EventBridge (CloudWatch Events) for Step Functions execution status changes

Amazon EventBridge is an AWS service that enables you to respond to state changes in an AWS resource. You can use AWS Step Functions Standard Workflows with EventBridge, while Express Workflows do not emit events to EventBridge. There are two ways to use Step Functions Standard Workflows with EventBridge.

You can configure Step Functions to emit EventBridge events when an execution status changes. This enables you to monitor your workflows without having to constantly poll using the DescribeExecution API. Based on changes in state machine executions you can use an EventBridge target to start new state machine executions, call AWS Lambda functions, publish messages to Amazon Simple Notification Service (Amazon SNS) topics, and more.

You can also configure a Step Functions state machine as a target in EventBridge. This enables you to trigger an execution of a Step Functions workflow in response to an event from another AWS service.

For more information, see the Amazon EventBridge User Guide .

EventBridge payloads

An EventBridge event can contain an input property in its definition. For some events, an EventBridge event can also contain an output property in its definition.

• If the combined escaped input and escaped output sent to EventBridge exceeds 248KB, then the input will be excluded. Similarly, if the escaped output exceeds 248KB, then the output will be excluded. This is a result of the EventBridge events quotas.

• You can determine whether a payload has been truncated with the inputDetails and outputDetails properties. For more information, see the CloudWatchEventsExecutionDataDetails Data Type.

• For Standard Workflows, you can see the full input and output by using DescribeExecution.

• DescribeExecution is not available for Express Workflows. If you want to see the full input/output, you can wrap your Express Workflow with a Standard Workflow. Another option is to use Amazon S3 ARNs. For information about using ARNs, see Use Amazon S3 ARNs instead of passing large payloads.

Step Functions event examples

The following are examples of Step Functions sending events to EventBridge:

Topics

• Execution started
• Execution succeeded
• Execution failed
• Execution timed out
• Execution aborted

In each case, the detail section in the event data provides the same information as the DescribeExecution API. The status field indicates the status of the execution at the time the event was sent, one of RUNNING, SUCCEEDED, FAILED, TIMED_OUT, or ABORTED depending on the event emitted.

Execution started

{
    "version": "0",
    "id": "315c1398-40ff-a850-213b-158f73e60175",
    "detail-type": "Step Functions Execution Status Change",
    "source": "aws.states",
    "account": "012345678912",
    "time": "2019-02-26T19:42:21Z",
    "region": "us-east-1",
    "resources": [
      "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name"
    ],
    "detail": {
        "executionArn": "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name",
        "stateMachineArn": "arn:aws:states:us-east-1:012345678912:stateMachine:state-machine",
        "name": "execution-name",
        "status": "RUNNING",
        "startDate": 1551225271984,
        "stopDate":  null,
        "input": "{}",
        "inputDetails": {
             "included": true
        },
        "output": null,
        "outputDetails": null
    }
}

Execution succeeded

{
    "version": "0",
    "id": "315c1398-40ff-a850-213b-158f73e60175",
    "detail-type": "Step Functions Execution Status Change",
    "source": "aws.states",
    "account": "012345678912",
    "time": "2019-02-26T19:42:21Z",
    "region": "us-east-1",
    "resources": [
      "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name"
    ],
    "detail": {
        "executionArn": "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name",
        "stateMachineArn": "arn:aws:states:us-east-1:012345678912:stateMachine:state-machine",
        "name": "execution-name",
        "status": "SUCCEEDED",
        "startDate": 1547148840101,
        "stopDate": 1547148840122,
        "input": "{}",
        "inputDetails": {
             "included": true
        },
        "output": "\"Hello World!\"",
        "outputDetails": {
             "included": true
        }
    }
}

Execution failed

{
    "version": "0",
    "id": "315c1398-40ff-a850-213b-158f73e60175",
    "detail-type": "Step Functions Execution Status Change",
    "source": "aws.states",
    "account": "012345678912",
    "time": "2019-02-26T19:42:21Z",
    "region": "us-east-1",
    "resources": [
      "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name"
    ],
    "detail": {
        "executionArn": "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name",
        "stateMachineArn": "arn:aws:states:us-east-1:012345678912:stateMachine:state-machine",
        "name": "execution-name",
        "status": "FAILED",
        "startDate": 1551225146847,
        "stopDate": 1551225151881,
        "input": "{}",
        "inputDetails": {
             "included": true
        },
        "output": null,
        "outputDetails": null
    }
}

Execution timed out

{
    "version": "0",
    "id": "315c1398-40ff-a850-213b-158f73e60175",
    "detail-type": "Step Functions Execution Status Change",
    "source": "aws.states",
    "account": "012345678912",
    "time": "2019-02-26T19:42:21Z",
    "region": "us-east-1",
    "resources": [
      "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name"
    ],
    "detail": {
        "executionArn": "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name",
        "stateMachineArn": "arn:aws:states:us-east-1:012345678912:stateMachine:state-machine",
        "name": "execution-name",
        "status": "TIMED_OUT",
        "startDate": 1551224926156,
        "stopDate": 1551224927157,
        "input": "{}",
        "inputDetails": {
             "included": true
        },
        "output": null,
        "outputDetails": null
    }
}

Execution aborted

{
    "version": "0",
    "id": "315c1398-40ff-a850-213b-158f73e60175",
    "detail-type": "Step Functions Execution Status Change",
    "source": "aws.states",
    "account": "012345678912",
    "time": "2019-02-26T19:42:21Z",
    "region": "us-east-1",
    "resources": [
      "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name"
    ],
    "detail": {
        "executionArn": "arn:aws:states:us-east-1:012345678912:execution:state-machine-name:execution-name",
        "stateMachineArn": "arn:aws:states:us-east-1:012345678912:stateMachine:state-machine",
        "name": "execution-name",
        "status": "ABORTED",
        "startDate": 1551225014968,
        "stopDate": 1551225017576,
        "input": "{}",
        "inputDetails": {
             "included": true
        },
        "output": null,
        "outputDetails": null
    }
}

Routing a Step Functions event to EventBridge in the EventBridge console

1. On the Details page of a state machine, choose Actions, Create EventBridge (CloudWatch Events) event rule.

   

   Alternatively, open the EventBridge console at https://console.aws.amazon.com/events/. In the navigation pane, choose Events, Rules.

2. Choose Create rule.

3. Under Event Source, ensure Event Pattern is selected.

4. For Service Name, choose Step Functions.

5. For Event Type, choose Step Functions Execution Status Change.

6. Optionally, configure a specific status, state machine Amazon Resource Name (ARN), or execution ARN.

7. Under Targets, choose Add target, and select a target from the list. For example, you could launch a Lambda function, or start an execution of a Step Functions state machine.

8. Add detailed information for your specific target.

9. Choose Configure details. On the Configure rule details page, enter a Name and Description.

10. Choose Create rule.