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https://issues.apache.org/jira/browse/LOG4J2-1094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14963603#comment-14963603
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Remko Popma commented on LOG4J2-1094:
-------------------------------------
Someone else may have a different issue with the same root cause:
http://stackoverflow.com/questions/33105357/log4j2-and-instancealreadyexistsexception-when-creating-a-logger/33219889
> Multi thread initialization problem
> -----------------------------------
>
> Key: LOG4J2-1094
> URL: https://issues.apache.org/jira/browse/LOG4J2-1094
> Project: Log4j 2
> Issue Type: Bug
> Affects Versions: 2.3
> Reporter: Luca Burgazzoli
>
> I wrote a very simple example which has a behaviour I do not expect:
> If I call LogManager.getLogger(..) from two threads, only one of the loggers
> logs what I'd expect but if I add an additional call to
> LogManager.getLogger(..) before the threads are started, I see what I'd
> expect so it looks like there is a problem in multi threaded initialization.
> You can find the code and the configuration here:
> -
> https://github.com/lburgazzoli/lb-chronicle/blob/master/chronicle-examples/chronicle-logger-log4j2/src/main/java/com.github.lburgazzoli.openhft.examples.chronicle.logger.log4j2/MtLogging.java
> -
> https://github.com/lburgazzoli/lb-chronicle/blob/master/chronicle-examples/chronicle-logger-log4j2/src/main/resources/log4j2.xml
> {code}
> public class MtLogging {
> public static void main(final String[] args) throws Exception {
> //LogManager.getLogger("main");
> Thread th1 = new Thread(() -> {
> final String name = "thread-1";
> final Logger log = LogManager.getLogger(name);
> System.out.println("write " + name);
> log.info("message");
> System.out.println("done " + name);
> });
> Thread th2 = new Thread(() -> {
> final String name = "thread-2";
> final Logger log = LogManager.getLogger(name);
> System.out.println("write " + name);
> log.info("message");
> System.out.println("done " + name);
> });
> th1.start();
> th2.start();
> th1.join();
> th2.join();
> }
> }
> {code}
> {code}
> <?xml version="1.0" encoding="UTF-8"?>
> <configuration>
> <appenders>
> <Console name="STDOUT" target="SYSTEM_OUT">
> <PatternLayout pattern="[TEST] [%-5p] %c - %m%n%throwable{none}"/>
> </Console>
> </appenders>
> <loggers>
> <root level="all">
> <appender-ref ref="STDOUT"/>
> </root>
> </loggers>
> </configuration>
> {code}
> The code above will show:
> {noformat}
> write thread-1
> done thread-1
> write thread-2
> [TEST] [INFO ] thread-2 - message
> done thread-2
> {noformat}
> Any call to LogManager makes it succeed (the problem no longer occurs):
> {code}
> LogManager.getContext(false);
> th1.start();
> th2.start();
> th1.join();
> th2.join();
> {code}
> New output:
> {noformat}
> write thread-2
> write thread-1
> [TEST] [INFO ] thread-2 - message
> done thread-2
> [TEST] [INFO ] thread-1 - message
> done thread-1
> {noformat}
> The funny thing is that the first thread to arrive is initialized with ERROR
> level instead of the ALL that is given to root. In other words it seems that
> the config has not loaded
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