runit java server process monitoring

[Andrea Quintavalle]

I need to start Apache Karaf inside a docker image with baseimage-docker, Karaf is a Java server normally started using karaf shell script that doesn't act as a daemon so halts shell when launched.

I created /etc/service/karaf/run script to execute it:

#!/bin/sh
exec 2>&1
exec /opt/karaf/bin/karaf server

The problem is that that shell script execute a java command so I think I can say that "it forks":

root@de46c21a2a5f:/opt/karaf# ps -eaf
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 10:31 ?        00:00:00 /usr/bin/python3 -u /sbin/my_init
root         7     1  0 10:31 ?        00:00:00 /usr/bin/runsvdir -P /etc/service
root         8     7  0 10:31 ?        00:00:00 runsv karaf
root         9     7  0 10:31 ?        00:00:00 runsv sshd
root        10     7  0 10:31 ?        00:00:00 runsv syslog-ng
root        11     7  0 10:31 ?        00:00:00 runsv syslog-forwarder
root        12     7  0 10:31 ?        00:00:00 runsv cron
root        13    12  0 10:31 ?        00:00:00 /usr/sbin/cron -f
root        14    10  0 10:31 ?        00:00:00 syslog-ng -F -p /var/run/syslog-ng.pid --no-caps
root        15    11  0 10:31 ?        00:00:00 tail -F -n 0 /var/log/syslog
root        16     8  0 10:31 ?        00:00:00 /bin/bash /opt/karaf/bin/karaf server
root        68    16 35 10:31 ?        00:00:10 /usr/lib/jvm/jdk1.7.0_80/bin/java -server -Xms128M -Xmx512M -XX:+UnlockDiagnosticVMOptions -XX:+UnsyncloadClass -Dcom.su
root       100     0  0 10:31 ?        00:00:00 /bin/bash
root       153   100  0 10:31 ?        00:00:00 ps -eaf
root@de46c21a2a5f:/opt/karaf#

Just take a look at PID 16 and 68, PID 16 is my runit shell script, PID 68 is Java process launched by it.

I know that this shouldn't be done 

Note that the shell script must run the daemon without letting it daemonize/fork it.

In fact I can't stop PID 68 using

sv down karaf

 

The only alternative that I know is calling java executable directly in runit script, but I don't want to do that because I should skip many checks done by karaf shell script and java commands wouldn't be recalculated by the script in some cases.

Executing my server at docker container startup is not a problem, but I'd like to use runit service restart features in case of java process crash to keep my server continously alive.

Does anyone have a solution to make this works? Consider that many Java server or applications acts in the same way, so it's a general problem.

Thanks for your support

Andrea