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https://issues.apache.org/jira/browse/LOG4J2-702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14060297#comment-14060297
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Sean Bridges commented on LOG4J2-702:
-------------------------------------
Sorry, I commented without seeing some of the posts.
Ralph, yes you are right, Remko's solution in his 10/Jul/14 17:05 comment
suffers from the flaw you mention. I think it is better to loop rather than
hardcode a fixed number of iterations. Another alternative to looping might be
to chain the configs. Something like,
{code}
//in PrivateConfig
volatile LoggerConfig next;
void log(...) {
counter.incrementAndGet();
if(next != null) {
counter.decrementAndGet();
next.log(...);
} else {
try {
...do stuff
} finally {
counter.decrementAndGet();
}
}
void stop(LoggerConfig next) {
this.next = next;
...cleanup
}
}
{code}
> LoggerConfig#waitForCompletion is not thread safe
> -------------------------------------------------
>
> Key: LOG4J2-702
> URL: https://issues.apache.org/jira/browse/LOG4J2-702
> Project: Log4j 2
> Issue Type: Bug
> Components: Core
> Affects Versions: 2.0-rc2
> Reporter: Sean Bridges
> Assignee: Matt Sicker
> Priority: Critical
> Fix For: 2.0
>
>
> This is in trunk, svn commit 1608156
> LoggerConfig#waitForCompletion uses an AtomicInteger counter to try to detect
> if there are any calls currently executing the log(Event) method, but it does
> not do so in a thread safe manner. Consider two threads A and B, where
> Thread A is calling clearAppenders(), and Thread B is calling log(Event),
> {code}
> Thread A loggerConfig.clearAppenders()
> Thread A loggerConfig.waitForCompletion()
> Thread A counter.get() //returns 0
> Thread A //loggerConfig.waitForCompletion() returns
> Thread B loggerConfig.log(Event)
> Thread B counter.increment()
> Thread A proceeds assuming no log calls are onging, but thread B is in the
> log method
> {code}
> I'm not sure what the requirements are, but if the requirement is to not lose
> logging events, I think you need some sort of synchronization outside of the
> LoggerConfig object.
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