Shutdown Hooks Not Running

[darkfrog26]

My configuration is fairly simple, but at startup I add a shutdown hook:

Runtime.getRuntime.addShutdownHook(...)

However, at re-stop (or ~re-start code change) the hook is never fired. The documentation explicitly states this is how shutdown should be handled. Is there additional configuration I need to specify to make those hooks fire?

[jrudolph]

We only have very coarse control over the spawned process. To stop it we use Process.destroy which I guess is equivalent to kill -9.

The first thing to do proper shutdown would be a platform independent way to signal a termination wish to a process. Do you know if there's a Java library doing this? (like using kill -SIGTERM in linux/unix, taskkill in windows, etc.)

[jrudolph]

Another possibility would be to allow a user-defined way of closing an application and leave the current force-close behavior as default or fallback.

[magnusart]

I have this problem as well. Shutdown is not handled correctly and then a new process is spawned but fails because it can't bind to the port that is taken. I have to shut down SBT every time I want to restart. My setup is a multi project setup. Even when I try to run re-stop it doesn't shut down the processes correctly.

[jrudolph]

Magnus, this sounds like quite the opposite problem: where the original issue was about the process being closed to eagerly so that the shutdown hooks are not run, what you are experiencing seems to be that Process.destroy is not working for some reason. Can you open a new issue for that and post an sbt console log exhibiting the problem?

[magnusart]

You're correct. I found that my issue was better described in the other bug and that fix seems to have made the trick for my issue. Thank you.

[jrudolph]

Closing...

[yanns]

Maybe we can let this issue opened, as it is present.

We could try a proper shutdown, then wait a bit and then kill the process if it's still there.
There does not seem to be any java lib to handle a proper shutdown.
A possibility seen on http://stackoverflow.com/questions/6356340/killing-a-process-using-java:

 Runtime rt = Runtime.getRuntime();
  if (System.getProperty("os.name").toLowerCase().indexOf("windows") > -1) 
     rt.exec("taskkill " +....);
   else
     rt.exec("kill -9 " +....);

[jrudolph]

Please open a new ticket if you have a concrete idea how to fix this. As written above, the current behavior is currently equivalent to kill -9. What would be nice if there would be an equivalent of kill -15 instead. The problem with your example is the ..... The java.lang.Process API has no access to the PID so we cannot call the external kill. (Using reflection tricks might get us there, though.)

[dwickern]

I don't this problem on UNIX/OSX because Process.destroy() sends a SIGTERM. Note that the I/O redirection stops so you won't see any stdout/stderr from your shutdown hook, but the hook is getting called.

I do have this problem on Windows. Process.destroy() calls the TerminateProcess Windows API which is like a kill -9. There's no workaround as far as I know. The way to gracefully stop a process on Windows is to send a WM_CLOSE message but that won't work for a command-line application.

[jrudolph]

@dwickern that's interesting, since that behavior seems to have changed for Unix only with Java 8. Since then there are two methods destroy and destroyForcibly, so the original behavior of destroy should do now what was asked for in this ticket originally.

That said, it seems you are also right about Windows. Should we keep that open as a reminder that it still doesn't work on Windows?