scala-sam-app

Simple Scala SAM App

https://github.com/awslabs/serverless-application-model

Requirements

AWS CLI already configured with Administrator permission
Java SE Development Kit 8 installed
Docker installed
SBT

Setup process

Installing dependencies

We use sbt to install our dependencies and package our application into a JAR file:

sbt assembly

Local development

Invoking function locally through local API Gateway

sam local start-api

If the previous command ran successfully you should now be able to hit the following local endpoint to invoke your function http://localhost:3000/hello

If you go to /hello/somestuff you'll note different input from the API gateway, as now we are capturing path parameter proxy

Invoking via Intellij+AWS toolkit

https://plugins.jetbrains.com/plugin/11349-aws-toolkit

Create a local lambda invocation, for java8, and helloworld.App::handleRequest, and some example input, like { "name": "Fred" }

SAM CLI is used to emulate both Lambda and API Gateway locally and uses our template.yaml to understand how to bootstrap this environment (runtime, where the source code is, etc.) - The following excerpt is what the CLI will read in order to initialize an API and its routes:

...
Events:
    HelloWorld:
        Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
        Properties:
            Path: /hello
            Method: get
    HelloWorld2:
        Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
        Properties:
            Path: /hello/{proxy+}
            Method: get

Packaging and deployment

AWS Lambda Java runtime accepts either a zip file or a standalone JAR file - We use the latter in this example. SAM will use CodeUri property to know where to look up for both application and dependencies:

...
    HelloWorldFunction:
        Type: AWS::Serverless::Function
        Properties:
            CodeUri: target/scala-2.12/scala-sam-app-assembly-0.1.jar
            Handler: helloworld.App::handleRequest

Firstly, we need a S3 bucket where we can upload our Lambda functions packaged as ZIP before we deploy anything - If you don't have a S3 bucket to store code artifacts then this is a good time to create one:

aws s3 mb s3://BUCKET_NAME

Next, run the following command to package our Lambda function to S3:

sam package \
    --output-template-file packaged.yaml \
    --s3-bucket REPLACE_THIS_WITH_YOUR_S3_BUCKET_NAME

Next, the following command will create a Cloudformation Stack and deploy your SAM resources.

sam deploy \
    --template-file packaged.yaml \
    --stack-name sam-app \
    --capabilities CAPABILITY_IAM

See Serverless Application Model (SAM) HOWTO Guide for more details in how to get started.

After deployment is complete you can run the following command to retrieve the API Gateway Endpoint URL:

aws cloudformation describe-stacks \
    --stack-name sam-app \
    --query 'Stacks[].Outputs'

Testing

We use Scalatest for testing our code and you can simply run the following command to run our tests:

sbt test

jimmystridh / scala-sam-app