How to implement Docker container self-start

Container auto-start

Docker provides a restart policy mechanism that can control the container to automatically start when the container exits or Docker is restarted. This Restart policy ensures that related containers are started in the correct order. Although this action can also be accomplished through process monitoring (such as systemd), Docker still recommends avoiding the use of process monitoring to "self-start" containers.

There is a difference between Docker's Restart policy and the --live-restore startup flag of the dockerd command: the --live-restore flag ensures that the container continues to run when Docker is upgraded, but the network and user terminal input will be interrupted.

So what exactly is a restart policy? Let's take a look at the actual situation.

Using restart policy

The restart policy is specified by the --restart flag when starting the container using docker run. This flag has multiple values ​​​​to choose from, and different values ​​​​have different behaviors, as listed in the following table:

For example: The following command starts a Redis container. When the Redis container is stopped or Docker is restarted, the Redis container will be restarted.

$ docker run -dit --restart unless-stopped redis

Restart policy details

When using restart policies, you need to pay attention to the following details:

(1) The restart policy takes effect only after the container is successfully started. "Successful start" here means that the container has been up for at least 10 seconds and has been supervised by Docker. This is to prevent containers that have not been successfully started from falling into an endless loop of restarting.

(2) If you manually stop a container (what is the difference from explicitly stopped above), the restart policy set for the container will be ignored unless the Docker daemon is restarted or the container is manually restarted. This avoids another vicious cycle.

(3) Restart policies can only be used for containers. For swarm services, restart policies have invalid configurations.

Process Monitoring

If the restart policies mentioned above cannot meet your needs, you can also use process monitoring management solutions, such as upstart, systemd or supervisor, etc.

In this solution, the process monitoring service runs in the container. It can monitor whether a process is running and can start the process if it is not running. Docker is completely unaware of all this happening.

Docker does not recommend this method for process monitoring. The reason is simple. This method is related to the system platform and even the Linux distribution.

Original: https://docs.docker.com/engine/admin/start-containers-automatically/#use-a-process-manager

Docker container automatically starts at boot

When starting the container with docker run, use the --restart parameter to set:

# docker run -m 512m --memory-swap 1G -it -p 58080:8080 --restart=alway

 --name bvrfis --volumes-from logdata mytomcat:4.0 /root/run.sh   

--restart specific parameter value details:

• no - when the container exits, do not restart the container;
• on-failure - restart the container only if it exits with a non-zero status;
• always - restart the container regardless of the exit status;

You can also specify the maximum number of times Docker will attempt to restart the container when using the on-failure strategy. By default, Docker will try to restart containers forever.

# sudo docker run --restart=on-failure:10 redis

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