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https://issues.apache.org/jira/browse/LOG4J2-1235?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15154019#comment-15154019
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Sascha Scholz commented on LOG4J2-1235:
---------------------------------------
I think I've found another race condition that is related to how appenders are
purged: In update(), appenders are put into the appendersUsage map with its
current usage time. In purge(), they are removed again if timeToLive has
expired, then the appender is deleted. So, we have three different execution
orders when update() and purge() run concurrently.
{noformat}
appendersUsage.remove()
routingAppender.delete()
appendersUsage.put()
{noformat}
This is ok. Appender is removed and deleted, and then added again. Appender is
only removed after put when next timeToLive expired.
{noformat}
appendersUsage.put()
appendersUsage.remove()
routingAppender.delete()
{noformat}
This is not optimal. The just added appender is removed and deleted, althouth
timeToLive is extended. This could be solved by using remove(entry.getKey(),
entry.getValue()) and then deleting the appender only on successful removal.
{noformat}
appendersUsage.remove()
appendersUsage.put()
routingAppender.delete()
{noformat}
This is the worst case. The appender is removed from the map, but immediately
added back. Afterwards the appender is deleted. On the next run of purge()
deletion will be re-attempted, which leads to a NPE in
RoutingAppender#deleteAppender because there appender.remove() returns null for
the already deleted appender.
Should I open this as a separate bug or should it be treated here?
> org.apache.logging.log4j.core.appender.routing.IdlePurgePolicy not working
> correctly
> ------------------------------------------------------------------------------------
>
> Key: LOG4J2-1235
> URL: https://issues.apache.org/jira/browse/LOG4J2-1235
> Project: Log4j 2
> Issue Type: Bug
> Components: Appenders
> Affects Versions: 2.5
> Reporter: Niranjan Rao
> Priority: Critical
>
> There is a problem in the function
> org.apache.logging.log4j.core.appender.routing.IdlePurgePolicy.scheduleNext().
> I got out of file handles errors despite of setting IdlePurgePolicy. I did
> some digging I believe following is the cause
> If the createTime is Long.MAX_VALUE, task is never scheduled. However
> function
> org.apache.logging.log4j.core.appender.routing.IdlePurgePolicy.update(String,
> LogEvent) checks if the future is not null before deciding to schedule.
> After appendersUsage becomes empty first time, appenders keep piling up.
> I believe fix will be to set future to null in the function scheduleNext in
> the else part of the condition where it checks for createTime
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