Lambada

Create more passionate AWS Lambda functions using clojure. The library works to create a seamless interface between Clojure and AWS Lambda, facilitating the development of serverless applications. This document outlines building, and deploying a Clojure-based AWS Lambda function.

Current version:

Usage

Defining the Lambda Handler

The Lambda handler is the function AWS Lambda invokes when your function is executed. In Clojure, we can define a Lambda handler using the deflambdafn macro provided by the lambada.core namespace.

Here is a step-by-step guide to set up your Lambda handler:

1. Namespace Declaration: Start by declaring your namespace and importing the required libraries.

(ns example.lambda
  (:require [lambada.core :refer [deflambdafn]]))

2. Defining the Function Logic: Create a function that contains the business logic of your Lambda function. This function will take an event map as its parameter and return a map representing the Lambda response.

(defn do-something
  [event-map]
  {:status 200
   :body "Hello, World!"})

3. Defining the Lambda Handler: Use the deflambdafn macro to define your Lambda handler. This macro takes three parameters: the input stream, the output stream, and the Lambda context.

(deflambdafn example.lambda.MyLambdaFn
  [in out ctx]
  (let [event (json/read (io/reader in))
        response (do-something event)]
    (with-open [w (io/writer out)]
      (json/write response w))))

Building the .jar

Once your Lambda handler is defined, the next step is to build the project into a .jar file, which can be uploaded to AWS Lambda. This .jar file will include all the necessary dependencies and compiled classes.

Simple Uberjar Deployment

The simplest way to deploy is to create an uberjar using tools like Leiningen or Boot. These tools will bundle your application and its dependencies into a single, executable JAR file.

For example, if you are using Leiningen, you can add the following to your project.clj file:

:uberjar-name "my-lambda-project.jar"

And then run:

$ lein uberjar

This command will generate the my-lambda-project.jar file in the target directory.

When this namespace is AOT compiled, it will generate a class called example.lambda.MyLambdaFn that implements the AWS Lambda RequestStreamHandler interface using the args and body provided.

Deploying to AWS

Once you have your uberjar ready, you can deploy your Clojure Lambda function to AWS.

AWS CLI

The AWS Command Line Interface (CLI) is a powerful tool to manage AWS services. You can use it to deploy your Lambda function with the following command:

$ aws lambda create-function \
    --region us-east-1 \
    --function-name my-lambda \
    --zip-file fileb://$(pwd)/target/my-lambda-project.jar \
    --role arn:aws:iam::YOUR-AWS-ACCOUNT-ID:role/lambda_basic_execution \
    --handler example.lambda.MyLambdaFn \
    --runtime java11 \
    --timeout 15 \
    --memory-size 512

Cloudformation

AWS CloudFormation provides a way to model and provision AWS infrastructure resources. You can define your Lambda function and its associated resources in a YAML template and deploy it using the AWS Management Console, AWS CLI, or AWS SDKs.

Below is a sample CloudFormation template to deploy your Lambda function:

AWSTemplateFormatVersion: '2010-09-09'
Resources:
  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      Handler: example.lambda.MyLambdaFn
      Role: arn:aws:iam::YOUR-AWS-ACCOUNT-ID:role/lambda_basic_execution
      Code:
        S3Bucket: <Your S3 Bucket Name>
        S3Key: <S3 Key to your my-lambda-project.jar file>
      Runtime: java11
      MemorySize: 512
      Timeout: 15

It can also be written in .json.

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "MyLambdaFunction": {
      "Type": "AWS::Lambda::Function",
      "Properties": {
        "Handler": "example.lambda.MyLambdaFn",
        "Role": "arn:aws:iam::YOUR-AWS-ACCOUNT-ID:role/lambda_basic_execution",
        "Code": {
          "S3Bucket": "<Your S3 Bucket Name>",
          "S3Key": "<S3 Key to your my-lambda-project.jar file>"
        },
        "Runtime": "java11",
        "MemorySize": 512,
        "Timeout": 15
      }
    }
  }
}

See here for an example project.

License

Copyright © 2015 Ragnar Dahlen Copyright © 2023 Kevin Ewing

Distributed under the Eclipse Public License, the same as Clojure.