[jira] [Commented] (KAFKA-9374) Worker can be disabled by blocked connectors

["Randall Hauch (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-9374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17358713#comment-17358713 ] 

Randall Hauch commented on KAFKA-9374:
--------------------------------------

Please ignore link to [GitHub Pull Request #10833|https://github.com/apache/kafka/pull/10833]. I created it with the wrong KAFKA issue number.

> Worker can be disabled by blocked connectors
> --------------------------------------------
>
>                 Key: KAFKA-9374
>                 URL: https://issues.apache.org/jira/browse/KAFKA-9374
>             Project: Kafka
>          Issue Type: Bug
>          Components: KafkaConnect
>    Affects Versions: 1.0.0, 1.0.1, 1.0.2, 1.1.0, 1.1.1, 2.0.0, 2.0.1, 2.1.0, 2.2.0, 2.1.1, 2.3.0, 2.2.1, 2.2.2, 2.4.0, 2.3.1
>            Reporter: Chris Egerton
>            Assignee: Chris Egerton
>            Priority: Major
>             Fix For: 2.6.0
>
>
> If a connector hangs during any of its {{initialize}}, {{start}}, {{stop}}, \{taskConfigs}}, {{taskClass}}, {{version}}, {{config}}, or {{validate}} methods, the worker will be disabled for some types of requests thereafter, including connector creation, connector reconfiguration, and connector deletion.
>  -This only occurs in distributed mode and is due to the threading model used by the [DistributedHerder|https://github.com/apache/kafka/blob/03f763df8a8d9482d8c099806336f00cf2521465/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java] class.- This affects both distributed and standalone mode. Distributed herders perform some connector work synchronously in their {{tick}} thread, which also handles group membership and some REST requests. The majority of the herder methods for the standalone herder are {{synchronized}}, including those for creating, updating, and deleting connectors; as long as one of those methods blocks, all subsequent calls to any of these methods will also be blocked.
>  
> One potential solution could be to treat connectors that fail to start, stop, etc. in time similarly to tasks that fail to stop within the [task graceful shutdown timeout period|https://github.com/apache/kafka/blob/03f763df8a8d9482d8c099806336f00cf2521465/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/WorkerConfig.java#L121-L126] by handling all connector interactions on a separate thread, waiting for them to complete within a timeout, and abandoning the thread (and transitioning the connector to the {{FAILED}} state, if it has been created at all) if that timeout expires.



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