Comments on: Java Daemon

By: Joao Thomazini Neto

Joao Thomazini Neto — Tue, 17 Jan 2012 22:46:55 +0000

Amazing information. Right on target. Many thanks.

By: VaderJM

VaderJM — Thu, 10 Nov 2011 17:48:09 +0000

This was a fantastic post. I was able to get a service running in only a couple days (saved me tons of time). Thank you.

By: Pablo

Pablo — Fri, 26 Aug 2011 13:51:31 +0000

The DaemonShutdownHook doesn’t hold the app to finalize, you must not finalize the shutdown method till you end the main thread. Why? Because after the shutdown method the Signal continues with System.exit, that means that if you didn’t end your tasks before that, you’re going to leave lines without execution. My way to fix it was:

static public void shutdown()
{
shutdownRequested = true;
while (!MainClass.endFlag){//put some wait if u want}
}

static public void main(String[] args)
{
endFlag=false;
Appender startupAppender = new ConsoleAppender(new SimpleLayout());
try
{
logger.addAppender(startupAppender);
// do sanity checks and startup actions
daemonize();
addDaemonShutdownHook();
}
catch (Throwable e)
{
logger.fatal(“Startup failed.”,e);
}
finally
{
logger.removeAppender(startupAppender);
}

while(!isShutdownRequested())
{
// wait for stimuli
// process stimulus
}

// do shutdown actions
//end thread shutdown hook
endFlag=true;
}

By: Eric

Eric — Wed, 17 Aug 2011 20:22:13 +0000

I have a working Daemon my problem is when it is run from services (i.e. Server reboots) The Jar is running and responding to status checks but exec() passthrus to Linux do not return or get executed

By: Vineet

Vineet — Fri, 24 Jun 2011 07:24:40 +0000

Good article.

However, I am seeing the same problem that Jeff Shaver is facing. I am running on Iced Tea JVM on Linux and the shutdown hook does not get executed when I kill the application.

Anyone else facing this problem?

By: Ron de Jong

Ron de Jong — Thu, 14 Apr 2011 09:46:19 +0000

Hi Peter,

Very appreciated all in all, but you’re completely ignoring the main java principle:

PLATFORM INDEPENDENCY !!!

Your solution needs to work on:
Microsoft OS’s to!!! so forget about those shell solutions!!!

By: Avi

Avi — Thu, 27 Jan 2011 17:31:44 +0000

Thanks for this artical. I have learned a lot.

By: Scott the Werewolf

Scott the Werewolf — Sun, 15 Aug 2010 05:18:50 +0000

Sounds impressive, but what would you use this java program for? Sorry for asking what may be a silly question…. =P

By: Jeff Shaver

Jeff Shaver — Thu, 03 Jun 2010 17:51:07 +0000

What is the solution in the case where the JVM ignores 'kill ' ? TERM, HUP, INT, and QUIT are all ignored. KILL, and USR1 do kill it, but the shutdown() code does not get run.

Thanks for a very useful article.

By: Jeremy Brooks

Jeremy Brooks — Tue, 19 Jan 2010 17:27:32 +0000

Sorry, forgot to include my solution for capturing stderr/stdout when needed:

if (System.getProperty(“detach”).equals(“false”)) {
// Log message about no detach or something
} else {
System.in.close();
System.out.close();
System.err.close();
}

Now if you are getting weird crashes and expect that you may have an out of memory error or something that is getting printed to stderr, just include the -Ddetach=false system property in your startup command. When you have captured the information you need, remove the system property, or set it to anything other than false, and your program will detach as expected.