Issues with SAM Script: EventBridge Rule Set for Multiple Lambdas Not Targeting Functions

Question

I'm currently utilizing serverless architecture with AWS SAM, employing Lambda, EventBridge, and SAM services for my application.

I'm encountering an issue with a Single EventBridge rule set that triggers multiple Lambda functions. The Lambda function names are correctly displayed in the event rule targets with ARN. However, when I inspect the Lambda function triggers, the names are not visible, and as a result, the functions are not being targeted.

Here's the relevant section of my SAM script:

```
## EventBridge rule to trigger Lambda functions
ScheduleRule:
  Type: AWS::Events::Rule
  Properties:
    Name: ScheduleRule-Event-Lambda
    Description: Event rule for scheduling Lambda
    EventBusName: default
    ScheduleExpression: rate(10 minutes) # Adjust the interval as needed
    State: ENABLED
    Targets:
      - Arn: !GetAtt function1.Arn
        Id: !Sub function1RuleTarget
      - Arn: !GetAtt function2.Arn
        Id: !Sub function2RuleTarget
```

When attempting to add this rule manually through the console, it works as expected. However, when using SAM, the addition is not allowed. I'm unsure if there's an issue with the script or if it's a permissions-related issue.

My ultimate goal is to establish a single rule for multiple Lambda functions without creating the same rule multiple times. Any insights into potential script or permission issues would be greatly appreciated.

Answer

Hello.

Have you set a resource-based policy on Lambda as shown below?  
```
Lambdafunction1Permission:
  Type: AWS::Lambda::Permission
  Properties:
    FunctionName:
      Ref: function1
    Action: lambda:InvokeFunction
    Principal: events.amazonaws.com
    SourceArn: !GetAtt ScheduleRule.Arn

Lambdafunction2Permission:
  Type: AWS::Lambda::Permission
  Properties:
    FunctionName:
      Ref: function2
    Action: lambda:InvokeFunction
    Principal: events.amazonaws.com
    SourceArn: !GetAtt ScheduleRule.Arn
```

Issues with SAM Script: EventBridge Rule Set for Multiple Lambdas Not Targeting Functions

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