feat(ecs): ExternalService support daemon scheduling strategy

packages/aws-cdk-lib/aws-ecs/lib/external/external-service.ts

@@ -27,6 +27,16 @@ export interface ExternalServiceProps extends BaseServiceOptions {
    * @default - A new security group is created.
    */
   readonly securityGroups?: ec2.ISecurityGroup[];
+
+  /**
+   * Specifies whether the service will use the daemon scheduling strategy.
+   * If true, the service scheduler deploys exactly one task on each container instance in your cluster.
+   *
+   * When you are using this strategy, do not specify a desired number of tasks or any task placement strategies.
+   *
+   * @default false
+   */
+  readonly daemon?: boolean;
 }
 
 /**
@@ -89,6 +99,14 @@ export class ExternalService extends BaseService implements IExternalService {
    * Constructs a new instance of the ExternalService class.
    */
   constructor(scope: Construct, id: string, props: ExternalServiceProps) {
+    if (props.daemon && props.desiredCount !== undefined) {
+      throw new Error('Daemon mode launches one task on every instance. Don\'t supply desiredCount.');
+    }
+
+    if (props.daemon && props.maxHealthyPercent !== undefined && props.maxHealthyPercent !== 100) {
+      throw new Error('Maximum percent must be 100 for daemon mode.');
+    }
+
     if (props.minHealthyPercent !== undefined && props.maxHealthyPercent !== undefined && props.minHealthyPercent >= props.maxHealthyPercent) {
       throw new Error('Minimum healthy percent must be less than maximum healthy percent.');
     }
@@ -114,15 +132,16 @@ export class ExternalService extends BaseService implements IExternalService {
     super(scope, id, {
       ...props,
       desiredCount: props.desiredCount,
-      maxHealthyPercent: props.maxHealthyPercent === undefined ? 100 : props.maxHealthyPercent,
-      minHealthyPercent: props.minHealthyPercent === undefined ? 0 : props.minHealthyPercent,
+      maxHealthyPercent: props.daemon || props.maxHealthyPercent === undefined ? 100 : props.maxHealthyPercent,
+      minHealthyPercent: props.daemon || props.minHealthyPercent === undefined ? 0 : props.minHealthyPercent,
       launchType: LaunchType.EXTERNAL,
       propagateTags: propagateTagsFromSource,
       enableECSManagedTags: props.enableECSManagedTags,
     },
     {
       cluster: props.cluster.clusterName,
       taskDefinition: props.deploymentController?.type === DeploymentControllerType.EXTERNAL ? undefined : props.taskDefinition.taskDefinitionArn,
+      schedulingStrategy: props.daemon ? 'DAEMON' : 'REPLICA',
     }, props.taskDefinition);
 
     this.node.addValidation({

packages/aws-cdk-lib/aws-ecs/test/external/external-service.test.ts

@@ -291,6 +291,85 @@ describe('external service', () => {
 
   });
 
+  test('errors if daemon and desiredCount both specified', () => {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'MyVpc', {});
+    const cluster = new ecs.Cluster(stack, 'EcsCluster', { vpc });
+    addDefaultCapacityProvider(cluster, stack, vpc);
+    const taskDefinition = new ecs.ExternalTaskDefinition(stack, 'TaskDef');
+    taskDefinition.addContainer('BaseContainer', {
+      image: ecs.ContainerImage.fromRegistry('test'),
+      memoryReservationMiB: 10,
+    });
+
+    // THEN
+    expect(() => {
+      new ecs.ExternalService(stack, 'ExternalService', {
+        cluster,
+        taskDefinition,
+        daemon: true,
+        desiredCount: 2,
+      });
+    }).toThrow(/Don't supply desiredCount/);
+
+  });
+
+  test('errors if daemon and maximumPercent not 100', () => {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'MyVpc', {});
+    const cluster = new ecs.Cluster(stack, 'EcsCluster', { vpc });
+    addDefaultCapacityProvider(cluster, stack, vpc);
+    const taskDefinition = new ecs.ExternalTaskDefinition(stack, 'TaskDef');
+    taskDefinition.addContainer('BaseContainer', {
+      image: ecs.ContainerImage.fromRegistry('test'),
+      memoryReservationMiB: 10,
+    });
+
+    // THEN
+    expect(() => {
+      new ecs.ExternalService(stack, 'ExternalService', {
+        cluster,
+        taskDefinition,
+        daemon: true,
+        maxHealthyPercent: 300,
+      });
+    }).toThrow(/Maximum percent must be 100 for daemon mode./);
+
+  });
+
+  test('sets daemon scheduling strategy', () => {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'MyVpc', {});
+    const cluster = new ecs.Cluster(stack, 'EcsCluster', { vpc });
+    addDefaultCapacityProvider(cluster, stack, vpc);
+    const taskDefinition = new ecs.ExternalTaskDefinition(stack, 'TaskDef');
+    taskDefinition.addContainer('BaseContainer', {
+      image: ecs.ContainerImage.fromRegistry('test'),
+      memoryReservationMiB: 10,
+    });
+
+    new ecs.ExternalService(stack, 'ExternalService', {
+      cluster,
+      taskDefinition,
+      daemon: true,
+    });
+
+    // THEN
+    Template.fromStack(stack).hasResourceProperties('AWS::ECS::Service', {
+      SchedulingStrategy: 'DAEMON',
+      DeploymentConfiguration: {
+        MaximumPercent: 100,
+        MinimumHealthyPercent: 0,
+      },
+      EnableECSManagedTags: false,
+      LaunchType: LaunchType.EXTERNAL,
+    });
+
+  });
+
   test('errors if minimum not less than maximum', () => {
     // GIVEN
     const stack = new cdk.Stack();