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https://issues.apache.org/jira/browse/BEAM-9399?focusedWorklogId=418992&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-418992
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ASF GitHub Bot logged work on BEAM-9399:
----------------------------------------
Author: ASF GitHub Bot
Created on: 08/Apr/20 23:43
Start Date: 08/Apr/20 23:43
Worklog Time Spent: 10m
Work Description: lukecwik commented on issue #11351: [BEAM-9399] Ensure
that empty messages are not flushed to handler.
URL: https://github.com/apache/beam/pull/11351#issuecomment-611249407
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Issue Time Tracking
-------------------
Worklog Id: (was: 418992)
Time Spent: 5h 50m (was: 5h 40m)
> Possible deadlock between DataflowWorkerLoggingHandler and overridden
> System.err PrintStream
> --------------------------------------------------------------------------------------------
>
> Key: BEAM-9399
> URL: https://issues.apache.org/jira/browse/BEAM-9399
> Project: Beam
> Issue Type: Bug
> Components: runner-dataflow
> Reporter: Sam Whittle
> Assignee: Sam Whittle
> Priority: Minor
> Fix For: 2.21.0
>
> Time Spent: 5h 50m
> Remaining Estimate: 0h
>
> When an exception is encountered in DataflowWorkerLoggingHandler the
> ErrorManager is used to log the exception. ErrorManager uses System.err
> which is overridden to be a PrintStream that writes back into
> DataflowWorkerLoggingHandler.
> This has the lock ordering DataflowWorkerLoggingHandler -> PrintStream.
> Other logging of System.err has the inverse lock ordering
> PrintStream->DataflowWorkerLoggingHandler so there is potential for deadlock.
> This is one known cause of the inversion, but any other System.err logs from
> inside DataflowWorkerLoggingHandler could cause the same issue.
> Proposed fix is to address low-hanging fruit of having ErrorManager output to
> the original System.err. A full fix would be to improve our override of
> System.err to a PrintStream that can detect the locking inversion or possibly
> we could use the PrintStream mutex in both cases.
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