Hugo, I agree about the benefits of immutability and encapsulation. But are
they so important for the case we are discussing? As far as code being super
fragile, hard to debug and being thread unsafe, I don’t really think its
applicable here. Can you elaborate on how does it make the code super fragile
and hard to debug? As far as it being thread unsafe is concerned,
KafkaSpoutConfig is anyway going to be serialized and reconstructed in worker.
And it’s always going to be one instance of it per executor. Correct me if I am
misunderstanding anything.
Stig, we could probably modify flux to do something like that. I need to put
more thought to see if any better semantic can be applied for supporting
builder pattern. For now, since you both prefer to keep the builder pattern we
can do with the current work around of public constructor like you said.
On 6/14/17, 2:21 PM, "Stig Døssing" <generalbas....@gmail.com> wrote:
It would obviously be ideal if Flux could be made to support object
creation via builders, but if that's not possible I think leaving the
KafkaSpoutConfig constructor public is a decent workaround. We are still
getting some of the benefits of the Builder pattern, even if Flux doesn't
use builder.build() to construct the KafkaSpoutConfig (immutability of
KafkaSpoutConfig, no telescoping constructors). I would prefer not to get
rid of it to work around a limitation in Flux.
My knowledge of Flux is very limited, but is there any reason it can't be
changed to support taking the result of a method call as a constructor
parameter? e.g.
components:
- id: "SpoutConfigBuilder"
className: "org.apache.storm.kafka.spout.KafkaSpoutConfig.Builder"
configMethods:
- name: "setProp"
args:
- "max.poll.records"
- 250
- id: "Spout"
className: "org.apache.storm.kafka.spout.KafkaSpout"
constructorArgs:
- ref: "SpoutConfigBuilder"
call: "build"
2017-06-14 22:09 GMT+02:00 Hugo Da Cruz Louro <hlo...@hortonworks.com>:
> Hi,
>
> Flux is simply a mechanism to enabling Java objects creation using a
> descriptor file. If Flux does not support creating classes that follow the
> Builder design pattern, that is a Flux limitation and has to be fixed. It
> is not reasonable to impose that no one can write a builder because Flux
> does not support it. My suggested approach was a simple solution to
quickly
> get around it. Let’s identify the proper way to fix it.
>
> I do not think it is reasonable not to respect immutability and
> encapsulation unless there is a very strong reason to do so. It makes the
> code super fragile, hard to debug, and thread unsafe.
>
> > On Jun 14, 2017, at 12:22 PM, Priyank Shah <ps...@hortonworks.com>
> wrote:
> >
> > Hi Stig/Hugo,
> >
> > That constructor is indeed public. I actually made that change but
> forgot about it. https://github.com/apache/storm/commit/
> 5ff7865cf0b86f40e99b54e789fa60b8843191aa The reason for making that
> change is to make it work with flux.
> >
> > I think changing flux code to access private constructor is a hack and I
> prefer not doing that. On the other hand, having a public constructor
> defeats the purpose of Builder pattern since builder.build() is supposed
to
> create the object. I personally don’t think immutability of
> KafkaSpoutConfig is that important here. I would rather get rid of the
> builder and have it with one or two constructors with some setXXX methods.
> Let me know what you guys think.
> >
> >
> > On 6/14/17, 9:46 AM, "Hugo Da Cruz Louro" <hlo...@hortonworks.com>
> wrote:
> >
> > @Harsha @Stig, I agree with you. Let’s make the de facto
> implementation manual partition assignment. I have already adjusted the
> KafkaTridentSpout code to reflect @Stig’s changes and things seem to be
> working very well for Trident as well. I am tracking that on
> https://issues.apache.org/jira/browse/STORM-2554 and I will submit a PR
> soon. There were a couple minor fixes that I had to provide to
> https://github.com/apache/storm/pull/2150 to make it work; I will mention
> them as comment in the PR.
> >
> > @Priyank, the KafkaSpoutConfig class should be immutable, as it is a
> configuration class, which should not be possible to change once it is
> passed onto the KafkaSpout or KafkaTridentSpout. The builder that @Stig
> referenced should indeed be private or at most package protected if needed
> for unit tests, not public. If we have to leave it public for now to make
> Flux work, so be it. However, the right fix for this would be to fix the
> Flux code to work with builders. Flux uses mostly Java reflection, so the
> fix may be as simple as allowing invocation of private constructors as
> described in here<https://stackoverflow.com/questions/11282265/how-to-
> call-a-private-method-from-outside-a-java-class>.
> >
> > We should try to eliminate as many constructors possible. There
> should be one or two constructors that enforce the dependencies that are
> absolutely required and for which there are no reasonable defaults. Any
> other optional, or non default, configuration setting should go in a
setter
> method. All the KafkaConsumer properties, as we seem to all agree, should
> be passed in a Map<String, Object> which is what KafkaConsumer needs in
its
> constructor.
> >
> > Hugo
> >
> >
> > On Jun 14, 2017, at 8:38 AM, Stig Døssing <generalbas....@gmail.com<
> mailto:generalbas....@gmail.com>> wrote:
> >
> > It looks public to me?
> > https://github.com/apache/storm/blob/38e997ed96ce6627cabb4054224d70
> 44fd2b40f9/external/storm-kafka-client/src/main/java/
> org/apache/storm/kafka/spout/KafkaSpoutConfig.java#L461
> >
> > I think its good to be able to avoid telescoping constructors, while
> at the
> > same time not having a bunch of setters on the KafkaSpoutConfig.
> That's the
> > main purpose I think the builder has, allowing KafkaSpoutConfig to be
> > immutable.
> >
> > I'd be happy to fiddle with it if you have an example to work from?
> >
> > 2017-06-14 1:11 GMT+02:00 Priyank Shah <ps...@hortonworks.com>:
> >
> > Hi Stig,
> >
> > I think KafkaSpoutConfig constructor is private and it's throwing
> errors
> > while using the approach that you mentioned. Making it public defeats
> be
> > purpose of the builder. Can you give it a shot and confirm at your
> end if
> > it's possible?
> >
> > Thanks
> > Priyank
> >
> > Sent from my iPhone
> >
> > On Jun 13, 2017, at 9:36 AM, Stig Døssing <generalbas....@gmail.com>
> > wrote:
> >
> > Hi Priyank,
> >
> > I changed my mind since those mails were sent. I don't think
> setKey/Value
> > are very useful. They couldn't be used with the default Kafka
> > deserializers, only for deserializers implemented by the user, and
> then
> > only if they were declared to implement SerializableDeserializer. I
> agree
> > that we should remove them, and I'm not going to undo anything
> currently
> > in
> > the PR (unless there are objections on the PR of course)
> >
> > With regard to getting rid of the builder pattern, I think it is a
> pretty
> > nice pattern for Java. It looks to me like it should be possible to
> > declare
> > and configure the builder with "component:", and then pass it to the
> > KafkaSpoutConfig constructor with "ref:" after (which lets you avoid
> > calling build()). Doesn't this work?
> >
> > 2017-06-12 23:32 GMT+02:00 Priyank Shah <ps...@hortonworks.com>:
> >
> > Hi Stig,
> >
> > I think PR https://github.com/apache/storm/pull/2155/files you
> created
> > gets rid of setKey and setValue. I am fine with it and in fact that’s
> > what
> > I was suggesting in first place. However, your last two email replies
> > suggest something else. Just making sure you are not going to undo
> > anything
> > in the PR and that we are same page about this change. i.e. no setKey
> or
> > setValue. Either for SerializableDeserializer implementations or
Kafka
> > Deserializer interface. Only string in fqcn as a property.
> >
> > The other thing I propose is to get rid of the builder class. Reason
> is
> > constructing an object with builder pattern requires builder.build
and
> > that
> > does work well with flux yaml. I think we should be careful about
> > implementing new connectors and make sure they work with yaml as
> well. I
> > have commented on the PR as well. Unless, someone else has a
different
> > opinion can you address that as well?
> >
> > On 6/10/17, 2:05 AM, "Stig Døssing" <generalbas....@gmail.com> wrote:
> >
> > Priyank, I was a bit too hasty in the last response. The
> setKey/Value
> > functions are necessary when users want to set only the key or the
> > value
> > deserializer. I think we should keep those. It may be possible to
> > deduplicate the functionality on the API by removing the Builder
> > constructors that takes deserializers, and by getting rid of the
> > setKey/Value functions that take Class instances, since those seem
> > like a
> > duplication of the consumer config functionality. This should get
> rid
> > of a
> > lot of the overloads.
> >
> > 2017-06-10 10:20 GMT+02:00 Stig Døssing <generalbas....@gmail.com>:
> >
> > Harsha,
> >
> > +1 for simplifying away those methods that are just setting consumer
> > config. The properties I think we should keep are all the spout
> > configuration (timeouts, retry handling, tuple construction). Maybe
> > we
> > deprecate the consumer config functions on 1.x and remove them on
> > master?
> >
> > Priyank,
> >
> > When the spout is declared, it takes type parameters to define the
> > key and
> > value types of the consumer. We are able to check at compile time
> > that the
> > deserializers match those expected types.
> > e.g.
> > SerializableDeserializer<Integer> des = ...
> >
> > KafkaSpoutConfig<Integer, String> config = KafkaSpoutConfig.builder("
> > dummy",
> > "dummy")
> > .setKey(des)
> > .build();
> >
> > KafkaSpout<String, String> wrongTypeSpout = new KafkaSpout<>(config);
> >
> > will not compile, while
> >
> > SerializableDeserializer<String> des = ...
> >
> > KafkaSpoutConfig<String, String> config = KafkaSpoutConfig.builder("
> > dummy",
> > "dummy")
> > .setKey(des)
> > .build();
> >
> > KafkaSpout<String, String> spout = new KafkaSpout<>(config);
> >
> > will. If we want to simplify the API, maybe we should just mirror the
> > KafkaConsumer API more closely and remove the Builder setKey/Value
> > methods.
> > I can't think of a reason why a user should need to create a Builder
> > of one
> > type, and then change the type later with setKey/Value. The
> > deserializers
> > can just go in through the Builder constructor.
> >
> > About KafkaTuple, I think it was done this way originally since
> > requiring
> > users to subclass KafkaTuple would be a breaking change. If we want
> > to do
> > it it should go in 2.x only. I'm not necessarily opposed to doing
> > it, but I
> > don't really have a strong opinion on it.
> >
> > Hugo,
> >
> > I appreciate that the subscribe API is a major new feature of the 0.9
> > consumer, but I can't come up with any reason to use it in Storm. I
> > don't
> > think we should support it just because it is there. As mentioned
> > upthread,
> > the features offered by that API are already covered by Storm, so
> > I'm not
> > seeing the value to having it. If we can't come up with a use case
> > for it I
> > don't see a reason to allow users to configure it, especially given
> > the
> > non-obvious problems users who choose it are likely to run into.
> >
> >
> > 2017-06-10 <20%2017%2006%2010> 6:03 GMT+02:00 Harsha <
> > st...@harsha.io>:
> >
> > Dynamic assignment is what causing all the issues that we see now.
> > 1. Duplicates at the start of the KafkaSpout and upon any rebalance
> > 2. Trident Kafka Spout not holding the transactional batches.
> > Many corner cases can easily produce duplicates.
> >
> > There is no point in keeping dynamic assignment given all the issues
> > that are showing up.
> > Here is the excerpt from Kafka consumer docs
> > https://www-us.apache.org/dist/kafka/0.10.0.1/javadoc/org/
> > apache/kafka/clients/consumer/KafkaConsumer.html
> > "If the process itself is highly available and will be restarted if
> > it
> > fails (perhaps using a cluster management framework like YARN,
> > Mesos, or
> > AWS facilities, or as part of a stream processing framework). In
> > this
> > case there is no need for Kafka to detect the failure and reassign
> > the
> > partition since the consuming process will be restarted on another
> > machine."
> >
> > Manual assignment is the right way to go.
> >
> > -Harsha
> >
> > On Jun 9, 2017, 4:09 PM -0700, Hugo Da Cruz Louro
> > <hlo...@hortonworks.com>, wrote:
> > +1 for simplifying KafkaSpoutConfig. Too many constructors and too
> > many
> > methods.. I am not sure it’s justifiable to have any methods that
> > simply
> > set KafkaConsumer properties. All of these properties should just
> > go in
> > a Map<String, Object>, which is what KafkaConsumer receives, and
> > what
> > was supported in the initial implementation. The names of the
> > properties
> > can be retrieved from org.apache.kafka.clients.
> > consumer.ConsumerConfig.
> > At this point we may have to keep in mind backwards compatibility.
> >
> > Not sure we should completely discontinue dynamic partition
> > assignment,
> > as it is one of primary features of the new Storm Kafka Client API.
> > With
> > this said, manual partition assignment should be supported and would
> > solve a lot of potential problems arising from dynamic partition
> > assignment.
> >
> > Hugo
> >
> > On Jun 9, 2017, at 3:33 PM, Harsha <st...@harsha.io> wrote:
> >
> > I think question why we need all those settings when a user can
> > pass it
> > via Properties with consumer properties defined or via Map conf
> > object.
> > Having the methods on top of consumer config means every time Kafka
> > consumer property added or changed one needs add a builder method.
> > We
> > need to get out of the way and let the user configure it like they
> > do it
> > for typical Kafka Consumer instead we've 10s of methods that sets
> > properties for ConsumerConfig.
> >
> > Examples:
> > https://github.com/apache/storm/blob/master/external/storm-
> > kafka-client/src/main/java/org/apache/storm/kafka/spout/
> > KafkaSpoutConfig.java#L317
> >
> > https://github.com/apache/storm/blob/master/external/storm-
> > kafka-client/src/main/java/org/apache/storm/kafka/spout/
> > KafkaSpoutConfig.java#L309
> > etc.. all of these are specific to KafkaConsumer config, users
> > should
> > be able to pass it via Properties all of these.
> >
> > https://github.com/apache/storm/blob/master/external/storm-
> > kafka-client/src/main/java/org/apache/storm/kafka/spout/
> > KafkaSpoutConfig.java#L327
> >
> > whats the benefit of adding that method? and we are forcing that to
> > set
> > the protocol to "SSL" in this method
> > https://github.com/apache/storm/blob/master/external/storm-
> > kafka-client/src/main/java/org/apache/storm/kafka/spout/
> > KafkaSpoutConfig.java#L318
> >
> > Users can set the ssl properties and then can select the
> > securityProtocol "SASL_SSL" which requires both kerberos and ssl
> > configs
> > to be set. In above case making a call setSSLTruststore changes the
> > security.protocol to "SSL". This could easily run into issues if the
> > users sets securityProtocol first with "SASL_SSL" then later calls
> > setSSLTruststore which changes it to "SSL".
> >
> > We are over-taking these settings instead of letting user to figure
> > out
> > from Kafka consumer config page.
> >
> > In contrast we've KafkaProducer which does this
> > https://github.com/apache/storm/blob/master/external/storm-
> > kafka-client/src/main/java/org/apache/storm/kafka/bolt/
> > KafkaBolt.java#L121
> > . I would add Properties object instead of deriving it from
> > topologyConf
> > but this is much more easier to understand for the users. The
> > contract
> > here is put whatever the producer configs that users wants in the
> > conf
> > object and we create producer out of that config.
> >
> > Honestly these interfaces needs to be simple and let the user have
> > control instead of adding our interpretation.
> >
> >
> >
> > Thanks,
> > Harsha
> > On Jun 9, 2017, 2:08 PM -0700, Stig Døssing <
> > generalbas....@gmail.com>,
> > wrote:
> > I'd be happy with a simpler KafkaSpoutConfig, but I think most of
> > the
> > configuration parameters have good reasons for being there. Any
> > examples
> > of
> > parameters you think we should remove?
> >
> > 2017-06-09 21:34 GMT+02:00 Harsha <st...@harsha.io>:
> >
> > +1 on using the manual assignment for the reasons specified below.
> > We
> > will see duplicates even in stable conditions which
> > is not good. I don’t see any reason not to switch to manual
> > assignment.
> > While we are at it we should refactor the KafkaConfig part.
> > It should be as simple as accepting the kafka consumer config or
> > properties file and forwarding it to KafkaConsumer. We made
> > it overly complex and unnecessary.
> >
> > Thanks,
> > Harsha
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
>
