Go to Play with Docker. You need 2 Instances.
Init your swarm:
docker swarm init --advertise-addr $(hostname -i)
Copy the join command (watch out for newlines) output and paste it in the other terminal.
Show members of swarm Type the below command in the first terminal:
docker node ls
That last line will show you a list of all the nodes, something like this:
ID HOSTNAME STATUS AVAILABILITY MANAGE
R STATUS
kytp4gq5mrvmdbb0qpifdxeiv * node1 Ready Active Leader
lz1j4d6290j8lityk4w0cxls5 node2 Ready Active
If you try to execute an administrative command in a non-leader node worker, you’ll get an error. Try it here:
docker node ls
Creating services The next step is to create a service and list out the services. This creates a single service called web that runs the latest nginx, type the below commands in the first terminal:
docker service create -p 80:80 --name web nginx:latest
docker service ls
You can check that nginx is running by executing the following command:
curl http://localhost:80
Scaling up We will be performing these actions in the first terminal. Next let’s inspect the service:
docker service inspect web
That’s lots of info! Now, let’s scale the service:
docker service scale web=15
Docker has spread the 15 services evenly over all of the nodes
docker service ps web
Updating nodes You can also drain a particular node, that is remove all services from that node. The services will automatically be rescheduled on other nodes.
docker node update --availability drain node2
docker service ps web
You can check out the nodes and see that node2 is still active but drained.
docker node ls
Scaling down You can also scale down the service
docker service scale web=10
Lets check our service status
docker service ps web
Now bring node2 back online and show it’s new availability
docker node update --availability active node2
docker node inspect node2 --pretty