Last year I was working on a POC. The target stack of the POC was to be 100% native AWS as much as possible. That’s when I came across Serverless. Back then it was still in beta, but I was really happy with it. After the POC was over I moved on to other things. A couple of days ago I was reminded how useful the framework is, so I thought I’d share some of those thoughts here.

Before I continue, a few words about the term, “serverless”. In short, it gets some folks riled up. I don’t want to debate whether or not it’s a useful term. What I like about the concept is that, as a developer, I can focus on my implementation details without worrying as much about the infrastructure the code is running on. In a “serverless” setup, my implementation is broken down into discrete functions that get instantiated and executed when invoked. Of course, there are servers somewhere, but I don’t have to give them a moment’s thought (nor do I have to pay to keep them running, at least not directly).

If your infrastructure provider of choice is AWS, functions run as part of a service offering called Lambda. If you want to expose those functions as RESTful endpoints, you can use the AWS API Gateway. Of course your Lambda functions can make calls to other AWS services such as Dynamo DB, S3, Simple Queue Service, and so on. For my POC, I leveraged all of those. And that’s where the serverless framework really comes in handy.

Anyone that has done anything with AWS knows it can often take a lot of clicks to get everything set up right. The serverless framework makes that easier by allowing me to declare my service, the functions that make up that service, and the resources those functions leverage, all in an easy-to-edit YAML file. Once you get that configuration done, you just tell serverless to deploy it, and it takes care of the rest.

Let’s say you want to create a simple service that returns some JSON. Serverless supports multiple languages including JavaScript, Python, and Java, but for now I’ll do a JavaScript example.

First, I’ll bootstrap the project:

serverless create --template aws-nodejs --path echo-service

The serverless framework creates a serverless.yml file and a sample function in handler.js that echoes back a lot of information about the request. It’s ready to deploy as-is. So, to test it out, I’ll deploy it with:

serverless deploy -v

Behind the scenes, the framework creates a cloud formation template and makes the AWS calls necessary to set everything up on the AWS side. This requires your AWS credentials to be configured, but that’s a one-time thing.

When the serverless framework is done deploying the service and its functions, I can invoke the sample function with:

serverless invoke -f hello -l

Which returns:

{
    "statusCode": 200,
    "body": "{\"message\":\"Go Serverless v1.0! Your function executed successfully!\",\"input\":{}}"
}

To invoke that function via a RESTful endpoint, I’ll edit serverless.yml file and add an HTTP event handler, like this:

functions:
  hello:
    handler: handler.hello
    events:
      - http:
          path: hello
          method: get

And then re-deploy:

serverless deploy -v

Now the function can be hit via curl:

curl https://someid999.execute-api.us-east-1.amazonaws.com/dev/hello

In this case, I showed an HTTP event triggering the function, but you can use other events to trigger functions, like when someone uploads something to S3, posts something to an SNS topic, or on a schedule. See the docs for a complete list.

To add additional functions, just edit handler.js and add a new function, then edit serverless.yml to update the list of functions.

Lambda functions cost nothing unless they are executed. AWS offers a generous free tier. Beyond the first million requests in a month it costs $0.20 per million requests (pricing).

I should also mention that if AWS is not your preferred provider, serverless also works with Azure, IBM, and Google.

Regardless of where you want to run it, if you’ve got 15 minutes you should definitely take a look at Serverless.