AWS Cloudwatch Event Rule - Invoke Lambda - with Parameter

Question

I am using AWS Clouwatch Event Rule to invoke a python lambda function based on Cron Schedule which is working fine.Now can I pass parameter into this lambda function from cloudwatch even rule using AWS Cloudformation? Could you please guide? Please see below my cfn template :

Step1 : parameter.Schedule=cron(0 21 ? * * *)

Step 2: "Schedule": {
            "Description": "Schedule for the Lambda function (cron or rate)",
            "Type": "String"
          },


Step 3:  "funcInvokeRule": {
            "Type": "AWS::Events::Rule",
            "Properties": {
                "ScheduleExpression": {"Ref": "Schedule"},
                "Targets": [{
                    "Id": "funcScheduler",
                    "Arn": {"Fn::GetAtt": ["Function","Arn"]}
                }]
            }
        },

pkarfs pkarfs · Accepted Answer · 2020-04-15T07:12:48

Following the AWS docs, your cloudformation resource could be as simple as:

Resources:  
  EventRule:
    Type: AWS::Events::Rule
    Properties:
      Name: {EVENTNAME}
      Description: "ScheduledRule"
      ScheduleExpression: cron(0 21 ? * * *)
      State: "ENABLED"
      RoleArn: {ROLE}

Replacing Name and RoleArn with your own values.

Note: Name is not a required parameter but does help identify your resources. However, as per the documentation, if you replace the resource in your cloudformation template you specify a new name.

If you were then also going to use cloudformation for your lambda using severless, personally I would then attached the rule to the lambda via permissions, that way you can attach up to 5 triggers on the rule without modifying the rule targets every time. e.g.

  Lambda:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName:{LAMBDANAME}
      Description: {Description}
      Role: {Role}
      Handler: {FileName}.lambda_handler
      Runtime: {x}
      CodeUri: {ObjectPath}
      MemorySize: {x}
      Timeout: {x}
  Lambdatrigger:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !Ref Lambda
      Action: lambda:InvokeFunction
      Principal: events.amazonaws.com
      SourceArn: !Ref EventRule

AWS Cloudwatch Event Rule - Invoke Lambda - with Parameter

2 Answers