How do I know when my docker mysql container is up and mysql is ready for taking queries?

Question

I am deploying a few different docker containers, mysql being the first one. I want to run scripts as soon as database is up and proceed to building other containers. The sc

Answer 1

This was more or less mentioned in comments to other answers, but I think it deserves its own entry.

First of all you can run your container in the following manner:

docker run --name mysql --health-cmd='mysqladmin ping --silent' -d mysql

There is also an equivalent in the Dockerfile.

With that command your docker ps and docker inspect will show you health status of your container. For mysql in particular this method has the advantage of mysqladmin being available inside the container, so you do not need to install it on the docker host.

Then you can simply loop in a bash script to wait on the status to become healthy. The following bash script is created by Dennis.

function getContainerHealth {
  docker inspect --format "{{.State.Health.Status}}" $1
}

function waitContainer {
  while STATUS=$(getContainerHealth $1); [ $STATUS != "healthy" ]; do 
    if [ $STATUS == "unhealthy" ]; then
      echo "Failed!"
      exit -1
    fi
    printf .
    lf=$'\n'
    sleep 1
  done
  printf "$lf"
}

Now you can do this in your script:

waitContainer mysql

and your script will wait until the container is up and running. The script will exit if the container becomes unhealthy, which is possible, if for example docker host is out of memory, so that the mysql cannot allocate enough of it for itself.