How do I check that a docker host is in swarm mode?
To check general swarm membership, my preferred method is to use the formatted output from docker info
. The possible values of this are currently inactive, pending, active, locked, and error:
case "$(docker info --format '{{.Swarm.LocalNodeState}}')" in
inactive)
echo "Node is not in a swarm cluster";;
pending)
echo "Node is not in a swarm cluster";;
active)
echo "Node is in a swarm cluster";;
locked)
echo "Node is in a locked swarm cluster";;
error)
echo "Node is in an error state";;
*)
echo "Unknown state $(docker info --format '{{.Swarm.LocalNodeState}}')";;
esac
To check for manager status, rather than just a node in a cluster, the field you want is .Swarm.ControlAvailable
:
docker info --format '{{.Swarm.ControlAvailable}}'
That will output "true" for managers, and "false" for any node that is a worker or not in a swarm.
To identify worker nodes, you can join to two:
if [ "$(docker info --format '{{.Swarm.LocalNodeState}}')" = "active" \
-a "$(docker info --format '{{.Swarm.ControlAvailable}}')" = "false" ]; then
echo "node is a worker"
else
echo "node is not a worker"
fi
You could also use docker info
to see the result of Swarm
property (inactive
or active
).
For example:
function isSwarmNode(){
if [ "$(docker info | grep Swarm | sed 's/Swarm: //g')" == "inactive" ]; then
echo false;
else
echo true;
fi
}
I don't have a swarm node handy at the moment, but it looks as if you could simply run something like docker node ls
. When targeting a docker daemon that is not in swarm node, that results in:
Error response from daemon: This node is not a swarm manager. Use "docker swarm init" or "docker swarm join" to connect this node to swarm and try again.
And it returns a nonzero exit code
$ echo $?
1
So the test would look something like:
if docker node ls > /dev/null 2>&1; then
echo this is a swarm node
else
echo this is a standalone node
fi