From d9f060e670c69d44d4dad1f12e4bc13a9edf36e5 Mon Sep 17 00:00:00 2001
From: Adam Ruka <adamruka@amazon.com>
Date: Fri, 2 Nov 2018 13:36:09 -0700
Subject: [PATCH] feat(aws-s3): do not poll by default in the CodePipeline
 source Action.

---
 packages/@aws-cdk/aws-s3/lib/bucket.ts        | 37 +++++++++++++++
 .../@aws-cdk/aws-s3/lib/pipeline-action.ts    | 13 +++--
 packages/@aws-cdk/aws-s3/package.json         |  4 +-
 .../aws-s3/test/test.notifications.ts         | 47 ++++++++++++++++++-
 4 files changed, 95 insertions(+), 6 deletions(-)

diff --git a/packages/@aws-cdk/aws-s3/lib/bucket.ts b/packages/@aws-cdk/aws-s3/lib/bucket.ts
index ffa144a1cf2f9..553f0e7d7735a 100644
--- a/packages/@aws-cdk/aws-s3/lib/bucket.ts
+++ b/packages/@aws-cdk/aws-s3/lib/bucket.ts
@@ -1,4 +1,5 @@
 import actions = require('@aws-cdk/aws-codepipeline-api');
+import events = require('@aws-cdk/aws-events');
 import iam = require('@aws-cdk/aws-iam');
 import kms = require('@aws-cdk/aws-kms');
 import { IBucketNotificationDestination } from '@aws-cdk/aws-s3-notifications';
@@ -131,6 +132,42 @@ export abstract class BucketRef extends cdk.Construct {
     });
   }
 
+  /**
+   * Defines a CloudWatch Event Rule that triggers upon putting an object into the Bucket.
+   *
+   * @param name the logical ID of the newly created Event Rule
+   * @param target the target of the Event Rule
+   * @param path the optional path inside the Bucket that will be watched for changes
+   * @returns a new {@link events.EventRule} instance
+   */
+  public onObjectPut(name: string, target?: events.IEventRuleTarget, path?: string): events.EventRule {
+    const eventRule = new events.EventRule(this, name, {
+      eventPattern: {
+        source: [
+          'aws.s3',
+        ],
+        detailType: [
+          'AWS API Call via CloudTrail',
+        ],
+        detail: {
+          eventSource: [
+            's3.amazonaws.com',
+          ],
+          eventName: [
+            'PutObject',
+          ],
+          resources: {
+            ARN: [
+              path ? this.arnForObjects(path) : this.bucketArn,
+            ],
+          },
+        },
+      },
+    });
+    eventRule.addTarget(target);
+    return eventRule;
+  }
+
   /**
    * Adds a statement to the resource policy for a principal (i.e.
    * account/role/service) to perform actions on this bucket and/or it's
diff --git a/packages/@aws-cdk/aws-s3/lib/pipeline-action.ts b/packages/@aws-cdk/aws-s3/lib/pipeline-action.ts
index a4f03b9c79be5..a4ad36c40b8c8 100644
--- a/packages/@aws-cdk/aws-s3/lib/pipeline-action.ts
+++ b/packages/@aws-cdk/aws-s3/lib/pipeline-action.ts
@@ -23,11 +23,11 @@ export interface CommonPipelineSourceActionProps extends codepipeline.CommonActi
    */
   bucketKey: string;
 
-  // TODO: use CloudWatch events instead
   /**
-   * Whether or not AWS CodePipeline should poll for source changes
+   * Whether AWS CodePipeline should poll for source changes.
+   * If this is `false`, the Pipeline will use CloudWatch Events to detect source changes instead.
    *
-   * @default true
+   * @default false
    */
   pollForSourceChanges?: boolean;
 }
@@ -53,11 +53,16 @@ export class PipelineSourceAction extends codepipeline.SourceAction {
       configuration: {
         S3Bucket: props.bucket.bucketName,
         S3ObjectKey: props.bucketKey,
-        PollForSourceChanges: props.pollForSourceChanges || true
+        PollForSourceChanges: props.pollForSourceChanges || false,
       },
       ...props,
     });
 
+    if (!props.pollForSourceChanges) {
+      props.bucket.onObjectPut(props.stage.pipeline.uniqueId + 'SourceEventRule',
+          props.stage.pipeline, props.bucketKey);
+    }
+
     // pipeline needs permissions to read from the S3 bucket
     props.bucket.grantRead(props.stage.pipeline.role);
   }
diff --git a/packages/@aws-cdk/aws-s3/package.json b/packages/@aws-cdk/aws-s3/package.json
index 76044d9f465f0..3b131ae275203 100644
--- a/packages/@aws-cdk/aws-s3/package.json
+++ b/packages/@aws-cdk/aws-s3/package.json
@@ -60,6 +60,7 @@
   },
   "dependencies": {
     "@aws-cdk/aws-codepipeline-api": "^0.18.1",
+    "@aws-cdk/aws-events": "^0.18.1",
     "@aws-cdk/aws-iam": "^0.18.1",
     "@aws-cdk/aws-kms": "^0.18.1",
     "@aws-cdk/aws-s3-notifications": "^0.18.1",
@@ -68,9 +69,10 @@
   "homepage": "https://github.com/awslabs/aws-cdk",
   "peerDependencies": {
     "@aws-cdk/aws-codepipeline-api": "^0.18.1",
+    "@aws-cdk/aws-events": "^0.18.1",
     "@aws-cdk/aws-iam": "^0.18.1",
     "@aws-cdk/aws-kms": "^0.18.1",
     "@aws-cdk/aws-s3-notifications": "^0.18.1",
     "@aws-cdk/cdk": "^0.18.1"
   }
-}
\ No newline at end of file
+}
diff --git a/packages/@aws-cdk/aws-s3/test/test.notifications.ts b/packages/@aws-cdk/aws-s3/test/test.notifications.ts
index 69e183f98049a..eac7130029135 100644
--- a/packages/@aws-cdk/aws-s3/test/test.notifications.ts
+++ b/packages/@aws-cdk/aws-s3/test/test.notifications.ts
@@ -298,5 +298,50 @@ export = {
     });
 
     test.done();
-  }
+  },
+
+  'CloudWatch Events': {
+    'onPutItem contains the Bucket ARN itself when path is undefined'(test: Test) {
+      const stack = new cdk.Stack();
+      const bucket = s3.BucketRef.import(stack, 'Bucket', {
+        bucketName: 'MyBucket',
+      });
+      bucket.onObjectPut('PutRule');
+
+      expect(stack).to(haveResource('AWS::Events::Rule', {
+        "EventPattern": {
+          "source": [
+            "aws.s3",
+          ],
+          "detail": {
+            "eventSource": [
+              "s3.amazonaws.com",
+            ],
+            "eventName": [
+              "PutObject",
+            ],
+            "resources": {
+              "ARN": [
+                {
+                  "Fn::Join": [
+                    "",
+                    [
+                      "arn:",
+                      {
+                        "Ref": "AWS::Partition",
+                      },
+                      ":s3:::MyBucket",
+                    ],
+                  ],
+                },
+              ],
+            },
+          },
+        },
+        "State": "ENABLED",
+      }));
+
+      test.done();
+    },
+  },
 };