#docker - August 2018

@Erik Osterman (Cloud Posse) has joined the channel

set the channel description: All things docker

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So for everyone who is dealing with docker signalling issues, I had some pain with it today with sidekiq not stopping gracefully inside docker. Docker stop sends a SIGTERM to docker pid. In most cases, with /bin/sh -c being the entrypoint, the SIGTERM will only reach the pid of /bin/sh and not the child processes of it. Inside my bash script I was already using exec, but I had to use exec in the CMD line of the Dockerfile to make it to work.

Note the exec.

CMD exec /$APP_DIR/bin/dispatch.sh

And note the exec Inside dispatch.sh

SIDEKIQ_COUNT=3 SIDEKIQ_MAXMEM_MB=2000 SIDEKIQ_PRELOAD=sidekiq_swarm exec sidekiqswarm -t 25 -C config/sidekiq.yml

https://hochzehn.com/insights/docker-stopping-containers-softly.html

Aha... so basically, it's running /bin/sh -c 'exec /$APP_DIR/bin/dispatch.sh', which then replaces PID1 with dispatch.sh
I've also run into problems with signal handling and shell scripts with docker.

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it feels like the format of shell commands can convey a lot of meaning:

SIDEKIQ_COUNT=3 SIDEKIQ_MAXMEM_MB=2000 SIDEKIQ_PRELOAD=sidekiq_swarm && 
    exec sidekiqswarm \
        -t 25 \
        -C config/sidekiq.yml

it's running /bin/sh ...

does CMD (and hence RUN) always pick /bin/sh, or does it use the named shebang #! shell at the top of:/$APP_DIR/bin/dispatch.sh ?

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@Igor Rodionov would this be nice for our local dev harness stuff? https://github.com/bcicen/ctop

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