Program hangs when terminating on v14.1

[Laurent Hasson]

Hello,

We use Log4J2 as our logging library both in a Web environment (under Tomcat), 
and in command-line utilities. I have noticed recently that our command-line 
utilities seem to hang when done: the normal JVM's exit is blocked.

I am on JDK 15 with log4j-web-2.14.1.jar, log4j-core-2.14.1.jar and 
log4j-api-2.14.1.jar in the classpath.

My configuration is:
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="info">
       <Properties>
              <Property 
name="log-path">C:\Projects\TomcatDevServer\logs\</Property>
              <Property name="now">${date:yyyy-MM-dd}</Property>
       </Properties>
       <Appenders>
              <RollingFile name="FILES" fileName="${log-path}/capsico.log" 
filePattern="${log-path}/capsico.${now}.%i.log.gz">
                     <PatternLayout>
                <pattern>%d{MMdd.HHmmss.SSS}#%-3t %level{length=1} %15.15c{1}| 
%m %ex{50}%n</pattern>
                     </PatternLayout>
                     <Policies>
                           <SizeBasedTriggeringPolicy size="100 MB" />
                     </Policies>
                     <DefaultRolloverStrategy max="99999" compressionLevel="6"/>
              </RollingFile>
              <Async name="ASYNC">
                     <AppenderRef ref="FILES" />
              </Async>
              <Console name="Console" target="SYSTEM_OUT">
                     <PatternLayout>
                 <pattern>%d{MMdd.HHmmss.SSS}#%-3t %level{length=1} %15.15c{1}| 
%m %ex{50}%n</pattern>
                     </PatternLayout>
        </Console>
       </Appenders>
       <Loggers>
              <Root level="debug">
            <AppenderRef ref="Console" />
<!--
            <AppenderRef ref="ASYNC" />
            <AppenderRef ref="Console" />
-->
              </Root>
       </Loggers>
</Configuration>

We switch between console when developing to async in production, thus the two 
options.

My test program is super simple:
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class Test
  {
    protected static final Logger LOG = 
LogManager.getLogger(Test.class.getName());

    public static void main(String[] args)
      {
         LOG.debug("Hello");
      }
  }

This program hangs and doesn't exit. If I replace the Log4J2 JARs with v12.1, 
all works as expected. I checked JDK 8 and JDK 11 with the same behavior.

If I remove the <Async> element, it works, pointing to that capability causing 
issues. My guess is that a thread is not getting closed and hangs the JVM's 
normal exist.

I did not see a reference to some API changes from v12 to v14 that would 
explain this, or maybe I missed something? Or maybe it's a bug?

Thank you,
Laurent Hasson