Serverless | How to connect a Lambda function as trigger to a DynamoDB table

Question

I'm trying to connect a Lambda function as a trigger for a DynamoDB table.

In my serverless.yml file, I have defined a Lambda function and a DynamoDB table.

Question: How can I attach the Lambda function as a trigger to the DynamoDB?

My serverless.yaml (simplified):

functions:
  pushLeadEvent:
    handler: handler.pushLeadEvent
    events:
      - /* WHAT TO DO HERE? */

resources:
  Resources:
    leadEvent:
      Type: AWS::DynamoDB::Table
      Properties:
        TableName: leadEvent
        BillingMode: PAY_PER_REQUEST
        AttributeDefinitions:
          - AttributeName: owner
            AttributeType: S
          - AttributeName: timestamp
            AttributeType: N
        KeySchema:
          - AttributeName: owner
            KeyType: HASH
          - AttributeName: timestamp
            KeyType: RANGE

PatrykMilewski · Accepted Answer · 2020-10-05 13:50:19Z

3

Based on Serverless Framework documentation and my personal experience, I would recommend this:

functions:
  pushLeadEvent:
    handler: handler.pushLeadEvent
    dependsOn:
     - leadEvent
    events:
     - stream:
       type: dynamodb
       arn: !GetAtt leadEvent.StreamArn
       batchSize: 100
       startingPosition: LATEST
       maximumRetryAttempts: 10
       bisectBatchOnFunctionError: true
       enabled: true

This will:

Subcribe your Lambda to all of the changes in leadEvent table.
Single batch can have up to 100 events.
Lambda will retry to process an event up to 10 times, if it fails
On each retry, if batch has more than 1 event, it will be splitted into 2 separated batches by half

edited Oct 5, 2020 at 13:50

answered Oct 5, 2020 at 12:06

PatrykMilewski

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3 Comments

Vingtoft Over a year ago

Thank you. I get the error: EventSourceArn.split is not a function.

PatrykMilewski Over a year ago

Could you try adding dependsOn: - leadEvent in function definition? Just under handler definition, on the same yaml level, leadEvent should be defined as first element of list, search "dependsOn" here for better example: serverless.com/framework/docs/providers/aws/guide/…

Vingtoft Over a year ago

I got it to work. Needed to add dependsOn (as you mentioned), but also set type: dynamodb Thank you for your help!

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