The Docker Engine 1.12 includes a new feature known as swarm mode which allows the native management of a cluster of Docker Engines. This cluster of Docker Engines or nodes is known as a swarm. Swarm Mode allows you to orchestrate services across all the nodes in a swarm. This is useful for the scaling, load balancing, distribution and availability of your services.
This tutorial shows you how to easily set up Catalyst Cloud compute instances to use with the Getting started with swarm mode tutorial, available as part of the docker documentation.
This tutorial will use Ansible to create three swarm nodes that correspond to the examples used in the Docker tutorial. After running the playbook, you will have access to three hosts exactly as described in the tutorial. A cleanup playbook is provided to remove all resources when you have completed the tutorial.
This tutorial assumes a number of things:
You are interested in Docker Swarm Mode and wish to complete the tutorial.
You are familiar with basic usage of the Catalyst Cloud (e.g. you have created your first instance as described at Overview)
You have sourced an openrc file, as described at Source an openstack RC file
You have a basic understanding of how to use Ansible on the Catalyst Cloud as shown at Command line methods
Firstly you need to install Ansible as shown at Command line methods.
When Ansible is installed, you should change directory to the
example-playbooks/docker-swarm-mode directory within the
catalystcloud-ansible git checkout.
$ cd example-playbooks/docker-swarm-mode
We can now run the create-swarm-hosts.yaml playbook to create the swarm:
$ ansible-playbook --ask-sudo-pass create-swarm-hosts.yaml
After this playbook successfully completes, you are ready to complete the tutorial. As described in the tutorial setup instructions, it provides:
three networked host machines
Docker Engine 1.12 or later installed
the IP address of the manager machine
open ports between the hosts
Start the tutorial with the Create a swarm section. For example the first two commands are:
$ ssh manager1
$ docker swarm init --advertise-addr 192.168.99.100
Swarm initialized: current node (dxn1zf6l61qsb1josjja83ngz) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join \
--token SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7c \
192.168.99.100:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
Note
The tutorial uses docker-machine ssh, you should omit docker-machine from the command as we did not create these nodes using Docker machine. If you would prefer to use Docker machine to set up the nodes you can follow the tutorial at Using docker machine on the Catalyst Cloud.
When you have completed the tutorial you can remove the swarm and its
associated resources by running the remove-swarm-hosts.yaml playbook:
$ ansible-playbook --ask-sudo-pass remove-swarm-hosts.yaml