/**
* # Elasticache
*
* Deploy a test redis replication group and then in-place migrate to Valkey
*
* ## Migration steps (takes around 17m):
* 1. Backup existing instance. Note the version and parameter group
* 2. In the example resource below, change apply-immediately, engine, engine-version, and parameter group.
*
* ## When redis was initially deployed:
* primary_endpoint = "lab-cache001.rw4ynm.ng.0001.ape1.cache.amazonaws.com"
* reader_endpoint = "lab-cache001-ro.rw4ynm.ng.0001.ape1.cache.amazonaws.com"
*
* ## After in-place migration to Valkey:
* primary_endpoint = "lab-cache001.rw4ynm.ng.0001.ape1.cache.amazonaws.com"
* reader_endpoint = "lab-cache001-ro.rw4ynm.ng.0001.ape1.cache.amazonaws.com"
*
* ## Fallback
* Simply reverting the code below will result in a replacement of the replication group. Meaning
* fallback is not supported. One will need to deploy a new instance and restore from backup
*/

resource "aws_elasticache_replication_group" "example" {
  automatic_failover_enabled  = true
  preferred_cache_cluster_azs = ["ap-east-1a", "ap-east-1b"]
  replication_group_id        = "lab-cache001"
  description                 = "Redis to be migrated to Valkey"
  node_type                   = "cache.t4g.micro"
  num_cache_clusters          = 2
  cluster_mode                = "enabled"
  # -------- in-place migration to valkey -------- #
  # engine_version       = "7.1"
  # engine               = "redis"
  # parameter_group_name = "default.redis7.cluster.on"
  apply_immediately    = true
  engine               = "valkey"
  engine_version       = "8.2"
  parameter_group_name = "default.valkey8.cluster.on"
  # -------- in-place migration to valkey -------- #
  port              = 6379
  subnet_group_name = aws_elasticache_subnet_group.subnets.name
}

resource "aws_elasticache_subnet_group" "subnets" {
  description = "Lab subnet group"
  name        = "lab-subnetgroup001"
  subnet_ids  = ["subnet-0927ba1b06ccfe6c5", "subnet-0551e96ffd016192a"]
}

output "cluster_endpoint" {
  value = aws_elasticache_replication_group.example.configuration_endpoint_address
}

output "primary_endpoint" {
  value = aws_elasticache_replication_group.example.primary_endpoint_address
}

output "reader_endpoint" {
  value = aws_elasticache_replication_group.example.reader_endpoint_address
}