The public documentation for the gruntwork-io/module-cache repo, which contains packages for running Redis or Memcached distributed cache clusters using Amazon’s ElastiCache Service
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README.md

Note: This public repo contains the documentation for the private GitHub repo https://github.com/gruntwork-io/module-cache. We publish the documentation publicly so it turns up in online searches, but to see the source code, you must be a Gruntwork customer. If you're already a Gruntwork customer, the original source for this file is at: https://github.com/gruntwork-io/module-cache/blob/master/README.md. If you're not a customer, contact us at info@gruntwork.io or http://www.gruntwork.io for info on how to get access!

Cache Modules

This repo contains modules for running Redis and Memcached distributed cache clusters using Amazon’s ElastiCache Service:

  • redis: Deploy an Elasticache redis cluster.
  • memcached: Deploy an ElastiCache memcached cluster.

What is a Gruntwork Module?

At Gruntwork, we've taken the thousands of hours we spent building infrastructure on AWS and condensed all that experience and code into pre-built packages or modules. Each module is a battle-tested, best-practices definition of a piece of infrastructure, such as a VPC, ECS cluster, or an Auto Scaling Group. Modules are versioned using Semantic Versioning to allow Gruntwork clients to keep up to date with the latest infrastructure best practices in a systematic way.

How do you use a Gruntwork Module?

Most of our modules contain either:

  1. Terraform code
  2. Scripts & binaries

Using a Terraform module

To use a module in your Terraform templates, create a module resource and set its source field to the Git URL of this repo. You should also set the ref parameter so you're fixed to a specific version of this repo, as the master branch may have backwards incompatible changes (see module sources).

For example, to use v1.0.8 of one of the data-cache modules, you would add the following:

module "redis_prod" {
  source = "git::git@github.com:gruntwork-io/module-cache.git//modules/redis?ref=v1.0.8"

  // set the parameters for the redis module
}

Note: the double slash (//) is intentional and required. It's part of Terraform's Git syntax (see module sources).

See the module's documentation and vars.tf file for all the parameters you can set. Run terraform get -update to pull the latest version of this module from this repo before running the standard terraform plan and terraform apply commands.

NOTE: To automatically enforce terraform best practices, we recommend using terragrunt.

Using scripts & binaries

You can install the scripts and binaries in the modules folder of any repo using the Gruntwork Installer. For example, if the scripts you want to install are in the modules/ecs-scripts folder of the https://github.com/gruntwork-io/module-ecs repo, you could install them as follows:

gruntwork-install --module-name "ecs-scripts" --repo "https://github.com/gruntwork-io/module-ecs" --tag "0.0.1"

See the docs for each script & binary for detailed instructions on how to use them.

What is ElastiCache?

Elasticache is Amazon's implementation of a best-practices setup for two popular caching engines, memcached and redis. It allows for easy establishment of a redundant caching cluster, backup and restore (redis only), and other popular features.

You pay a moderate premium over running the services yourself and everything is pre-configured for you.

Developing a module

Versioning

We are following the principles of Semantic Versioning. During initial development, the major version is to 0 (e.g., 0.x.y), which indicates the code does not yet have a stable API. Once we hit 1.0.0, we will follow these rules:

  1. Increment the patch version for backwards-compatible bug fixes (e.g., v1.0.8 -> v1.0.9).
  2. Increment the minor version for new features that are backwards-compatible (e.g., v1.0.8 -> 1.1.0).
  3. Increment the major version for any backwards-incompatible changes (e.g. 1.0.8 -> 2.0.0).

The version is defined using Git tags. Use GitHub to create a release, which will have the effect of adding a git tag.

Tests

See the test folder for details.

License

Please see LICENSE.txt for details on how the code in this repo is licensed.