feat: Add construct for EC2-based infrastructure alarm (#439)

src/constructs/cloudwatch/__snapshots__/ec2-alarms.test.ts.snap

@@ -0,0 +1,232 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`The Gu5xxPercentageAlarm construct should create the correct alarm resource with minimal config 1`] = `
+Object {
+  "Mappings": Object {
+    "stagemapping": Object {
+      "CODE": Object {
+        "alarmActionsEnabled": false,
+      },
+      "PROD": Object {
+        "alarmActionsEnabled": true,
+      },
+    },
+  },
+  "Parameters": Object {
+    "Stage": Object {
+      "AllowedValues": Array [
+        "CODE",
+        "PROD",
+      ],
+      "Default": "CODE",
+      "Description": "Stage name",
+      "Type": "String",
+    },
+  },
+  "Resources": Object {
+    "ApplicationLoadBalancerTesting172A253B": Object {
+      "Properties": Object {
+        "LoadBalancerAttributes": Array [
+          Object {
+            "Key": "deletion_protection.enabled",
+            "Value": "true",
+          },
+        ],
+        "Scheme": "internal",
+        "SecurityGroups": Array [
+          Object {
+            "Fn::GetAtt": Array [
+              "ApplicationLoadBalancerTestingSecurityGroup883A01A4",
+              "GroupId",
+            ],
+          },
+        ],
+        "Subnets": Array [
+          "",
+        ],
+        "Tags": Array [
+          Object {
+            "Key": "App",
+            "Value": "testing",
+          },
+          Object {
+            "Key": "gu:cdk:version",
+            "Value": "TEST",
+          },
+          Object {
+            "Key": "Stack",
+            "Value": "test-stack",
+          },
+          Object {
+            "Key": "Stage",
+            "Value": Object {
+              "Ref": "Stage",
+            },
+          },
+        ],
+      },
+      "Type": "AWS::ElasticLoadBalancingV2::LoadBalancer",
+    },
+    "ApplicationLoadBalancerTestingSecurityGroup883A01A4": Object {
+      "Properties": Object {
+        "GroupDescription": "Automatically created Security Group for ELB TestApplicationLoadBalancerTesting8F9EA5A8",
+        "SecurityGroupEgress": Array [
+          Object {
+            "CidrIp": "255.255.255.255/32",
+            "Description": "Disallow all traffic",
+            "FromPort": 252,
+            "IpProtocol": "icmp",
+            "ToPort": 86,
+          },
+        ],
+        "Tags": Array [
+          Object {
+            "Key": "App",
+            "Value": "testing",
+          },
+          Object {
+            "Key": "gu:cdk:version",
+            "Value": "TEST",
+          },
+          Object {
+            "Key": "Stack",
+            "Value": "test-stack",
+          },
+          Object {
+            "Key": "Stage",
+            "Value": Object {
+              "Ref": "Stage",
+            },
+          },
+        ],
+        "VpcId": "test",
+      },
+      "Type": "AWS::EC2::SecurityGroup",
+    },
+    "testAF53AC38": Object {
+      "Properties": Object {
+        "ActionsEnabled": Object {
+          "Fn::FindInMap": Array [
+            "stagemapping",
+            Object {
+              "Ref": "Stage",
+            },
+            "alarmActionsEnabled",
+          ],
+        },
+        "AlarmActions": Array [
+          Object {
+            "Fn::Join": Array [
+              "",
+              Array [
+                "arn:aws:sns:",
+                Object {
+                  "Ref": "AWS::Region",
+                },
+                ":",
+                Object {
+                  "Ref": "AWS::AccountId",
+                },
+                ":test-topic",
+              ],
+            ],
+          },
+        ],
+        "AlarmDescription": "testing exceeded 1% error rate",
+        "AlarmName": Object {
+          "Fn::Join": Array [
+            "",
+            Array [
+              "High 5XX error % from testing in ",
+              Object {
+                "Ref": "Stage",
+              },
+            ],
+          ],
+        },
+        "ComparisonOperator": "GreaterThanThreshold",
+        "EvaluationPeriods": 1,
+        "Metrics": Array [
+          Object {
+            "Expression": "100*(m1+m2)/m3",
+            "Id": "expr_1",
+            "Label": "% of 5XX responses served for testing (load balancer and instances combined)",
+          },
+          Object {
+            "Id": "m1",
+            "MetricStat": Object {
+              "Metric": Object {
+                "Dimensions": Array [
+                  Object {
+                    "Name": "LoadBalancer",
+                    "Value": Object {
+                      "Fn::GetAtt": Array [
+                        "ApplicationLoadBalancerTesting172A253B",
+                        "LoadBalancerFullName",
+                      ],
+                    },
+                  },
+                ],
+                "MetricName": "HTTPCode_ELB_5XX_Count",
+                "Namespace": "AWS/ApplicationELB",
+              },
+              "Period": 300,
+              "Stat": "Sum",
+            },
+            "ReturnData": false,
+          },
+          Object {
+            "Id": "m2",
+            "MetricStat": Object {
+              "Metric": Object {
+                "Dimensions": Array [
+                  Object {
+                    "Name": "LoadBalancer",
+                    "Value": Object {
+                      "Fn::GetAtt": Array [
+                        "ApplicationLoadBalancerTesting172A253B",
+                        "LoadBalancerFullName",
+                      ],
+                    },
+                  },
+                ],
+                "MetricName": "HTTPCode_Target_5XX_Count",
+                "Namespace": "AWS/ApplicationELB",
+              },
+              "Period": 300,
+              "Stat": "Sum",
+            },
+            "ReturnData": false,
+          },
+          Object {
+            "Id": "m3",
+            "MetricStat": Object {
+              "Metric": Object {
+                "Dimensions": Array [
+                  Object {
+                    "Name": "LoadBalancer",
+                    "Value": Object {
+                      "Fn::GetAtt": Array [
+                        "ApplicationLoadBalancerTesting172A253B",
+                        "LoadBalancerFullName",
+                      ],
+                    },
+                  },
+                ],
+                "MetricName": "RequestCount",
+                "Namespace": "AWS/ApplicationELB",
+              },
+              "Period": 300,
+              "Stat": "Sum",
+            },
+            "ReturnData": false,
+          },
+        ],
+        "Threshold": 1,
+        "TreatMissingData": "notBreaching",
+      },
+      "Type": "AWS::CloudWatch::Alarm",
+    },
+  },
+}
+`;

src/constructs/cloudwatch/__snapshots__/lambda-alarms.test.ts.snap

@@ -1,6 +1,6 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`The GuLambdaErrorPercentageAlarm pattern should create the correct alarm resource with minimal config 1`] = `
+exports[`The GuLambdaErrorPercentageAlarm construct should create the correct alarm resource with minimal config 1`] = `
 Object {
   "Mappings": Object {
     "stagemapping": Object {

src/constructs/cloudwatch/ec2-alarms.test.ts

@@ -0,0 +1,73 @@
+import "@aws-cdk/assert/jest";
+import { SynthUtils } from "@aws-cdk/assert";
+import { Vpc } from "@aws-cdk/aws-ec2";
+import { Stack } from "@aws-cdk/core";
+import { simpleGuStackForTesting } from "../../utils/test";
+import type { AppIdentity } from "../core/identity";
+import { GuApplicationLoadBalancer } from "../loadbalancing";
+import { Gu5xxPercentageAlarm } from "./ec2-alarms";
+
+const vpc = Vpc.fromVpcAttributes(new Stack(), "VPC", {
+  vpcId: "test",
+  availabilityZones: [""],
+  publicSubnetIds: [""],
+});
+
+const app: AppIdentity = {
+  app: "testing",
+};
+
+describe("The Gu5xxPercentageAlarm construct", () => {
+  it("should create the correct alarm resource with minimal config", () => {
+    const stack = simpleGuStackForTesting();
+    const alb = new GuApplicationLoadBalancer(stack, "ApplicationLoadBalancer", { ...app, vpc });
+    const props = {
+      tolerated5xxPercentage: 1,
+      snsTopicName: "test-topic",
+    };
+    new Gu5xxPercentageAlarm(stack, "test", { ...app, loadBalancer: alb, ...props });
+    expect(SynthUtils.toCloudFormation(stack)).toMatchSnapshot();
+  });
+
+  it("should use a custom description if one is provided", () => {
+    const stack = simpleGuStackForTesting();
+    const alb = new GuApplicationLoadBalancer(stack, "ApplicationLoadBalancer", { ...app, vpc });
+    const props = {
+      alarmDescription: "test-custom-alarm-description",
+      tolerated5xxPercentage: 1,
+      snsTopicName: "test-topic",
+    };
+    new Gu5xxPercentageAlarm(stack, "test", { ...app, loadBalancer: alb, ...props });
+    expect(stack).toHaveResource("AWS::CloudWatch::Alarm", {
+      AlarmDescription: "test-custom-alarm-description",
+    });
+  });
+
+  it("should use a custom alarm name if one is provided", () => {
+    const stack = simpleGuStackForTesting();
+    const alb = new GuApplicationLoadBalancer(stack, "ApplicationLoadBalancer", { ...app, vpc });
+    const props = {
+      alarmName: "test-custom-alarm-name",
+      tolerated5xxPercentage: 1,
+      snsTopicName: "test-topic",
+    };
+    new Gu5xxPercentageAlarm(stack, "test", { ...app, loadBalancer: alb, ...props });
+    expect(stack).toHaveResource("AWS::CloudWatch::Alarm", {
+      AlarmName: "test-custom-alarm-name",
+    });
+  });
+
+  it("should adjust the number of evaluation periods if a custom value is provided", () => {
+    const stack = simpleGuStackForTesting();
+    const alb = new GuApplicationLoadBalancer(stack, "ApplicationLoadBalancer", { ...app, vpc });
+    const props = {
+      tolerated5xxPercentage: 1,
+      numberOfFiveMinutePeriodsToEvaluate: 3,
+      snsTopicName: "test-topic",
+    };
+    new Gu5xxPercentageAlarm(stack, "test", { ...app, loadBalancer: alb, ...props });
+    expect(stack).toHaveResource("AWS::CloudWatch::Alarm", {
+      EvaluationPeriods: 3,
+    });
+  });
+});

src/constructs/cloudwatch/ec2-alarms.ts

@@ -0,0 +1,50 @@
+import { ComparisonOperator, MathExpression, TreatMissingData } from "@aws-cdk/aws-cloudwatch";
+import { HttpCodeElb, HttpCodeTarget } from "@aws-cdk/aws-elasticloadbalancingv2";
+import type { GuStack } from "../core";
+import type { AppIdentity } from "../core/identity";
+import type { GuApplicationLoadBalancer } from "../loadbalancing";
+import type { GuAlarmProps } from "./alarm";
+import { GuAlarm } from "./alarm";
+
+/**
+ * Creates an alarm which is triggered whenever the percentage of requests with a 5xx response code exceeds
+ * the specified threshold.
+ */
+export interface Gu5xxPercentageMonitoringProps
+  extends Omit<GuAlarmProps, "evaluationPeriods" | "metric" | "period" | "threshold" | "treatMissingData">,
+    AppIdentity {
+  tolerated5xxPercentage: number;
+  numberOfFiveMinutePeriodsToEvaluate?: number;
+  noMonitoring?: false;
+}
+
+interface GuLoadBalancerAlarmProps extends Gu5xxPercentageMonitoringProps {
+  loadBalancer: GuApplicationLoadBalancer;
+}
+
+export class Gu5xxPercentageAlarm extends GuAlarm {
+  constructor(scope: GuStack, id: string, props: GuLoadBalancerAlarmProps) {
+    const mathExpression = new MathExpression({
+      expression: "100*(m1+m2)/m3",
+      usingMetrics: {
+        m1: props.loadBalancer.metricHttpCodeElb(HttpCodeElb.ELB_5XX_COUNT),
+        m2: props.loadBalancer.metricHttpCodeTarget(HttpCodeTarget.TARGET_5XX_COUNT),
+        m3: props.loadBalancer.metricRequestCount(),
+      },
+      label: `% of 5XX responses served for ${props.app} (load balancer and instances combined)`,
+    });
+    const defaultAlarmName = `High 5XX error % from ${props.app} in ${scope.stage}`;
+    const defaultDescription = `${props.app} exceeded ${props.tolerated5xxPercentage}% error rate`;
+    const alarmProps = {
+      ...props,
+      metric: mathExpression,
+      treatMissingData: TreatMissingData.NOT_BREACHING,
+      threshold: props.tolerated5xxPercentage,
+      comparisonOperator: ComparisonOperator.GREATER_THAN_THRESHOLD,
+      alarmName: props.alarmName ?? defaultAlarmName,
+      alarmDescription: props.alarmDescription ?? defaultDescription,
+      evaluationPeriods: props.numberOfFiveMinutePeriodsToEvaluate ?? 1,
+    };
+    super(scope, id, alarmProps);
+  }
+}

src/constructs/cloudwatch/index.ts

@@ -1,3 +1,4 @@
 export * from "./alarm";
+export * from "./ec2-alarms";
 export * from "./lambda-alarms";
 export * from "./no-monitoring";

src/constructs/cloudwatch/lambda-alarms.test.ts

@@ -5,7 +5,7 @@ import { simpleGuStackForTesting } from "../../utils/test";
 import { GuLambdaFunction } from "../lambda";
 import { GuLambdaErrorPercentageAlarm } from "./lambda-alarms";
 
-describe("The GuLambdaErrorPercentageAlarm pattern", () => {
+describe("The GuLambdaErrorPercentageAlarm construct", () => {
   it("should create the correct alarm resource with minimal config", () => {
     const stack = simpleGuStackForTesting();
     const lambda = new GuLambdaFunction(stack, "lambda", {