Graeme Matthieson: Automate All The Things
Graeme Matthieson (@mathie) was talking about building your development and production environments with vagrant and puppet at Whisky Web II, these are my notes from his talk.
- Apply configuration quickly
- Handles dependencies
- Applies configuration consistently
- Mimic production in staging - especially useful for QA testing
- Mimic production in development
This makes it very easy to test scenarios at any stage of developement and release cycle and reliably apply.
- Up front effort - can take time to set up (days)
- You have to be much more rigorous - one mistake goes everywhere
(In the order I tried them)
- LCFG: Local configuration system. Now LCFG2 and still actively maintained.
- CFEngine: 1983, one of the first open source systems and still actively developed. Theoretically very good.
- Puppet: Spawned from frustration with CFEngine, written in Ruby. Thick server - thin client.
- Chef: All the cool kids like this. Spawned from frustration with Puppet. Thin server - thick client.
All have their pros and cons.
Vagrant is kind of neat. Turned up in the last two years and started as a way of manging Virtual Box VMs. Now supports different VM providers including AWS.
Controlled through a vagrantfine which is pure Ruby.
- Start with a very basic install with next to no config.
- Create network configs including port forwarding.
- Share folders between host and VM.
- Provisioning (Puppet or Chef): use the shell to run commands using shell scripts it uploads.
- Multiple views: Can run multiple VMs to model an entire production environment.
- Vagrant config is Ruby: You can use Ruby to do things.
- Manage the cluster: Boot, Destroy, Pause, Resume, SSH.
This is the awkward bit, you are starting with a new machine with nothing on it. Gets as far as being able to run the Puppet agent.
- Set the host name
- Set the Puppet master's IP address so we don't need DNS
- Install Puppet - latest stable, some distros are quite out of date
- Get the Puppet repository
- Run Puppet apply to load a minimal configuration from a local file that lets it talk to the master
- The nodes then get their configuration from the Puppet master
The node tells the Puppet system what it's supposed to do - i.e. what type of server this is: app, database, &c.
Classes can be used to group configurations of nodes.
Groups of classes are modules that then provide a service. Can define which modules and versions to install and how to configure them. Can get complex if you try to generalise them across multiple platforms.
This is what Puppet can manage.
- Ensure they're running
- Install or remove
- Manage versions
- What ever you can think of and code
There are providers for each system that will abstract the operating system away from the config. It's not perfect as package names can vary for the same thing which require conditionals in the config.
Puppet at work
Puppet master provides information to Puppet clients that run a service that checks the master periodically over SSL connections. The Puppet master compiles the list of information that a client needs so it only gets the minimum it needs. Once it has a configuration it checks to see if it has changed since last time and, if so, runs the changes.