Setup lambda + API Gateway using localstack

README.md

About

Example on how to run locally an AWS Lambda via API Gateway using localstack.

Based on...

1. https://stackoverflow.com/questions/44547574/create-api-gateway-in-localstack/48682628
2. https://ig.nore.me/2016/03/setting-up-lambda-and-a-gateway-through-the-cli/

Usage

1. Build a zip containing lambda.js, name it api-handler.zip
2. Launch localstack in whatever way you can. See sample docker-compose.yml.
3. Run setup.sh

Pending

1. Catch any URL /api/whatever.
2. Pass all HTTP verbs. Only GET is configured here. Other verbs require their own integration as ANY is not supported yet.
3. No query parameters yet.

docker-compose.yml

version: '2.1'

services:
  localstack:
    image: localstack/localstack
    ports:
      - "4567-4583:4567-4583"
      - "${PORT_WEB_UI-4566}:${PORT_WEB_UI-8080}"
    environment:
      - SERVICES=${SERVICES-lambda,apigateway }
      - DEBUG=${DEBUG- }
      - DATA_DIR=${DATA_DIR- }
      - PORT_WEB_UI=${PORT_WEB_UI- }
      - LAMBDA_EXECUTOR=${LAMBDA_EXECUTOR-docker-reuse }
      - KINESIS_ERROR_PROBABILITY=${KINESIS_ERROR_PROBABILITY- }
      - DOCKER_HOST=unix:///var/run/docker.sock
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"

lambda.js

'use strict'

const apiHandler = (payload, context, callback) => {
    console.log(`Function apiHandler called with payload ${JSON.stringify(payload)}`);
    callback(null, {
        statusCode: 201,
        body: JSON.stringify({
            message: 'Hello World'
        }),
        headers: {
            'X-Custom-Header': 'ASDF'
        }
    }); 
}
    
module.exports = {
    apiHandler,
}

setup.sh

#!/bin/sh

API_NAME=api
REGION=us-east-1
STAGE=test

function fail() {
    echo $2
    exit $1
}

awslocal lambda create-function \
    --region ${REGION} \
    --function-name ${API_NAME} \
    --runtime nodejs8.10 \
    --handler lambda.apiHandler \
    --memory-size 128 \
    --zip-file fileb://api-handler.zip \
    --role arn:aws:iam::123456:role/irrelevant

[ $? == 0 ] || fail 1 "Failed: AWS / lambda / create-function"

LAMBDA_ARN=$(awslocal lambda list-functions --query "Functions[?FunctionName==\`${API_NAME}\`].FunctionArn" --output text --region ${REGION})

awslocal apigateway create-rest-api \
    --region ${REGION} \
    --name ${API_NAME}

[ $? == 0 ] || fail 2 "Failed: AWS / apigateway / create-rest-api"

API_ID=$(awslocal apigateway get-rest-apis --query "items[?name==\`${API_NAME}\`].id" --output text --region ${REGION})
PARENT_RESOURCE_ID=$(awslocal apigateway get-resources --rest-api-id ${API_ID} --query 'items[?path==`/`].id' --output text --region ${REGION})

awslocal apigateway create-resource \
    --region ${REGION} \
    --rest-api-id ${API_ID} \
    --parent-id ${PARENT_RESOURCE_ID} \
    --path-part "{somethingId}"

[ $? == 0 ] || fail 3 "Failed: AWS / apigateway / create-resource"

RESOURCE_ID=$(awslocal apigateway get-resources --rest-api-id ${API_ID} --query 'items[?path==`/{somethingId}`].id' --output text --region ${REGION})

awslocal apigateway put-method \
    --region ${REGION} \
    --rest-api-id ${API_ID} \
    --resource-id ${RESOURCE_ID} \
    --http-method GET \
    --request-parameters "method.request.path.somethingId=true" \
    --authorization-type "NONE" \

[ $? == 0 ] || fail 4 "Failed: AWS / apigateway / put-method"

awslocal apigateway put-integration \
    --region ${REGION} \
    --rest-api-id ${API_ID} \
    --resource-id ${RESOURCE_ID} \
    --http-method GET \
    --type AWS_PROXY \
    --integration-http-method POST \
    --uri arn:aws:apigateway:${REGION}:lambda:path/2015-03-31/functions/${LAMBDA_ARN}/invocations \
    --passthrough-behavior WHEN_NO_MATCH \

[ $? == 0 ] || fail 5 "Failed: AWS / apigateway / put-integration"

awslocal apigateway create-deployment \
    --region ${REGION} \
    --rest-api-id ${API_ID} \
    --stage-name ${STAGE} \

[ $? == 0 ] || fail 6 "Failed: AWS / apigateway / create-deployment"

ENDPOINT=http://localhost:4567/restapis/${API_ID}/${STAGE}/_user_request_/HowMuchIsTheFish

echo "API available at: ${ENDPOINT}"

echo "Testing GET:"
curl -i ${ENDPOINT}

echo "Testing POST:"
curl -iX POST ${ENDPOINT}