[jira] [Resolved] (KAFKA-3627) New consumer doesn't run delayed tasks while under load

["Ewen Cheslack-Postava (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-3627?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ewen Cheslack-Postava resolved KAFKA-3627.
------------------------------------------
       Resolution: Fixed
    Fix Version/s: 0.10.1.0

Issue resolved by pull request 1295
[https://github.com/apache/kafka/pull/1295]

> New consumer doesn't run delayed tasks while under load
> -------------------------------------------------------
>
>                 Key: KAFKA-3627
>                 URL: https://issues.apache.org/jira/browse/KAFKA-3627
>             Project: Kafka
>          Issue Type: Bug
>          Components: consumer
>    Affects Versions: 0.9.0.1
>            Reporter: Rob Underwood
>            Assignee: Jason Gustafson
>            Priority: Blocker
>             Fix For: 0.10.1.0, 0.10.0.0
>
>         Attachments: DelayedTaskBugConsumer.java, kafka-3627-output.log
>
>
> If the new consumer receives a steady flow of fetch responses it will not run delayed tasks, which means it will not heartbeat or perform automatic offset commits.
> The main cause is the code that attempts to pipeline fetch responses and keep the consumer fed.  Specifically, in KafkaConsumer::pollOnce() there is a check that skips calling client.poll() if there are fetched records ready (line 903 in the 0.9.0 branch of this writing).  Then in KafkaConsumer::poll(), if records are returned it will initiate another fetch and perform a quick poll, which will send/receive fetch requests/responses but will not run delayed tasks.
> If the timing works out, and the consumer is consistently receiving fetched records, it won't run delayed tasks until it doesn't receive a fetch response during its quick poll.  That leads to a rebalance since the consumer isn't heartbeating, and typically means all the consumed records will be re-delivered since the automatic offset commit wasn't able to run either.
> h5. Steps to reproduce
> # Start up a cluster with *at least 2 brokers*.  This seems to be required to reproduce the issue, I'm guessing because the fetch responses all arrive together when using a single broker.
> # Create a topic with a good number of partitions
> #* bq. bin/kafka-topics.sh --zookeeper localhost:2181 --create --topic delayed-task-bug --partitions 10 --replication-factor 1
> # Generate some test data so the consumer has plenty to consume.  In this case I'm just using uuids
> #* bq. for ((i=0;i<100;++i)) do; cat /proc/sys/kernel/random/uuid >>  /tmp/test-messages; done
> #* bq. bin/kafka-console-producer.sh --broker-list localhost:9092 --topic delayed-task-bug < /tmp/test-messages
> # Start up a consumer with a small max fetch size to ensure it only pulls a few records at a time.  The consumer can simply sleep for a moment when it receives a record.
> #* I'll attach an example in Java
> # There's a timing aspect to this issue so it may take a few attempts to reproduce



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)