Terraform DynamoDB Autoscaling

terraform_dynamodb.tf

provider "aws" {
  region = "us-west-1"
}

resource "aws_dynamodb_table" "test-database" {
  name           = "tenants"
  read_capacity  = 20
  write_capacity = 20
  hash_key       = "roomNumber"
  range_key      = "name"

  attribute {
    name = "roomNumber"
    type = "S"
  }

  attribute {
    name = "name"
    type = "S"
  }

  attribute {
    name = "age"
    type = "N"
  }
  attribute {
    name = "ethnicity"
    type = "S"
  }

  ttl {
    attribute_name = "deletionTerm"
    enabled = true
  }
  global_secondary_index {
    name               = "NameAgeIndex"
    hash_key           = "ethnicity"
    range_key          = "age"
    write_capacity     = 10   #This will be ignored but we only included it to meet the required
    read_capacity      = 10   #This will also be ignored
    projection_type    = "INCLUDE"
    non_key_attributes = ["school","last4"]  #This attributes 
  }
  local_secondary_index {
    name               = "roomNumberNameIndex"
    range_key          = "age"
    projection_type    = "KEYS_ONLY"  #we are not projecting any other attributes
  }
  tags {
    Name        = "dynamodb-test-table"
  }
  lifecycle {
     ignore_changes = ["read_capacity","write_capacity"]  #We want this ignored so that we can use app autoscaling
  }
}

resource "aws_appautoscaling_target" "dynamodb_table_read_target" {
  max_capacity       = 100
  min_capacity       = 5
  resource_id        = "table/tenants"
  scalable_dimension = "dynamodb:table:ReadCapacityUnits"
  service_namespace  = "dynamodb"
}

resource "aws_appautoscaling_policy" "dynamodb_table_read_policy" {
  name               = "DynamoDBReadCapacityUtilization:${aws_appautoscaling_target.dynamodb_table_read_target.resource_id}"
  policy_type        = "TargetTrackingScaling"
  resource_id        = "${aws_appautoscaling_target.dynamodb_table_read_target.resource_id}"
  scalable_dimension = "${aws_appautoscaling_target.dynamodb_table_read_target.scalable_dimension}"
  service_namespace  = "${aws_appautoscaling_target.dynamodb_table_read_target.service_namespace}"

  target_tracking_scaling_policy_configuration {
    predefined_metric_specification {
      predefined_metric_type = "DynamoDBReadCapacityUtilization"
    }

    target_value = 55  #set utilization to 55%
  }
}