I'm just getting my feet wet with Docker Swarm because we're looking at ways to configure our compute cluster to make it more containerized. Basically we have a small farm of 16 computers and I'd like to be able to have each node pull down the same image, run the same container, and accept jobs from an OpenMPI program running on a master node.
Nothing is really OpenMPI specific about this, just that the containers have to be able to open SSH ports and the master must be able to log into them. I've got this working with a single Docker container and it works.
Now I'm learning Docker Machine and Docker Swarm as a way to manage the 16 nodes. From what I can tell, once I set up a swarm, I can then set it as the DOCKER_HOST (or use -H) to send a "docker run", and the swarm manager will decide which node runs the requested container. I got this basically working using a simple node list instead of messing with discovery services, and so far so good.
But I actually want to run the same container on all nodes in one command. Is this possible?
Docker 1.12 introduced global services and passing --mode global to run command Docker will schedule service to all nodes.
Using Docker Swarm you can use labels and negative affinity filters to gain the same result:
openmpi:
environment:
- "affinity:container!=*openmpi*"
labels:
- "com.myself.name=openmpi"