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I am facing a problem regarding Process and Threads. My Scenario is:

My Java Application, call it 'Starter-App', starts another exe Application (Diagnosis.exe) with ProcessBuilder within a named Thread:

Thread startGXThread = new Thread(new Runnable() {  
    @Override       
    public void run() {
        try {
            ...
            File gxExe = new File(pathToGX); // Path to Diagnosis.exe
            gxp = pb.start();
            gxp.waitFor();

        } catch (IOException e) {
            LOG.error("Can't start module");
            LOG.error(e.getMessage(), e);
        } catch (InterruptedException e) {
            LOG.debug("thread interrupted. Destroy process");
            LOG.debug(e.getMessage(), e);
            if (gxp != null) {
                gxp.destroy();
                LOG.debug("process exit value: " + gxp.exitValue());
            }
        }
    }
}, "diag_thrd");

Afterwards a jetty webserver (ServiceWebApp) is started with a webapp.
start chromium and 'Starter-App' listen when its closed.

Once chromium closes 'Starter-App' recognizes this and stops jetty and also terminate the startet application.Diagnosis.exe. This is done by:

Runtime.getRuntime().addShutdownHook(new Thread() {
    @Override
    public void run() {
        stopAsync();
    }
});

public static void stopAsync() {
    Thread diag = getThread("diag_thrd");
    if (diag != null) {
        diag.interrupt();
    }
    if (gxp != null) {
        gxp.destroy();
        LOG.debug("process exit value: " + gxp.exitValue());
    }
}

Question: I need to be able to stop the startet Diagnosis.exe from within the webapp and start it again, while still be able to destroy/shutdown the Diagnosis.exe once chromium stops within 'Starter-App'. I hope I could explain my problem and hope for suggestions.

So the Starter-App starts Diagnosis.exe, a jetty server and Chromium? — Sonata, Dec 20 '16 at 09:38
That is right. The 'Starter-App' starts Diagnosis.exe, Jetty (with a deployed webapp), and Chromium (with url to the webapp). Once Chromium closes (by user) 'Starter-App' recognizes this and shuts down jetty and Diagnosis.exe. — kism3t, Dec 20 '16 at 09:47

score 2 · Accepted Answer · edited May 23 '17 at 10:30

2

Building on Anands answer, I think you need some form of IPC between the Diagnosis.exe and your Starter-App, using websockets, or a number of other options, for some ideas: How to have 2 JVMs talk to one another.

The webapp would send a request for restarting Diagnosis.exe to the Starter-App and the Starter-App would stay in charge of managing the application trio at all time.

edited May 23 '17 at 10:30

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answered Dec 20 '16 at 09:59

Sonata

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Liked this idea - The webapp would send a request for restarting Diagnosis.exe to the Starter-App and the Starter-App would stay in charge of managing the application trio at all time. – Anand Vaidya Dec 20 '16 at 10:15

score 1 · Answer 2 · edited May 23 '17 at 12:02

1

I think there is a solution but a but tricky to implement.

You can always use *nix api's like ps kill #pid as explained in the example here Killing a process using Java

But your webserver has to know which PID's to look for. The only option I see to implement such thing is using sockets or webservices. So you keep track of what is the current pid of Diagnosis.exe process, and use that Id before killing.

edited May 23 '17 at 12:02

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answered Dec 20 '16 at 09:29

Anand Vaidya

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I am using windows. So it would probably not be `ps kill`. I could pass the pid as a system paramter to the webapp but once the web app is shut down the 'starter-app's reference is not valid anymore. – kism3t Dec 20 '16 at 09:32
Yeah. Windows will have different option. Also I would not recommend sending PID as system parameter, but that should be sent as a heart-beat or some RMI/Webservice call. because There is a possibility of webserver restarting the process. So whosoever restarts the Diagnostic.exe notifies other of the new process Id to look for. – Anand Vaidya Dec 20 '16 at 09:35

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