Daemon (starting / stopping)

[klingoni]

Hi everybody

I'm writing a daemon in java which is started from the console on several machines. Now, my question is, what is the easiest way to be able to start / stop daemons from the console. How can I find out if the daemon is already running (if, for example, someone wants to start it again) or how can I shut it down cleanly if it is running already? I'm thinking of something like this:

starting: [blue]java myDaemon start [additional args][/blue]
stopping: [blue]java myDaemon stop[/blue]

Somehow, I have to check if there already is a Daemon instance in the JVM when it is invoked with the start or stop argument. But I don't really know how to do this? I also don't know how to tear down (destruct) the deamon, if it is running and should be shut down??

Any help greatly appreciated

Sebastian

 

[sedj]

Operating System ?

 

[stefanwagner]

To prevent a second instance to be started, you could use a Lockfile (java.nio.channels.FileLock).
To send a stop-signal to an already running process, I would try to use a socket, or rmi (which should work on localhost too) - I didn't tried this.

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[hologram]

I would also go for the socket appoach (maybe in combination with the lock). You could make a (small) http server to manage yout daemon(s) in the same way as you can configure / manage a router or any network attached device. Since your daemons are running on several machines, you can administer them centrally or from any "pc" with a web browser.
PS : The daemon and the http server are threads in the same process.
[Instead you could pop up a gui, but that would only work on the local machine.]