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https://issues.apache.org/jira/browse/LOG4J2-174?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13596092#comment-13596092
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Ralph Goers edited comment on LOG4J2-174 at 3/7/13 5:35 PM:
------------------------------------------------------------
Log4j 2 supports multiple applications writing to the same file with the
FileAppender. At this time it does not support it for the RollingFileAppender,
primarily because it isn't clear how to do the rollover safely.
Normally the file is "rolled" by renaming it and then compressing it, if
requested. On some systems the rename will fail if the file is opened by
another application. On others the rename will succeed but the other
applications will still have a handle to the renamed file and not be aware they
should write to a new file. If the rename fails the RollingFileAppender will
instead try to copy the file to the renamed file and then delete the original
file. Again, on some systems the delete will fail if the file is in use while
on others it will succeed but the other apps will still have a handle to the
deleted file and, in effect, will be writing to /dev/null.
Because the file is being renamed or copied just using a file lock on the file
doesn't really work. Instead, a second file object would be needed to block
other applications while the rollover is in progress, but even then I have
doubts that the rename/copy-delete would work in all cases.
My recommendation for this is to use something like Flume to aggregate your
logging content and then have Flume write to the file.
We haven't implemented receivers yet, but you could add a SocketServer to one
of your instances and then have all your instances log to that "master" server.
was (Author: [email protected]):
Log4j 2 supports multiple applications writing to the same file with the
FileAppender. At this time it does not support it for the RollingFileAppender,
primarily because it isn't clear how to do the rollover safely.
Normally the file is "rolled" by renaming it and then compressing it, if
requested. On some systems the rename will fail if the file is opened by
another application. On others the rename will succeed but the other
applications will still have a handle to the renamed file and not be aware they
should write to a new file. If the rename fails the RollingFileAppender will
instead try to copy the file to the renamed file and then delete the original
file. Again, on some systems the delete will fail if the file is in use while
on others it will succeed but the other apps will still have a handle to the
deleted file and, in effect, will be writing to /dev/null.
Because the file is being renamed or copied just using a file lock on the file
doesn't really work. Instead, a second file object would be needed to block
other applications while the rollover is in progress, but even then I have
doubts that the rename/copy-delete would work in all cases.
My recommendation for this is to use something like Flume to aggregate your
logging content and then have Flume write to the file.
> Multiple instances of same application server cause 2 problems - want to know
> if they are solved in log4j 2
> -----------------------------------------------------------------------------------------------------------
>
> Key: LOG4J2-174
> URL: https://issues.apache.org/jira/browse/LOG4J2-174
> Project: Log4j 2
> Issue Type: Question
> Components: Appenders
> Environment: Unix based OS and Java based application servers
> Reporter: Jas Gill
>
> When we start multiple instances of application server using log4j 1.2 and
> all instances read same configuration file, two problems are noticed.
> 1. At rollover time first app server doing rollover will do its job properly
> but when subsequent ones will do rollover again and we lose logs. May be
> log4j should check that if rolled over file is already present, it should
> skip rollover.
> 2. After rollover only one instance is logging and others stop logging. The
> problem is that the active file was rolled over and new file is created. Only
> one server has pointer to it.
> <appender name="ROLLING"
> class="org.apache.log4j.rolling.RollingFileAppender">
> <param name="Threshold" value="ALL"/>
> <param name="Append" value="true" />
> <rollingPolicy name="CONSOLE"
> class="org.apache.log4j.rolling.TimeBasedRollingPolicy">
> <param name="FileNamePattern"
> value="${LOG_FILE}.%d{yyyy-MM-dd-HH-mm}" />
> <param name="ActiveFileName" value="${LOG_FILE}" />
>
> </rollingPolicy>
> <layout class="org.apache.log4j.PatternLayout">
> <param name="ConversionPattern" value="%d{ISO8601} %-5p
> [%t]%x %c{2} - %m%n"/>
> </layout>
> </appender>
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