Send a custom event to an EventBridge event bus

This sample project demonstrates how to use Step Functions to send a custom event to an event bus that matches a rule with multiple targets (Amazon EventBridge, AWS Lambda, Amazon Simple Notification Service, Amazon Simple Queue Service).

For more information about Step Functions and Step Functions service integrations, see the following:

• Integrating services with Step Functions

• Add EventBridge events with Step Functions

Note

This sample project may incur charges.

For new AWS users, a free usage tier is available. On this tier, services are free below a certain level of usage. For more information about AWS costs and the Free Tier, see EventBridge Pricing.

Step 1: Create the state machine

1. Open the Step Functions console and choose Create state machine.

2. Type Send a custom event to EventBridge in the search box, and then choose Send a custom event to EventBridge from the search results that are returned.

3. Choose Next to continue.

4. Choose Run a demo to create a read-only and ready-to-deploy workflow, or choose Build on it to create an editable state machine definition that you can build on and later deploy.

   This sample project deploys the following resources:

   • An Amazon EventBridge event

   • An Amazon SNS topic

   • An Amazon SQS queue

   • A Lambda function

   • An AWS Step Functions state machine

   • Related AWS Identity and Access Management (IAM) roles

   The following image shows the workflow graph for the Send a custom event to EventBridge sample project:

   

5. Choose Use template to continue with your selection.

Next steps depend on your previous choice:

1. Run a demo – You can review the state machine before you create a read-only project with resources deployed by AWS CloudFormation to your AWS account.

   You can view the state machine definition, and when you are ready, choose Deploy and run to deploy the project and create the resources.

   Deploying can take up to 10 minutes to create resources and permissions. You can use the Stack ID link to monitor progress in AWS CloudFormation.

   After deploy completes, you should see your new state machine in the console.

2. Build on it – You can review and edit the workflow definition. You might need to set values for placeholders in the sample project before attemping to run your custom workflow.

Note

Standard charges might apply for services deployed to your account.

Step 2: Run the state machine

1. On the State machines page, choose your sample project.

2. On the sample project page, choose Start execution.

3. In the Start execution dialog box, do the following:

   1. (Optional) Enter a custom execution name to override the generated default.

      Non-ASCII names and logging

      Step Functions accepts names for state machines, executions, activities, and labels that contain non-ASCII characters. Because such characters will not work with Amazon CloudWatch, we recommend using only ASCII characters so you can track metrics in CloudWatch.

   2. (Optional) In the Input box, enter input values as JSON. You can skip this step if you are running a demo.

   3. Choose Start execution.

   The Step Functions console will direct you to an Execution Details page where you can choose states in the Graph view to explore related information in the Step details pane.

Example State Machine Code

The state machine in this sample project integrates with EventBridge by sending a custom event to an EventBridge event bus. The event sent to the event bus matches an EventBridge rule that triggers a Lambda function that sends messages to an Amazon SNS topic and an Amazon SQS queue.

Browse through this example state machine to see how Step Functions manages EventBridge.

For more information about how AWS Step Functions can control other AWS services, see Integrating services with Step Functions.

{
  "Comment": "An example of the Amazon States Language for sending a custom event to Amazon EventBridge",
  "StartAt": "Send a custom event",
  "States": {
    "Send a custom event": {
      "Resource": "arn:<PARTITION>:states:::events:putEvents",
      "Type": "Task",
      "Parameters": {
        "Entries": [{
          "Detail": {
            "Message": "Hello from Step Functions!"
          },
          "DetailType": "MessageFromStepFunctions",
          "EventBusName": "<EVENT_BUS_NAME>",
          "Source": "my.statemachine"
        }]
      },
      "End": true
    }
  }
}

For information about how to configure IAM when using Step Functions with other AWS services, see How Step Functions generates IAM policies for integrated services.

IAM Example

These example AWS Identity and Access Management (IAM) policies generated by the sample project include the least privilege necessary to execute the state machine and related resources. We recommend that you include only those permissions that are necessary in your IAM policies.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "events:PutEvents"
            ],
            "Resource": [
                "arn:aws:events:us-east-1:1234567890:event-bus/stepfunctions-sampleproject-eventbus"
            ],
            "Effect": "Allow"
        }
    ]
}

For information about how to configure IAM when using Step Functions with other AWS services, see How Step Functions generates IAM policies for integrated services.