Stop command handling: await grace period after stop command

Changes the way the stop command is treated. With this change, the stop
command can either be synchronous or asynchronous. Before it was only
possible to use synchronous commands, as the main process was destroyed
immediately after the stop command exited. Now the grace period is
awaited in case an asynchronous trigger causes the main process to exit
within that period.

Request: MO
Change-Id: Ia72eb54f8c895b19e1a117a5e6a953206db30ce5

Author: mduft

pcu/src/main/java/io/bdeploy/pcu/ProcessController.java

@@ -830,6 +830,7 @@ private void doInvokeStopCommand(List<String> stopCommand) {
         }
         try {
             logger.log(l -> l.info("Invoking configured stop command {}.", stopCommand));
+            long stopCommandStartTime = System.currentTimeMillis();
             Process p = launch(stopCommand, true);
             boolean exited = p.waitFor(processConfig.processControl.gracePeriod, TimeUnit.MILLISECONDS);
             if (!exited) {
@@ -845,9 +846,22 @@ private void doInvokeStopCommand(List<String> stopCommand) {
                 // stop command completed within the timeout, check status
                 int exitValue = p.exitValue();
                 if (exitValue != 0) {
-                    logger.log(l -> l.warn("Stop command exited with non-zero code: {} ", exitValue));
+                    logger.log(l -> l.warn("Stop command exited with non-zero code: {}", exitValue));
                 } else {
-                    logger.log(l -> l.info("Stop command exited with return code 0 "));
+                    long remainingGracePeriod = processConfig.processControl.gracePeriod
+                            - (System.currentTimeMillis() - stopCommandStartTime);
+                    logger.log(l -> l.info("Stop command exited with return code 0, remaining grace period: {}",
+                            remainingGracePeriod));
+
+                    // stop command exited, lets give the process a little extra time to exit as well.
+                    try {
+                        processExit.get(remainingGracePeriod, TimeUnit.MILLISECONDS);
+                        logger.log(l -> l.info("Stop command successfullly terminated main process"));
+                    } catch (TimeoutException e) {
+                        logger.log(l -> l.warn("Main process did not exit after stop grace period"));
+                    } catch (Exception e) {
+                        logger.log(l -> l.warn("Exception while waiting for application to terminate.", e));
+                    }
                 }
             }
         } catch (Exception e) {