Docker Swarm health check example
This example shows how health check works in Docker Swarm and how it heals the service.
What does this container do?
Container runs a nginx server and it also runs a script which writes a
/usr/share/nginx/html/status file on every odd run which is then
picked by the health check that expects
alive status from the nginx running
in the container.
So every odd run the container gets
Then you can observe that running this container in Docker Engine alone will
not restart it. Hence we will run it as a service in the Docker Swarm which
will ensure the container gets restarted until it gets
docker build -t healthcheck-test .
Setting up env
Make sure you have recent Docker Engine installed.
docker swarm init
Running the service
docker service create \ --name test1 \ --mount type=bind,src=/tmp,dst=/usr/share/nginx/html \ --detach healthcheck-test
Watching the health check
First, the container will start in
unhealthy mode as expected, health check
will pick this and Docker Swarm will restart that container which then will
start in a
docker ps |grep test1 docker service ls
docker service rm test1 docker swarm leave --force sudo rm -f -- /tmp/status docker rmi healthcheck-test
If you want to restart the container manually, you need to downscale it to 0 first and then upscale it back again.
docker service scale test1=0 docker service scale test1=1