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https://issues.apache.org/jira/browse/LOG4J2-1343?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15231625#comment-15231625
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Remko Popma edited comment on LOG4J2-1343 at 4/8/16 4:50 AM:
-------------------------------------------------------------
The current implementation that coarsely locks on the Appender Manager causes a
deadlock in {{org.apache.logging.log4j.core.ThreadedTest}}.
The call sequence became clear after I added some system printouts:
{noformat}
pool-2-thread-1 ThreadedTest$LoggingRunnable@7df67951 calling
logger.debug(state)
pool-2-thread-2 ThreadedTest$StateSettingRunnable@20afdd66 locking on state to
call state.setState
pool-2-thread-2 ThreadedTest$State@7c7a06ec locked on state, entered setState,
calling logger.debug...
pool-2-thread-3 ThreadedTest$LoggingRunnable@215a8856 calling
logger.debug(state)
pool-2-thread-4 ThreadedTest$StateSettingRunnable@5f8707b5 locking on state to
call state.setState
pool-2-thread-5 ThreadedTest$LoggingRunnable@51b48833 calling
logger.debug(state)
pool-2-thread-6 ThreadedTest$StateSettingRunnable@2ba8331b locking on state to
call state.setState
pool-2-thread-7 ThreadedTest$LoggingRunnable@1a12ff63 calling
logger.debug(state)
pool-2-thread-8 ThreadedTest$StateSettingRunnable@452a6c88 locking on state to
call state.setState
pool-2-thread-7 File.directEncodeEvent() synchronizing on manager
pool-2-thread-2 File.directEncodeEvent() synchronizing on manager
pool-2-thread-5 File.directEncodeEvent() synchronizing on manager
pool-2-thread-1 File.directEncodeEvent() synchronizing on manager
pool-2-thread-3 File.directEncodeEvent() synchronizing on manager
pool-2-thread-7 ThreadedTest$State@7c7a06ec locking on state to call
state.getState
(deadlock)
{noformat}
In the above example thread 2 has a lock on state, and tries to lock on manager
(in {{logger.debug("hello")}}, while thread 7 is calling
{{logger.debug(state)}}, has a lock on manager and tries to lock on state (from
{{state.toString()}}.
This means we cannot hold locks while turning the LogEvent into text. It is
probably okay to hold a lock while turning that text into bytes though.
was (Author: rem...@yahoo.com):
The current implementation that coarsely locks on the Appender Manager causes a
deadlock in {{org.apache.logging.log4j.core.ThreadedTest}}.
The call sequence became clear after I added some system printouts:
{noformat}
pool-2-thread-1 ThreadedTest$LoggingRunnable@7df67951 calling
logger.debug(state)
pool-2-thread-2 ThreadedTest$StateSettingRunnable@20afdd66 locking on state to
call state.setState
pool-2-thread-2 ThreadedTest$State@7c7a06ec locked on state, entered setState,
calling logger.debug...
pool-2-thread-3 ThreadedTest$LoggingRunnable@215a8856 calling
logger.debug(state)
pool-2-thread-4 ThreadedTest$StateSettingRunnable@5f8707b5 locking on state to
call state.setState
pool-2-thread-5 ThreadedTest$LoggingRunnable@51b48833 calling
logger.debug(state)
pool-2-thread-6 ThreadedTest$StateSettingRunnable@2ba8331b locking on state to
call state.setState
pool-2-thread-7 ThreadedTest$LoggingRunnable@1a12ff63 calling
logger.debug(state)
pool-2-thread-8 ThreadedTest$StateSettingRunnable@452a6c88 locking on state to
call state.setState
pool-2-thread-7 File.directEncodeEvent() synchronizing on manager
pool-2-thread-2 File.directEncodeEvent() synchronizing on manager
pool-2-thread-5 File.directEncodeEvent() synchronizing on manager
pool-2-thread-1 File.directEncodeEvent() synchronizing on manager
pool-2-thread-3 File.directEncodeEvent() synchronizing on manager
pool-2-thread-7 ThreadedTest$State@7c7a06ec locking on state to call
state.getState
(deadlock)
{noformat}
In the above example thread 2 has a lock on state, and tries to lock on manager
(in {{logger.debug("hello")}}, while thread 7 is calling
{{logger.debug(state)}}, has a lock on manager and tries to lock on state (from
{{state.toString()}}.
> Update ConsoleAppender to utilize gc-free Layout method
> -------------------------------------------------------
>
> Key: LOG4J2-1343
> URL: https://issues.apache.org/jira/browse/LOG4J2-1343
> Project: Log4j 2
> Issue Type: Improvement
> Components: Appenders
> Affects Versions: 2.5
> Reporter: Remko Popma
> Assignee: Remko Popma
> Fix For: 2.6
>
>
> TBD: would we want to include this in the upcoming 2.6 release?
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