Chef for Rails and Mongo

The goal of this example is to have a "rolling restart" capable base system for Rails apps with Mongodb backends.

Target system

• Ubuntu 11.04 Natty
• Ruby 1.9.2-p290
• Nginx 1.0.6
• Mongodb 2.0.0
• Unicorn
• Rails 3.1

To install the latest ruby, it will help to have a .deb package available. I followed the instructions here. I also packaged nginx 1.0.6 according to these instructions.

I created the Ruby and Nginx cookbooks from scratch because they were relatively easy. Mostly they just copy the cookbook file .deb package to /tmp and then install.

For MongoDB, I used the Opscode community cookbook:

knife cookbook site vendor mongodb

I had to modify it to work with Ubuntu's Upstart system. Wherever there was a service block in the cookbook files I added this line inside the block:

provider Chef::Provider::Service::Upstart

Later, the recipe was getting stuck with adding the PPA repo so I decided to include the .deb file.

The Unicorn cookbook is relatively simple so I vendored it as well:

knife cookbook site vendor unicorn

The Rails cookbook was built from scratch. It includes configuration for both nginx and unicorn. See roles/chef-rails-mongo.rb and data_bags/apps/chef-rails-mongo.json for an example role and data bag that will provide a working Rails app.

Provision

Assuming a properly configured knife.rb and the proper keys for AWS and Chef Server, you can simply run a command like this:

knife ec2 server create --node-name chef-rails-mongo --groups single_instance_production --image ami-e2af508b --flavor m1.small --distro ubuntu11.04-apt --ssh-key keyname -i ~/.ec2/keyname -x ubuntu --environment production --run-list 'role[base],role[mongodb],role[chef-rails-mongo]'

Be sure you have an EC2 security group named single_instance_production with ports 22 (SSH) and 80 (HTTP) opened.

Deploy

To redeploy the app after pushing to the app repo you can do this:

knife ssh name:chef-rails-mongo "sudo chef-client" -a ec2.public_hostname -i ~/.ec2/keyname -x ubuntu

Cleanup

You can easily get rid of all those branches created by knife like so:

git branch -D `git for-each-ref --format="%(refname:short)" refs/heads/chef-vendor\*`

TO-DO

• Configure a monitoring service such as bluepill or Monit.
• Set up automated backup to S3
• Postfix or other mail service