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engine: restructure mult-service container page
Signed-off-by: David Karlsson <david.karlsson@docker.com>
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@ -10,8 +10,8 @@ title: Run multiple services in a container
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---
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A container's main running process is the `ENTRYPOINT` and/or `CMD` at the
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end of the `Dockerfile`. It is generally recommended that you separate areas of
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concern by using one service per container. That service may fork into multiple
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end of the `Dockerfile`. It's best practice to separate areas of concern by
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using one service per container. That service may fork into multiple
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processes (for example, Apache web server starts multiple worker processes).
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It's ok to have multiple processes, but to get the most benefit out of Docker,
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avoid one container being responsible for multiple aspects of your overall
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@ -28,91 +28,97 @@ container exits. Handling such processes this way is superior to using a
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full-fledged init process such as `sysvinit`, `upstart`, or `systemd` to handle
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process lifecycle within your container.
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If you need to run more than one service within a container, you can accomplish
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If you need to run more than one service within a container, you can achieve
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this in a few different ways.
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- Put all of your commands in a wrapper script, complete with testing and
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debugging information. Run the wrapper script as your `CMD`. This is a very
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naive example. First, the wrapper script:
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## Use a wrapper script
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```bash
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#!/bin/bash
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Put all of your commands in a wrapper script, complete with testing and
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debugging information. Run the wrapper script as your `CMD`. This is a very
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naive example. First, the wrapper script:
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# Start the first process
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./my_first_process &
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# Start the second process
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./my_second_process &
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# Wait for any process to exit
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wait -n
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# Exit with status of process that exited first
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exit $?
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```
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```bash
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#!/bin/bash
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Next, the Dockerfile:
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# Start the first process
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./my_first_process &
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```dockerfile
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# syntax=docker/dockerfile:1
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FROM ubuntu:latest
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COPY my_first_process my_first_process
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COPY my_second_process my_second_process
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COPY my_wrapper_script.sh my_wrapper_script.sh
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CMD ./my_wrapper_script.sh
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```
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# Start the second process
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./my_second_process &
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- If you have one main process that needs to start first and stay running but
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you temporarily need to run some other processes (perhaps to interact with
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the main process) then you can use bash's job control to facilitate that.
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First, the wrapper script:
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# Wait for any process to exit
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wait -n
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```bash
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#!/bin/bash
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# turn on bash's job control
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set -m
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# Start the primary process and put it in the background
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./my_main_process &
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# Start the helper process
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./my_helper_process
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# the my_helper_process might need to know how to wait on the
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# primary process to start before it does its work and returns
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# now we bring the primary process back into the foreground
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# and leave it there
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fg %1
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```
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# Exit with status of process that exited first
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exit $?
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```
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```dockerfile
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# syntax=docker/dockerfile:1
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FROM ubuntu:latest
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COPY my_main_process my_main_process
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COPY my_helper_process my_helper_process
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COPY my_wrapper_script.sh my_wrapper_script.sh
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CMD ./my_wrapper_script.sh
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```
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Next, the Dockerfile:
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- Use a process manager like `supervisord`. This is a moderately heavy-weight
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approach that requires you to package `supervisord` and its configuration in
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your image (or base your image on one that includes `supervisord`), along with
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the different applications it manages. Then you start `supervisord`, which
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manages your processes for you. Here is an example Dockerfile using this
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approach, that assumes the pre-written `supervisord.conf`, `my_first_process`,
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and `my_second_process` files all exist in the same directory as your
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Dockerfile.
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```dockerfile
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# syntax=docker/dockerfile:1
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FROM ubuntu:latest
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COPY my_first_process my_first_process
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COPY my_second_process my_second_process
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COPY my_wrapper_script.sh my_wrapper_script.sh
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CMD ./my_wrapper_script.sh
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```
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```dockerfile
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# syntax=docker/dockerfile:1
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FROM ubuntu:latest
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RUN apt-get update && apt-get install -y supervisor
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RUN mkdir -p /var/log/supervisor
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COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf
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COPY my_first_process my_first_process
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COPY my_second_process my_second_process
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CMD ["/usr/bin/supervisord"]
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```
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## Use Bash job controls
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If you have one main process that needs to start first and stay running but
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you temporarily need to run some other processes (perhaps to interact with
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the main process) then you can use bash's job control to facilitate that.
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First, the wrapper script:
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```bash
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#!/bin/bash
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# turn on bash's job control
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set -m
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# Start the primary process and put it in the background
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./my_main_process &
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# Start the helper process
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./my_helper_process
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# the my_helper_process might need to know how to wait on the
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# primary process to start before it does its work and returns
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# now we bring the primary process back into the foreground
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# and leave it there
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fg %1
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```
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```dockerfile
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# syntax=docker/dockerfile:1
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FROM ubuntu:latest
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COPY my_main_process my_main_process
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COPY my_helper_process my_helper_process
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COPY my_wrapper_script.sh my_wrapper_script.sh
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CMD ./my_wrapper_script.sh
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```
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## Use a process manager
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Use a process manager like `supervisord`. This is a moderately heavy-weight
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approach that requires you to package `supervisord` and its configuration in
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your image (or base your image on one that includes `supervisord`), along with
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the different applications it manages. Then you start `supervisord`, which
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manages your processes for you. Here is an example Dockerfile using this
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approach, that assumes the pre-written `supervisord.conf`, `my_first_process`,
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and `my_second_process` files all exist in the same directory as your
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Dockerfile.
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```dockerfile
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# syntax=docker/dockerfile:1
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FROM ubuntu:latest
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RUN apt-get update && apt-get install -y supervisor
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RUN mkdir -p /var/log/supervisor
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COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf
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COPY my_first_process my_first_process
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COPY my_second_process my_second_process
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CMD ["/usr/bin/supervisord"]
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```
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