Chef Helpers

This cookbook handles configuring Elastic Load Balancers at AWS

Installation

The easiest way to install this is to use knife-github-cookbooks:

gem install knife-github-cookbooks
knife github cookbook install websterclay/chef-elb

Usage

This cookbook is designed to be run on a single node in your infrastructure. I have a role called the 'rooster' I assign to one node to coordinate AWS API calls based on the presence of other nodes.

Put recipe[elb] in the runlist of your coordinating node to install the required dependeicnes on that node. Then, in a recipe also in that node's runlist:

# Load your AWS credentials databag
aws = data_bag_item("aws", "main")

elb_load_balancer "http-frontend" do
  aws_access_key        aws['aws_access_key_id']
  aws_secret_access_key aws['aws_secret_access_key']
  search_query          "role:app"
  action :create
end

This will automatically create a Elastic Load Balancer that listens on port 80 and forwards requests to all servers that match the specified search on port 80. You can change those defaults by specifying the listeners attribute:

elb_load_balancer "http-frontend" do
  aws_access_key        aws['aws_access_key_id']
  aws_secret_access_key aws['aws_secret_access_key']
  search_query          "role:app"
  listeners             [{"InstancePort" => 8080, "Protocol" => "HTTP", "LoadBalancerPort" => 80}]
  action :create
end

You can also specify the region attribute to change what region the ELB is created in, or specify the instances manually if you don't want to use a search:

elb_load_balancer "ap-tcp-frontend" do
  aws_access_key        aws['aws_access_key_id']
  aws_secret_access_key aws['aws_secret_access_key']
  instances             ['i-xxxxx', 'i-xxxxx']
  region                'ap-southeast-1'
  listeners             [{"InstancePort" => 1234, "Protocol" => "TCP", "LoadBalancerPort" => 1234}]
  action :create
end

You can configure the health check parameters from the defaults by specifying the health_check attribute with a hash:

elb_load_balancer "ap-tcp-frontend" do
  aws_access_key        aws['aws_access_key_id']
  aws_secret_access_key aws['aws_secret_access_key']
  instances             ['i-xxxxx', 'i-xxxxx']
  region                'ap-southeast-1'
  listeners             [{"InstancePort" => 1234, "Protocol" => "TCP", "LoadBalancerPort" => 1234}]
  health_check          [{"HealthyThreshold" => 10, "Interval" => 30, "Target" => "HTTP:80/ping", "Timeout" => 5, "UnhealthyThreshold" =>2}]
  action :create
end

You can also do SSL, but it's a little funky.

First, you have to upload your cert.

Then setup your listeners array like so:

elb_load_balancer "http-and-https" do
  aws_access_key        aws['aws_access_key_id']
  aws_secret_access_key aws['aws_secret_access_key']
  search_query          "chef_environment:#{node.chef_environment} AND role:my_ssl_app"
  listeners             [
    {
      "InstancePort"     => 80,
      "Protocol"         => "HTTP",
      "LoadBalancerPort" => 80
    },
    {
      "InstancePort"     => 80,
      "Protocol"         => "HTTPS",
      "LoadBalancerPort" => 443,
      "SSLCertificateId" => "arn:aws:iam::xxxxxxxx:server-certificate/YourCertName"
    }
  ]
  action :create
end

This resource can't update the cert ID for you yet because of missing support in Fog - it will only do that on ELB creation, but you should update it to reflect reality.

Caveats

The cookbook automates determining what availability zones your instances are in and automatically registers the instances. ELB's distribute traffic equally between all enabled Availibity Zones. It's up to you to confirm that your instance distribution is equal if you have instances on more than one AZ.

Resources

ELB Docs

Author

Jesse Newland jesse@websterclay.com @jnewland jnewland on freenode

License

Author:: Jesse Newland (<jesse@websterclay.com>)
Copyright:: Copyright (c) 2011 Webster Clay, LLC
License:: Apache License, Version 2.0

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.