How can I make my Docker compose “wait-for-it” script invoke the original container ENTRYPOINT or CMD?

Question

According to Controlling startup order in Compose, one can control the order in which Docker Compose starts containers by using a \"wait-for-it\" script. Script wait-for-it.sh

Answer 1

However, if one uses this option, the container will no longer run its default ENTRYPOINT or CMD command because entrypoint: overrides the default.

That is expected, which is why the wait-for-it is presented as a wrapper script.
It does allow to execute a "subcommand" though:

wait-for-it.sh host:port [-s] [-t timeout] [-- command args]
                                               ^^^^^^^^^^^^

The subcommand will be executed regardless if the service is up or not.
If you wish to execute the subcommand only if the service is up, add the --strict argument.

That means the CMD part of your image can be used for your actual container command, as its parameters will passed in parameters to the ENTRYPOINT command:

entrypoint: wait-for-it.sh host:port --
cmd: mycmd myargs

This should work... except for docker-compose issue 3140 (mentioned by the OP Derek Mahar in the comments)

entrypoint defined in docker-compose.yml wipes out CMD defined in Dockerfile

That issue suggests (Jan. 2021)

If you have a custom image you can add a startscript to the build and call it inside the dockerfile and in the docker-compose you can call it again.
Thats a way to avoid duplicate for more complicated entrypoints.