Building Swarm Mode on a PC or Mac

This guide exemplifies 5 VMs created with Vagrant and configured with Ansible, however one can use Docker Swarm Mode with Docker-Machine (https://docs.docker.com/machine/) as well.

Table of Contents

• Building Swarm Mode on a PC or Mac
  • Table of Contents
    • 1. Prerequisites
  • Virtualbox, Vagrant and Ansible
  • Preparing the environment
    • 2. Create the Swarm
  • Create the cluster from node1:
  • Adding nodes to the Swarm
    • 3. Building and pushing your own stack services with Compose file
  • Inspecting stacks
  • Scaling up services (e.g. ElasticSearch)

1. Prerequisites

Virtualbox, Vagrant and Ansible

• Virtualbox: https://www.virtualbox.org/wiki/Downloads

• Vagrant: https://www.vagrantup.com/downloads.html

  • install vagrant-vbguest plugin (https://github.com/dotless-de/vagrant-vbguest)

• Ansible:

  • install PIP and Ansible's prerequisites:

      sudo easy_install pip
      sudo pip install paramiko PyYAML Jinja2 httplib2 six pycrypto
    

  • Install Ansible:

    sudo pip install ansible
    

  • source the setup script to make Ansible available on this terminal session:

    source path/to/your-ansible-clone/hacking/env-setup
    

  • the last step needs to be repeated every time new terminal session is open and want to use any Ansible command (but you'll probably only need to run it once).

Preparing the environment

Download the Vagrant, Ansible, and SSH config files from https://github.com/ATTX-project/platform-deployment/tree/feature-swarm-mode/swarm-mode.

Run the following commands:

vagrant up
chmod 600 private-key
ansible-playbook provisioning.yml

Now you should be able to ssh on node1 using:

ssh vagrant@10.10.10.10 -i private-key

These are the default IP addresses for the nodes:

    10.10.10.10 node1
    10.10.10.20 node2
    10.10.10.30 node3
    10.10.10.40 node4
    10.10.10.50 node5

2. Create the Swarm

Reference: https://docs.docker.com/engine/swarm/swarm-tutorial/

The cluster is initialised with docker swarm init, executed on a first, seed node.

DO NOT execute docker swarm init on multiple nodes (possibility of multiple disjoint clusters).

Create the cluster from node1:

docker swarm init

Checking that Swarm mode is enabled

Run the docker info command:

docker info

The output should include:

Swarm: active
NodeID: 8jud7o8dax3zxbags3f8yox4b
Is Manager: true
ClusterID: 2vcw2oa9rjps3a24m91xhvv0c
...

When running in Swarm mode, each node advertises its address to the others (i.e. it tells them "you can contact me on 10.1.2.3:2377"). If the node has only one IP address (other than 127.0.0.1) it is used automatically, otherwise, you must specify which one to use (Docker refuses to pick one randomly)

• You can also specify an IP address or an interface name, and also a port number (otherwise, the default port 2377 will be used)

Example:

docker swarm init --advertise-addr eth1

Adding nodes to the Swarm

Show the worker token again:

docker swarm join-token worker

Switch to node2 and copy-paste the docker swarm join ... command with the token output that was displayed just before.

Switch back to node1 and display the cluster information (node1 is a manager):

docker node ls

The output should be similar to the following:

ID             HOSTNAME  STATUS  AVAILABILITY  MANAGER STATUS
8jud...ox4b *  node1     Ready   Active        Leader
ehb0...4fvx    node2     Ready   Active

To add more managers, display the manager token with docker swarm join-token manager from any manager node (e.g. node1), and copy-paste the output command to your desired node.

To add more workers, display the manager token with docker swarm join-token worker from any manager node (e.g. node1), and copy-paste the output command to your desired node

3. Building and pushing your own stack services with Compose file

Docker Compose can be directly used by a Swarm cluster through docker stack ... commands (New in Docker Engine 1.13), but it requires docker-compose YML version 3.

For example:

docker stack deploy my_stack --compose-file my_stack_file.yml

Inspecting stacks

docker stack ps shows the detailed state of all services of a stack, for example:

docker stack ps my_stack

Confirm that we get the same output with the following command:

docker service ps my_stack_mystack

Scaling up services (e.g. ElasticSearch)

Create an ElasticSearch service and scale it up with the replicas

docker service create --name ES --publish 9200:9200 --replicas 7 \
     elasticsearch:2

Monitor your new ElasticSearch service:

watch docker service ps search