feat(ecs): allow ECS to be used declaratively

Minor changes to the ECS APIs so that they can be instantiated via a declarative
template (see deCDK #1618).

Merge `IContainerImage` and the base `ContainerImage` into an abstract class
so it's now an "enum-like" class with static methods. It also improves discoverability
for all other users and more aligned with how other constructs expose union types
(e.g. `lambda.Code`).

Normalize the ctor of `ContainerDefinition` to "scope, id, props" so that it can
be instantiated as a deCDK resource.

packages/@aws-cdk/aws-ecs/lib/base/task-definition.ts

@@ -1,6 +1,6 @@
 import iam = require('@aws-cdk/aws-iam');
 import cdk = require('@aws-cdk/cdk');
-import { ContainerDefinition, ContainerDefinitionProps } from '../container-definition';
+import { ContainerDefinition, ContainerDefinitionOptions } from '../container-definition';
 import { CfnTaskDefinition } from '../ecs.generated';
 import { isEc2Compatible, isFargateCompatible } from '../util';
 
@@ -225,14 +225,18 @@ export class TaskDefinition extends cdk.Construct {
   /**
    * Create a new container to this task definition
    */
-  public addContainer(id: string, props: ContainerDefinitionProps) {
-    const container = new ContainerDefinition(this, id, this, props);
+  public addContainer(id: string, props: ContainerDefinitionOptions) {
+    return new ContainerDefinition(this, id, { task: this, ...props });
+  }
+
+  /**
+   * (internal) Links a container to this task definition.
+   */
+  public _linkContainer(container: ContainerDefinition) {
     this.containers.push(container);
     if (this.defaultContainer === undefined && container.essential) {
       this.defaultContainer = container;
     }
-
-    return container;
   }
 
   /**

packages/@aws-cdk/aws-ecs/lib/container-definition.ts

@@ -1,23 +1,20 @@
 import iam = require('@aws-cdk/aws-iam');
 import cdk = require('@aws-cdk/cdk');
 import { NetworkMode, TaskDefinition } from './base/task-definition';
-import { IContainerImage } from './container-image';
+import { ContainerImage } from './container-image';
 import { CfnTaskDefinition } from './ecs.generated';
 import { LinuxParameters } from './linux-parameters';
 import { LogDriver } from './log-drivers/log-driver';
 
-/**
- * Properties of a container definition
- */
-export interface ContainerDefinitionProps {
+export interface ContainerDefinitionOptions {
   /**
    * The image to use for a container.
    *
    * You can use images in the Docker Hub registry or specify other
    * repositories (repository-url/image:tag).
    * TODO: Update these to specify using classes of IContainerImage
    */
-  image: IContainerImage;
+  image: ContainerImage;
 
   /**
    * The CMD value to pass to the container.
@@ -173,6 +170,16 @@ export interface ContainerDefinitionProps {
   logging?: LogDriver;
 }
 
+/**
+ * Properties of a container definition
+ */
+export interface ContainerDefinitionProps extends ContainerDefinitionOptions {
+  /**
+   * The task this container definition belongs to.
+   */
+  task: TaskDefinition;
+}
+
 /**
  * A definition for a single container in a Task
  */
@@ -222,14 +229,15 @@ export class ContainerDefinition extends cdk.Construct {
    */
   private readonly links = new Array<string>();
 
-  constructor(scope: cdk.Construct, id: string, taskDefinition: TaskDefinition, private readonly props: ContainerDefinitionProps) {
+  constructor(scope: cdk.Construct, id: string, private readonly props: ContainerDefinitionProps) {
     super(scope, id);
     this.essential = props.essential !== undefined ? props.essential : true;
-    this.taskDefinition = taskDefinition;
+    this.taskDefinition = props.task;
     this.memoryLimitSpecified = props.memoryLimitMiB !== undefined || props.memoryReservationMiB !== undefined;
 
     props.image.bind(this);
     if (props.logging) { props.logging.bind(this); }
+    props.task._linkContainer(this);
   }
 
   /**

packages/@aws-cdk/aws-ecs/lib/container-image.ts

@@ -2,29 +2,11 @@ import ecr = require('@aws-cdk/aws-ecr');
 import cdk = require('@aws-cdk/cdk');
 
 import { ContainerDefinition } from './container-definition';
-import { AssetImage, AssetImageProps } from './images/asset-image';
-import { DockerHubImage } from './images/dockerhub';
-import { EcrImage } from './images/ecr';
-
-/**
- * A container image
- */
-export interface IContainerImage {
-  /**
-   * Name of the image
-   */
-  readonly imageName: string;
-
-  /**
-   * Called when the image is used by a ContainerDefinition
-   */
-  bind(containerDefinition: ContainerDefinition): void;
-}
 
 /**
  * Constructs for types of container images
  */
-export class ContainerImage {
+export abstract class ContainerImage {
   /**
    * Reference an image on DockerHub
    */
@@ -45,4 +27,18 @@ export class ContainerImage {
   public static fromAsset(scope: cdk.Construct, id: string, props: AssetImageProps) {
     return new AssetImage(scope, id, props);
   }
+
+  /**
+   * Name of the image
+   */
+  public abstract readonly imageName: string;
+
+  /**
+   * Called when the image is used by a ContainerDefinition
+   */
+  public abstract bind(containerDefinition: ContainerDefinition): void;
 }
+
+import { AssetImage, AssetImageProps } from './images/asset-image';
+import { DockerHubImage } from './images/dockerhub';
+import { EcrImage } from './images/ecr';

packages/@aws-cdk/aws-ecs/lib/images/asset-image.ts

@@ -1,7 +1,7 @@
 import { DockerImageAsset } from '@aws-cdk/assets-docker';
 import cdk = require('@aws-cdk/cdk');
 import { ContainerDefinition } from '../container-definition';
-import { IContainerImage } from '../container-image';
+import { ContainerImage } from '../container-image';
 
 export interface AssetImageProps {
   /**
@@ -13,16 +13,18 @@ export interface AssetImageProps {
 /**
  * An image that will be built at synthesis time
  */
-export class AssetImage extends DockerImageAsset implements IContainerImage {
+export class AssetImage extends ContainerImage {
+  private readonly asset: DockerImageAsset;
   constructor(scope: cdk.Construct, id: string, props: AssetImageProps) {
-    super(scope, id, { directory: props.directory });
+    super();
+    this.asset = new DockerImageAsset(scope, id, { directory: props.directory });
   }
 
   public bind(containerDefinition: ContainerDefinition): void {
-    this.repository.grantPull(containerDefinition.taskDefinition.obtainExecutionRole());
+    this.asset.repository.grantPull(containerDefinition.taskDefinition.obtainExecutionRole());
   }
 
   public get imageName() {
-    return this.imageUri;
+    return this.asset.imageUri;
   }
 }

packages/@aws-cdk/aws-ecs/lib/images/dockerhub.ts

@@ -1,11 +1,12 @@
 import { ContainerDefinition } from "../container-definition";
-import { IContainerImage } from "../container-image";
+import { ContainerImage } from "../container-image";
 
 /**
  * A DockerHub image
  */
-export class DockerHubImage implements IContainerImage {
+export class DockerHubImage extends ContainerImage {
   constructor(public readonly imageName: string) {
+    super();
   }
 
   public bind(_containerDefinition: ContainerDefinition): void {

packages/@aws-cdk/aws-ecs/lib/images/ecr.ts

@@ -1,15 +1,16 @@
 import ecr = require('@aws-cdk/aws-ecr');
 import { ContainerDefinition } from '../container-definition';
-import { IContainerImage } from '../container-image';
+import { ContainerImage } from '../container-image';
 
 /**
  * An image from an ECR repository
  */
-export class EcrImage implements IContainerImage {
+export class EcrImage extends ContainerImage {
   public readonly imageName: string;
   private readonly repository: ecr.IRepository;
 
   constructor(repository: ecr.IRepository, tag: string) {
+    super();
     this.imageName = repository.repositoryUriForTag(tag);
     this.repository = repository;
   }

packages/@aws-cdk/aws-ecs/lib/load-balanced-service-base.ts

@@ -3,7 +3,7 @@ import elbv2 = require('@aws-cdk/aws-elasticloadbalancingv2');
 import cdk = require('@aws-cdk/cdk');
 import { BaseService } from './base/base-service';
 import { ICluster } from './cluster';
-import { IContainerImage } from './container-image';
+import { ContainerImage } from './container-image';
 
 export enum LoadBalancerType {
   Application,
@@ -19,7 +19,7 @@ export interface LoadBalancedServiceBaseProps {
   /**
    * The image to start.
    */
-  image: IContainerImage;
+  image: ContainerImage;
 
   /**
    * The container port of the application load balancer attached to your Fargate service. Corresponds to container port mapping.

packages/@aws-cdk/aws-ecs/package.json

@@ -106,7 +106,6 @@
     "exclude": [
       "resource-attribute:@aws-cdk/aws-ecs.ICluster.clusterArn",
       "construct-ctor:@aws-cdk/aws-ecs.BaseService.<initializer>",
-      "construct-ctor:@aws-cdk/aws-ecs.ContainerDefinition.<initializer>",
       "construct-ctor:@aws-cdk/aws-ecs.LoadBalancedFargateServiceApplet.<initializer>.params[0]"
     ]
   }