@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/38e997ed96ce6627cabb4054224d7044fd2b40f9/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
