Using AWS SAM

This tutorial implements a serverless application and deploy it to AWS Lambda using AWS SAM.

See Using Serverless Framework, if you prefer Serverless Framework over SAM.

Step 1: Create database on Upstash

If you do not have one, create a database following this guide.

Step 2: Project Setup

If you do not have it already install AWS SAM as described here

In any folder run sam init and select Hello World Example as below:

➜  serverless-tutorials > ✗ sam init

        SAM CLI now collects telemetry to better understand customer needs.

        You can OPT OUT and disable telemetry collection by setting the
        environment variable SAM_CLI_TELEMETRY=0 in your shell.
        Thanks for your help!

        Learn More: https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-telemetry.html

Which template source would you like to use?
        1 - AWS Quick Start Templates
        2 - Custom Template Location
Choice: 1
What package type would you like to use?
        1 - Zip (artifact is a zip uploaded to S3)
        2 - Image (artifact is an image uploaded to an ECR image repository)
Package type: 1

Which runtime would you like to use?
        1 - nodejs14.x
        2 - python3.8
        3 - ruby2.7
        4 - go1.x
        5 - java11
        6 - dotnetcore3.1
        7 - nodejs12.x
        8 - nodejs10.x
        9 - python3.7
        10 - python3.6
        11 - python2.7
        12 - ruby2.5
        13 - java8.al2
        14 - java8
        15 - dotnetcore2.1
Runtime: 1

Project name [sam-app]: using-aws-sam

Cloning app templates from https://github.com/aws/aws-sam-cli-app-templates

AWS quick start application templates:
        1 - Hello World Example
        2 - Step Functions Sample App (Stock Trader)
        3 - Quick Start: From Scratch
        4 - Quick Start: Scheduled Events
        5 - Quick Start: S3
        6 - Quick Start: SNS
        7 - Quick Start: SQS
        8 - Quick Start: Web Backend
Template selection: 1

    -----------------------
    Generating application:
    -----------------------
    Name: using-aws-sam
    Runtime: nodejs14.x
    Dependency Manager: npm
    Application Template: hello-world
    Output Directory: .

    Next steps can be found in the README file at ./using-aws-sam/README

Inside the hello-world folder install the redis client with:

npm install ioredis

Edit hello-world>app.js file as below. Replace the Redis URL (copy ioredis url from your Upstash console).

let response;
var Redis = require("ioredis");

if (typeof client === "undefined") {
  var client = new Redis(REDIS_URL);
}

exports.lambdaHandler = async (event, context) => {
  try {
    console.log("hello");
    await client.set("hello", "world");
    let res = await client.get("hello");
    response = {
      statusCode: 200,
      body: JSON.stringify({
        message: "hello " + res,
        // location: ret.data.trim()
      }),
    };
  } catch (err) {
    console.log(err);
    return err;
  }

  return response;
};

This example uses ioredis, you can copy the connection string from the Node tab in the console.

Step 3: Deploy Your Function

In the project folder run:

sam build

The output will be:

➜  using-aws-sam git:(master) ✗ sam build
Building codeuri: /Users/enes/dev/serverless-tutorials/using-aws-sam/hello-world runtime: nodejs14.x metadata: {} functions: ['HelloWorldFunction']
Running NodejsNpmBuilder:NpmPack
Running NodejsNpmBuilder:CopyNpmrc
Running NodejsNpmBuilder:CopySource
Running NodejsNpmBuilder:NpmInstall
Running NodejsNpmBuilder:CleanUpNpmrc

Build Succeeded

Built Artifacts  : .aws-sam/build
Built Template   : .aws-sam/build/template.yaml

Commands you can use next
=========================
[*] Invoke Function: sam local invoke
[*] Deploy: sam deploy --guided

Deploy your function via sam deploy --guided.

You can run your function locally with sam local invoke

You can also test your function using AWS console. In your AWS Lambda section, click on your function. Scroll down to the code sections and click on the Test button on the top right.

Congratulations, now your lambda function inserts entry to your Upstash database.

What can be the next?

• You can write and deploy another function to just get values from the database.
• You can integrate API Gateway so you can call your function via http.
• You can learn about how to monitor your functions from CloudWatch as described here.

Redis Connections in AWS Lambda

Although Redis connections are very lightweight, a new connection inside each Lambda function can cause a notable latency. On the other hand, reusing Redis connections inside the AWS Lambda functions has its own drawbacks. When AWS scales out Lambda functions, the number of open connections can rapidly increase. Fortunately, Upstash detects and terminates the idle and zombie connections thanks to its smart connection handling algorithm. Thanks to this algorithm; we have been recommending caching your Redis connection in serverless functions.

See the blog post about the database connections in serverless functions.