How can I get started with lambda and nodejs in 5 minutes?

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I know these learn-to-do-x in 5 minutes type articles are a dime a dozen. But it’s true, we’re short on time, and we just wanna jump in. So let’s go!

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Rather than go the old route of doing everything manually, and struggling, we’re going to give ourselves a skeleton to start with.





Enter, serverless framework. What’s it do? It’s a command line tool written in nodejs, which allows you to create a lambda project from a template.

From there you edit a yml file to tell serverless what to build & how. Then you put your code inside of the handler.js file. Sounds simple right?

1. Create

If you haven’t already done it, install nodejs. There are lots of docs on the interwebs. For mac users, “brew install node” does the trick!

Next install the serverless package.

$ npm install serverless

Great! If you got dependency errors, get digging. Those moments of troubleshooting & patience teach you a lot. ๐Ÿ™‚

Ok, now let’s kick the tires. We’ll create our new project.

$ serverless create --template aws-nodejs --path myEndpoint
$ cd myEndpoint

Related: 30 questions to ask a serverless fanboy

2. Edit serverless.yml

service: myEndpoint

frameworkVersion: ">=1.1.0 <2.0.0"

provider:
  name: aws
  runtime: nodejs4.3

functions:
  currentTime:
    handler: handler.endpoint
    events:
      - http:
          path: ping
          method: get

Ok, what are we looking at here? Framework is the version of the serverless framework. Provider is aws, because serverless is attempting to build cross-platform support. You may also use azure, openwhisk, google cloud functions etc. Runtime is your language.

Under functions, our main one is currentTime. handler tells serverless framework what code to matchup with your function name. And finally events tell serverless about the API endpoint to configure.

There's a lot of magic going on under the hood. The serverless framework us using CloudFormation to build things in the background for you. CloudFormation is like Latin, it is a foundational construct to the entire AWS world. You can formalize any object, from servers to sqs queues, dynamodb tables, security groups, IAM users, S3 buckets, ebs volumes etc etc. You get the idea.

Want to see what serverless did? Head over to your aws dashboard, navigate to CloudFormation. You should see a new stack there called myEndpoint-dev. Scroll down and click the "Template" tab. You'll see the exact JSON code in all it's gory detail!

Related: 5 surprising features of Amazon Lambda serverless computing

3. Edit handler.js

Next up let's add a bit of code.

'use strict';

// return the current time in JSON format
module.exports.endpoint = (event, context, callback) => {
  const response = {
    statusCode: 200,
    body: JSON.stringify({
      message: `Hello, the current time is ${new Date().toTimeString()}.`,
    }),
  };

  callback(null, response);
};

Whenever this function gets called, we'll just return the current time. Pretty self explanatory.

Related: Are you getting errors building lambda functions? I got you covered!

4. Deploy!

Now the fun party. Let's deploy the code.

$ serverless deploy

Simple command, but it's doing a lot of work. Serverless framework is packaging up your nodejs code into a zip file and uploading it to aws for you. You should see some output telling you what happened.

$ serverless deploy
Serverless: Packaging service...
Serverless: Excluding development dependencies...
Serverless: Uploading CloudFormation file to S3...
Serverless: Uploading artifacts...
Serverless: Uploading service .zip file to S3 (1.2 KB)...
Serverless: Validating template...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
........................
Serverless: Stack update finished...
Service Information
service: myEndpoint
stage: dev
region: us-east-1
stack: myEndpoint-dev
api keys:
  None
endpoints:
  GET - https://ABCDEFGHIJK.execute-api.us-east-1.amazonaws.com/dev/ping
functions:
  currentTime: myEndpoint-dev-currentTime
$

Related: Is Amazon too big to fail?

5. Test

Awesome, now it's time to make sure it's working.

You can invoke the function directly using serverless' "invoke" command like this:

$ serverless invoke --function currentTime --log
{
    "statusCode": 200,
    "body": "{\"message\":\"Hello, the current time is 20:46:02 GMT+0000 (UTC).\"}"
}
--------------------------------------------------------------------
START RequestId: ed5e427c-fe22-11e7-90cc-a1fe66d674ce Version: $LATEST
END RequestId: ed5e427c-fe22-11e7-90cc-a1fe66d674ce
REPORT RequestId: ed5e427c-fe22-11e7-90cc-a1fe66d674ce	Duration: 0.67 ms	Billed Duration: 100 ms 	Memory Size: 1024 MB	Max Memory Used: 21 MB	


$

But we created an API endpoint didn't we? Yep. You can hit that. If you have a browser open, go ahead and copy/past the url listed in the endpoints section of your deploy process.

You can also use curl like this:

$ curl https://ABCDEFGHIJK.execute-api.us-east-1.amazonaws.com/dev/ping
{"message":"Hello, the current time is 20:46:18 GMT+0000 (UTC)."}
$ 

Related: Is Amazon Web Services too complex for small dev teams?

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