AWS Lambda
Developer Guide

Sample Function Code

Sample code is available for the following languages.

Node.js

The following example processes messages from DynamoDB, and logs their contents.

Example ProcessDynamoDBStream.js

console.log('Loading function'); exports.lambda_handler = function(event, context, callback) { console.log(JSON.stringify(event, null, 2)); event.Records.forEach(function(record) { console.log(record.eventID); console.log(record.eventName); console.log('DynamoDB Record: %j', record.dynamodb); }); callback(null, "message"); };

Zip up the sample code to create a deployment package. For instructions, see AWS Lambda Deployment Package in Node.js.

Java 8

The following example processes messages from DynamoDB, and logs their contents. handleRequest is the handler that AWS Lambda invokes and provides event data. The handler uses the predefined DynamodbEvent class, which is defined in the aws-lambda-java-events library.

Example DDBEventProcessor.java

package example; import com.amazonaws.services.lambda.runtime.Context; import com.amazonaws.services.lambda.runtime.LambdaLogger; import com.amazonaws.services.lambda.runtime.RequestHandler; import com.amazonaws.services.lambda.runtime.events.DynamodbEvent; import com.amazonaws.services.lambda.runtime.events.DynamodbEvent.DynamodbStreamRecord; public class DDBEventProcessor implements RequestHandler<DynamodbEvent, String> { public String handleRequest(DynamodbEvent ddbEvent, Context context) { for (DynamodbStreamRecord record : ddbEvent.getRecords()){ System.out.println(record.getEventID()); System.out.println(record.getEventName()); System.out.println(record.getDynamodb().toString()); } return "Successfully processed " + ddbEvent.getRecords().size() + " records."; } }

If the handler returns normally without exceptions, Lambda considers the input batch of records as processed successfully and begins reading new records in the stream. If the handler throws an exception, Lambda considers the input batch of records as not processed and invokes the function with the same batch of records again.

Dependencies

  • aws-lambda-java-core

  • aws-lambda-java-events

Build the code with the Lambda library dependencies to create a deployment package. For instructions, see AWS Lambda Deployment Package in Java.

C#

The following example processes messages from DynamoDB, and logs their contents. ProcessDynamoEvent is the handler that AWS Lambda invokes and provides event data. The handler uses the predefined DynamoDbEvent class, which is defined in the Amazon.Lambda.DynamoDBEvents library.

Example ProcessingDynamoDBStreams.cs

using System; using System.IO; using System.Text; using Amazon.Lambda.Core; using Amazon.Lambda.DynamoDBEvents; using Amazon.Lambda.Serialization.Json; namespace DynamoDBStreams { public class DdbSample { private static readonly JsonSerializer _jsonSerializer = new JsonSerializer(); public void ProcessDynamoEvent(DynamoDBEvent dynamoEvent) { Console.WriteLine($"Beginning to process {dynamoEvent.Records.Count} records..."); foreach (var record in dynamoEvent.Records) { Console.WriteLine($"Event ID: {record.EventID}"); Console.WriteLine($"Event Name: {record.EventName}"); string streamRecordJson = SerializeObject(record.Dynamodb); Console.WriteLine($"DynamoDB Record:"); Console.WriteLine(streamRecordJson); } Console.WriteLine("Stream processing complete."); } private string SerializeObject(object streamRecord) { using (var ms = new MemoryStream()) { _jsonSerializer.Serialize(streamRecord, ms); return Encoding.UTF8.GetString(ms.ToArray()); } } } }

Replace the Program.cs in a .NET Core project with the above sample. For instructions, see .NET Core CLI.

Python 3

The following example processes messages from DynamoDB, and logs their contents.

Example ProcessDynamoDBStream.py

from __future__ import print_function def lambda_handler(event, context): for record in event['Records']: print(record['eventID']) print(record['eventName']) print('Successfully processed %s records.' % str(len(event['Records'])))

Zip up the sample code to create a deployment package. For instructions, see AWS Lambda Deployment Package in Python.

Go

The following example processes messages from DynamoDB, and logs their contents.

import ( "strings" "github.com/aws/aws-lambda-go/events" ) func handleRequest(ctx context.Context, e events.DynamoDBEvent) { for _, record := range e.Records { fmt.Printf("Processing request data for event ID %s, type %s.\n", record.EventID, record.EventName) // Print new values for attributes of type String for name, value := range record.Change.NewImage { if value.DataType() == events.DataTypeString { fmt.Printf("Attribute name: %s, value: %s\n", name, value.String()) } } } }

Zip up the sample code to create a deployment package. For instructions, see AWS Lambda Deployment Package in Python.

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