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Delvin Defoe edited this page Jan 17, 2024 · 1 revision

Trigger Your Lambda Function with DynamoDB Stream

There are multiple ways to trigger or invoke your AWS Lambda function. You can invoke your function directly using

  • the AWS Lambda console
  • a function URL HTTP(S) endpoint
  • the Lambda API
  • an AWS SDK
  • the AWS Command Line Interface (AWS CLI)
  • AWS toolkits

You can also configure Lambda to read items from a DynamoDB stream and invoke your function to process them. This is what we will focus on in this article.

Trigger lambda function to process items from DynamoDB stream

Consider the following code snippet.

    import { DynamoEventSource } from 'aws-cdk-lib/aws-lambda-event-sources';
    import * as dynamodb from 'aws-cdk-lib/aws-dynamodb';
    import * as lambda from 'aws-cdk-lib/aws-lambda';

    // Provision your lambda function and complete its configuration
    declare const lambdaFunction : lambda.Function;

    
    // Provision your DynamoDb table with stream
    const catalogTable = new dynamodb.Table(this, 'CatalogTable', {
        partitionKey: {
            name: 'id',
            type: dynamodb.AttributeType.STRING,
        },
        stream: dynamodb.StreamViewType.NEW_IMAGE,
    });

    // Setup filter criteria for Lambda event filtering
    const filterCriteria = {
        dynamodb: {
            NewImage: {
                // filter criteria to process records with given author
                author: {
                    S: lambda.FilterRule.isEqual('Author One')
                },
                completionDateTime: {
                    N: lambda.FilterRule.notExists()
                } // AND no completion date time
            }
        }
    };

    // Add event source to trigger your function
    lambdaFunction.addEventSource(DynamoEventSource(table, {
        startingPosition: lambda.StartingPosition.TRIM_HORIZON,
        bisectBatchOnError: true,
        batchSize: 100,
        reportBatchItemFailures: true,
        parallelizationFactor: 10,
        filters: [lambda.FilterCriteria.filter(filterCriteria)],
    }));

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