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  1. Flink
  2. FLINK-20886

Add the option to get a threaddump on checkpoint timeouts




      For debugging checkpoint timeouts, I was thinking about the following addition to Flink:

      When a checkpoint times out and the async thread is still running, create a thread dump [1] and either add this to the checkpoint stats, log it, or write it out.

      This may help identifying where the checkpoint is stuck (maybe a lock, could also be in a third party lib like the FS connectors,...). It would give us some insights into what the thread is currently doing.

      Limiting the scope of the threads would be nice but may not be possible in the general case since additional threads (spawned by the FS connector lib, or otherwise connected) may interact with the async thread(s) by e.g. going through the same locks. Maybe we can reduce the thread dumps to all async threads of the failed checkpoint + all thready that interact with it, e.g. via locks?

      I'm also not sure whether the ability to have thread dumps or not should be user-configurable (Could it contain sensitive information from other jobs if you run a session cluster? Is that even relevant since we don't give isolation guarantees anyway?). If it is configurable, it should be on by default.

      [1] https://crunchify.com/how-to-generate-java-thread-dump-programmatically/


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              Zakelly Zakelly Lan
              nkruber Nico Kruber
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