Replace bash image with java’s in akka-bash-template

[michalrus]

There’s no need to keep the bash process running. Also, bash does not forward SIGTERM etc. to its child processes, so killing bash did not kill the java process.

[muuki88]

thanks @michalrus for your pull request. This topic has been discussed/tested a lot.
You only removed the exec for this akka microkernel? Is it working for the regular
bash script?

See #168 (!!), #206 , #99, #149

[michalrus]

@muuki88, I’ve only added exec to akka-microkernel script, because that is the only script I’m using. Sorry for not looking through the existing & closed issues, I treated this as a really quick fix. 😺

The issue is quite straightforward to me. I don’t want to have this in my process tree:

init(0)
  → bash              // known PID, *the* script I edited
    → java            // unknown PID :-(

Because:

1. Killing bash (via SIGTERM) will not kill java.
2. It's not easy to get java’s PID (e.g. to write to a PID file).
3. When stopping the app, I've got to kill both java and bash.

However, with this tree:

init(0)
  → java              // known PID, because the bash used `exec java …`

… after starting the script, I can use $! to get java’s PID.

$ nohup bin/some-app >some-app.log &
$ echo $! >some-app.pid
$ cat some-app.pid
44877

SIGTERM-ing the PID will signal Akka to shutdown.

Another pro might be bash using 1–2M RAM on amd64, but I doubt anybody cares about that. 😸

Right now I’m using sed to add the exec before deploying, so… The decision is all yours. 😸 I'm fine with current situation.

[muuki88]

Oh no! Sorry... I.... well I missread the one line code -.-
Thanks for adding this missing piece :) :) Happy new year

[michalrus]

Thank you and have a happy new year, too. =)