This Terraform module will create an Amazon ElastiCache for Redis cluster for use on the Cloud Platform.

module "redis" {
  source = "github.com/ministryofjustice/cloud-platform-terraform-elasticache-cluster?ref=version" # use the latest release

  # VPC configuration
  vpc_name = var.vpc_name

  # Redis cluster configuration
  node_type               = "cache.t4g.micro"
  engine_version          = "7.0"
  parameter_group_name    = "default.redis7"
  auth_token_rotated_date = "2023-08-30"

  # Tags
  business_unit          = var.business_unit
  application            = var.application
  is_production          = var.is_production
  team_name              = var.team_name
  namespace              = var.namespace
  environment_name       = var.environment
  infrastructure_support = var.infrastructure_support
}

See the examples/ folder for more information.

Your redis instance is reachable only from inside the cluster VPC, but you can use the same technique to access it from your development environment as for accessing an RDS instance

1. Run a port-forward pod

kubectl \
  -n [your namespace] \
  run port-forward-pod \
  --generator=run-pod/v1 \
  --image=ministryofjustice/port-forward \
  --port=6379 \
  --env="REMOTE_HOST=[your redis cluster hostname]" \
  --env="LOCAL_PORT=6379" \
  --env="REMOTE_PORT=6379"

2. Forward local traffic to the port-forward-pod

kubectl \
  -n [your namespace] \
  port-forward \
  port-forward-pod 6379:6379

You need to leave this running as long as you are accessing the redis cluster.

3. Use the ruby redis client to access redis

At the time of writing, the redis-cli command-line tool cannot use encrypted redis connections (i.e. those with a URL starting rediss://... as opposed to redis://...). So, this section describes how to use the redis ruby gem to connect to your elasticache cluster.

export REDIS_URL=[modified URL from namespace secret]

The value here should be the redis URL from your namespace secret, but with the hostname replaced with localhost

For instance, if the redis URL in your namespace secret is this:

url: rediss://dummyuser:6a36be5513564382b436b36be55e15a5@master.cp-8f56be55d06be5548.iwfvzo.euw2.cache.amazonaws.com:6379

...then the value you need for REDIS_URL is:

rediss://dummyuser:6a36be5513564382b436b36be55e15a5@localhost:6379

Then you can use the ruby redis client like this:

ruby -r redis -e 'redis = Redis.new(uri: ENV.fetch("REDIS_URL")); redis.set("foo", 123); puts redis.get("foo")'

No modules.

Some of the inputs for this module are tags. All infrastructure resources must be tagged to meet the MOJ Technical Guidance on Documenting owners of infrastructure.

You should use your namespace variables to populate these. See the Usage section for more information.

• Cloud Platform user guide
• Amazon ElastiCache for Redis user guide
• Redis documentation