That's right. MM2 is at-least-once for now, same as legacy MirrorMaker. You
can follow https://issues.apache.org/jira/browse/KAFKA-6080 for updates on
exactly-once semantics in Connect.
Ryanne
On Tue, Oct 15, 2019 at 1:24 PM Vishal Santoshi <vishal.santo...@gmail.com>
wrote:
> >> You are correct. I'm working on a KIP and PoC to introduce
> transactions to
> >> Connect for this exact purpose :)
>
> That is awesome. Any time frame ?
>
>
> In the mean time the SLA as of now
>
> 1. It is conceivable that we flush the producer to the target cluster but
> fail to offset commit. If there was a restart before the next successful
> offset commit, there will be duplicates and a part of data is replayed (
> at least once ) ?
>
> 2. The same can be said about partial flushes, though am not sure about
> how kafka addresses flush ( Is a flush either success or a failure, and
> nothing in between )
>
> Thanks..
>
> On Tue, Oct 15, 2019 at 12:34 PM Ryanne Dolan <ryannedo...@gmail.com>
> wrote:
>
> > Hey Vishal, glad to hear you're making progress.
> >
> > > 1. It seems though that flushing [...] the producer and setting the
> > > offset to the compacting topic is not atomic OR do we use
> > > transactions here ?
> >
> > You are correct. I'm working on a KIP and PoC to introduce transactions
> to
> > Connect for this exact purpose :)
> >
> > > I think these are 4 threads ( b'coz num.tasks=4 ), and I have 2 topics
> > with
> > > 1 partition each. Do I assume this right, as in there are 4 consumer
> > groups
> > > ( on CG per thread ) ...
> >
> > Some details here:
> > - tasks.max controls the maximum number of tasks created per Connector
> > instance. Both MirrorSourceConnector and MirrorCheckpointConnector will
> > create multiple tasks (up to tasks.max), but MirrorHeartbeatConnector
> only
> > ever creates a single task. Moreover, there cannot be more tasks than
> > topic-partitions (for MirrorSourceConnector) or consumer groups (for
> > MirrorCheckpointConnector). So if you have two topics with one partition
> > each and 1 consumer group total, you'll have two MirrorSourceConnector
> > tasks, one MirrorHeartbeatConnector task, and one
> MirrorCheckpointConnector
> > tasks, for a total of four. And that's in one direction only: if you have
> > multiple source->target herders enabled, each will create tasks
> > independently.
> > - There are no consumer groups in MM2, technically. The Connect framework
> > uses the Coordinator API and internal topics to divide tasks among
> workers
> > -- not a consumer group per se. The MM2 connectors use the assign() API,
> > not the subscribe() API, so there are no consumer groups there either. In
> > fact, they don't commit() either. This is nice, as it eliminates a lot of
> > the rebalancing problems legacy MirrorMaker has been plagued with. With
> > MM2, rebalancing only occurs when the number of workers changes or when
> the
> > assignments change (e.g. new topics are discovered).
> >
> > Ryanne
> >
> > On Tue, Oct 15, 2019 at 10:23 AM Vishal Santoshi <
> > vishal.santo...@gmail.com>
> > wrote:
> >
> > > Hey Ryanne,
> > >
> > >
> > > The test was on topics that had a 7 day retention. Which
> > > generally implies that the batch size for flush is pretty high ( till
> the
> > > consumption becomes current ). The offset.flush.timeout.ms defaults
> to
> > 5
> > > seconds and the code will not send in the offsets if the flush is not
> > > complete. Increasing that time out did solve the "not sending the
> offset
> > to
> > > topic" issue.
> > >
> > > Two questions ( I am being greedy here :) )
> > >
> > > 1. It seems though that flushing the flushing the producer and setting
> > the
> > > offset to the compacting topic is not atomic OR do we use
> > > transactions here ?
> > >
> > > 2. I see
> > >
> > > WorkerSourceTask{id=MirrorHeartbeatConnector-0} flushing 956435
> > >
> > > WorkerSourceTask{id=MirrorSourceConnector-1} flushing 356251
> > >
> > > WorkerSourceTask{id=MirrorCheckpointConnector-2} flushing 0
> > >
> > > WorkerSourceTask{id=MirrorCheckpointConnector-3} flushing 0
> outstanding
> > > messages
> > >
> > >
> > > I think these are 4 threads ( b'coz num.tasks=4 ), and I have 2 topics
> > with
> > > 1 partition each. Do I assume this right, as in there are 4 consumer
> > groups
> > > ( on CG per thread ) ...
> > >
> > >
> > >
> > >
> > >
> > > THANKS A LOT
> > >
> > >
> > > Vishal.
> > >
> > >
> > >
> > > On Mon, Oct 14, 2019 at 3:42 PM Ryanne Dolan <ryannedo...@gmail.com>
> > > wrote:
> > >
> > > > > timed out
> > > > while waiting for producer to flush outstanding
> > > >
> > > > Yeah, that's what I'd expect to see if Connect was unable to send
> > records
> > > > to the downstream remote topics, e.g. if min.in-sync.replicas were
> > > > misconfigured. Given some data seems to arrive, it's possible that
> > > > everything is configured correctly but with too much latency to
> > > > successfully commit within the default timeouts. You may want to
> > increase
> > > > the number of tasks substantially to achieve more parallelism and
> > > > throughput.
> > > >
> > > > Ryanne
> > > >
> > > > On Mon, Oct 14, 2019, 2:30 PM Vishal Santoshi <
> > vishal.santo...@gmail.com
> > > >
> > > > wrote:
> > > >
> > > > > Aah no.. this is more to it. Note sure if related to the above.
> > > > >
> > > > >
> > > > >
> > > >
> > >
> >
> https://github.com/axbaretto/kafka/blob/master/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/SourceTaskOffsetCommitter.java#L114
> > > > >
> > > > >
> > > > > Is timing out based on
> > > > >
> > > > >
> > > >
> > >
> >
> https://github.com/axbaretto/kafka/blob/master/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/WorkerConfig.java#L133
> > > > >
> > > > > [2019-10-14 18:55:20,820] ERROR
> > > > > WorkerSourceTask{id=MirrorSourceConnector-0} Failed to flush, timed
> > out
> > > > > while waiting for producer to flush outstanding 36478 messages
> > > > > (org.apache.kafka.connect.runtime.WorkerSourceTask:423)
> > > > >
> > > > >
> > > > >
> > > > > On Mon, Oct 14, 2019 at 3:15 PM Vishal Santoshi <
> > > > vishal.santo...@gmail.com
> > > > > >
> > > > > wrote:
> > > > >
> > > > > > I think this might be it.. Could you confirm. It seems to be on
> the
> > > > path
> > > > > > to commit the offsets.. but not sure...
> > > > > >
> > > > > > [2019-10-14 15:29:14,531] ERROR Scheduler for
> MirrorSourceConnector
> > > > > caught
> > > > > > exception in scheduled task: syncing topic ACLs
> > > > > > (org.apache.kafka.connect.mirror.Scheduler:102)
> > > > > >
> > > > > > java.util.concurrent.ExecutionException:
> > > > > > org.apache.kafka.common.errors.SecurityDisabledException: No
> > > Authorizer
> > > > > is
> > > > > > configured on the broker
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> org.apache.kafka.common.internals.KafkaFutureImpl.wrapAndThrow(KafkaFutureImpl.java:45)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> org.apache.kafka.common.internals.KafkaFutureImpl.access$000(KafkaFutureImpl.java:32)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> org.apache.kafka.common.internals.KafkaFutureImpl$SingleWaiter.await(KafkaFutureImpl.java:89)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> org.apache.kafka.common.internals.KafkaFutureImpl.get(KafkaFutureImpl.java:260)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> org.apache.kafka.connect.mirror.MirrorSourceConnector.listTopicAclBindings(MirrorSourceConnector.java:273)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> org.apache.kafka.connect.mirror.MirrorSourceConnector.syncTopicAcls(MirrorSourceConnector.java:214)
> > > > > >
> > > > > > at
> > > > > > org.apache.kafka.connect.mirror.Scheduler.run(Scheduler.java:93)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> org.apache.kafka.connect.mirror.Scheduler.executeThread(Scheduler.java:112)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> org.apache.kafka.connect.mirror.Scheduler.lambda$scheduleRepeating$0(Scheduler.java:50)
> > > > > >
> > > > > > at
> > > > > >
> > > java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> > > > > >
> > > > > > at
> > > > > > java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> > > > > >
> > > > > > at
> > > > > >
> > > > >
> > > >
> > >
> >
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> > > > > >
> > > > > > at java.lang.Thread.run(Thread.java:748)
> > > > > >
> > > > > > Caused by:
> > org.apache.kafka.common.errors.SecurityDisabledException:
> > > No
> > > > > > Authorizer is configured on the broker
> > > > > >
> > > > > > On Mon, Oct 14, 2019 at 12:30 PM Ryanne Dolan <
> > ryannedo...@gmail.com
> > > >
> > > > > > wrote:
> > > > > >
> > > > > >> > I do not have a single record in the offsets topic
> > > > > >>
> > > > > >> That's definitely not normal. You are correct that without
> records
> > > in
> > > > > that
> > > > > >> topic, MM2 will restart from EARLIEST. The offsets should be
> > stored
> > > > > >> periodically and whenever the connectors gracefully shutdown or
> > > > restart.
> > > > > >>
> > > > > >> Is it possible the topics don't have required ACLs or something?
> > > Also
> > > > > >> note:
> > > > > >> Connect wants the offsets topic to have a large number of
> > partitions
> > > > and
> > > > > >> to
> > > > > >> be compacted. Though I can't imagine either would prevent
> commits
> > > from
> > > > > >> being sent.
> > > > > >>
> > > > > >> Ryanne
> > > > > >>
> > > > > >> On Mon, Oct 14, 2019 at 10:46 AM Vishal Santoshi <
> > > > > >> vishal.santo...@gmail.com>
> > > > > >> wrote:
> > > > > >>
> > > > > >> > 2nd/restore issue ( I think I need to solve the offsets topic
> > > issue
> > > > > >> > before I go with the scale up and down issue )
> > > > > >> >
> > > > > >> > As you had indicated, I went ahead and created the offsets
> > topic.
> > > > The
> > > > > >> > status of the cluster ( destination ) is thus
> > > > > >> >
> > > > > >> > opic# Partitions# BrokersBrokers Spread %Brokers Skew %Brokers
> > > > Leader
> > > > > >> > Skew %# ReplicasUnder Replicated %Leader SizeProducer
> > > > > Message/SecSummed
> > > > > >> > Recent Offsets
> > > > > >> > s8k.checkpoints.internal
> > > > > >> > <
> > > > > >>
> > > > >
> > > >
> > >
> >
> https://kafka-manager.bf2.tumblr.net/clusters/grete_test/topics/s8k.checkpoints.internal
> > > > > >> >
> > > > > >> > 1 3 60 0 0 3 0 0.00 0
> > > > > >> > s8k.act_search_page
> > > > > >> > <
> > > > > >>
> > > > >
> > > >
> > >
> >
> https://kafka-manager.bf2.tumblr.net/clusters/grete_test/topics/s8k.act_search_page
> > > > > >> >
> > > > > >> > 1 3 60 0 0 3 0 6675.30 4,166,842
> > > > > >> > s8k.act_reach
> > > > > >> > <
> > > > > >>
> > > > >
> > > >
> > >
> >
> https://kafka-manager.bf2.tumblr.net/clusters/grete_test/topics/s8k.act_reach
> > > > > >> >
> > > > > >> > 1 3 60 0 0 3 0 20657.92 11,579,529
> > > > > >> > mm2-status.s8k.internal
> > > > > >> > <
> > > > > >>
> > > > >
> > > >
> > >
> >
> https://kafka-manager.bf2.tumblr.net/clusters/grete_test/topics/mm2-status.s8k.internal
> > > > > >> >
> > > > > >> > 5 5 100 0 0 3 0 0.00 10
> > > > > >> > mm2-offsets.s8k_test.internal
> > > > > >> > <
> > > > > >>
> > > > >
> > > >
> > >
> >
> https://kafka-manager.bf2.tumblr.net/clusters/grete_test/topics/mm2-offsets.s8k_test.internal
> > > > > >> >
> > > > > >> > 1 3 60 0 0 3 0 0.00 0
> > > > > >> > mm2-offsets.s8k.internal
> > > > > >> > <
> > > > > >>
> > > > >
> > > >
> > >
> >
> https://kafka-manager.bf2.tumblr.net/clusters/grete_test/topics/mm2-offsets.s8k.internal
> > > > > >> >
> > > > > >> > 1 3 60 0 0 3 0 0.00 0
> > > > > >> > mm2-configs.s8k.internal
> > > > > >> > <
> > > > > >>
> > > > >
> > > >
> > >
> >
> https://kafka-manager.bf2.tumblr.net/clusters/grete_test/topics/mm2-configs.s8k.internal
> > > > > >> >
> > > > > >> > 1 3 60 0 0 3 0 0.00 13
> > > > > >> >
> > > > > >> > You can see . that we have the 5 ( I created bot the offsets,
> > to
> > > be
> > > > > >> safe
> > > > > >> > for the below )
> > > > > >> >
> > > > > >> > *clusters = s8k, s8k_test*
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> > *s8k.bootstrap.servers = .....*
> > > > > >> >
> > > > > >> > *s8k_test.bootstrap.servers = ......*
> > > > > >> >
> > > > > >> >
> > > > > >> > *# only allow replication dr1 -> dr2*
> > > > > >> >
> > > > > >> > *s8k->s8k_test.enabled = true*
> > > > > >> >
> > > > > >> > *s8k->s8k_test.topics = act_search_page|act_reach*
> > > > > >> >
> > > > > >> > *s8k->s8k_test.emit.heartbeats.enabled = false*
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> > *s8k_test->s8k.enabled = false*
> > > > > >> >
> > > > > >> > *s8k_test->s8k.emit.heartbeats.enabled = false*
> > > > > >> >
> > > > > >> > *s8k_test.replication.factor = 3*
> > > > > >> >
> > > > > >> > *s8k.replication.factor = 3*
> > > > > >> >
> > > > > >> > *offsets.storage.replication.factor = 3*
> > > > > >> >
> > > > > >> > *replication.factor = 3*
> > > > > >> >
> > > > > >> > *replication.policy.separator = .*
> > > > > >> >
> > > > > >> > *tasks.max = 4*
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> > What seems strange is that I do not have a single record in
> the
> > > > > offsets
> > > > > >> > topic.. Is that normal ? I would imagine that without a
> > record,
> > > > > there
> > > > > >> is
> > > > > >> > no way that a restore would happen.... And that is obvious
> when
> > I
> > > > > >> restart
> > > > > >> > the mm2 instance... Find the screenshot attached. In essence
> the
> > > > > latency
> > > > > >> > avg lag is reset \when the mm2 instance is reset indicating no
> > > > restore
> > > > > >> but
> > > > > >> > restart from EARLIEST... I must be missing some thing simple
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> > On Sun, Oct 13, 2019 at 7:41 PM Ryanne Dolan <
> > > ryannedo...@gmail.com
> > > > >
> > > > > >> > wrote:
> > > > > >> >
> > > > > >> >> Vishal, the first issue is easy: you must set tasks.max to
> > > > something
> > > > > >> above
> > > > > >> >> 1 (the default) in order to achieve any parallelism. This
> > > property
> > > > is
> > > > > >> >> passed along to the internal Connect workers. It's
> unfortunate
> > > that
> > > > > >> >> Connect
> > > > > >> >> is not smart enough to default this property to the number of
> > > > > workers.
> > > > > >> I
> > > > > >> >> suspect that will improve before long.
> > > > > >> >>
> > > > > >> >> For the second issue, is it possible you are missing the
> > offsets
> > > > > >> topic? It
> > > > > >> >> should exist alongside the config and status topics. Connect
> > > should
> > > > > >> create
> > > > > >> >> this topic, but there are various reasons this can fail, e.g.
> > if
> > > > the
> > > > > >> >> replication factor is misconfigured. You can try creating
> this
> > > > topic
> > > > > >> >> manually or changing offsets.storage.replication.factor.
> > > > > >> >>
> > > > > >> >> Ryanne
> > > > > >> >>
> > > > > >> >> On Sun, Oct 13, 2019, 5:13 PM Vishal Santoshi <
> > > > > >> vishal.santo...@gmail.com>
> > > > > >> >> wrote:
> > > > > >> >>
> > > > > >> >> > Using
> > > https://github.com/apache/kafka/tree/trunk/connect/mirror
> > > > > as a
> > > > > >> >> > guide,
> > > > > >> >> > I have build from source the origin/KIP-382 of
> > > > > >> >> > https://github.com/apache/kafka.git.
> > > > > >> >> >
> > > > > >> >> > I am seeing 2 issues
> > > > > >> >> >
> > > > > >> >> > * I brought up 2 processes on 2 different nodes ( they are
> > > > actually
> > > > > >> >> pods on
> > > > > >> >> > k8s but that should not matter ). They share the
> > mm2.properties
> > > > > file
> > > > > >> and
> > > > > >> >> > are replicating ( 1-way ) 3 topics with 8 partitions in
> > total.
> > > > > That
> > > > > >> >> seems
> > > > > >> >> > to be the way to create a standalone mm2 cluster. I do not
> > > > however
> > > > > >> see(
> > > > > >> >> at
> > > > > >> >> > least the mbeans do not show ) any attempt to rebalance.
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >>
> > > > > >>
> > > > >
> > > >
> > >
> >
> https://github.com/apache/kafka/tree/trunk/connect/mirror#monitoring-an-mm2-process
> > > > > >> >> > mbeans
> > > > > >> >> > are all on a single node
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > * I restart the processes on the 2 nodes ( hard stop ans
> > start
> > > ).
> > > > > The
> > > > > >> >> > offsets for replication seem to be reset to the earliest,
> as
> > if
> > > > it
> > > > > >> is a
> > > > > >> >> > brand new mirroring. It is also obvious from the
> > > > > >> >> > "record-age-ms-avg|replication-latency-ms-avg"
> > > > > >> >> > which I track through the restart.
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > This implies that
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > 1. Load balancing by rebalancing is not working. I cannot
> > scale
> > > > up
> > > > > or
> > > > > >> >> down
> > > > > >> >> > by adding nodes to the mm2 cluster or removing them.
> > > > > >> >> >
> > > > > >> >> > 2. Restore on a mirror is not working. If the MM2 cluster
> is
> > > > > brought
> > > > > >> >> down,
> > > > > >> >> > it does not start mirroring from the last known state. I
> see
> > > the,
> > > > > >> >> > state/config topics etc created as expected..
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > The mm2.properties is pretty mimimal
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > *clusters = a , b*
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > *a.bootstrap.servers = k.....*
> > > > > >> >> >
> > > > > >> >> > *b.bootstrap.servers = k.....*
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > *# only allow replication dr1 -> dr2*
> > > > > >> >> >
> > > > > >> >> > *a->b.enabled = true*
> > > > > >> >> >
> > > > > >> >> > *a->b.topics = act_search_page*
> > > > > >> >> >
> > > > > >> >> > *a->b.emit.heartbeats.enabled = false*
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > *b->a..enabled = false*
> > > > > >> >> >
> > > > > >> >> > *b->a.emit.heartbeats.enabled = false*
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > What do you think is the issue ?
> > > > > >> >> >
> > > > > >> >> >
> > > > > >> >> > Thanks
> > > > > >> >> >
> > > > > >> >>
> > > > > >> >
> > > > > >>
> > > > > >
> > > > >
> > > >
> > >
> >
>
