Read more in docker-compose documentation and docker documentation.

2: reserved - do not use this exit code.

1: unhealthy - the container is not working correctly.

0: success - the container is healthy and ready for use.

The command’s exit status indicates the health status of the container. healthcheck CMD /bin/check-running) or an exec array (as with other Dockerfile commands). The command after the CMD keyword can be either a shell command (e.g. If you list more than one then only the last healthcheck will take effect. There can only be one healthcheck instruction in a Dockerfile. However, if a health check succeeds during the start period, the container is considered started and all consecutive failures will be counted towards the maximum number of retries. Probe failure during that period will not be counted towards the maximum number of retries. Start period provides initialization time for containers that need time to bootstrap.

It takes retries consecutive failures of the health check for the container to be considered unhealthy. If a single run of the check takes longer than timeout seconds then the check is considered to have failed. The health check will first run interval seconds after the container is started, and then again interval seconds after each previous check completes. After a certain number of consecutive failures, it becomes unhealthy.

Whenever a health check passes, it becomes healthy (whatever state it was previously in). When a container has a healthcheck specified, it has a health status in addition to its normal status. This can detect cases such as a web server that is stuck in an infinite loop and unable to handle new connections, even though the server process is still running. The healthcheck instruction tells Docker how to test a container to check that it is still working. Healthcheck configures a check that’s run to determine whether or not containers for this service are “healthy”.

It is not exactly what it is supposed to be used for, but we can make it work for us just as well. One of the possible ways of doing it is using the healthcheck configuration option. This can be done manually once the container has properly started, but it would be even better if our docker-compose.yml could do it itself automatically when starting up the containers. In short, to run a MongoDB server as a replica set, two things are necessary - start the mongod daemon with -replSet parameter (more on it below), and initiate the replica set using rs.initiate() command. This one merits a longer background story. MONGO_INITDB_ROOT_USERNAME: $ -quiet) -eq 1 docker/mongodb/data/log/:/var/log/mongodb/

docker/mongodb/initdb.d/:/docker-entrypoint-initdb.d/ Related: MongoDB container with Docker Compose // docker-compose.yml

How to start mongodb server on bash