Tutorial: Schedule AWS Lambda functions using EventBridge

You can set up a rule to run an AWS Lambda function on a schedule. This tutorial shows how to use the AWS Management Console or the AWS CLI to create the rule. If you want to use the AWS CLI but haven't installed it, see the Installing, updating, and uninstalling the AWS CLI version 2.

For schedules, EventBridge doesn't provide second-level precision in schedule expressions. The finest resolution using a cron expression is one minute. Due to the distributed nature of EventBridge and the target services, there can be a delay of several seconds between the time the scheduled rule is triggered and the time the target service runs the target resource.

Step 1: Create a Lambda function

Create a Lambda function to log the scheduled events.

To create a Lambda function

1. Open the AWS Lambda console at https://console.aws.amazon.com/lambda/.

2. Choose Create function.

3. Choose Author from scratch.

4. Enter a name and description for the Lambda function. For example, name the function LogScheduledEvent.

5. Leave the rest of the options as the defaults and choose Create function.

6. On the Code tab of the function page, double-click index.js.

7. Replace the existing code with the following code.

   'use strict';
   
   exports.handler = (event, context, callback) => {
       console.log('LogScheduledEvent');
       console.log('Received event:', JSON.stringify(event, null, 2));
       callback(null, 'Finished');
   };

8. Choose Deploy.

Step 2: Create a Rule

Create a rule to run the Lambda function you created in step 1 on a schedule.

You can use either the console or the AWS CLI to create the rule. To use the AWS CLI, you first grant the rule permission to invoke your Lambda function. Then you can create the rule and add the Lambda function as a target.

To create a rule (console)

1. Open the Amazon EventBridge console at https://console.aws.amazon.com/events/.

2. In the navigation pane, choose Rules.

3. Choose Create rule.

4. Enter a name and description for the rule.

   A rule can't have the same name as another rule in the same Region and on the same event bus.

5. For Event bus, choose the event bus that you want to associate with this rule. If you want this rule to match events that come from your account, select AWS default event bus. When an AWS service in your account emits an event, it always goes to your account’s default event bus.

6. For Rule type, choose Schedule.

7. Choose Next.

8. For Schedule pattern, choose A schedule that runs at a regular rate, such as every 10 minutes. and enter 5 and choose Minutes from the drop-down list.

9. Choose Next.

10. For Target types, choose AWS service.

11. For Select a target, choose Lambda function from the drop-down list.

12. For Function, select the Lambda function that you created in the Step 1: Create a Lambda function section. In this example, select LogScheduledEvent.

13. Choose Next.

14. Choose Next.

15. Review the details of the rule and choose Create rule.

To create a rule (AWS CLI)

1. To create a rule that runs on a schedule, use the put-rule command.

   aws events put-rule \
   --name my-scheduled-rule \
   --schedule-expression 'rate(5 minutes)'

   When this rule runs, it creates an event and then sends it to the targets. The following is an example event.

   {
       "version": "0",
       "id": "53dc4d37-cffa-4f76-80c9-8b7d4a4d2eaa",
       "detail-type": "Scheduled Event",
       "source": "aws.events",
       "account": "123456789012",
       "time": "2015-10-08T16:53:06Z",
       "region": "us-east-1",
       "resources": [
           "arn:aws:events:us-east-1:123456789012:rule/my-scheduled-rule"
       ],
       "detail": {}
   }

2. To grant the EventBridge service principal (events.amazonaws.com) permission to run the rule, use the add-permission command.

   aws lambda add-permission \
   --function-name LogScheduledEvent \
   --statement-id my-scheduled-event \
   --action 'lambda:InvokeFunction' \
   --principal events.amazonaws.com \
   --source-arn arn:aws:events:us-east-1:123456789012:rule/my-scheduled-rule

3. Create the file targets.json with the following contents.

   [
     {
       "Id": "1", 
       "Arn": "arn:aws:lambda:us-east-1:123456789012:function:LogScheduledEvent"
     }
   ]

4. To add the Lambda function that you created in step 1 to the rule, use the put-targetscommand .

   aws events put-targets --rule my-scheduled-rule --targets file://targets.json

Step 3: Verify the rule

Wait at least five minutes after completing step 2, and then you can verify that your Lambda function was invoked.

View the output from your Lambda function

1. Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.

2. In the navigation pane, choose Logs.

3. Select the name of the log group for your Lambda function (/aws/lambda/function-name).

4. Select the name of the log stream to view the data provided by the function for the instance that you launched.

Step 4: Confirm success

If you see the Lambda event in the CloudWatch logs, you've successfully completed this tutorial. If the event isn't in your CloudWatch logs, start troubleshooting by verifying the rule was created successfully and, if the rule looks correct, verify the code of your Lambda function is correct.

Step 5: Clean up your resources

You can now delete the resources that you created for this tutorial, unless you want to retain them. By deleting AWS resources that you are no longer using, you prevent unnecessary charges to your AWS account.

To delete the EventBridge rule(s)

1. Open the Rules page of the EventBridge console.

2. Select the rule(s) that you created.

3. Choose Delete.

4. Choose Delete.

To delete the Lambda function(s)

1. Open the Functions page of the Lambda console.

2. Select the function(s) that you created.

3. Choose Actions, Delete.

4. Choose Delete.