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https://issues.apache.org/jira/browse/FLINK-7143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16082617#comment-16082617
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ASF GitHub Bot commented on FLINK-7143:
---------------------------------------
GitHub user tzulitai opened a pull request:
https://github.com/apache/flink/pull/4302
(master) [FLINK-7143] [kafka] Stricter tests for deterministic partition
assignment
This is the forward port of the fix in #4301. The `master` branch does not
require a fix, because the new `AbstractPartitionDiscoverer` already correctly
uses `partition.hashCode % numTasks` for the partition discovery filtering.
This PR simply makes the tests for partition assignment more strict, to
guard against breaking deterministic assignment in the future.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/tzulitai/flink FLINK-7143-master
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/4302.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #4302
----
----
> Partition assignment for Kafka consumer is not stable
> -----------------------------------------------------
>
> Key: FLINK-7143
> URL: https://issues.apache.org/jira/browse/FLINK-7143
> Project: Flink
> Issue Type: Bug
> Components: Kafka Connector
> Affects Versions: 1.3.1
> Reporter: Steven Zhen Wu
> Assignee: Tzu-Li (Gordon) Tai
> Priority: Blocker
> Fix For: 1.3.2
>
>
> while deploying Flink 1.3 release to hundreds of routing jobs, we found some
> issues with partition assignment for Kafka consumer. some partitions weren't
> assigned and some partitions got assigned more than once.
> Here is the bug introduced in Flink 1.3.
> {code}
> protected static void initializeSubscribedPartitionsToStartOffsets(...)
> {
> ...
> for (int i = 0; i < kafkaTopicPartitions.size(); i++) {
> if (i % numParallelSubtasks == indexOfThisSubtask) {
> if (startupMode !=
> StartupMode.SPECIFIC_OFFSETS) {
>
> subscribedPartitionsToStartOffsets.put(kafkaTopicPartitions.get(i),
> startupMode.getStateSentinel());
> }
> ...
> }
> {code}
> The bug is using array index {{i}} to mod against {{numParallelSubtasks}}. if
> the {{kafkaTopicPartitions}} has different order among different subtasks,
> assignment is not stable cross subtasks and creates the assignment issue
> mentioned earlier.
> fix is also very simple, we should use partitionId to do the mod {{if
> (kafkaTopicPartitions.get\(i\).getPartition() % numParallelSubtasks ==
> indexOfThisSubtask)}}. That would result in stable assignment cross subtasks
> that is independent of ordering in the array.
> marking it as blocker because of its impact.
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