AWS Configuration

The AWS backend for the autocluster supports two different node discovery, Autoscaling Group membership and EC2 tags.

The following settings impact the behavior of the AWS backend. See the AWS API Credentials section below for additional settings.

Autoscaling

Cluster based upon membership in an Autoscaling Group. Set to true to enable.

EC2 Tags

Filter the cluster node list with the specified tags. Use a comma delimiter for multiple tags when specifying as an environment variable.

NOTE: If this is your first time setting up RabbitMQ with the autoscaling cluster and are doing so for R&D purposes, you may want to check out the gavinmroy/alpine-rabbitmq-autocluster Docker Image repository for a working example of the plugin using a CloudFormation template that creates everything required for an Autoscaling Group based cluster.

Details

Environment Variable	Setting Key	Type	Default
AWS_AUTOSCALING	aws_autoscaling	atom	false
AWS_EC2_TAGS	aws_ec2_tags	string()

Notes

If aws_autoscaling is enabled, the EC2 backend will dynamically determine the autoscaling group that the node is a member of and attempt to join the other nodes in the autoscaling group.

If aws_autoscaling is disabled, you must specify EC2 tags to use to filter the nodes that the backend should cluster with.

AWS API Configuration and Credentials

As with the AWS CLI, the autocluster plugin configures the AWS API requests by attempting to resolve the values in a number of steps.

The configuration values are discovered in the following order:

1. Explicitly configured in the autocluster configuration.
2. Environment variables
3. Configuration file
4. EC2 Instance Metadata Service (for Region)

The credentials values are discovered in the following order:

1. Explicitly configured in the autocluster configuration.
2. Environment variables
3. Credentials file
4. EC2 Instance Metadata Service

AWS Credentials and Configuration Settings

The following settings and environment variables impact the configuration and credentials behavior. For more information see the Amazon AWS CLI documentation.

Environment Variable	Setting Key	Type	Default
AWS_ACCESS_KEY_ID	aws_access_key	string
AWS_SECRET_ACCESS_KEY	aws_secret_key	string
AWS_DEFAULT_REGION	aws_ec2_region	string	us-east-1
AWS_DEFAULT_PROFILE	N/A	string
AWS_CONFIG_FILE	N/A	string
AWS_SHARED_CREDENTIALS_FILE	N/A	string

IAM Policy

If you intend to use the EC2 Instance Metadata Service along with an IAM Role that is assigned to EC2 instances, you will need a policy that allows the plugin to discover the node list. The following is an example of such a policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "autoscaling:DescribeAutoScalingInstances",
                "ec2:DescribeInstances"
            ],
            "Resource": [
                "*"
            ]
        }
    ]
}

Example Configuration

The following configuration example enables the autoscaling based cluster discovery and sets the EC2 region to us-west-2:

[
  {rabbit, [
    {log_levels, [{autocluster, info}, {connection, info}]}
  ]},
  {autocluster, [
    {backend, aws},
    {aws_autoscaling, true},
    {aws_ec2_region, "us-west-2"}
  ]}
].

For non-autoscaling group based clusters, the following configuration demonstrates how to limit EC2 instances in the cluster to nodes with the tags region=us-west-2 and service=rabbitmq. It also specifies the AWS access key and AWS secret key.

[
  {rabbit, [
    {log_levels, [{autocluster, info}, {connection, info}]}
  ]},
  {autocluster, [
    {backend, aws},
    {aws_ec2_tags, [{"region", "us-west-2"}, {"service", "rabbitmq"}]},
    {aws_ec2_region, "us-east-1"},
    {aws_access_key, "AKIDEXAMPLE"},
    {aws_secret_key, "wJalrXUtnFEMI/K7MDENG+bPxRfiCYEXAMPLEKEY"}
  ]}
].

When using environment variables, the tags must be provided in JSON format:

AWS_EC2_TAGS="{\"region\": \"us-west-2\",\"service\": \"rabbitmq\"}"

Example Cloud-Init

The following is an example cloud-init that was tested with Ubuntu Trusty for use with an Autoscaling Group:

#cloud-config
apt_update: true
apt_upgrade: true
apt_sources:
 - source: deb https://apt.dockerproject.org/repo ubuntu-trusty main
   keyid: 58118E89F3A912897C070ADBF76221572C52609D
   filename: docker.list
packages:
 - docker-engine
runcmd:
 - docker run -d --name rabbitmq --net=host -p 4369:4369 -p 5672:5672 -p 15672:15672 -p 25672:25672 gavinmroy/rabbitmq-autocluster