SAM Local Installation

Install SAM Local on Windows 10 Enterprise. Test SAM Local with a simple Lambda function.

According to AWS, 'sam is the AWS CLI tool for managing Serverless applications written with AWS Serverless Application Model (SAM). SAM Local can be used to test functions locally, start a local API Gateway from a SAM template, validate a SAM template, and generate sample payloads for various event sources.'

Install Docker for Windows

SAM Local requires Docker. Link to Docker for Windows. Choose the Stable or Edge version of Docker for Windows.

You will need to close and logout.

Windows will ask you to restart to enable Hyper-V and Containers features.

Install AWS SAM Local

Install aws-sam-local npm package globally. Assumes Node.js/npm already installed.

npm install -g aws-sam-local
sam --version

Sample Lambda Function

Example is a combination of several public AWS samples.

Lambda: index.js

'use strict';

console.log('Loading function');

exports.handler = (event, context, callback) => {
  console.log('Received event:', JSON.stringify(event, null, 2));
  console.log('value1 =', event.key1);
  console.log('value2 =', event.key2);
  console.log('value3 =', event.key3);
  callback(null, {
    statusCode: 200,
    headers: {
      "x-custom-header": event.key1
    },
    body: event.key2
  });
};

Test Event: event.json

{
  "key3": "Lambda",
  "key2": "Serverless",
  "key1": "API Gateway"
}

SAM Template: template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: A starter AWS Lambda function.
Resources:
  helloworld:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: index.handler
      Runtime: nodejs6.10
      CodeUri: .
      Description: A starter AWS Lambda function.
      MemorySize: 128
      Timeout: 3
      Events:
        Api:
          Type: Api
          Properties:
            Path: /test
            Method: get

Invoke Lambda with an Event file

To test SAM Local, execute npm test or sam local invoke -e event.json.

The first time you run SAM Local, you will need to share access to your C: drive.

Deploy API to AWS

Execute the two commands below to deploy of the Lambda function and associated API to AWS, using SAM. Commands require you have sufficient privileges to AWS resources.

These commands will create an S3 bucket (you will need to substitute a unique bucket name for the bucket), API, in the API Gateway, titled test-api, matching the CloudFormation stack name. The Lambda will also be created, titled similar to test-stack-helloworld-1SOIAN9J9EUJS. The Lambda function will be associated with the GET method of the /test API endpoint.

aws s3 mb s3://<unique_bucket_name>

aws cloudformation package \
  --template-file template.yaml \
  --s3-bucket <unique_bucket_name> \
  --output-template-file packaged-template.yaml

aws cloudformation deploy \
  --template-file packaged-template.yaml \
  --stack-name test-api \
  --capabilities CAPABILITY_IAM

SAM Local References

• SAM Local Requirements
• SAM Local Guide
• SAM Node Hello World Sample