aws-sdk-java-v2 VS AWSLambdaJavaSnapStart

In this article we'll now add another dimension to our measurements : the choice of HTTP Client implementation. This is also interesting, because starting from AWS SDK for Java version 2.22 AWS added support for their own implementation of the synchronous CRT HTTP Client. The asynchronous CRT HTTP client has been generally available since February 2023. In this article we'll explore synchronous HTTP clients first and leave asynchronous ones for the next article.

The updates could be parsed from the github repo's CHANGELOG files (ex: javascript, java, python). I'm picturing an RSS feed generated for a specific language and module (ex: python s3, javascript s3, java sqs)

Meanwhile the [SDK doesn't provide samples or an API for USER_SRP_AUTH AuthFlow](https://github.com/aws/aws-sdk-java-v2/issues/2851). (I don't think that's the right choice, anyway, because if I'm right I'd have to register my user in my new app, and I don't want to do that).

Bonus: AWS SDK for Java v2 - this one I'm not sure of their reasons, but this request to add nullability annotations was filed 4.5 years ago, and there has been virtually no movement or feedback on it, so I can only speculate about their reasons for not fixing this.

If you think its a genuine bug in the API or the client somehow I think opening an issue in the github repo for the sdk might be a good place to start https://github.com/aws/aws-sdk-java-v2/issues .

Should be possible to just issue a GetObject with a range for the initial request skipping a head request. See here for caveats about how the Content Range data is returned in the response header: https://github.com/aws/aws-sdk-java-v2/issues/1209

V2 AWS SDK for Dynamo DB, SNS, and SQS

DynamoDB mapper AWS SDK v2 readme

In the part 2 of the series we introduced AWS Serverless Java Container and in the part 3 we demonstrated how to write AWS Lambda with AWS Serverless Java Container using Java 21 and Spring Boot 3.2. In this article of the series, we'll measure the cold and warm start time including enabling SnapStart on the Lambda function but also applying various priming techniques like priming the DynamoDB invocation and priming the whole web request. We'll use Spring Boot 3.2 sample application for our measurements, and for all Lambda functions use JAVA_TOOL_OPTIONS: "-XX:+TieredCompilation -XX:TieredStopAtLevel=1" and give them all 1024 MB memory.

In our experiment we'll re-use the application introduced in part 8 for this. Here is the code for the sample application. There are basically 2 Lambda functions which both respond to the API Gateway requests and retrieve product by id received from the Api Gateway from DynamoDB. One Lambda function GetProductByIdWithPureJava17Lambda can be used with and without SnapStart and the second one GetProductByIdWithPureJava17LambdaAndPriming uses SnapStart and DynamoDB request invocation priming. We'll measure cold starts using the following memory settings in MBs : 256, 512, 768, 1024, 1536 and 2048.

For the sake of explanation we'll use our Spring Boot 3.2 sample application and use Java 21 runtime for our Lambda functions.

Medium Size application with DynamoDB persistence. We'll re-use the application introduced in part 8 for this. There are basically 2 Lambda functions which both respond to the API Gateway requests and retrieve product by id received from the API Gateway from DynamoDB. One Lambda function can be used with and without SnapStart and the second one uses SnapStart and DynamoDB request invocation priming. There are bunch of dependencies declared in pom.xml like aws-lambda-java-core, aws-lambda-java-events, slf4j-simple, crac, dynamodb and url-connection-client. The deployment size of such application is 15 MB.

and others will be a part of a separate project and therefore also used without the usage of the all other AWS Serverless Java Container APIs only for purpose of mocking the API Gateway Request/Response (i.e. for Priming). I've already used them for Priming requests for Quarkus and Micronaut frameworks. Dependency to the AWS Serverless Java Container was included by default for the Micronaut on AWS Lambda SnapStart Priming example and needed to be added explicitly for the Quarkus on AWS Lambda SnapStart Priming example only to implement web request priming. We'll make use of these abstractions in one of our subsequent articles when we'll discuss cold and warm start time improvements for Spring Boot 3 application on AWS Lambda using AWS Lambda SnapStart in conjunction with priming techniques.

Using the asynchronous DynamoDBClient means that we'll be using the asynchronous programming model, so the invocation of getItem will return CompletableFuture and this is the code to retrieve the item itself (for the complete code see)

Let's figure out how to configure the HTTP Client. There are 2 places to do it : pom.xml and DynamoProductDao

In our experiment we'll re-use the application introduced in part 9 for this. There are basically 2 Lambda functions which both respond to the API Gateway requests and retrieve product by id received from the API Gateway from DynamoDB. One Lambda function GetProductByIdWithPureJava21Lambda can be used with and without SnapStart and the second one GetProductByIdWithPureJava21LambdaAndPriming uses SnapStart and DynamoDB request invocation priming. We'll measure cold and warm starts using the following memory settings in MBs : 256, 512, 768, 1024, 1536 and 2048. I also put the cold starts measured in the part 12 into the tables to see both cold and warm starts in one place. The results of the experiment below were based on reproducing more than 100 cold and approximately 100.000 warm starts for the duration of our experiment which ran for approximately 1 hour. Here is the code for the sample application. For it (and experiments from my previous article) I used the load test tool hey, but you can use whatever tool you want, like Serverless-artillery or Postman. Abbreviation c is for the cold start and w is for the warm start.

Small HelloWorld-style application which consists of Lambda receiving the APIGateway request with product id and basically prints this id out. There is no persistence layer involved. The application is that simple, that there is now priming to be applied. There are only several dependencies declared in pom.xml like aws-lambda-java-core and slf4j-simple. The deployment artifact size of such application is 137 KB only.

For measurement purposes I created/copied the sample application and configured Lambda functions to use Java 17 runtime for Lambda and 1024 MB memory .