Merge pull request #30 from cfln123/patch-2

Auto scaling replica

aurora-mysql.cfhighlander.rb

@@ -1,6 +1,7 @@
 CfhighlanderTemplate do
   Name 'aurora-mysql'
   DependsOn 'vpc'
+  DependsOn 'lib-iam'
 
   Parameters do
     ComponentParam 'EnvironmentName', 'dev', isGlobal: true
@@ -9,6 +10,8 @@
     ComponentParam 'NetworkPrefix', '10', isGlobal: true
     ComponentParam 'DnsDomain'
     ComponentParam 'SnapshotID'
+    ComponentParam 'ScalableTargetMinCapacity'
+    ComponentParam 'ScalableTargetMaxCapacity'
 
     if engine_mode == 'provisioned'
       ComponentParam 'WriterInstanceType'
@@ -30,5 +33,7 @@
     ComponentParam 'PerformanceInsightsRetentionPeriod', defined?(performance_insights) && defined?(insights_retention)  ? insights_retention.to_i : 7
 
     ComponentParam 'NamespaceId' if defined? service_discovery
+
+    ComponentParam 'EnableReplicaAutoScaling', 'false', isGlobal: true
   end
 end

aurora-mysql.cfndsl.rb

@@ -5,7 +5,7 @@
   Condition("UseUsernameAndPassword", FnEquals(Ref(:SnapshotID), ''))
   Condition("UseSnapshotID", FnNot(FnEquals(Ref(:SnapshotID), '')))
   Condition("EnablePerformanceInsights", FnEquals(Ref(:EnablePerformanceInsights), 'true'))
-
+  Condition("EnableReplicaAutoScaling", FnAnd([FnEquals(Ref(:EnableReplicaAutoScaling), 'true'), FnEquals(Ref(:EnableReader), 'true')]))
 
   tags = []
   tags << { Key: 'Environment', Value: Ref(:EnvironmentName) }
@@ -195,4 +195,77 @@
     Export FnSub("${EnvironmentName}-#{external_parameters[:component_name]}-dbcluster-id")
   }
 
+  IAM_Role(:RDSReplicaAutoScaleRole) do
+    DependsOn [:DBCluster,:DBClusterInstanceReader]
+    Condition 'EnableReplicaAutoScaling'
+    AssumeRolePolicyDocument service_assume_role_policy('application-autoscaling')
+    Path '/'
+    Policies ([
+      PolicyName: FnSub("${EnvironmentName}-rds-replica-scaling"),
+      PolicyDocument: {
+        Statement: [
+          {
+            Effect: "Allow",
+            Action: "iam:CreateServiceLinkedRole",
+            Resource: FnSub("arn:aws:iam::${AWS::AccountId}:role/aws-service-role/rds.application-autoscaling.amazonaws.com/AWSServiceRoleForApplicationAutoScaling_RDSCluster"),
+            Condition: ({
+              StringLike: {
+                "iam:AWSServiceName":"rds.application-autoscaling.amazonaws.com"
+               }
+            })
+          },
+          {
+            Effect: "Allow",
+            Action: ['cloudwatch:DescribeAlarms','cloudwatch:PutMetricAlarm','cloudwatch:DeleteAlarms'],
+            Resource: "*"
+          }
+        ]
+    }])
+  end
+
+  scaling_policy = external_parameters.fetch(:scaling_policy, {})
+
+  if scaling_policy['up'].kind_of?(Hash)
+    scaling_policy['up'] = [scaling_policy['up']]
+  end
+
+  if scaling_policy['down'].kind_of?(Hash)
+    scaling_policy['down'] = [scaling_policy['down']]
+  end
+
+  if scaling_policy['target'].kind_of?(Hash)
+    scaling_policy['target'] = [scaling_policy['target']]
+  end
+
+  ApplicationAutoScaling_ScalableTarget(:ServiceScalingTarget) do
+    DependsOn 'RDSReplicaAutoScaleRole'
+    Condition 'EnableReplicaAutoScaling'
+    MaxCapacity Ref(:ScalableTargetMaxCapacity)
+    MinCapacity Ref(:ScalableTargetMinCapacity)
+    ResourceId FnJoin(':',["cluster",Ref(:DBCluster)])
+    RoleARN FnGetAtt(:RDSReplicaAutoScaleRole,:Arn)
+    ScalableDimension "rds:cluster:ReadReplicaCount"
+    ServiceNamespace "rds"
+  end
+
+  scaling_policy['target'].each_with_index do |scale_target_policy, i|
+    logical_scaling_policy_name = "ServiceTargetTrackingPolicy" + (i > 0 ? "#{i+1}" : "")
+    policy_name = "target-tracking-policy" + (i > 0 ? "-#{i+1}" : "")
+    ApplicationAutoScaling_ScalingPolicy(logical_scaling_policy_name) do
+      DependsOn 'ServiceScalingTarget'
+      Condition 'EnableReplicaAutoScaling'
+      PolicyName FnJoin('-', [ Ref('EnvironmentName'), component_name, policy_name])
+      PolicyType 'TargetTrackingScaling'
+      ScalingTargetId Ref(:ServiceScalingTarget)
+      TargetTrackingScalingPolicyConfiguration({
+        TargetValue: scale_target_policy['target_value'],
+        ScaleInCooldown: scale_target_policy['scale_in_cooldown'].to_s,
+        ScaleOutCooldown: scale_target_policy['scale_out_cooldown'].to_s,
+        PredefinedMetricSpecification: {
+          PredefinedMetricType: scale_target_policy['metric_type'] || 'RDSReaderAverageCPUUtilization'
+        }
+      })
+    end
+  end unless scaling_policy['target'].nil?
+
 end

tests/replica-scaling.yaml

@@ -0,0 +1,15 @@
+test_metadata:
+  type: config
+  name: replica scaling
+  description: replica scaling
+
+scaling_policy:
+  target:
+    - metric_type: RDSReaderAverageCPUUtilization
+      scale_in_cooldown: 180
+      scale_out_cooldown: 60
+      target_value: 70
+    - metric_type: RDSReaderAverageDatabaseConnections
+      scale_in_cooldown: 180
+      scale_out_cooldown: 60
+      target_value: 500