How to add triggers for a AWS Lambda function created using a CloudFormation template?

Question

I am trying to create a lambda function from a CloudFormation template based on this example:

http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/quickref-lambda.html

As can be seen from this link:

http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-lambda-function.html

there is no way to add a trigger for the lambda function (like a S3 upload trigger).

Is there a workaround to specify the trigger while writing the template?

Solution 1

You can use cloudwatch rule to trigger your lambda function :

    AWSTemplateFormatVersion: '2010-09-09'
    Resources:
      MyCloudWatchRule:
        Type: "AWS::Events::Rule"
        Properties:
          Description: "Rule to trigger lambda"
          Name: "MyCloudWatchRule"
          EventPattern: <Provide Valid JSON Event pattern>
          State: "ENABLED"
          Targets:
            - Arn: "arn:aws:lambda:us-west-2:12345678:function:MyLambdaFunction"
              Id: "1234567-acvd-awse-kllpk-123456789"

Ref :

• https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/CloudWatchEventsandEventPatterns.html
• https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-events-rule.html#aws-resource-events-rule-syntax
• https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-events-rule-target.html

Solution 2

It's been a while so I imagine you've solved the problem, but I'll put in my 2 cents to help others.

It's best to use SAM (Serverless Application Model) for this kind of things. So use AWS::Serverless::Function instead of AWS::Lambda::Function

https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/sam-resource-function.html

In there, you can specify an EventSource which accepts the following possible values:

• S3
• SNS
• Kinesis
• DynamoDB
• SQS
• Api
• Schedule
• CloudWatchEvent
• CloudWatchLogs
• IoTRule
• AlexaSkill
• Cognito
• HttpApi

SAM does the rest of the work. Follow this guide for the rest of the details: https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-deploying.html

Solution 3

Nowadays, this issue is fixed by Amazon: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-events-rule.html#aws-resource-events-rule--examples

Just create Lambda permissions like in the example.

Solution 4

Lambda function can be triggered by several AWS resources such as S3, SNS, SQS, API, etc. Checkout for the full list at AWS docs

I suggest you use Altostra Designer, which let you create and configure Lambda Function super quick and also choose what will trigger it.

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Comments

[Varun Chandak]

or can use DependsOn or add a wait time.

[Roelant]

Always nice to add the example for when the link get's deleted :)