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Added the ability to specify custom metrics for autoscaling. #275

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105 changes: 105 additions & 0 deletions examples/autoscaling/main.tf
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Original file line number Diff line number Diff line change
@@ -0,0 +1,105 @@
provider "aws" {

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Missing version constraint for provider "aws" in `required_providers`

Raw Output:
main.tf:1:1: warning: Missing version constraint for provider "aws" in `required_providers` ()

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GitHub Actions / terraform-module / CI / Lint (./examples/autoscaling) 

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Missing version constraint for provider "aws" in `required_providers`

Raw Output:
main.tf:1:1: warning: Missing version constraint for provider "aws" in `required_providers` ()
region = "us-west-1"
}

module "rds_cluster_autoscaling_mysql_predefined" {
source = "../../"
name = "autoscaling_predefined_metrics"
engine = "aurora-mysql"
cluster_family = "aurora-mysql8.0"
cluster_size = 2
namespace = "eg"
stage = "dev"
admin_user = "admin1"
admin_password = "Test123456789"
db_name = "dbname"
db_port = 5432
instance_type = "db.r4.large"
vpc_id = "vpc-xxxxxxxx"
security_groups = ["sg-xxxxxxxx"]
subnets = ["subnet-xxxxxxxx", "subnet-xxxxxxxx"]
zone_id = "Zxxxxxxxx"

autoscaling_enabled = true
autoscaling_scale_in_cooldown = 300
autoscaling_scale_out_cooldown = 300
autoscaling_min_capacity = 1
autoscaling_max_capacity = 3
autoscaling_policy_type = "TargetTrackingScaling"
autoscaling_target_metrics = "RDSReaderAverageCPUUtilization" // or "RDSReaderAverageDatabaseConnections"
}

module "rds_cluster_autoscaling_mysql_custom_cluster_level" {
source = "../../"
name = "autoscaling_custom_metrics_cluster"
engine = "aurora-mysql"
cluster_family = "aurora-mysql8.0"
cluster_size = 2
namespace = "eg"
stage = "dev"
admin_user = "admin1"
admin_password = "Test123456789"
db_name = "dbname"
db_port = 5432
instance_type = "db.r4.large"
vpc_id = "vpc-xxxxxxxx"
security_groups = ["sg-xxxxxxxx"]
subnets = ["subnet-xxxxxxxx", "subnet-xxxxxxxx"]
zone_id = "Zxxxxxxxx"

autoscaling_enabled = true
autoscaling_scale_in_cooldown = 300
autoscaling_scale_out_cooldown = 300
autoscaling_min_capacity = 1
autoscaling_max_capacity = 3
autoscaling_policy_type = "TargetTrackingScaling"
autoscaling_target_metrics = "Custom"
autoscaling_target_value = 60
autoscaling_custom_metric = {
namespace = "AWS/RDS"
metric_name = "AuroraReplicaLagMaximum" # any valid Aurora metric under AWS/RDS
statistic = "Average"
# unit = "Milliseconds" # optional, if you want to pin it
dimensions = [
{ name = "DBClusterIdentifier", value = "my-aurora-cluster" }
]
}
}

# WARNING: Edge case for which i could not find a real use yet.
module "rds_cluster_autoscaling_mysql_custom_instances_level" {
source = "../../"
name = "autoscaling_custom_metrics_instances"
engine = "aurora-mysql"
cluster_family = "aurora-mysql8.0"
cluster_size = 2
namespace = "eg"
stage = "dev"
admin_user = "admin1"
admin_password = "Test123456789"
db_name = "dbname"
db_port = 5432
instance_type = "db.r4.large"
vpc_id = "vpc-xxxxxxxx"
security_groups = ["sg-xxxxxxxx"]
subnets = ["subnet-xxxxxxxx", "subnet-xxxxxxxx"]
zone_id = "Zxxxxxxxx"

autoscaling_enabled = true
autoscaling_scale_in_cooldown = 300
autoscaling_scale_out_cooldown = 300
autoscaling_min_capacity = 1
autoscaling_max_capacity = 3
autoscaling_policy_type = "TargetTrackingScaling"
autoscaling_target_metrics = "Custom"
autoscaling_target_value = 60
autoscaling_custom_metric = {
namespace = "AWS/RDS"
metric_name = "CPUUtilization" # any valid Aurora metric under AWS/RDS
statistic = "Average"
# unit = "Percent" # optional, if you want to pin it
dimensions = [
{ name = "DBInstanceIdentifier", value = "my-aurora-reader-1" }
]
}
}
42 changes: 40 additions & 2 deletions main.tf
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Expand Up @@ -15,6 +15,11 @@ locals {
ignore_admin_credentials = var.replication_source_identifier != "" || var.snapshot_identifier != null
reserved_instance_engine = var.engine
use_reserved_instances = var.use_reserved_instances && !local.is_serverless

use_predefined_metric = contains([
"RDSReaderAverageCPUUtilization",
"RDSReaderAverageDatabaseConnections",
], var.autoscaling_target_metrics)
}

data "aws_partition" "current" {
Expand Down Expand Up @@ -492,23 +497,56 @@ resource "aws_appautoscaling_target" "replicas" {
max_capacity = var.autoscaling_max_capacity
}

resource "aws_appautoscaling_policy" "replicas" {
count = local.enabled && var.autoscaling_enabled ? 1 : 0
# --- Predefined metric policy (only when using the two reader metrics) ---
resource "aws_appautoscaling_policy" "replicas_predefined" {
count = (local.enabled && var.autoscaling_enabled && local.use_predefined_metric) ? 1 : 0
name = module.this.id
service_namespace = join("", aws_appautoscaling_target.replicas[*].service_namespace)
scalable_dimension = join("", aws_appautoscaling_target.replicas[*].scalable_dimension)
resource_id = join("", aws_appautoscaling_target.replicas[*].resource_id)
policy_type = var.autoscaling_policy_type

target_tracking_scaling_policy_configuration {
disable_scale_in = false
target_value = var.autoscaling_target_value
scale_in_cooldown = var.autoscaling_scale_in_cooldown
scale_out_cooldown = var.autoscaling_scale_out_cooldown

predefined_metric_specification {
predefined_metric_type = var.autoscaling_target_metrics
}
}
}

# --- Customized metric policy (everything else) ---
resource "aws_appautoscaling_policy" "replicas_custom" {
count = (local.enabled && var.autoscaling_enabled && !local.use_predefined_metric) ? 1 : 0
name = module.this.id
service_namespace = join("", aws_appautoscaling_target.replicas[*].service_namespace)
scalable_dimension = join("", aws_appautoscaling_target.replicas[*].scalable_dimension)
resource_id = join("", aws_appautoscaling_target.replicas[*].resource_id)
policy_type = var.autoscaling_policy_type

target_tracking_scaling_policy_configuration {
disable_scale_in = false
target_value = var.autoscaling_target_value
scale_in_cooldown = var.autoscaling_scale_in_cooldown
scale_out_cooldown = var.autoscaling_scale_out_cooldown

customized_metric_specification {
metric_name = var.autoscaling_custom_metric.metric_name
namespace = var.autoscaling_custom_metric.namespace
statistic = var.autoscaling_custom_metric.statistic
unit = try(var.autoscaling_custom_metric.unit, null)

dynamic "dimensions" {
for_each = try(var.autoscaling_custom_metric.dimensions, [])
content {
name = dimensions.value.name
value = dimensions.value.value
}
}
}
}
}

Expand Down
22 changes: 21 additions & 1 deletion variables.tf
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Expand Up @@ -403,7 +403,27 @@ variable "autoscaling_policy_type" {
variable "autoscaling_target_metrics" {
type = string
default = "RDSReaderAverageCPUUtilization"
description = "The metrics type to use. If this value isn't provided the default is CPU utilization"
description = "The metrics type to use. If this value isn't provided the default is CPU utilization. IF the value is not `RDSReaderAverageCPUUtilization` nor `RDSReaderAverageDatabaseConnections` a custom metric for autoscaling must be specified"
}

variable "autoscaling_custom_metric" {
type = object({
metric_name = string
namespace = string
statistic = string
unit = optional(string)
dimensions = optional(list(object({
name = string,
value = string
})))
})
default = {
metric_name = ""
namespace = ""
statistic = "Average"
dimensions = []
}
description = "Specification for a custom Autoscaling metric to use. Will be used if autoscaling_target_metrics os neither `RDSReaderAverageCPUUtilization` nor `RDSReaderAverageDatabaseConnections`"
}

variable "autoscaling_target_value" {
Expand Down
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