Share Process / Thread

Question

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.

Answer 1

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.

Answer 2

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.