Log4j2 Unable to log shutdown because JVM shutdown
I am trying to use log4j2 in a tomcat based web application, so I added the log4j web module along with other important jars. However, when stopping this web application, I get the following exception.
FATAL Unable to register shutdown hook because JVM is shutting down
Why am I getting this error and what can I do to prevent this error?
Thank!
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As explained in Puria's answer, you are probably trying to use Log4j2 when your application is already halting without properly shutting down. Since you are talking about Tomcat web application, I will assume you are using Servlets. (If you don't, see the second part below). Then you have to declare this in your ContextListener:
public class ContextListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent evt) {
String appenderName = evt.getServletContext().getInitParameter("log4jContextName");
File file = new File(evt.getServletContext().getInitParameter("log4jConfiguration"));
if(!file.exists()){
logger = LogManager.getRootLogger();
} else{
logger = LogManager.getLogger(appenderName);
}
}
}
@Override
public void contextDestroyed(ServletContextEvent evt) {
// You don't really need to do anything here, about the logger.
// The log4j2 JAR will handle it properly.
}
As usual in web applications, the Log4J2 configuration file must be referenced in the web.xml file like:
<?xml version="1.0" encoding="UTF-8"?>
<web-app ... >
<context-param>
<param-name>log4jContextName</param-name>
<param-value>myApplication</param-value>
</context-param>
<context-param>
<param-name>log4jConfiguration</param-name>
<param-value>/the/path/to/your/log4j.properties.file</param-value>
</context-param>
</web-app>
If you are using a regular application instead, you need to explicitly add your disconnect hook:
public static void main( String[] args ) {
...
File file = new File(logFileName);
if(!file.exists()){
logger = LogManager.getRootLogger();
} else {
System.setProperty("log4j.configurationFile", file.toURI().toURL().toString());
logger = LogManager.getLogger("yourProgramName");
}
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
logger.info("Shutting down - closing application");
// Shut down everything (e.g. threads) that you need to.
// then shut down log4j
if( LogManager.getContext() instanceof LoggerContext ) {
logger.debug("Shutting down log4j2");
Configurator.shutdown((LoggerContext)LogManager.getContext());
} else
logger.warn("Unable to shutdown log4j2");
// logger not usable anymore
System.out.println("Done.");
}
});
}
The shutdown key will be called when your application is terminated (i.e. when you call System.exit(0)
.
You also need to add this to your Log4J2 config file:
XML version:
<?xml version="1.0" encoding="UTF-8"?>
<Configuration shutdownHook="disable">
...
</Configuration>
Json version:
{"configuration":
{
"shutdownHook":"disable",
....
}
}
This will tell Log4j2 that you are handling the Logger shutdown yourself.
(Since in a normal application you don't have a web.xml file, you must restore the config file somehow).
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