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https://issues.apache.org/jira/browse/LOG4J2-1094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17719807#comment-17719807
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Björn Kautler commented on LOG4J2-1094:
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I've also his several problems with multi-thread initialization when using
log4j in parallel tests when creating logger contexts for each test and if the
tests start to run in parallel, do the same initialization like enum type
converter registration or mbean registration which then results in at least
warnings being logged.
I was able to mitigate it by creating one logger context up-front before the
actual tests start.
But couldn't there some double-checked locking initizalization be done, so that
after initialization there is no need for obtaining the locks while preventing
competing initializations be done by multiple threads?
> 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
> Assignee: Ralph Goers
> Priority: Major
>
> 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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