feat(elasticloadbalancingv2): health check interval greater than timeout (#29075)

Closes #29062.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: msambol

Diff for: packages/aws-cdk-lib/aws-elasticloadbalancingv2/lib/nlb/network-target-group.ts

@@ -280,9 +280,6 @@ export class NetworkTargetGroup extends TargetGroupBase implements INetworkTarge
       if (timeoutSeconds < lowHealthCheckTimeout || timeoutSeconds > highHealthCheckTimeout) {
         ret.push(`Health check timeout '${timeoutSeconds}' not supported. Must be a number between ${lowHealthCheckTimeout} and ${highHealthCheckTimeout}.`);
       }
-      if (healthCheck.interval && healthCheck.interval.toSeconds() < timeoutSeconds) {
-        ret.push(`Health check timeout '${timeoutSeconds}' must not be greater than the interval '${healthCheck.interval.toSeconds()}'`);
-      }
     }
 
     return ret;

Diff for: packages/aws-cdk-lib/aws-elasticloadbalancingv2/lib/shared/base-target-group.ts

@@ -280,6 +280,7 @@ export abstract class TargetGroupBase extends Construct implements ITargetGroup
     this.targetGroupName = this.resource.attrTargetGroupName;
     this.defaultPort = additionalProps.port;
 
+    this.node.addValidation({ validate: () => this.validateHealthCheck() });
     this.node.addValidation({ validate: () => this.validateTargetGroup() });
   }
 
@@ -351,6 +352,22 @@ export abstract class TargetGroupBase extends Construct implements ITargetGroup
 
     return ret;
   }
+
+  protected validateHealthCheck(): string[] {
+    const ret = new Array<string>();
+
+    const intervalSeconds = this.healthCheck.interval?.toSeconds();
+    const timeoutSeconds = this.healthCheck.timeout?.toSeconds();
+
+    if (intervalSeconds && timeoutSeconds) {
+      if (intervalSeconds < timeoutSeconds) {
+        // < instead of <= for backwards compatibility, see discussion in https://github.com/aws/aws-cdk/pull/26031
+        ret.push('Health check interval must be greater than or equal to the timeout; received interval ' +
+        `${intervalSeconds}, timeout ${timeoutSeconds}.`);
+      }
+    }
+    return ret;
+  }
 }
 
 /**

Diff for: packages/aws-cdk-lib/aws-elasticloadbalancingv2/test/alb/target-group.test.ts

@@ -549,6 +549,45 @@ describe('tests', () => {
     }).toThrow('Healthcheck interval 1 minute must be greater than the timeout 2 minute');
   });
 
+  test('Throws error for health check interval less than timeout', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'Stack');
+    const vpc = new ec2.Vpc(stack, 'Vpc');
+
+    new elbv2.ApplicationTargetGroup(stack, 'TargetGroup', {
+      vpc,
+      port: 80,
+      healthCheck: {
+        interval: cdk.Duration.seconds(10),
+        timeout: cdk.Duration.seconds(20),
+      },
+    });
+
+    expect(() => {
+      app.synth();
+    }).toThrow('Health check interval must be greater than or equal to the timeout; received interval 10, timeout 20.');
+  });
+
+  // for backwards compatibility these can be equal, see discussion in https://github.com/aws/aws-cdk/pull/26031
+  test('Throws error for health check interval less than timeout', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'Stack');
+    const vpc = new ec2.Vpc(stack, 'Vpc');
+
+    new elbv2.ApplicationTargetGroup(stack, 'TargetGroup', {
+      vpc,
+      port: 80,
+      healthCheck: {
+        interval: cdk.Duration.seconds(10),
+        timeout: cdk.Duration.seconds(20),
+      },
+    });
+
+    expect(() => {
+      app.synth();
+    }).toThrow('Health check interval must be greater than or equal to the timeout; received interval 10, timeout 20.');
+  });
+
   test('imported targetGroup has targetGroupName', () => {
     // GIVEN
     const app = new cdk.App();

Diff for: packages/aws-cdk-lib/aws-elasticloadbalancingv2/test/nlb/listener.test.ts

@@ -408,7 +408,7 @@ describe('tests', () => {
     // THEN
     const validationErrors: string[] = targetGroup.node.validate();
     expect(validationErrors).toEqual([
-      "Health check timeout '40' must not be greater than the interval '30'",
+      'Health check interval must be greater than or equal to the timeout; received interval 30, timeout 40.',
     ]);
   });
 

Diff for: packages/aws-cdk-lib/aws-elasticloadbalancingv2/test/nlb/target-group.test.ts

@@ -144,6 +144,45 @@ describe('tests', () => {
     }).toThrow(/Health check interval '3' not supported. Must be between 5 and 300./);
   });
 
+  test('Throws error for health check interval less than timeout', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'Stack');
+    const vpc = new ec2.Vpc(stack, 'Vpc');
+
+    new elbv2.NetworkTargetGroup(stack, 'Group', {
+      vpc,
+      port: 80,
+      healthCheck: {
+        interval: cdk.Duration.seconds(10),
+        timeout: cdk.Duration.seconds(20),
+      },
+    });
+
+    expect(() => {
+      app.synth();
+    }).toThrow('Health check interval must be greater than or equal to the timeout; received interval 10, timeout 20.');
+  });
+
+  // for backwards compatibility these can be equal, see discussion in https://github.com/aws/aws-cdk/pull/26031
+  test('No error for health check interval == timeout', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'Stack');
+    const vpc = new ec2.Vpc(stack, 'Vpc');
+
+    new elbv2.NetworkTargetGroup(stack, 'Group', {
+      vpc,
+      port: 80,
+      healthCheck: {
+        interval: cdk.Duration.seconds(10),
+        timeout: cdk.Duration.seconds(10),
+      },
+    });
+
+    expect(() => {
+      app.synth();
+    }).not.toThrow();
+  });
+
   test('targetGroupName unallowed: more than 32 characters', () => {
     // GIVEN
     const app = new cdk.App();