Mikael Ståldal created LOG4J2-1012:
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Summary: AsyncAppender hang on shutdown if delegate Appender hangs
Key: LOG4J2-1012
URL: https://issues.apache.org/jira/browse/LOG4J2-1012
Project: Log4j 2
Issue Type: Bug
Components: Appenders
Affects Versions: 2.2
Reporter: Mikael Ståldal
I have a custom appender which sometimes hangs forever on
Appender.append(LogEvent). To make sure that this does not affect my
application, I have wrapped it with a non-blocking AsyncAppender like this. (I
rather lose some log events than lock-up my application).
{code:xml}
<Configuration status="WARN">
<Appenders>
<Custom name="Custom">
</Custom>
<Async name="AsyncCustom" blocking="false">
<AppenderRef ref="Custom"/>
</Async>
</Appenders>
<Loggers>
<Root level="INFO">
<AppenderRef ref="AsyncCustom"/>
</Root>
</Loggers>
</Configuration>
{code}
This works fine as long as the application runs, but when I shut down, it can
hang forever, from jstack:
{code}
"pool-1-thread-1" prio=10 tid=0x00007f3e840cd800 nid=0x3945 in Object.wait()
[0x00007f3e765de000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007490d2b88> (a
org.apache.logging.log4j.core.appender.AsyncAppender$AsyncThread)
at java.lang.Thread.join(Thread.java:1281)
- locked <0x00000007490d2b88> (a
org.apache.logging.log4j.core.appender.AsyncAppender$AsyncThread)
at java.lang.Thread.join(Thread.java:1355)
at
org.apache.logging.log4j.core.appender.AsyncAppender.stop(AsyncAppender.java:119)
at
org.apache.logging.log4j.core.config.AbstractConfiguration.stop(AbstractConfiguration.java:228)
at
org.apache.logging.log4j.core.LoggerContext.stop(LoggerContext.java:224)
at
org.apache.logging.log4j.core.LoggerContext$1.run(LoggerContext.java:185)
at
org.apache.logging.log4j.core.util.DefaultShutdownCallbackRegistry$1.run(DefaultShutdownCallbackRegistry.java:101)
at
org.apache.logging.log4j.core.util.DefaultShutdownCallbackRegistry.run(DefaultShutdownCallbackRegistry.java:75)
at java.lang.Thread.run(Thread.java:745)
Locked ownable synchronizers:
- <0x00000007490e9360> (a
java.util.concurrent.locks.ReentrantLock$NonfairSync)
"AsyncAppender-AsyncCustom" daemon prio=10 tid=0x00007f3e84676000 nid=0x386b
waiting on condition [0x00007f3e77df6000]
[...hang in CustomAppender...]
org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:99)
at
org.apache.logging.log4j.core.appender.AsyncAppender$AsyncThread.callAppenders(AsyncAppender.java:290)
at
org.apache.logging.log4j.core.appender.AsyncAppender$AsyncThread.run(AsyncAppender.java:241)
Locked ownable synchronizers:
- None
{code}
It would be nice if AsyncAppender could fully protect you from faulty appenders
and have some timeout on shutdown (at least when you specify blocking=false).
Proper shutdown of the application is important for me.
(I know that I should fix my faulty custom appender, but I want an extra safety
net to make my application reliable and robust.)
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