The content of this repository showcases ways to prime and improve the latency of your Java Lambda functions using runtime hooks supported by AWS Lambda. Runtime hooks are available as part of the open source CRaC (Coordinated Restore at Checkpoint) project. You can use the "beforeCheckpoint()" hook to run code immediately before a snapshot is taken, and use the "afterRestore()" hook to run code immediately after restoring a snapshot.

Priming is a mechanism to further optimize and enhance the performance of Lambda function performance, especially for use cases requiring consistent low latency, such as APIs and real-time data processing services.

• Create an AWS account if you do not already have one and log in. The IAM user that you use must have sufficient permissions to make necessary AWS service calls and manage AWS resources.
• AWS CLI installed and configured
• Git Installed
• AWS Cloud Development Kit (AWS CDK) installed
• Java 21
• Maven
• curl

1. Create a new directory, navigate to that directory in a terminal and clone the GitHub repository:

   git clone https://github.com/aws-samples/lambda-priming-crac-java-cdk
   

2. Change directory to the infrastructure directory:

   cd lambda-priming-crac-java-cdk/infrastructure
   

3. Deploy the stack:

   cdk deploy --require-approval never --all 2>&1 | tee cdk_output.txt
   

1. Extract URLs:

   ONDEMAND_URL=$(grep -oE 'https://[a-zA-Z0-9.-]+\.execute-api\.[a-zA-Z0-9-]+\.amazonaws\.com/prod/' "cdk_output.txt" | head -n 1) \
   NOPRIMING_URL=$(grep -oE 'https://[a-zA-Z0-9.-]+\.execute-api\.[a-zA-Z0-9-]+\.amazonaws\.com/prod/' "cdk_output.txt" | head -n 2 | tail -n 1) \
   INVOKEPRIMING_URL=$(grep -oE 'https://[a-zA-Z0-9.-]+\.execute-api\.[a-zA-Z0-9-]+\.amazonaws\.com/prod/' "cdk_output.txt" | head -n 3 | tail -n 1) \
   CLASSPRIMING_URL=$(grep -oE 'https://[a-zA-Z0-9.-]+\.execute-api\.[a-zA-Z0-9-]+\.amazonaws\.com/prod/' "cdk_output.txt" | head -n 4 | tail -n 1) \
   SETUP_URL=$(grep -oE 'https://[a-zA-Z0-9.-]+\.execute-api\.[a-zA-Z0-9-]+\.amazonaws\.com/prod/' "cdk_output.txt" | head -n 5 | tail -n 1)
   

2. Initialize the database:

   curl -X GET "$SETUP_URL"
   

3. It should return:

   {"message":"Database schema initialized and data loaded"}
   

4. Run load test:

   artillery run -t "$ONDEMAND_URL" -v '{ "url": "/unicorn" }' ./loadtest.yaml && \
   artillery run -t "$NOPRIMING_URL" -v '{ "url": "/unicorn" }' ./loadtest.yaml && \
   artillery run -t "$INVOKEPRIMING_URL" -v '{ "url": "/unicorn" }' ./loadtest.yaml && \
   artillery run -t "$CLASSPRIMING_URL" -v '{ "url": "/unicorn" }' ./loadtest.yaml
   

You can use the following AWS CloudWatch Insights query to measure the duration your SnapStart Lambda function.

filter @type = "REPORT"
  | parse @log /\d+:\/aws\/lambda\/(?<function>.*)/
  | parse @message /Restore Duration: (?<restoreDuration>.*?) ms/
  | stats
count(*) as invocations,
pct(@duration+coalesce(@initDuration,0)+coalesce(restoreDuration,0), 50) as p50,
pct(@duration+coalesce(@initDuration,0)+coalesce(restoreDuration,0), 90) as p90,
pct(@duration+coalesce(@initDuration,0)+coalesce(restoreDuration,0), 99) as p99,
pct(@duration+coalesce(@initDuration,0)+coalesce(restoreDuration,0), 99.9) as p99.9
group by function, (ispresent(@initDuration) or ispresent(restoreDuration)) as coldstart
  | sort by function asc | sort by coldstart desc

Select the log groups bellow:

/aws/lambda/PrimingLogGroup-1_ON_DEMAND
/aws/lambda/PrimingLogGroup-2_SnapStart_NO_PRIMING
/aws/lambda/PrimingLogGroup-3_SnapStart_INVOKE_PRIMING
/aws/lambda/PrimingLogGroup-4_SnapStart_CLASS_PRIMING

You can run the lambdas, PrimingJavaLambdaFunction-5_DB_LOADER and PrimingJavaLambdaFunction-4_SnapStart_CLASS_PRIMING, locally with the commands below:

• Docker installed and configured
• AWS Serverless Application Model (AWS SAM) installed

1. Start Postgres locally using Docker:

   docker-compose --file local/docker-compose.yml up
   

2. Init the database using the DB_LOADER lambda:

   sam local invoke PrimingJavaLambdaFunction-5_DB_LOADER --env-vars local/env-vars.json --template cdk.out/LambdaPrimingCracJavaCdkStack.template.json --docker-network host
   

3. Testing lambda functions locally:

   sam local invoke PrimingJavaLambdaFunction-1_ON_DEMAND --env-vars local/env-vars.json --template cdk.out/LambdaPrimingCracJavaCdkStack.template.json --docker-network host
   
   sam local invoke PrimingJavaLambdaFunction-2_SnapStart_NO_PRIMING --env-vars local/env-vars.json --template cdk.out/LambdaPrimingCracJavaCdkStack.template.json --docker-network host
   
   sam local invoke PrimingJavaLambdaFunction-3_SnapStart_INVOKE_PRIMING --env-vars local/env-vars.json --template cdk.out/LambdaPrimingCracJavaCdkStack.template.json --docker-network host
   
   sam local invoke PrimingJavaLambdaFunction-4_SnapStart_CLASS_PRIMING --env-vars local/env-vars.json --template cdk.out/LambdaPrimingCracJavaCdkStack.template.json --docker-network host
   

cdk destroy --require-approval never --all