39. Docker Constrainr and Label
Example 1: Run replicas only on worker nodes.
docker service create --name mynginx_worker --constraint node.role==worker --replicas 4 nginx
docker service ps mynginx_worker
Example 2: Run replicas on a particular node.
docker node ls
docker node update --label-add mynode=node1 [name of the node1]
docker node update --label-add mynode=node2 [name of the node2]
docker service create --name mynginx_node1 --constraint node.labels.mynode==node1 --replicas 3 nginx
docker service ps mynginx_node1
docker service create --name mynginx_node2 --constraint node.labels.mynode!=node1 --constraint node.role==worker --replicas 2 nginx
docker service ps mynginx_node2
Example 3: Spread the tasks evenly across all nodes having label as mynode.
docker service create --name mynginx_spread --placement-pref spread=node.label.mynode --constraint node.role==worker --replicas 2 nginx
docker service ps mynginx_spread
