terraform-consul-cluster

This repo demonstrates how to create a resilient Consul cluster running on AWS, using Terraform. It is the companion project to my article 'Creating a Resilient Consul Cluster for Docker Microservice Discovery with Terraform and AWS'.

Prerequisites

Please install the following components:

Docker
Terraform - brew update && brew install terraform.

You must also have an AWS account. If you don't, this cluster will run happily on the AWS Free Tier which only takes ten minutes to sign up with.

You will need to set up your AWS credentials. The preferred way is to install the AWS CLI and quickly run aws configure:

$ aws configure
AWS Access Key ID [None]: <Enter Access Key ID>
AWS Secret Access Key [None]: <Enter Secret Key>
Default region name [None]: ap-southeast-1
Default output format [None]:

This will keep your AWS credentials in the $HOME/.aws/credentials file, which Terraform can use. This and all other options are documented in the Terraform: AWS Provider documentation.

Creating the Cluster

The cluster is implemented as a Terraform Module. To launch, just run:

# Create the module.
terraform get

# See what we will create, or do a dry run!
terraform plan

# Create the cluster!
terraform apply

You will be asked for a region to deploy in, use us-east-1 should work fine! You can configure the nuances of how the cluster is created in the main.tf file. Once created, you will see a message like:

$ terraform apply
var.region
  Region to deploy the Consul Cluster into

  Enter a value: ap-southeast-1

...

Apply complete! Resources: 20 added, 0 changed, 0 destroyed.

...

Outputs:

consul-dns = consul-lb-1577031185.ap-southeast-1.elb.amazonaws.com

Navigate to port 8500 at address provided (e.g. http://consul-lb-1577031185.ap-southeast-1.elb.amazonaws.com:8500) and you will see the Consul interface.

Destroying the Cluster

Bring everything down with:

terraform destroy

Project Structure

The module has the following structure:

main.tf                   # Cluster definition.
variables.tf              # Basic config.
modules/consul/main.tf    # Main cluster setup.
modules/consul/variables.tf    # Inputs for the module.
modules/consul/outputs.tf # Outputs for the module.
modules/consul/01-vpc.tf  # Network configuration. Defines the VPC, subnets, access etc.
modules/consul/02-consul-node-role.tf  # Defines policies and a role for cluster nodes.
modules/consul/files/consul-node.sh # Setup script for the cluster nodes.
example-service/          # A goofy example microservice used to test the project.
article/                  # The text and images for the article on dwmkerr.com

More info

A detailed write up of how this code works is available at:

http://www.dwmkerr.com/creating-a-resilient-consul-cluster-for-docker-microservice-discovery-with-terraform-and-aws/

Troubleshooting

Trying to plan or apply gives the error No valid credential sources found for AWS Provider.

This means you've not set up your AWS credentials - check the Prerequisites section of this guide and try again, or check here: https://www.terraform.io/docs/providers/aws/index.html.

EntityAlreadyExists: Role with name consul-instance-role already exists.

'Already exists' errors are not uncommon with Terraform, due to the fact that some AWS resource creation can have timing or synchronisation issues. In this case, just try to create again with terraform apply.

Contributors

arehmandev - Felt inspired by this project and ended up modularising it!

Tested 11/01/17, terraform 0.8.3

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