Pooja Pandey created LOG4J2-3447:
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Summary: Log4j 1.x 2.17.2 bridge - Synchronization issue in
multithreading (Losing huge data in multithreading)
Key: LOG4J2-3447
URL: https://issues.apache.org/jira/browse/LOG4J2-3447
Project: Log4j 2
Issue Type: Bug
Components: Log4j 1.2 bridge
Affects Versions: 2.17.2
Reporter: Pooja Pandey
Attachments: JavaLoggingMultiThTest.txt
In our application we have migrated from log4j1.x to log4j1.x 2.17.2 bridge.
With Log4j1.x there was no issue with multithreading but with log4j 1.x bridge
we have noticed that in multithreading environment there is a huge data loss
while logging, however single thread works fine. I see that in Category.java
which Logger extends; many methods are not synchronized any more in log4j1.x
bridge however which were synchronized in case of log4j1.x. I suspect this
could be root causes of this multithreading problem.
So as per my understanding synchronized class Category.java in the log4j1.x has
become unsynchronized in log4j1.x 2.17.2 bridge. I am not sure if I am missing
something.
We wanted to know how to achieve successful multithreading logging using log4j
1.x 2.17.2 bridge.
For reference, few methods which were synchronized earlier in log4j1.x but not
anymore in log4j1.x bridge.
# public void addAppender(final Appender appender)
# public Appender getAppender(final String name)
# public void removeAppender(final Appender appender)
# public void removeAllAppenders()
# In log4j 1.x bridge following method is used for logging which doesn't look
like synchronized. -> void maybeLog(final String fqcn, final
org.apache.logging.log4j.Level level, final Object message, final Throwable
throwable); However in log4j1.x following method was used which looks like
synchronized. -> void forcedLog(String fqcn, Priority level, Object message,
Throwable t) -> void callAppenders(LoggingEvent event), where method void
callAppenders(LoggingEvent event) looks snychronized.
I am attaching sample test program as well which I have used to test
multithreading logging in my application. (Please Note that in this test
program, class CustomLogger is a dummy class, which you would need to replace
with your logger). We are using Custom Rolling Appender in our application and
following is the content of log4j properties file. [^JavaLoggingMultiThTest.txt]
#Custom Rolling Appender
log4j.appender.R=test.CustomMultiProcessRollingAppender
log4j.appender.R.File=${user.home}/log4j-multithreading-test.log
log4j.appender.R.RollOverOnStartup=true
log4j.appender.R.RollOverOnSize=false
log4j.appender.R.RollOverMaxFileSize=100MB
log4j.appender.R.RollOverMaxBackupIndex=10
log4j.appender.R.RollOverOnPeriodic=false
log4j.appender.R.RollOverPeriodicStartDate=
log4j.appender.R.RollOverPeriodicFrequency=1
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%d %-8M [%t] - %m%n
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