m1a2st opened a new pull request, #20899:
URL: https://github.com/apache/kafka/pull/20899
## Problem
While running Kafka e2e tests, various tests were failing with
`TimeoutError('Kafka node failed to stop in 60 seconds')`. In Kafka e2e tests,
we check the PID to ensure the Kafka server has shut down. After investigating
this issue, I found that the Kafka process was a zombie process in the
container:
```bash
ducker@ducker05:/$ jcmd
285 kafka.Kafka /mnt/kafka/kafka.properties
18207 jdk.jcmd/sun.tools.jcmd.JCmd
ducker@ducker05:/$ cat /proc/285/status | grep -i state
State: Z (zombie)
```
## Root Cause
This issue is related to [this
change](https://github.com/apache/kafka/pull/17554/files#r1845737954). When
using `CMD ["sudo", "service", "ssh", "start", "-D"]`, PID 1 becomes the SSH
service, which does not handle `SIGCHLD` signals and therefore won't reap
zombie processes:
```bash
ducker@ducker05:/$ cat /proc/1/cmdline | tr '\0' ' '
sudo service ssh start -D
```
However, with the old syntax `CMD sudo service ssh start && tail -f
/dev/null`, PID 1 is `/bin/sh`, which is a shell that properly reaps zombie
processes:
```bash
ducker@ducker05:/$ cat /proc/1/cmdline | tr '\0' ' '
/bin/sh -c sudo service ssh start && tail -f /dev/null
```
## Solution
Use `tini` as PID 1 to properly manage processes and avoid zombie processes
from remaining in the system.
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