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https://issues.apache.org/jira/browse/LOG4J2-3549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17570422#comment-17570422
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Ralph Goers commented on LOG4J2-3549:
-------------------------------------
Whether it helps or not is dependent on choices you make.
When logging asynchronously the logs are written to a ring buffer and control
is returned to the application. Another thread then reads from the buffer and
writes the to disk. If writing is slower than logs are being written eventually
the buffer will fill up. The default behavior is for the thread to block until
an entry in the buffer is available, so basically you will be back in the same
situation. However, you can also chose a strategy that discards the log events
when the buffer is full. Thus your application won't slow down but it will lose
log events, which you might find unacceptable.
There is one other scenario where async logging could help.
You have not provided your configuration but from the code it looks like you
have immediateFlush set to true (the default). Performing a flush for every log
event is pretty slow and if your application is logging a lot it would be
recommended to set it to false. The area where async logging could help is that
it automatically forces immediateFlush to false since it makes no sense if you
are logging asynchronously.
> The printed thread blocked
> --------------------------
>
> Key: LOG4J2-3549
> URL: https://issues.apache.org/jira/browse/LOG4J2-3549
> Project: Log4j 2
> Issue Type: Bug
> Components: Log4j 1.2 bridge
> Affects Versions: 2.17.2
> Reporter: yimiluo
> Priority: Minor
> Attachments: image-2022-07-08-20-20-11-818.png
>
>
> When we were printing the log, the printed thread was blocked, causing the
> service to go down. The following is the exception information:
> !image-2022-07-08-20-20-11-818.png|width=895,height=537!
> {code:java}
> [arthas@1]$ thread -b
> "http-nio-8080-exec-5" Id=97 RUNNABLE (in native)
> at java.base@11.0.8-ga/java.io.FileOutputStream.writeBytes(Native Method)
> at
> java.base@11.0.8-ga/java.io.FileOutputStream.write(FileOutputStream.java:354)
> at
> java.base@11.0.8-ga/java.io.BufferedOutputStream.write(BufferedOutputStream.java:123)
> - locked java.io.BufferedOutputStream@ea9396a
> at java.base@11.0.8-ga/java.io.PrintStream.write(PrintStream.java:559)
> - locked java.io.PrintStream@3ff1e46c
> at
> org.apache.logging.log4j.core.util.CloseShieldOutputStream.write(CloseShieldOutputStream.java:53)
> at
> org.apache.logging.log4j.core.appender.OutputStreamManager.writeToDestination(OutputStreamManager.java:250)
> at
> org.apache.logging.log4j.core.appender.OutputStreamManager.flushBuffer(OutputStreamManager.java:283)
> - locked
> org.apache.logging.log4j.core.appender.OutputStreamManager@7ba4158c <---- but
> blocks 236 other threads!
> at
> org.apache.logging.log4j.core.appender.OutputStreamManager.flush(OutputStreamManager.java:294)
> - locked
> org.apache.logging.log4j.core.appender.OutputStreamManager@7ba4158c <---- but
> blocks 236 other threads!
> at
> org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:199)
> at
> org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:190)
> at
> org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:181)
> at
> org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:161)
> at
> org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:134)
> at
> org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:125)
> at
> org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:89)
> at
> org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:542)
> at
> org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:500)
> at
> org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:483)
> at
> org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:417)
> at
> org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:82)
> at org.apache.logging.log4j.core.Logger.log(Logger.java:161)
> at
> org.apache.logging.log4j.spi.AbstractLogger.tryLogMessage(AbstractLogger.java:2205)
> at
> org.apache.logging.log4j.spi.AbstractLogger.logMessageTrackRecursion(AbstractLogger.java:2159)
> at
> org.apache.logging.log4j.spi.AbstractLogger.logMessageSafely(AbstractLogger.java:2142)
> at
> org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2028)
> at
> org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1891)
> at org.apache.logging.slf4j.Log4jLogger.info(Log4jLogger.java:194) {code}
>
> I don't know what the solution is now. I would be very grateful if you could
> reply.
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