Vagrant Multimachine With Ansible

Alternative title: How to stop ansible.limit and enjoy parallel provisioning.

I use Vagrant and Ansible together almost every day for creating quick development environments. It's a really powerful combo, but Vagrant with Virtualbox does not support parallel provisioning.

Basically, if you don't optimize anything, it's painfully slow to make multimachine environments. Here's a couple tricks to use parallel Ansible provisioning with Virtualbox!

Setting Up the Vagrantfile

Recently, I've been using Multimachine to provision a local Kubernetes cluster using kubeadm for experimenting and hacking on. The same techniques will work if you're just creating, say, a web and database server.

Regardless of what you are building, your starter Vagrantfile probably looks something like this:

# Vagrantfile

Vagrant.configure("2") do |config|
  config.vm.box = 'ubuntu/bionic64'
  config.vm.define :master do |master|
    master.vm.network = "private_network", ip: "192.168.10.33"
    master.vm.hostname = "k8s-master"
  end
  config.vm.define :node do |node|
    node.vm.network = "private_network", ip: "192.168.10.34"
    node.vm.hostname = "k8s-node"
  end
end

We have two machines here set up on a private network, both based on the ubuntu/bionic64 image. Running vagrant up at this point will spin them both up, but we haven't included Ansible yet. Thankfully, just adding Ansible is pretty easy!

Adding Ansible

Your project directory can be arranged however you'd like. Mine usually looks like this for starters:

.
├── ansible
│   ├── playbook.yml
│   └── roles
│       └── base
│           └── tasks
│               └── main.yml
└── Vagrantfile

5 directories, 4 files

Now we have to make some edits to the Vagrantfile, and this is where it gets interesting.

Vagrant does a fair bit of magic to create Ansible host files, build groups for all machines, and run the provisioner on only the active machine. With a single node setup, this magic does the right thing... and on multiple machines it runs them all in series.

We can tell Vagrant to do the right thing, however (with a little bit of a hack):

# Vagrantfile

Vagrant.configure("2") do |config|
  config.vm.box = 'ubuntu/bionic64'
  config.vm.define :master do |master|
    master.vm.network = "private_network", ip: "192.168.10.33"
    master.vm.hostname = "k8s-master"

    # Here's our counterspell for Vagrant's magic
    master.vm.provision :k8s, type: "ansible", run: "never" do |ansible|
      ansible.compatibility_mode = "2.0"
      ansible.limit = "all"
      ansible.extra_vars = { ansible_python_interpreter:"/usr/bin/python3" }
      ansible.playbook = "ansible/playbook.yml"
    end
  end
  config.vm.define :node do |node|
    node.vm.network = "private_network", ip: "192.168.10.34"
    node.vm.hostname = "k8s-node"
  end
end

We've added a named provisioner for creating Kubernetes clusters. By setting ansible.limit to all, Vagrant does the right thing and provisions all the machines from the auto generated hosts file.

This provisioner is using run: "never" because we want to wait for all machines to be up. Once all machines are active from vagrant up, you can provision them all at once with vagrant provision --provision-with k8s. Cool right?

Finally, the provisioner is put in the master node because if it was placed in the top level, it would run multiple times, and that's probably not what anyone wants.

Using Ansible Groups

More than likely you need to run different provisioning steps for each machine. Adding Ansible groups into our Vagrantfile is straightforward:

# Modify your ansible provisioner
master.vm.provision :k8s, type: "ansible", run: "never" do |ansible|
  ansible.compatibility_mode = "2.0"
  ansible.limit = "all"
  ansible.extra_vars = { ansible_python_interpreter:"/usr/bin/python3" }

  # Groups here
  ansible.groups = {
    "masters" => ["master"],
    "workers" => ["node"],
  }
  ansible.playbook = "ansible/playbook.yml"
end

Now you can group your tasks in Ansible, just like you would in a regular playbook!

---
# ansible/playbook.yml

- name: Stuff for All Machines
  hosts: all
  remote_user: vagrant
  tasks:
    - base

- name: Stuff for Master Machines
  hosts: masters
  remote_user: vagrant
  tasks:
    - master

You're all set up! Just to recap, to create your machines, run:

vagrant up
vagrant provision --provision-with ansible

Ansible will run in parallel on all of your machines, just like it's designed to.

Conclusions and Further Reading

There is a lot of information around the web on using Ansible and Vagrant effectively:

• The Ansible Documentation is comprehensive and useful when writing new playbooks.
• The Vagrant Documentation has a section on Vagrant-Ansible specifc options and tips for effective usage.
• And if you've never used Vagrant, there is a great guide at the documentation too.

I hope you found this quick tip helpful! Please feel free to contact me if you have any questions or feedback!