jashburn8020/micronaut-lambda

Using Micronaut to implement an AWS Lambda function

Using Micronaut to implement an AWS Lambda function

Setup

• Create an application of the serverless function type using the Micronaut Command Line Interface
  • mn create-function-app <package>.<project_name> --features=aws-lambda --build=gradle --lang=java
    • <package>: the Java package for the Micronaut code
    • <project_name>: the name of the project root directory
  • e.g., the following will create the application in the micronaut-lambda directory with code in the com.jashburn.micronaut.lambda package:

$ mn create-function-app com.jashburn.micronaut.lambda.micronaut-lambda --features=aws-lambda --build=gradle --lang=java
| Application created at /home/jashburn/devel/sandbox/java/micronaut-lambda

$ cat settings.gradle 
rootProject.name="micronaut-lambda"

$ ls src/main/java/com/jashburn/micronaut/lambda/
FunctionRequestHandler.java

• If using IntelliJ IDEA, launch it and open the project root directory as a project
  • downloads various libraries
  • enable annotation processing
• Function handler code: src/main/java/com/jashburn/micronaut/lambda/FunctionRequestHandler.java
• Function test code: src/test/java/com/jashburn/micronaut/lambda/FunctionRequestHandlerTest.java
  • test: ./gradlew test
  • test report in build/reports/tests/test/index.html

$ ./gradlew test
Starting a Gradle Daemon (subsequent builds will be faster)

> Task :compileJava
Note: Creating bean classes for 1 type elements
warning: unknown enum constant When.MAYBE
  reason: class file for javax.annotation.meta.When not found
1 warning

BUILD SUCCESSFUL in 7s
4 actionable tasks: 4 executed

Deploy via AWS Console

Create a function in AWS

• Author from scratch
• Basic information:
  • function name: micronaut-lambda-simple
  • runtime: Java 11 (Corretto)
  • architecture: x86_64
  • permissions:
    • execution role: Create a new role with basic Lambda permissions
    • creates an execution role: micronaut-lambda-simple-role-<random>
      • e.g., micronaut-lambda-simple-role-b2fxbj9z
      • contains a policy: AWSLambdaBasicExecutionRole-<random>
        • e.g., AWSLambdaBasicExecutionRole-e19b426c-4e36-4440-a8fc-bfa263b41e09
        • allows upload logs to CloudWatch Logs
        • CloudWatch policy statements can be replaced by attaching the AWS-managed AWSLambdaBasicExecutionRole policy

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "logs:CreateLogGroup",
            "Resource": "arn:aws:logs:eu-west-2:612248661359:*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogStream",
                "logs:PutLogEvents"
            ],
            "Resource": [
                "arn:aws:logs:eu-west-2:612248661359:log-group:/aws/lambda/micronaut-lambda-simple:*"
            ]
        }
    ]
}

Upload code

• Create an executable jar including all dependencies
  • gradlew shadowJar
  • fat/uber jar created in build/libs/

$ ./gradlew shadowJar
Starting a Gradle Daemon, 1 incompatible and 1 stopped Daemons could not be reused, use --status for details

BUILD SUCCESSFUL in 7s
3 actionable tasks: 1 executed, 2 up-to-date

$ ls build/libs/
micronaut-lambda-0.1-all.jar

• Upload the jar file to the function
  • code source
    • upload from: .zip or .jar file
• Set the handler for the function
  • runtime settings
    • handler: com.jashburn.micronaut.lambda.FunctionRequestHandler

Test the function

• Test event
  • not necessary to provide an event name and/or use a template if you don't intend to save it
  • Event JSON:

{
  "path": "/",
  "httpMethod": "GET",
  "headers": {
    "Accept": "application/json"
  }
}

• Output:

{
  "statusCode": 200,
  "body": "{\"message\":\"Hello World\"}"
}

• Logs in CloudWatch log group: /aws/lambda/micronaut-lambda-simple

Clean up

• Delete function: micronaut-lambda-simple
• Delete role: micronaut-lambda-simple-role-<random>
• Delete policy: AWSLambdaBasicExecutionRole-<random>
• Delete log group /aws/lambda/micronaut-lambda-simple

Sources

• "Deploy a Serverless Micronaut Function to AWS Lambda Java 11 Runtime." Micronaut.io, 2022, guides.micronaut.io/latest/mn-serverless-function-aws-lambda-gradle-java.html. Accessed 20 November 2022.