Docker Cookbook

202 | Chapter 7: The Docker Ecosystem: Tools

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$ docker-machine create -d digitalocean --swarm --swarm-discovery \
token://31e61710169a7d3568502b0e9fb09d66 worker-00
...
$ docker-machine create -d azure --swarm --swarm-discovery \
token://31e61710169a7d3568502b0e9fb09d66 swarm-worker-01
...
Your Swarm cluster is now ready. Your Swarm head node is running locally in a Vir‐
tualBox VM, one worker node is running in DigitalOcean, and another one in Azure.
You can set the local 
docker-machine
binary to use the head node running in Virtual‐
Box and start using the Swarm subcommands:
$ eval "$(docker-machine env --swarm head)"
$ docker info
Containers: 4
Nodes: 3
head: 192.168.99.103:2376
└ Containers: 2
└ Reserved CPUs: 0 / 4
└ Reserved Memory: 0 B / 999.9 MiB
worker-00: 45.55.160.223:2376
└ Containers: 1
└ Reserved CPUs: 0 / 1
└ Reserved Memory: 0 B / 490 MiB
swarm-worker-01: swarm-worker-01.cloudapp.net:2376
└ Containers: 1
└ Reserved CPUs: 0 / 1
└ Reserved Memory: 0 B / 1.639 GiB
Discussion
If you start a container, Swarm will schedule it in round-robin fashion on the cluster.
For example, you can start three Nginx containers in a 
for
loop:
$ for i in `seq 1 3`;do docker run -d -p 80:80 nginx;done
This leads to three Nginx containers on the three nodes in your cluster. Remember
that you will need to open port 80 on the instances running in the cloud to access the
container (e.g., see 
Recipe 8.6
):
$ docker ps
... IMAGE ... PORTS NAMES
... nginx:1.7 ... 443/tcp, 104.210.33.180:80->80/tcp swarm-worker-01/
loving_torvalds
... nginx:1.7 ... 443/tcp, 45.55.160.223:80->80/tcp worker-00/drunk_swartz
... nginx:1.7 ... 443/tcp, 192.168.99.103:80->80/tcp head/condescending_galileo