, since there is > > only one message set to be written to the log, partial produce failures > are > > no longer possible. The full message set is either successfully written > to > > the log (and replicated) or it is not." > > > > The schema and size field don't seem to be an issue, as KIP-712 already > > addresses. > > > > The partial produce failure issue is something I don't understand. I > can't > > tell if this was done out of convenience at the time or if there is > > something incompatible with partial produce success/failure and EOS. Does > > anyone know? > > > > Ryanne > > > > On Mon, Mar 29, 2021, 1:41 AM Ismael Juma wrote: > > > > > Ryanne, > > > > > > You misunderstood the referenced comment. It is about the produce > request > > > change to have multiple batches: > > > > > > "Up to ProduceRequest V2, a ProduceRequest can contain multiple batches > > of > > > messages stored in the record_set field, but this was disabled in V3. > We > > > are proposing to bring the multiple batches feature back to improve the > > > network throughput of the mirror maker producer when the original batch > > > size from source broker is too small." > > > > > > This is unrelated to shallow iteration. > > > > > > Ismael > > > > > > On Sun, Mar 28, 2021, 10:15 PM Ryanne Dolan > > wrote: > > > > > > > Ismael, I don't think KIP-98 is related. Shallow iteration was > removed > > in > > > > KAFKA-732, which predates KIP-98 by a few years. > > > > > > > > Ryanne > > > > > > > > On Sun, Mar 28, 2021, 11:25 PM Ismael Juma > wrote: > > > > > > > > > Thanks for the KIP. I have a few high level comments: > > > > > > > > > > 1. Like Tom, I'm not convinced about the proposal to make this > change > > > to > > > > > MirrorMaker 1 if we intend to deprecate it and remove it. I would > > > rather > > > > us > > > > > focus our efforts on the implementation we intend to support going > > > > forward. > > > > > 2. The producer/consumer configs seem pretty dangerous for general > > > usage, > > > > > but the KIP doesn't address the potential downsides. > > > > > 3. How does the ProducerRequest change impact exactly-once (if at > > all)? > > > > The > > > > > change we are reverting was done as part of KIP-98. Have we > > considered > > > > the > > > > > original reasons for the change? > > > > > > > > > > Thanks, > > > > > Ismael > > > > > > > > > > On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < > > > > > vahid.hashem...@gmail.com> > > > > > wrote: > > > > > > > > > > > Retitled the thread to conform to the common format. > > > > > > > > > > > > On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang < > ning2008w...@gmail.com> > > > > > wrote: > > > > > > > > > > > > > Hello Henry, > > > > > > > > > > > > >
Re: [DISCUSS] KIP-712: Shallow Mirroring
It's interesting this VOTE thread finally becomes a DISCUSS thread. For MM2 concern, I will take a look to see whether I can add the support for MM2. For Ismael's concern on multiple batches in the ProduceRequest (conflicting with KIP-98), here is my take: 1. We do need to group multiple batches in the same request otherwise the network performance will suffer. 2. For the concern on transactional message support as in KIP-98, since MM1 and MM2 currently don't support transactional messages, KIP-712 will not attempt to support transactions either. I will add a config option on producer config: allowMultipleBatches. By default this option will be off and the user needs to explicitly turn on this option to use the shallow mirror feature. And if we detect both this option and transaction is turned on we will throw an exception to protect current transaction processing. 3. In the future, when MM2 starts to support exact-once and transactional messages (is that KIP-656?), we can revisit this code. The current transactional message already makes the compromise that the messages in the same RecordBatch (MessageSet) are sharing the same sequence-id/transaction-id, so those messages need to be committed all together. I think when we support the shallow mirror with transactional semantics, we will group all batches in the same ProduceRequest in the same transaction boundary, they need to be committed all together. On the broker side, all batches coming from ProduceRequest (or FetchResponse) are committed in the same log segment file as one unit (current behavior). On Mon, Mar 29, 2021 at 8:46 AM Ryanne Dolan wrote: > Ah, I see, thanks Ismael. Now I understand your concern. > > From KIP-98, re this change in v3: > > "This allows us to remove the message set size since each message set > already contains a field for the size. More importantly, since there is > only one message set to be written to the log, partial produce failures are > no longer possible. The full message set is either successfully written to > the log (and replicated) or it is not." > > The schema and size field don't seem to be an issue, as KIP-712 already > addresses. > > The partial produce failure issue is something I don't understand. I can't > tell if this was done out of convenience at the time or if there is > something incompatible with partial produce success/failure and EOS. Does > anyone know? > > Ryanne > > On Mon, Mar 29, 2021, 1:41 AM Ismael Juma wrote: > > > Ryanne, > > > > You misunderstood the referenced comment. It is about the produce request > > change to have multiple batches: > > > > "Up to ProduceRequest V2, a ProduceRequest can contain multiple batches > of > > messages stored in the record_set field, but this was disabled in V3. We > > are proposing to bring the multiple batches feature back to improve the > > network throughput of the mirror maker producer when the original batch > > size from source broker is too small." > > > > This is unrelated to shallow iteration. > > > > Ismael > > > > On Sun, Mar 28, 2021, 10:15 PM Ryanne Dolan > wrote: > > > > > Ismael, I don't think KIP-98 is related. Shallow iteration was removed > in > > > KAFKA-732, which predates KIP-98 by a few years. > > > > > > Ryanne > > > > > > On Sun, Mar 28, 2021, 11:25 PM Ismael Juma wrote: > > > > > > > Thanks for the KIP. I have a few high level comments: > > > > > > > > 1. Like Tom, I'm not convinced about the proposal to make this change > > to > > > > MirrorMaker 1 if we intend to deprecate it and remove it. I would > > rather > > > us > > > > focus our efforts on the implementation we intend to support going > > > forward. > > > > 2. The producer/consumer configs seem pretty dangerous for general > > usage, > > > > but the KIP doesn't address the potential downsides. > > > > 3. How does the ProducerRequest change impact exactly-once (if at > all)? > > > The > > > > change we are reverting was done as part of KIP-98. Have we > considered > > > the > > > > original reasons for the change? > > > > > > > > Thanks, > > > > Ismael > > > > > > > > On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < > > > > vahid.hashem...@gmail.com> > > > > wrote: > > > > > > > > > Retitled the thread to conform to the common format. > > > > > > > > > > On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang > > > > wrote: > > > > > > > > > > > Hello Henry, > > > > > > > > > > > > This is a very interesting proposal. > > > > > > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the > > > similar > > > > > > concern of re-compressing data in mirror maker. > > > > > > > > > > > > Probably one thing may need to clarify is: how "shallow" > mirroring > > is > > > > > only > > > > > > applied to mirrormaker use case, if the changes need to be made > on > > > > > generic > > > > > > consumer and producer (e.g. by adding `fetch.raw.bytes` and > > > > > > `send.raw.bytes` to producer and consumer config) > > > > > > > > > > > > On 2021/02/05 00:59:57, Henry Cai > > >
Re: [DISCUSS] KIP-712: Shallow Mirroring
Ah, I see, thanks Ismael. Now I understand your concern. >From KIP-98, re this change in v3: "This allows us to remove the message set size since each message set already contains a field for the size. More importantly, since there is only one message set to be written to the log, partial produce failures are no longer possible. The full message set is either successfully written to the log (and replicated) or it is not." The schema and size field don't seem to be an issue, as KIP-712 already addresses. The partial produce failure issue is something I don't understand. I can't tell if this was done out of convenience at the time or if there is something incompatible with partial produce success/failure and EOS. Does anyone know? Ryanne On Mon, Mar 29, 2021, 1:41 AM Ismael Juma wrote: > Ryanne, > > You misunderstood the referenced comment. It is about the produce request > change to have multiple batches: > > "Up to ProduceRequest V2, a ProduceRequest can contain multiple batches of > messages stored in the record_set field, but this was disabled in V3. We > are proposing to bring the multiple batches feature back to improve the > network throughput of the mirror maker producer when the original batch > size from source broker is too small." > > This is unrelated to shallow iteration. > > Ismael > > On Sun, Mar 28, 2021, 10:15 PM Ryanne Dolan wrote: > > > Ismael, I don't think KIP-98 is related. Shallow iteration was removed in > > KAFKA-732, which predates KIP-98 by a few years. > > > > Ryanne > > > > On Sun, Mar 28, 2021, 11:25 PM Ismael Juma wrote: > > > > > Thanks for the KIP. I have a few high level comments: > > > > > > 1. Like Tom, I'm not convinced about the proposal to make this change > to > > > MirrorMaker 1 if we intend to deprecate it and remove it. I would > rather > > us > > > focus our efforts on the implementation we intend to support going > > forward. > > > 2. The producer/consumer configs seem pretty dangerous for general > usage, > > > but the KIP doesn't address the potential downsides. > > > 3. How does the ProducerRequest change impact exactly-once (if at all)? > > The > > > change we are reverting was done as part of KIP-98. Have we considered > > the > > > original reasons for the change? > > > > > > Thanks, > > > Ismael > > > > > > On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < > > > vahid.hashem...@gmail.com> > > > wrote: > > > > > > > Retitled the thread to conform to the common format. > > > > > > > > On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang > > > wrote: > > > > > > > > > Hello Henry, > > > > > > > > > > This is a very interesting proposal. > > > > > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the > > similar > > > > > concern of re-compressing data in mirror maker. > > > > > > > > > > Probably one thing may need to clarify is: how "shallow" mirroring > is > > > > only > > > > > applied to mirrormaker use case, if the changes need to be made on > > > > generic > > > > > consumer and producer (e.g. by adding `fetch.raw.bytes` and > > > > > `send.raw.bytes` to producer and consumer config) > > > > > > > > > > On 2021/02/05 00:59:57, Henry Cai > > wrote: > > > > > > Dear Community members, > > > > > > > > > > > > We are proposing a new feature to improve the performance of > Kafka > > > > mirror > > > > > > maker: > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring > > > > > > > > > > > > The current Kafka MirrorMaker process (with the underlying > Consumer > > > and > > > > > > Producer library) uses significant CPU cycles and memory to > > > > > > decompress/recompress, deserialize/re-serialize messages and copy > > > > > multiple > > > > > > times of messages bytes along the mirroring/replicating stages. > > > > > > > > > > > > The KIP proposes a *shallow mirror* feature which brings back the > > > > shallow > > > > > > iterator concept to the mirror process and also proposes to skip > > the > > > > > > unnecessary message decompression and recompression steps. We > > argue > > > in > > > > > > many cases users just want a simple replication pipeline to > > replicate > > > > the > > > > > > message as it is from the source cluster to the destination > > cluster. > > > > In > > > > > > many cases the messages in the source cluster are already > > compressed > > > > and > > > > > > properly batched, users just need an identical copy of the > message > > > > bytes > > > > > > through the mirroring without any transformation or > repartitioning. > > > > > > > > > > > > We have a prototype implementation in house with MirrorMaker v1 > and > > > > > > observed *CPU usage dropped from 50% to 15%* for some mirror > > > pipelines. > > > > > > > > > > > > We name this feature: *shallow mirroring* since it has some > > > resemblance > > > > > to > > > > > > the old Kafka 0.7 namesake feature but the implementations are > not > > > > quite > > > > > > the same. ‘*Shallow*’ means 1. we
Re: [DISCUSS] KIP-712: Shallow Mirroring
Ryanne, You misunderstood the referenced comment. It is about the produce request change to have multiple batches: "Up to ProduceRequest V2, a ProduceRequest can contain multiple batches of messages stored in the record_set field, but this was disabled in V3. We are proposing to bring the multiple batches feature back to improve the network throughput of the mirror maker producer when the original batch size from source broker is too small." This is unrelated to shallow iteration. Ismael On Sun, Mar 28, 2021, 10:15 PM Ryanne Dolan wrote: > Ismael, I don't think KIP-98 is related. Shallow iteration was removed in > KAFKA-732, which predates KIP-98 by a few years. > > Ryanne > > On Sun, Mar 28, 2021, 11:25 PM Ismael Juma wrote: > > > Thanks for the KIP. I have a few high level comments: > > > > 1. Like Tom, I'm not convinced about the proposal to make this change to > > MirrorMaker 1 if we intend to deprecate it and remove it. I would rather > us > > focus our efforts on the implementation we intend to support going > forward. > > 2. The producer/consumer configs seem pretty dangerous for general usage, > > but the KIP doesn't address the potential downsides. > > 3. How does the ProducerRequest change impact exactly-once (if at all)? > The > > change we are reverting was done as part of KIP-98. Have we considered > the > > original reasons for the change? > > > > Thanks, > > Ismael > > > > On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < > > vahid.hashem...@gmail.com> > > wrote: > > > > > Retitled the thread to conform to the common format. > > > > > > On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang > > wrote: > > > > > > > Hello Henry, > > > > > > > > This is a very interesting proposal. > > > > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the > similar > > > > concern of re-compressing data in mirror maker. > > > > > > > > Probably one thing may need to clarify is: how "shallow" mirroring is > > > only > > > > applied to mirrormaker use case, if the changes need to be made on > > > generic > > > > consumer and producer (e.g. by adding `fetch.raw.bytes` and > > > > `send.raw.bytes` to producer and consumer config) > > > > > > > > On 2021/02/05 00:59:57, Henry Cai > wrote: > > > > > Dear Community members, > > > > > > > > > > We are proposing a new feature to improve the performance of Kafka > > > mirror > > > > > maker: > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring > > > > > > > > > > The current Kafka MirrorMaker process (with the underlying Consumer > > and > > > > > Producer library) uses significant CPU cycles and memory to > > > > > decompress/recompress, deserialize/re-serialize messages and copy > > > > multiple > > > > > times of messages bytes along the mirroring/replicating stages. > > > > > > > > > > The KIP proposes a *shallow mirror* feature which brings back the > > > shallow > > > > > iterator concept to the mirror process and also proposes to skip > the > > > > > unnecessary message decompression and recompression steps. We > argue > > in > > > > > many cases users just want a simple replication pipeline to > replicate > > > the > > > > > message as it is from the source cluster to the destination > cluster. > > > In > > > > > many cases the messages in the source cluster are already > compressed > > > and > > > > > properly batched, users just need an identical copy of the message > > > bytes > > > > > through the mirroring without any transformation or repartitioning. > > > > > > > > > > We have a prototype implementation in house with MirrorMaker v1 and > > > > > observed *CPU usage dropped from 50% to 15%* for some mirror > > pipelines. > > > > > > > > > > We name this feature: *shallow mirroring* since it has some > > resemblance > > > > to > > > > > the old Kafka 0.7 namesake feature but the implementations are not > > > quite > > > > > the same. ‘*Shallow*’ means 1. we *shallowly* iterate > RecordBatches > > > > inside > > > > > MemoryRecords structure instead of deep iterating records inside > > > > > RecordBatch; 2. We *shallowly* copy (share) pointers inside > > ByteBuffer > > > > > instead of deep copying and deserializing bytes into objects. > > > > > > > > > > Please share discussions/feedback along this email thread. > > > > > > > > > > > > > > > > > > -- > > > > > > Thanks! > > > --Vahid > > > > > >
Re: [DISCUSS] KIP-712: Shallow Mirroring
Ismael, I don't think KIP-98 is related. Shallow iteration was removed in KAFKA-732, which predates KIP-98 by a few years. Ryanne On Sun, Mar 28, 2021, 11:25 PM Ismael Juma wrote: > Thanks for the KIP. I have a few high level comments: > > 1. Like Tom, I'm not convinced about the proposal to make this change to > MirrorMaker 1 if we intend to deprecate it and remove it. I would rather us > focus our efforts on the implementation we intend to support going forward. > 2. The producer/consumer configs seem pretty dangerous for general usage, > but the KIP doesn't address the potential downsides. > 3. How does the ProducerRequest change impact exactly-once (if at all)? The > change we are reverting was done as part of KIP-98. Have we considered the > original reasons for the change? > > Thanks, > Ismael > > On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < > vahid.hashem...@gmail.com> > wrote: > > > Retitled the thread to conform to the common format. > > > > On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang > wrote: > > > > > Hello Henry, > > > > > > This is a very interesting proposal. > > > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the similar > > > concern of re-compressing data in mirror maker. > > > > > > Probably one thing may need to clarify is: how "shallow" mirroring is > > only > > > applied to mirrormaker use case, if the changes need to be made on > > generic > > > consumer and producer (e.g. by adding `fetch.raw.bytes` and > > > `send.raw.bytes` to producer and consumer config) > > > > > > On 2021/02/05 00:59:57, Henry Cai wrote: > > > > Dear Community members, > > > > > > > > We are proposing a new feature to improve the performance of Kafka > > mirror > > > > maker: > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring > > > > > > > > The current Kafka MirrorMaker process (with the underlying Consumer > and > > > > Producer library) uses significant CPU cycles and memory to > > > > decompress/recompress, deserialize/re-serialize messages and copy > > > multiple > > > > times of messages bytes along the mirroring/replicating stages. > > > > > > > > The KIP proposes a *shallow mirror* feature which brings back the > > shallow > > > > iterator concept to the mirror process and also proposes to skip the > > > > unnecessary message decompression and recompression steps. We argue > in > > > > many cases users just want a simple replication pipeline to replicate > > the > > > > message as it is from the source cluster to the destination cluster. > > In > > > > many cases the messages in the source cluster are already compressed > > and > > > > properly batched, users just need an identical copy of the message > > bytes > > > > through the mirroring without any transformation or repartitioning. > > > > > > > > We have a prototype implementation in house with MirrorMaker v1 and > > > > observed *CPU usage dropped from 50% to 15%* for some mirror > pipelines. > > > > > > > > We name this feature: *shallow mirroring* since it has some > resemblance > > > to > > > > the old Kafka 0.7 namesake feature but the implementations are not > > quite > > > > the same. ‘*Shallow*’ means 1. we *shallowly* iterate RecordBatches > > > inside > > > > MemoryRecords structure instead of deep iterating records inside > > > > RecordBatch; 2. We *shallowly* copy (share) pointers inside > ByteBuffer > > > > instead of deep copying and deserializing bytes into objects. > > > > > > > > Please share discussions/feedback along this email thread. > > > > > > > > > > > > > -- > > > > Thanks! > > --Vahid > > >
Re: [DISCUSS] KIP-712: Shallow Mirroring
Thanks for the KIP. I have a few high level comments: 1. Like Tom, I'm not convinced about the proposal to make this change to MirrorMaker 1 if we intend to deprecate it and remove it. I would rather us focus our efforts on the implementation we intend to support going forward. 2. The producer/consumer configs seem pretty dangerous for general usage, but the KIP doesn't address the potential downsides. 3. How does the ProducerRequest change impact exactly-once (if at all)? The change we are reverting was done as part of KIP-98. Have we considered the original reasons for the change? Thanks, Ismael On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian wrote: > Retitled the thread to conform to the common format. > > On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang wrote: > > > Hello Henry, > > > > This is a very interesting proposal. > > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the similar > > concern of re-compressing data in mirror maker. > > > > Probably one thing may need to clarify is: how "shallow" mirroring is > only > > applied to mirrormaker use case, if the changes need to be made on > generic > > consumer and producer (e.g. by adding `fetch.raw.bytes` and > > `send.raw.bytes` to producer and consumer config) > > > > On 2021/02/05 00:59:57, Henry Cai wrote: > > > Dear Community members, > > > > > > We are proposing a new feature to improve the performance of Kafka > mirror > > > maker: > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring > > > > > > The current Kafka MirrorMaker process (with the underlying Consumer and > > > Producer library) uses significant CPU cycles and memory to > > > decompress/recompress, deserialize/re-serialize messages and copy > > multiple > > > times of messages bytes along the mirroring/replicating stages. > > > > > > The KIP proposes a *shallow mirror* feature which brings back the > shallow > > > iterator concept to the mirror process and also proposes to skip the > > > unnecessary message decompression and recompression steps. We argue in > > > many cases users just want a simple replication pipeline to replicate > the > > > message as it is from the source cluster to the destination cluster. > In > > > many cases the messages in the source cluster are already compressed > and > > > properly batched, users just need an identical copy of the message > bytes > > > through the mirroring without any transformation or repartitioning. > > > > > > We have a prototype implementation in house with MirrorMaker v1 and > > > observed *CPU usage dropped from 50% to 15%* for some mirror pipelines. > > > > > > We name this feature: *shallow mirroring* since it has some resemblance > > to > > > the old Kafka 0.7 namesake feature but the implementations are not > quite > > > the same. ‘*Shallow*’ means 1. we *shallowly* iterate RecordBatches > > inside > > > MemoryRecords structure instead of deep iterating records inside > > > RecordBatch; 2. We *shallowly* copy (share) pointers inside ByteBuffer > > > instead of deep copying and deserializing bytes into objects. > > > > > > Please share discussions/feedback along this email thread. > > > > > > > > -- > > Thanks! > --Vahid >
Re: [DISCUSS] KIP-712: Shallow Mirroring
> so as to avoid creating a perverse incentive for users to not adopt MM2? Tom, I know there are several of us chomping at the bit to enable this in MM2, so I don't think that's a problem. AFAICT there won't be a separate KIP required -- we just need to enable this new option in MM2 by default. Ryanne On Fri, Mar 26, 2021 at 12:53 PM Tom Bentley wrote: > Hi, > > Thanks for the KIP. I've not yet read it in detail, so have no technical > points to make at this point. > > I'm having trouble reconciling KIP-720's deprecation of MM1 with this > proposal to add a new feature to MM1 and not to MM2. I think this would > create a confusing impression to users. Given that the change to MM2 is > supposed to be straightforward is there any reason why not to implement it > as part of this KIP, so as to avoid creating a perverse incentive for users > to not adopt MM2? > > Kind regards, > > Tom > > On Mon, Mar 22, 2021 at 6:21 PM Henry Cai > wrote: > > > If there are no additional comments you’d start a vote in a couple of > days. > > > > On Sat, Feb 27, 2021 at 9:26 AM A S wrote: > > > > > +1 to adding latency metrics. > > > > > > To add context on why CPU, memory and GC has a bigger impact than > network > > > in a Mirror for compressed topics without KIP-712 is: *a failing / > > > unstable mirror cluster will have lag perpetually spiking having much > > > larger impact on e2e latencies*. To explain a bit more: > > > > > > Less data moved: > > > Compressed topics "usually" should move less data over the network and > > are > > > useful to reduce the network cost / footprint of replication. > Therefore, > > > network usage may naturally be less than if this data were > uncompressed. > > > Instead the CPU usage bottleneck hits first due to decompression of > data. > > > Prior to KIP-712 we had never been able to operate a mirror at wire > > speed. > > > > > > Stability: > > > If there is a load spike, there can be a few scenarios played out: > > > - more data in a batch i.e. larger uncompressed size i.e. larger memory > > > footprint > > > - more number of batches i.e. larger memory footprint > > > > > > In either case higher memory usage and more CPU cycles are used due to > > > this. > > > If the GC throughput or heap size is insufficient leads to OOMs. > > > > > > Domino Effect: > > > Just like any Kafka Consumer, if a consumer instance in a consumer > group > > > terminates it triggers a rebalance. In this case that rebalance happens > > due > > > to an OOM. If a Mirror instance that fails due to an OOM triggered by > > > traffic load (explained above) will result in a domino effect of more > > > Mirror instances having OOMs as the load increases due to an even > smaller > > > number of running instances remaining in the group. Eventually leading > > to a > > > total failure of the mirror cluster. > > > > > > Memory Limits & Ineffective workarounds: > > > A question that could be asked couldn't we configure the Mirror > instance > > > in such a way that this doesn't happen? The answer is it's expensive > and > > > difficult. > > > Let's say we are using a 4 core host with X GBs of memory and configure > > > the Mirror to use 4 Streams and this configuration leads to an OOM, we > > > could try to reduce the number of Streams to 3 or 2. That's a 25-50% > loss > > > in efficiency i.e. we may now need 2x the number of nodes (& 2x cost) > > > without any guarantees that this configuration will never result in an > > OOM > > > (since future traffic characteristics are unpredictable) but it may > > reduce > > > the probability of an OOM. > > > > > > Summary: > > > Since the root cause is memory usage due to decompression of data in > > > flight, the ideal way to resolve this was to eliminate the > decompression > > of > > > data which isn't a hard requirement for the mirror to operate since it > > was > > > not performing any transformation or repartitioning in our case. > > > > > > Thanks, > > > - Ambud > > > > > > On Mon, Feb 22, 2021 at 9:20 AM Vahid Hashemian < > > vahid.hashem...@gmail.com> > > > wrote: > > > > > >> As Henry mentions in the KIP, we are seeing a great deal of > improvements > > >> and efficiency by using the mirroring enhancement proposed in this > KIP, > > >> and > > >> believe it would be equally beneficial to everyone that runs Kafka and > > >> Kafka Mirror at scale. > > >> > > >> I'm bumping up this thread in case there are additional feedback or > > >> comments. > > >> > > >> Thanks, > > >> --Vahid > > >> > > >> On Sat, Feb 13, 2021, 13:59 Ryanne Dolan > wrote: > > >> > > >> > Glad to hear that latency and thruput aren't negatively affected > > >> somehow. I > > >> > would love to see this KIP move forward. > > >> > > > >> > Ryanne > > >> > > > >> > On Sat, Feb 13, 2021, 3:00 PM Henry Cai wrote: > > >> > > > >> > > Ryanne, > > >> > > > > >> > > Yes, network performance is also important. In our deployment, we > > are > > >> > > bottlenecked on the CPU/memory on the mirror hosts. We are
Re: [DISCUSS] KIP-712: Shallow Mirroring
Hi, Thanks for the KIP. I've not yet read it in detail, so have no technical points to make at this point. I'm having trouble reconciling KIP-720's deprecation of MM1 with this proposal to add a new feature to MM1 and not to MM2. I think this would create a confusing impression to users. Given that the change to MM2 is supposed to be straightforward is there any reason why not to implement it as part of this KIP, so as to avoid creating a perverse incentive for users to not adopt MM2? Kind regards, Tom On Mon, Mar 22, 2021 at 6:21 PM Henry Cai wrote: > If there are no additional comments you’d start a vote in a couple of days. > > On Sat, Feb 27, 2021 at 9:26 AM A S wrote: > > > +1 to adding latency metrics. > > > > To add context on why CPU, memory and GC has a bigger impact than network > > in a Mirror for compressed topics without KIP-712 is: *a failing / > > unstable mirror cluster will have lag perpetually spiking having much > > larger impact on e2e latencies*. To explain a bit more: > > > > Less data moved: > > Compressed topics "usually" should move less data over the network and > are > > useful to reduce the network cost / footprint of replication. Therefore, > > network usage may naturally be less than if this data were uncompressed. > > Instead the CPU usage bottleneck hits first due to decompression of data. > > Prior to KIP-712 we had never been able to operate a mirror at wire > speed. > > > > Stability: > > If there is a load spike, there can be a few scenarios played out: > > - more data in a batch i.e. larger uncompressed size i.e. larger memory > > footprint > > - more number of batches i.e. larger memory footprint > > > > In either case higher memory usage and more CPU cycles are used due to > > this. > > If the GC throughput or heap size is insufficient leads to OOMs. > > > > Domino Effect: > > Just like any Kafka Consumer, if a consumer instance in a consumer group > > terminates it triggers a rebalance. In this case that rebalance happens > due > > to an OOM. If a Mirror instance that fails due to an OOM triggered by > > traffic load (explained above) will result in a domino effect of more > > Mirror instances having OOMs as the load increases due to an even smaller > > number of running instances remaining in the group. Eventually leading > to a > > total failure of the mirror cluster. > > > > Memory Limits & Ineffective workarounds: > > A question that could be asked couldn't we configure the Mirror instance > > in such a way that this doesn't happen? The answer is it's expensive and > > difficult. > > Let's say we are using a 4 core host with X GBs of memory and configure > > the Mirror to use 4 Streams and this configuration leads to an OOM, we > > could try to reduce the number of Streams to 3 or 2. That's a 25-50% loss > > in efficiency i.e. we may now need 2x the number of nodes (& 2x cost) > > without any guarantees that this configuration will never result in an > OOM > > (since future traffic characteristics are unpredictable) but it may > reduce > > the probability of an OOM. > > > > Summary: > > Since the root cause is memory usage due to decompression of data in > > flight, the ideal way to resolve this was to eliminate the decompression > of > > data which isn't a hard requirement for the mirror to operate since it > was > > not performing any transformation or repartitioning in our case. > > > > Thanks, > > - Ambud > > > > On Mon, Feb 22, 2021 at 9:20 AM Vahid Hashemian < > vahid.hashem...@gmail.com> > > wrote: > > > >> As Henry mentions in the KIP, we are seeing a great deal of improvements > >> and efficiency by using the mirroring enhancement proposed in this KIP, > >> and > >> believe it would be equally beneficial to everyone that runs Kafka and > >> Kafka Mirror at scale. > >> > >> I'm bumping up this thread in case there are additional feedback or > >> comments. > >> > >> Thanks, > >> --Vahid > >> > >> On Sat, Feb 13, 2021, 13:59 Ryanne Dolan wrote: > >> > >> > Glad to hear that latency and thruput aren't negatively affected > >> somehow. I > >> > would love to see this KIP move forward. > >> > > >> > Ryanne > >> > > >> > On Sat, Feb 13, 2021, 3:00 PM Henry Cai wrote: > >> > > >> > > Ryanne, > >> > > > >> > > Yes, network performance is also important. In our deployment, we > are > >> > > bottlenecked on the CPU/memory on the mirror hosts. We are using > >> c5.2x > >> > and > >> > > m5.2x nodes in AWS, before the deployment, CPU would peak to 80% but > >> > there > >> > > is enough network bandwidth left on those hosts. Having said that, > we > >> > > maintain the same network throughput before and after the switch. > >> > > > >> > > On Fri, Feb 12, 2021 at 12:20 PM Ryanne Dolan < > ryannedo...@gmail.com> > >> > > wrote: > >> > > > >> > >> Hey Henry, great KIP. The performance improvements are impressive! > >> > >> However, often cpu, ram, gc are not the metrics most important to a > >> > >> replication pipeline -- often the network is mostly
Re: [DISCUSS] KIP-712: Shallow Mirroring
If there are no additional comments you’d start a vote in a couple of days. On Sat, Feb 27, 2021 at 9:26 AM A S wrote: > +1 to adding latency metrics. > > To add context on why CPU, memory and GC has a bigger impact than network > in a Mirror for compressed topics without KIP-712 is: *a failing / > unstable mirror cluster will have lag perpetually spiking having much > larger impact on e2e latencies*. To explain a bit more: > > Less data moved: > Compressed topics "usually" should move less data over the network and are > useful to reduce the network cost / footprint of replication. Therefore, > network usage may naturally be less than if this data were uncompressed. > Instead the CPU usage bottleneck hits first due to decompression of data. > Prior to KIP-712 we had never been able to operate a mirror at wire speed. > > Stability: > If there is a load spike, there can be a few scenarios played out: > - more data in a batch i.e. larger uncompressed size i.e. larger memory > footprint > - more number of batches i.e. larger memory footprint > > In either case higher memory usage and more CPU cycles are used due to > this. > If the GC throughput or heap size is insufficient leads to OOMs. > > Domino Effect: > Just like any Kafka Consumer, if a consumer instance in a consumer group > terminates it triggers a rebalance. In this case that rebalance happens due > to an OOM. If a Mirror instance that fails due to an OOM triggered by > traffic load (explained above) will result in a domino effect of more > Mirror instances having OOMs as the load increases due to an even smaller > number of running instances remaining in the group. Eventually leading to a > total failure of the mirror cluster. > > Memory Limits & Ineffective workarounds: > A question that could be asked couldn't we configure the Mirror instance > in such a way that this doesn't happen? The answer is it's expensive and > difficult. > Let's say we are using a 4 core host with X GBs of memory and configure > the Mirror to use 4 Streams and this configuration leads to an OOM, we > could try to reduce the number of Streams to 3 or 2. That's a 25-50% loss > in efficiency i.e. we may now need 2x the number of nodes (& 2x cost) > without any guarantees that this configuration will never result in an OOM > (since future traffic characteristics are unpredictable) but it may reduce > the probability of an OOM. > > Summary: > Since the root cause is memory usage due to decompression of data in > flight, the ideal way to resolve this was to eliminate the decompression of > data which isn't a hard requirement for the mirror to operate since it was > not performing any transformation or repartitioning in our case. > > Thanks, > - Ambud > > On Mon, Feb 22, 2021 at 9:20 AM Vahid Hashemian > wrote: > >> As Henry mentions in the KIP, we are seeing a great deal of improvements >> and efficiency by using the mirroring enhancement proposed in this KIP, >> and >> believe it would be equally beneficial to everyone that runs Kafka and >> Kafka Mirror at scale. >> >> I'm bumping up this thread in case there are additional feedback or >> comments. >> >> Thanks, >> --Vahid >> >> On Sat, Feb 13, 2021, 13:59 Ryanne Dolan wrote: >> >> > Glad to hear that latency and thruput aren't negatively affected >> somehow. I >> > would love to see this KIP move forward. >> > >> > Ryanne >> > >> > On Sat, Feb 13, 2021, 3:00 PM Henry Cai wrote: >> > >> > > Ryanne, >> > > >> > > Yes, network performance is also important. In our deployment, we are >> > > bottlenecked on the CPU/memory on the mirror hosts. We are using >> c5.2x >> > and >> > > m5.2x nodes in AWS, before the deployment, CPU would peak to 80% but >> > there >> > > is enough network bandwidth left on those hosts. Having said that, we >> > > maintain the same network throughput before and after the switch. >> > > >> > > On Fri, Feb 12, 2021 at 12:20 PM Ryanne Dolan >> > > wrote: >> > > >> > >> Hey Henry, great KIP. The performance improvements are impressive! >> > >> However, often cpu, ram, gc are not the metrics most important to a >> > >> replication pipeline -- often the network is mostly saturated >> anyway. Do >> > >> you know how this change affects latency or thruput? I suspect less >> GC >> > >> pressure means slightly less p99 latency, but it would be great to >> see >> > that >> > >> confirmed. I don't think it's necessary that this KIP improves these >> > >> metrics, but I think it's important to show that they at least aren't >> > made >> > >> worse. >> > >> >> > >> I suspect any improvement in MM1 would be magnified in MM2, given >> there >> > >> is a lot more machinery between consumer and producer in MM2. >> > >> >> > >> >> > >> I'd like to do some performance analysis based on these changes. >> Looking >> > >> forward to a PR! >> > >> >> > >> Ryanne >> > >> >> > >> On Wed, Feb 10, 2021, 3:50 PM Henry Cai wrote: >> > >> >> > >>> On the question "whether shallow mirror is only applied on mirror >> maker
Re: [DISCUSS] KIP-712: Shallow Mirroring
+1 to adding latency metrics. To add context on why CPU, memory and GC has a bigger impact than network in a Mirror for compressed topics without KIP-712 is: *a failing / unstable mirror cluster will have lag perpetually spiking having much larger impact on e2e latencies*. To explain a bit more: Less data moved: Compressed topics "usually" should move less data over the network and are useful to reduce the network cost / footprint of replication. Therefore, network usage may naturally be less than if this data were uncompressed. Instead the CPU usage bottleneck hits first due to decompression of data. Prior to KIP-712 we had never been able to operate a mirror at wire speed. Stability: If there is a load spike, there can be a few scenarios played out: - more data in a batch i.e. larger uncompressed size i.e. larger memory footprint - more number of batches i.e. larger memory footprint In either case higher memory usage and more CPU cycles are used due to this. If the GC throughput or heap size is insufficient leads to OOMs. Domino Effect: Just like any Kafka Consumer, if a consumer instance in a consumer group terminates it triggers a rebalance. In this case that rebalance happens due to an OOM. If a Mirror instance that fails due to an OOM triggered by traffic load (explained above) will result in a domino effect of more Mirror instances having OOMs as the load increases due to an even smaller number of running instances remaining in the group. Eventually leading to a total failure of the mirror cluster. Memory Limits & Ineffective workarounds: A question that could be asked couldn't we configure the Mirror instance in such a way that this doesn't happen? The answer is it's expensive and difficult. Let's say we are using a 4 core host with X GBs of memory and configure the Mirror to use 4 Streams and this configuration leads to an OOM, we could try to reduce the number of Streams to 3 or 2. That's a 25-50% loss in efficiency i.e. we may now need 2x the number of nodes (& 2x cost) without any guarantees that this configuration will never result in an OOM (since future traffic characteristics are unpredictable) but it may reduce the probability of an OOM. Summary: Since the root cause is memory usage due to decompression of data in flight, the ideal way to resolve this was to eliminate the decompression of data which isn't a hard requirement for the mirror to operate since it was not performing any transformation or repartitioning in our case. Thanks, - Ambud On Mon, Feb 22, 2021 at 9:20 AM Vahid Hashemian wrote: > As Henry mentions in the KIP, we are seeing a great deal of improvements > and efficiency by using the mirroring enhancement proposed in this KIP, and > believe it would be equally beneficial to everyone that runs Kafka and > Kafka Mirror at scale. > > I'm bumping up this thread in case there are additional feedback or > comments. > > Thanks, > --Vahid > > On Sat, Feb 13, 2021, 13:59 Ryanne Dolan wrote: > > > Glad to hear that latency and thruput aren't negatively affected > somehow. I > > would love to see this KIP move forward. > > > > Ryanne > > > > On Sat, Feb 13, 2021, 3:00 PM Henry Cai wrote: > > > > > Ryanne, > > > > > > Yes, network performance is also important. In our deployment, we are > > > bottlenecked on the CPU/memory on the mirror hosts. We are using c5.2x > > and > > > m5.2x nodes in AWS, before the deployment, CPU would peak to 80% but > > there > > > is enough network bandwidth left on those hosts. Having said that, we > > > maintain the same network throughput before and after the switch. > > > > > > On Fri, Feb 12, 2021 at 12:20 PM Ryanne Dolan > > > wrote: > > > > > >> Hey Henry, great KIP. The performance improvements are impressive! > > >> However, often cpu, ram, gc are not the metrics most important to a > > >> replication pipeline -- often the network is mostly saturated anyway. > Do > > >> you know how this change affects latency or thruput? I suspect less GC > > >> pressure means slightly less p99 latency, but it would be great to see > > that > > >> confirmed. I don't think it's necessary that this KIP improves these > > >> metrics, but I think it's important to show that they at least aren't > > made > > >> worse. > > >> > > >> I suspect any improvement in MM1 would be magnified in MM2, given > there > > >> is a lot more machinery between consumer and producer in MM2. > > >> > > >> > > >> I'd like to do some performance analysis based on these changes. > Looking > > >> forward to a PR! > > >> > > >> Ryanne > > >> > > >> On Wed, Feb 10, 2021, 3:50 PM Henry Cai wrote: > > >> > > >>> On the question "whether shallow mirror is only applied on mirror > maker > > >>> v1", the code change is mostly on consumer and producer code path, > the > > >>> change to mirrormaker v1 is very trivial. We chose to modify the > > >>> consumer/producer path (instead of creating a new mirror product) so > > other > > >>> use cases can use that feature as well. The
Re: [DISCUSS] KIP-712: Shallow Mirroring
As Henry mentions in the KIP, we are seeing a great deal of improvements and efficiency by using the mirroring enhancement proposed in this KIP, and believe it would be equally beneficial to everyone that runs Kafka and Kafka Mirror at scale. I'm bumping up this thread in case there are additional feedback or comments. Thanks, --Vahid On Sat, Feb 13, 2021, 13:59 Ryanne Dolan wrote: > Glad to hear that latency and thruput aren't negatively affected somehow. I > would love to see this KIP move forward. > > Ryanne > > On Sat, Feb 13, 2021, 3:00 PM Henry Cai wrote: > > > Ryanne, > > > > Yes, network performance is also important. In our deployment, we are > > bottlenecked on the CPU/memory on the mirror hosts. We are using c5.2x > and > > m5.2x nodes in AWS, before the deployment, CPU would peak to 80% but > there > > is enough network bandwidth left on those hosts. Having said that, we > > maintain the same network throughput before and after the switch. > > > > On Fri, Feb 12, 2021 at 12:20 PM Ryanne Dolan > > wrote: > > > >> Hey Henry, great KIP. The performance improvements are impressive! > >> However, often cpu, ram, gc are not the metrics most important to a > >> replication pipeline -- often the network is mostly saturated anyway. Do > >> you know how this change affects latency or thruput? I suspect less GC > >> pressure means slightly less p99 latency, but it would be great to see > that > >> confirmed. I don't think it's necessary that this KIP improves these > >> metrics, but I think it's important to show that they at least aren't > made > >> worse. > >> > >> I suspect any improvement in MM1 would be magnified in MM2, given there > >> is a lot more machinery between consumer and producer in MM2. > >> > >> > >> I'd like to do some performance analysis based on these changes. Looking > >> forward to a PR! > >> > >> Ryanne > >> > >> On Wed, Feb 10, 2021, 3:50 PM Henry Cai wrote: > >> > >>> On the question "whether shallow mirror is only applied on mirror maker > >>> v1", the code change is mostly on consumer and producer code path, the > >>> change to mirrormaker v1 is very trivial. We chose to modify the > >>> consumer/producer path (instead of creating a new mirror product) so > other > >>> use cases can use that feature as well. The change to mirror maker v2 > >>> should be straightforward as well but we don't have that environment in > >>> house. I think the community can easily port this change to mirror > maker > >>> v2. > >>> > >>> > >>> > >>> On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < > >>> vahid.hashem...@gmail.com> wrote: > >>> > Retitled the thread to conform to the common format. > > On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang > wrote: > > > Hello Henry, > > > > This is a very interesting proposal. > > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the > similar > > concern of re-compressing data in mirror maker. > > > > Probably one thing may need to clarify is: how "shallow" mirroring > is > only > > applied to mirrormaker use case, if the changes need to be made on > generic > > consumer and producer (e.g. by adding `fetch.raw.bytes` and > > `send.raw.bytes` to producer and consumer config) > > > > On 2021/02/05 00:59:57, Henry Cai > wrote: > > > Dear Community members, > > > > > > We are proposing a new feature to improve the performance of Kafka > mirror > > > maker: > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring > > > > > > The current Kafka MirrorMaker process (with the underlying > Consumer > and > > > Producer library) uses significant CPU cycles and memory to > > > decompress/recompress, deserialize/re-serialize messages and copy > > multiple > > > times of messages bytes along the mirroring/replicating stages. > > > > > > The KIP proposes a *shallow mirror* feature which brings back the > shallow > > > iterator concept to the mirror process and also proposes to skip > the > > > unnecessary message decompression and recompression steps. We > argue in > > > many cases users just want a simple replication pipeline to > replicate the > > > message as it is from the source cluster to the destination > cluster. In > > > many cases the messages in the source cluster are already > compressed and > > > properly batched, users just need an identical copy of the message > bytes > > > through the mirroring without any transformation or > repartitioning. > > > > > > We have a prototype implementation in house with MirrorMaker v1 > and > > > observed *CPU usage dropped from 50% to 15%* for some mirror > pipelines. > > > > > > We name this feature: *shallow mirroring* since it has some > resemblance > > to > > > the old
Re: [DISCUSS] KIP-712: Shallow Mirroring
Glad to hear that latency and thruput aren't negatively affected somehow. I would love to see this KIP move forward. Ryanne On Sat, Feb 13, 2021, 3:00 PM Henry Cai wrote: > Ryanne, > > Yes, network performance is also important. In our deployment, we are > bottlenecked on the CPU/memory on the mirror hosts. We are using c5.2x and > m5.2x nodes in AWS, before the deployment, CPU would peak to 80% but there > is enough network bandwidth left on those hosts. Having said that, we > maintain the same network throughput before and after the switch. > > On Fri, Feb 12, 2021 at 12:20 PM Ryanne Dolan > wrote: > >> Hey Henry, great KIP. The performance improvements are impressive! >> However, often cpu, ram, gc are not the metrics most important to a >> replication pipeline -- often the network is mostly saturated anyway. Do >> you know how this change affects latency or thruput? I suspect less GC >> pressure means slightly less p99 latency, but it would be great to see that >> confirmed. I don't think it's necessary that this KIP improves these >> metrics, but I think it's important to show that they at least aren't made >> worse. >> >> I suspect any improvement in MM1 would be magnified in MM2, given there >> is a lot more machinery between consumer and producer in MM2. >> >> >> I'd like to do some performance analysis based on these changes. Looking >> forward to a PR! >> >> Ryanne >> >> On Wed, Feb 10, 2021, 3:50 PM Henry Cai wrote: >> >>> On the question "whether shallow mirror is only applied on mirror maker >>> v1", the code change is mostly on consumer and producer code path, the >>> change to mirrormaker v1 is very trivial. We chose to modify the >>> consumer/producer path (instead of creating a new mirror product) so other >>> use cases can use that feature as well. The change to mirror maker v2 >>> should be straightforward as well but we don't have that environment in >>> house. I think the community can easily port this change to mirror maker >>> v2. >>> >>> >>> >>> On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < >>> vahid.hashem...@gmail.com> wrote: >>> Retitled the thread to conform to the common format. On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang wrote: > Hello Henry, > > This is a very interesting proposal. > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the similar > concern of re-compressing data in mirror maker. > > Probably one thing may need to clarify is: how "shallow" mirroring is only > applied to mirrormaker use case, if the changes need to be made on generic > consumer and producer (e.g. by adding `fetch.raw.bytes` and > `send.raw.bytes` to producer and consumer config) > > On 2021/02/05 00:59:57, Henry Cai wrote: > > Dear Community members, > > > > We are proposing a new feature to improve the performance of Kafka mirror > > maker: > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring > > > > The current Kafka MirrorMaker process (with the underlying Consumer and > > Producer library) uses significant CPU cycles and memory to > > decompress/recompress, deserialize/re-serialize messages and copy > multiple > > times of messages bytes along the mirroring/replicating stages. > > > > The KIP proposes a *shallow mirror* feature which brings back the shallow > > iterator concept to the mirror process and also proposes to skip the > > unnecessary message decompression and recompression steps. We argue in > > many cases users just want a simple replication pipeline to replicate the > > message as it is from the source cluster to the destination cluster. In > > many cases the messages in the source cluster are already compressed and > > properly batched, users just need an identical copy of the message bytes > > through the mirroring without any transformation or repartitioning. > > > > We have a prototype implementation in house with MirrorMaker v1 and > > observed *CPU usage dropped from 50% to 15%* for some mirror pipelines. > > > > We name this feature: *shallow mirroring* since it has some resemblance > to > > the old Kafka 0.7 namesake feature but the implementations are not quite > > the same. ‘*Shallow*’ means 1. we *shallowly* iterate RecordBatches > inside > > MemoryRecords structure instead of deep iterating records inside > > RecordBatch; 2. We *shallowly* copy (share) pointers inside ByteBuffer > > instead of deep copying and deserializing bytes into objects. > > > > Please share discussions/feedback along this email thread. > > > -- Thanks! --Vahid >>>
Re: [DISCUSS] KIP-712: Shallow Mirroring
Ryanne, Yes, network performance is also important. In our deployment, we are bottlenecked on the CPU/memory on the mirror hosts. We are using c5.2x and m5.2x nodes in AWS, before the deployment, CPU would peak to 80% but there is enough network bandwidth left on those hosts. Having said that, we maintain the same network throughput before and after the switch. On Fri, Feb 12, 2021 at 12:20 PM Ryanne Dolan wrote: > Hey Henry, great KIP. The performance improvements are impressive! > However, often cpu, ram, gc are not the metrics most important to a > replication pipeline -- often the network is mostly saturated anyway. Do > you know how this change affects latency or thruput? I suspect less GC > pressure means slightly less p99 latency, but it would be great to see that > confirmed. I don't think it's necessary that this KIP improves these > metrics, but I think it's important to show that they at least aren't made > worse. > > I suspect any improvement in MM1 would be magnified in MM2, given there is > a lot more machinery between consumer and producer in MM2. > > > I'd like to do some performance analysis based on these changes. Looking > forward to a PR! > > Ryanne > > On Wed, Feb 10, 2021, 3:50 PM Henry Cai wrote: > >> On the question "whether shallow mirror is only applied on mirror maker >> v1", the code change is mostly on consumer and producer code path, the >> change to mirrormaker v1 is very trivial. We chose to modify the >> consumer/producer path (instead of creating a new mirror product) so other >> use cases can use that feature as well. The change to mirror maker v2 >> should be straightforward as well but we don't have that environment in >> house. I think the community can easily port this change to mirror maker >> v2. >> >> >> >> On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < >> vahid.hashem...@gmail.com> wrote: >> >>> Retitled the thread to conform to the common format. >>> >>> On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang >>> wrote: >>> >>> > Hello Henry, >>> > >>> > This is a very interesting proposal. >>> > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the similar >>> > concern of re-compressing data in mirror maker. >>> > >>> > Probably one thing may need to clarify is: how "shallow" mirroring is >>> only >>> > applied to mirrormaker use case, if the changes need to be made on >>> generic >>> > consumer and producer (e.g. by adding `fetch.raw.bytes` and >>> > `send.raw.bytes` to producer and consumer config) >>> > >>> > On 2021/02/05 00:59:57, Henry Cai wrote: >>> > > Dear Community members, >>> > > >>> > > We are proposing a new feature to improve the performance of Kafka >>> mirror >>> > > maker: >>> > > >>> > >>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring >>> > > >>> > > The current Kafka MirrorMaker process (with the underlying Consumer >>> and >>> > > Producer library) uses significant CPU cycles and memory to >>> > > decompress/recompress, deserialize/re-serialize messages and copy >>> > multiple >>> > > times of messages bytes along the mirroring/replicating stages. >>> > > >>> > > The KIP proposes a *shallow mirror* feature which brings back the >>> shallow >>> > > iterator concept to the mirror process and also proposes to skip the >>> > > unnecessary message decompression and recompression steps. We argue >>> in >>> > > many cases users just want a simple replication pipeline to >>> replicate the >>> > > message as it is from the source cluster to the destination >>> cluster. In >>> > > many cases the messages in the source cluster are already compressed >>> and >>> > > properly batched, users just need an identical copy of the message >>> bytes >>> > > through the mirroring without any transformation or repartitioning. >>> > > >>> > > We have a prototype implementation in house with MirrorMaker v1 and >>> > > observed *CPU usage dropped from 50% to 15%* for some mirror >>> pipelines. >>> > > >>> > > We name this feature: *shallow mirroring* since it has some >>> resemblance >>> > to >>> > > the old Kafka 0.7 namesake feature but the implementations are not >>> quite >>> > > the same. ‘*Shallow*’ means 1. we *shallowly* iterate RecordBatches >>> > inside >>> > > MemoryRecords structure instead of deep iterating records inside >>> > > RecordBatch; 2. We *shallowly* copy (share) pointers inside >>> ByteBuffer >>> > > instead of deep copying and deserializing bytes into objects. >>> > > >>> > > Please share discussions/feedback along this email thread. >>> > > >>> > >>> >>> >>> -- >>> >>> Thanks! >>> --Vahid >>> >>
Re: [DISCUSS] KIP-712: Shallow Mirroring
Hey Henry, great KIP. The performance improvements are impressive! However, often cpu, ram, gc are not the metrics most important to a replication pipeline -- often the network is mostly saturated anyway. Do you know how this change affects latency or thruput? I suspect less GC pressure means slightly less p99 latency, but it would be great to see that confirmed. I don't think it's necessary that this KIP improves these metrics, but I think it's important to show that they at least aren't made worse. I suspect any improvement in MM1 would be magnified in MM2, given there is a lot more machinery between consumer and producer in MM2. I'd like to do some performance analysis based on these changes. Looking forward to a PR! Ryanne On Wed, Feb 10, 2021, 3:50 PM Henry Cai wrote: > On the question "whether shallow mirror is only applied on mirror maker > v1", the code change is mostly on consumer and producer code path, the > change to mirrormaker v1 is very trivial. We chose to modify the > consumer/producer path (instead of creating a new mirror product) so other > use cases can use that feature as well. The change to mirror maker v2 > should be straightforward as well but we don't have that environment in > house. I think the community can easily port this change to mirror maker > v2. > > > > On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian < > vahid.hashem...@gmail.com> wrote: > >> Retitled the thread to conform to the common format. >> >> On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang wrote: >> >> > Hello Henry, >> > >> > This is a very interesting proposal. >> > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the similar >> > concern of re-compressing data in mirror maker. >> > >> > Probably one thing may need to clarify is: how "shallow" mirroring is >> only >> > applied to mirrormaker use case, if the changes need to be made on >> generic >> > consumer and producer (e.g. by adding `fetch.raw.bytes` and >> > `send.raw.bytes` to producer and consumer config) >> > >> > On 2021/02/05 00:59:57, Henry Cai wrote: >> > > Dear Community members, >> > > >> > > We are proposing a new feature to improve the performance of Kafka >> mirror >> > > maker: >> > > >> > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring >> > > >> > > The current Kafka MirrorMaker process (with the underlying Consumer >> and >> > > Producer library) uses significant CPU cycles and memory to >> > > decompress/recompress, deserialize/re-serialize messages and copy >> > multiple >> > > times of messages bytes along the mirroring/replicating stages. >> > > >> > > The KIP proposes a *shallow mirror* feature which brings back the >> shallow >> > > iterator concept to the mirror process and also proposes to skip the >> > > unnecessary message decompression and recompression steps. We argue >> in >> > > many cases users just want a simple replication pipeline to replicate >> the >> > > message as it is from the source cluster to the destination cluster. >> In >> > > many cases the messages in the source cluster are already compressed >> and >> > > properly batched, users just need an identical copy of the message >> bytes >> > > through the mirroring without any transformation or repartitioning. >> > > >> > > We have a prototype implementation in house with MirrorMaker v1 and >> > > observed *CPU usage dropped from 50% to 15%* for some mirror >> pipelines. >> > > >> > > We name this feature: *shallow mirroring* since it has some >> resemblance >> > to >> > > the old Kafka 0.7 namesake feature but the implementations are not >> quite >> > > the same. ‘*Shallow*’ means 1. we *shallowly* iterate RecordBatches >> > inside >> > > MemoryRecords structure instead of deep iterating records inside >> > > RecordBatch; 2. We *shallowly* copy (share) pointers inside ByteBuffer >> > > instead of deep copying and deserializing bytes into objects. >> > > >> > > Please share discussions/feedback along this email thread. >> > > >> > >> >> >> -- >> >> Thanks! >> --Vahid >> >
Re: [DISCUSS] KIP-712: Shallow Mirroring
On the question "whether shallow mirror is only applied on mirror maker v1", the code change is mostly on consumer and producer code path, the change to mirrormaker v1 is very trivial. We chose to modify the consumer/producer path (instead of creating a new mirror product) so other use cases can use that feature as well. The change to mirror maker v2 should be straightforward as well but we don't have that environment in house. I think the community can easily port this change to mirror maker v2. On Wed, Feb 10, 2021 at 12:58 PM Vahid Hashemian wrote: > Retitled the thread to conform to the common format. > > On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang wrote: > > > Hello Henry, > > > > This is a very interesting proposal. > > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the similar > > concern of re-compressing data in mirror maker. > > > > Probably one thing may need to clarify is: how "shallow" mirroring is > only > > applied to mirrormaker use case, if the changes need to be made on > generic > > consumer and producer (e.g. by adding `fetch.raw.bytes` and > > `send.raw.bytes` to producer and consumer config) > > > > On 2021/02/05 00:59:57, Henry Cai wrote: > > > Dear Community members, > > > > > > We are proposing a new feature to improve the performance of Kafka > mirror > > > maker: > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring > > > > > > The current Kafka MirrorMaker process (with the underlying Consumer and > > > Producer library) uses significant CPU cycles and memory to > > > decompress/recompress, deserialize/re-serialize messages and copy > > multiple > > > times of messages bytes along the mirroring/replicating stages. > > > > > > The KIP proposes a *shallow mirror* feature which brings back the > shallow > > > iterator concept to the mirror process and also proposes to skip the > > > unnecessary message decompression and recompression steps. We argue in > > > many cases users just want a simple replication pipeline to replicate > the > > > message as it is from the source cluster to the destination cluster. > In > > > many cases the messages in the source cluster are already compressed > and > > > properly batched, users just need an identical copy of the message > bytes > > > through the mirroring without any transformation or repartitioning. > > > > > > We have a prototype implementation in house with MirrorMaker v1 and > > > observed *CPU usage dropped from 50% to 15%* for some mirror pipelines. > > > > > > We name this feature: *shallow mirroring* since it has some resemblance > > to > > > the old Kafka 0.7 namesake feature but the implementations are not > quite > > > the same. ‘*Shallow*’ means 1. we *shallowly* iterate RecordBatches > > inside > > > MemoryRecords structure instead of deep iterating records inside > > > RecordBatch; 2. We *shallowly* copy (share) pointers inside ByteBuffer > > > instead of deep copying and deserializing bytes into objects. > > > > > > Please share discussions/feedback along this email thread. > > > > > > > > -- > > Thanks! > --Vahid >
Re: [DISCUSS] KIP-712: Shallow Mirroring
Retitled the thread to conform to the common format. On Fri, Feb 5, 2021 at 4:00 PM Ning Zhang wrote: > Hello Henry, > > This is a very interesting proposal. > https://issues.apache.org/jira/browse/KAFKA-10728 reflects the similar > concern of re-compressing data in mirror maker. > > Probably one thing may need to clarify is: how "shallow" mirroring is only > applied to mirrormaker use case, if the changes need to be made on generic > consumer and producer (e.g. by adding `fetch.raw.bytes` and > `send.raw.bytes` to producer and consumer config) > > On 2021/02/05 00:59:57, Henry Cai wrote: > > Dear Community members, > > > > We are proposing a new feature to improve the performance of Kafka mirror > > maker: > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-712%3A+Shallow+Mirroring > > > > The current Kafka MirrorMaker process (with the underlying Consumer and > > Producer library) uses significant CPU cycles and memory to > > decompress/recompress, deserialize/re-serialize messages and copy > multiple > > times of messages bytes along the mirroring/replicating stages. > > > > The KIP proposes a *shallow mirror* feature which brings back the shallow > > iterator concept to the mirror process and also proposes to skip the > > unnecessary message decompression and recompression steps. We argue in > > many cases users just want a simple replication pipeline to replicate the > > message as it is from the source cluster to the destination cluster. In > > many cases the messages in the source cluster are already compressed and > > properly batched, users just need an identical copy of the message bytes > > through the mirroring without any transformation or repartitioning. > > > > We have a prototype implementation in house with MirrorMaker v1 and > > observed *CPU usage dropped from 50% to 15%* for some mirror pipelines. > > > > We name this feature: *shallow mirroring* since it has some resemblance > to > > the old Kafka 0.7 namesake feature but the implementations are not quite > > the same. ‘*Shallow*’ means 1. we *shallowly* iterate RecordBatches > inside > > MemoryRecords structure instead of deep iterating records inside > > RecordBatch; 2. We *shallowly* copy (share) pointers inside ByteBuffer > > instead of deep copying and deserializing bytes into objects. > > > > Please share discussions/feedback along this email thread. > > > -- Thanks! --Vahid
