Merge pull request #2255 from guardian/add-asg-group-metrics-by-default

feat: Add useful ASG group metrics (`TOTAL_INSTANCES`, etc) by default

.changeset/nice-cups-study.md

@@ -0,0 +1,5 @@
+---
+"@guardian/cdk": patch
+---
+
+Add useful ASG group metrics (TOTAL_INSTANCES, etc) by default

src/constructs/autoscaling/asg.ts

@@ -1,5 +1,5 @@
 import { Tags, Token } from "aws-cdk-lib";
-import { AutoScalingGroup } from "aws-cdk-lib/aws-autoscaling";
+import { AutoScalingGroup, GroupMetric, GroupMetrics } from "aws-cdk-lib/aws-autoscaling";
 import type { AutoScalingGroupProps, CfnAutoScalingGroup } from "aws-cdk-lib/aws-autoscaling";
 import { LaunchTemplate, OperatingSystemType, UserData } from "aws-cdk-lib/aws-ec2";
 import type { InstanceType, ISecurityGroup, MachineImageConfig } from "aws-cdk-lib/aws-ec2";
@@ -85,6 +85,7 @@ export class GuAutoScalingGroup extends GuAppAwareConstruct(AutoScalingGroup) {
       imageId = new GuAmiParameter(scope, { app }),
       imageRecipe,
       instanceType,
+      groupMetrics = [new GroupMetrics(GroupMetric.TOTAL_INSTANCES, GroupMetric.IN_SERVICE_INSTANCES)],
       minimumInstances,
       maximumInstances,
       role = new GuInstanceRole(scope, { app }),
@@ -139,6 +140,7 @@ export class GuAutoScalingGroup extends GuAppAwareConstruct(AutoScalingGroup) {
       launchTemplate,
       maxCapacity: maximumInstances ?? minimumInstances * 2,
       minCapacity: minimumInstances,
+      groupMetrics: groupMetrics,
 
       // Omit userData, instanceType, blockDevices & role from asgProps
       // As this are specified by the LaunchTemplate and must not be duplicated

src/patterns/ec2-app/__snapshots__/base.test.ts.snap

@@ -88,6 +88,15 @@ exports[`the GuEC2App pattern can produce a restricted EC2 app locked to specifi
           },
         },
         "MaxSize": "2",
+        "MetricsCollection": [
+          {
+            "Granularity": "1Minute",
+            "Metrics": [
+              "GroupTotalInstances",
+              "GroupInServiceInstances",
+            ],
+          },
+        ],
         "MinSize": "1",
         "Tags": [
           {
@@ -1095,6 +1104,15 @@ exports[`the GuEC2App pattern should produce a functional EC2 app with minimal a
           },
         },
         "MaxSize": "2",
+        "MetricsCollection": [
+          {
+            "Granularity": "1Minute",
+            "Metrics": [
+              "GroupTotalInstances",
+              "GroupInServiceInstances",
+            ],
+          },
+        ],
         "MinSize": "1",
         "Tags": [
           {