feat(events): dead-letter queue support for StepFunctions

packages/@aws-cdk/aws-events-targets/README.md

@@ -89,3 +89,39 @@ const rule = new events.Rule(this, 'rule', {
 
 rule.addTarget(new targets.CloudWatchLogGroup(logGroup));
 ```
+
+## Trigger a State Machine
+
+Use the `SfnStateMachine` target to trigger a State Machine.
+
+The code snippet below creates a Simple StateMachine that is triggered every minute with a
+dummy object as input.
+You can optionally attach a
+[dead letter queue](https://docs.aws.amazon.com/eventbridge/latest/userguide/rule-dlq.html)
+to the target.
+
+```ts
+import * as iam from '@aws-sdk/aws-iam';
+import * as sqs from '@aws-sdk/aws-sqs';
+import * as sfn from '@aws-cdk/aws-stepfunctions';
+import * as targets from "@aws-cdk/aws-events-targets";
+
+const rule = new events.Rule(stack, 'Rule', {
+  schedule: events.Schedule.rate(cdk.Duration.minutes(1)),
+});
+
+const dlq = new sqs.Queue(stack, 'DeadLetterQueue');
+
+const role = new iam.Role(stack, 'Role', {
+  assumedBy: new iam.ServicePrincipal('events.amazonaws.com'),
+});
+const stateMachine = new sfn.StateMachine(stack, 'SM', {
+  definition: new sfn.Wait(stack, 'Hello', { time: sfn.WaitTime.duration(cdk.Duration.seconds(10)) }),
+  role,
+});
+
+rule.addTarget(new targets.SfnStateMachine(stateMachine, {
+  input: events.RuleTargetInput.fromObject({ SomeParam: 'SomeValue' }),
+  deadLetterQueue: dlq,
+}));
+```

packages/@aws-cdk/aws-events-targets/lib/state-machine.ts

@@ -1,7 +1,8 @@
 import * as events from '@aws-cdk/aws-events';
 import * as iam from '@aws-cdk/aws-iam';
+import * as sqs from '@aws-cdk/aws-sqs';
 import * as sfn from '@aws-cdk/aws-stepfunctions';
-import { singletonEventRole } from './util';
+import { addToDeadLetterQueueResourcePolicy, singletonEventRole } from './util';
 
 /**
  * Customize the Step Functions State Machine target
@@ -20,6 +21,18 @@ export interface SfnStateMachineProps {
    * @default - a new role will be created
    */
   readonly role?: iam.IRole;
+
+  /**
+   * The SQS queue to be used as deadLetterQueue.
+   * Check out the [considerations for using a dead-letter queue](https://docs.aws.amazon.com/eventbridge/latest/userguide/rule-dlq.html#dlq-considerations).
+   *
+   * The events not successfully delivered are automatically retried for a specified period of time,
+   * depending on the retry policy of the target.
+   * If an event is not delivered before all retry attempts are exhausted, it will be sent to the dead letter queue.
+   *
+   * @default - no dead-letter queue
+   */
+  readonly deadLetterQueue?: sqs.IQueue;
 }
 
 /**
@@ -43,9 +56,14 @@ export class SfnStateMachine implements events.IRuleTarget {
    * @see https://docs.aws.amazon.com/eventbridge/latest/userguide/resource-based-policies-eventbridge.html#sns-permissions
    */
   public bind(_rule: events.IRule, _id?: string): events.RuleTargetConfig {
+    if (this.props.deadLetterQueue) {
+      addToDeadLetterQueueResourcePolicy(_rule, this.props.deadLetterQueue);
+    }
+
     return {
       id: '',
       arn: this.machine.stateMachineArn,
+      deadLetterConfig: this.props.deadLetterQueue ? { arn: this.props.deadLetterQueue?.queueArn } : undefined,
       role: this.role,
       input: this.props.input,
       targetResource: this.machine,

packages/@aws-cdk/aws-events-targets/test/stepfunctions/statemachine.test.ts

@@ -1,6 +1,7 @@
 import '@aws-cdk/assert/jest';
 import * as events from '@aws-cdk/aws-events';
 import * as iam from '@aws-cdk/aws-iam';
+import * as sqs from '@aws-cdk/aws-sqs';
 import * as sfn from '@aws-cdk/aws-stepfunctions';
 import * as cdk from '@aws-cdk/core';
 import * as targets from '../../lib';
@@ -110,3 +111,95 @@ test('Existing role can be used for State machine Rule target', () => {
     },
   });
 });
+
+test('use a Dead Letter Queue for the rule target', () => {
+  // GIVEN
+  const app = new cdk.App();
+  const stack = new cdk.Stack(app, 'Stack');
+
+  const rule = new events.Rule(stack, 'Rule', {
+    schedule: events.Schedule.rate(cdk.Duration.minutes(1)),
+  });
+
+  const dlq = new sqs.Queue(stack, 'DeadLetterQueue');
+
+  const role = new iam.Role(stack, 'Role', {
+    assumedBy: new iam.ServicePrincipal('events.amazonaws.com'),
+  });
+  const stateMachine = new sfn.StateMachine(stack, 'SM', {
+    definition: new sfn.Wait(stack, 'Hello', { time: sfn.WaitTime.duration(cdk.Duration.seconds(10)) }),
+    role,
+  });
+
+  // WHEN
+  rule.addTarget(new targets.SfnStateMachine(stateMachine, {
+    input: events.RuleTargetInput.fromObject({ SomeParam: 'SomeValue' }),
+    deadLetterQueue: dlq,
+  }));
+
+  // the Permission resource should be in the event stack
+  expect(stack).toHaveResource('AWS::Events::Rule', {
+    ScheduleExpression: 'rate(1 minute)',
+    State: 'ENABLED',
+    Targets: [
+      {
+        Arn: {
+          Ref: 'SM934E715A',
+        },
+        DeadLetterConfig: {
+          Arn: {
+            'Fn::GetAtt': [
+              'DeadLetterQueue9F481546',
+              'Arn',
+            ],
+          },
+        },
+        Id: 'Target0',
+        Input: '{"SomeParam":"SomeValue"}',
+        RoleArn: {
+          'Fn::GetAtt': [
+            'SMEventsRoleB320A902',
+            'Arn',
+          ],
+        },
+      },
+    ],
+  });
+
+  expect(stack).toHaveResource('AWS::SQS::QueuePolicy', {
+    PolicyDocument: {
+      Statement: [
+        {
+          Action: 'sqs:SendMessage',
+          Condition: {
+            ArnEquals: {
+              'aws:SourceArn': {
+                'Fn::GetAtt': [
+                  'Rule4C995B7F',
+                  'Arn',
+                ],
+              },
+            },
+          },
+          Effect: 'Allow',
+          Principal: {
+            Service: 'events.amazonaws.com',
+          },
+          Resource: {
+            'Fn::GetAtt': [
+              'DeadLetterQueue9F481546',
+              'Arn',
+            ],
+          },
+          Sid: 'AllowEventRuleStackRuleF6E31DD0',
+        },
+      ],
+      Version: '2012-10-17',
+    },
+    Queues: [
+      {
+        Ref: 'DeadLetterQueue9F481546',
+      },
+    ],
+  });
+});