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arnaudsj / monit

Monit is a free open source utility for managing and monitoring, processes, files, directories and filesystems on a UNIX system. Monit conducts automatic maintenance and repair and can execute meaningful causal actions in error situations. (unofficial mirror)

Home Page:http://mmonit.com/monit/

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Reap random zombies

kasbert opened this issue · comments

commented

If monit is used as init process in docker, it does not reap extra zombie processes created by services. It would be nice, if it did so.

Example Dockerfile:

FROM ubuntu:22.04
RUN \
 apt-get update && \
 DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends monit && \
 apt clean
RUN \
 printf '#!/bin/bash\nnohup date&' > /necromancer && \
 chmod 755 /necromancer && \
 printf 'check process hello matching nothing start "/necromancer"' > /etc/monit/conf-enabled/hello
ENTRYPOINT ["monit"]
CMD ["-I", "-B", "-v" , "-d", "10"]

Build and run:

docker build -t monit-test .
docker run --rm -d --name test monit-test

The zombie processes start invading the container:

docker exec -it test ps -ef

UID          PID    PPID  C STIME TTY          TIME CMD
root           1       0  1 06:21 ?        00:00:06 monit -I -B -v -d 10
root           8       1  0 06:21 ?        00:00:00 [date] <defunct>
root          16       1  0 06:21 ?        00:00:00 [date] <defunct>
root          18       1  0 06:22 ?        00:00:00 [date] <defunct>
root          20       1  0 06:23 ?        00:00:00 [date] <defunct>
root          22       1  0 06:23 ?        00:00:00 [date] <defunct>
root          30       1  0 06:24 ?        00:00:00 [date] <defunct>
root          32       1  0 06:25 ?        00:00:00 [date] <defunct>
root          34       1  0 06:25 ?        00:00:00 [date] <defunct>
root          36       1  3 06:26 ?        00:00:00 [date] <defunct>
root          37       0  0 06:26 pts/0    00:00:00 ps -ef
commented

As a workaround I use tini as the entrypoint

FROM ubuntu:22.04
RUN \
 apt-get update && \
 DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends monit tini && \
 apt clean
RUN \
 printf '#!/bin/bash\nnohup date&' > /necromancer && \
 chmod 755 /necromancer && \
 printf 'check process hello matching nothing start "/necromancer"' > /etc/monit/conf-enabled/hello
ENTRYPOINT ["tini"]
CMD ["-vv", "-g", "--", "monit", "-I", "-B", "-v" , "-d", "10"]