chore: remove tidb slowlog container

[cjc7373]

Slowlog is stored in file. This container merely displays it. Due to some signal handling problems, this container blocks the pod grace shutdown process. So I think the easiest way is to delete it.

[shanshanying]

can we TRAP the TERM signal ?

[cjc7373]

I have tested two ways.

The first is to trap sigterm. However, it seems busybox's sh won't handle signal until the runnning command ends. Tested with:

      command:
        - bin/sh
        - -c
        - |
          trap "echo 'received SIGTERM, sleeping 10s...'; sleep 10; echo 'exiting now'; exit 0" SIGTERM
          echo "starting..."
          sleep 20

PS. bash also has similar behavior, excerpt from bash manual:

If Bash is waiting for a command to complete and receives a signal for which a trap has been set, it will not execute the trap until the command completes.

The second is to use exec to replace current shell process:

      command:
        - bin/sh
        - -c
        - |
          echo "starting..."
          touch /tmp/log.txt
          exec tail -n0 -F /tmp/log.txt

It doesn't work either. Looks like busybox's tail won't handle sigterm.

[shanshanying]

It seems sleep blocks TERM. can we for example, kill the TAIL task by PID on receiving the signal
e.g

# trap TERM
trap graceful_exit TERM INT

# get tail pid and wait for it
tail -n0 -F /tmp/log.txt &
TAIL_PID=$!
wait $TAIL_PID

and this graceful_exit function kill the TAIL_PID, for example:

    graceful_exit() {
      kill -TERM $TAIL_PID 2>/dev/null
      exit 0
    }

[cjc7373]

Yes, this can work!