how to write entrypoint scripts on windows - docker

Question

I was asked to build an image for python programs and for example if we create 3 python programs and create a an image for them and if we run that image, basically a container will be created and will execute and will exit, and for the second program another container will be created.
that's what usually will happen. but here i was informed that a single container should be created for all the programs and it should be in the run state continuously and if we give the program name in the run command it should execute that program, not the other two programs, and it should start and stop based on the commands i give.
for this to happen i was given a hint/suggestion i should say that if i create an entrypoint script and copy that in the docker file it'll work. but unfortunately, when i researched on it in internet the entrypoint scripts are available for linux, but I'm using windows here.

Answer 1

So, first to explain why the container exits after you run it: Containers are not like VMs. Docker (or the container runtime you choose) will check for what is running on the containers. This "what is running" is defined on the ENTRYPOINT on your dockerfile. If you don't have an entrypoint, there's nothing running and Docker stops the containers. Or it might be the case that something ran and the container stopped after it executed.
Now, the Windows Server base images don't have an entrypoint. If you just ask to run the container, it will start and stop immediately. That is a problem for background services like web servers, for example IIS. To solve that, Microsoft created a service called Service Monitor. If you look for the docker file of the IIS image that Microsoft produces, you'll notice that the entrypoint is the service monitor that in turn checks the status of the IIS service. If IIS is running, service monitor will continue to run and thus the container keeps running indefinitely. (Here's the dockerfile: https://github.com/Microsoft/iis-docker/blob/main/windowsservercore-ltsc2022/Dockerfile)
Now, for your case, what you need is a job on your python container. Look at the description on the link provided by Mihai: https://hub.docker.com/_/python
This is their example docker file:
FROM python:3
WORKDIR /usr/src/app
COPY requirements.txt ./
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
CMD [ "python", "./your-daemon-or-script.py" ]
Note the last line. It's not an entry point, which means that the python app will run and exit, which will stop the container. IF you need the container to run indefinetly, either you leverage something like service monitor (but need to build a service in the background) or you create your own logic to keep something running. For example, a infinte loop.
Does that helps?