In the previous chapter, we learned how to use the AWS Management Console to create Lambda functions and APIs. Now, we will use the Serverless framework to programmatically create APIs and Lambda functions. We will use the serverless command-line interface to deploy and test our functions. This will tremendously speed up our development processes.

The termserverless generally refers to applications that make heavy use of third-party cloud services, such as AWS Lambda. These services are also sometimes referred to as cloud functions, serverless microservices, or serverless functions. This doesn't mean that there are no servers involved anymore, just that you haven't installed to manage and operate these servers yourself. This is handled by the cloud provider, who takes care of things like scalability, high availability, security, performance...

Here, we are going to take a look at the Serverless framework documentation. We will then take a look at how to install it, and then we'll try out our first commands.

In the previous section, we installed the Serverless framework and tried out the command line. Now, let's create our first serverless project. We are going to use the Serverless framework to create a simple Node.js lambda function and a REST API. Open Terminal and create a directory where you can place your serverless project files. I named itapp, but you can name it whatever you want. Go to that directory and open your preferred IDE. I used the Atom editor. When the Atom editor was opened in my empty directory, I used an Atom package at terminal plus to open a new Terminal window inside my IDE. This makes it easier because I don't need to switch between writing code and typing in commands. So, let's type in a command to scaffold a serverless service:

serverless create --template aws-nodejs

The command for creating a service is created...

Now, let's learn a little bit more about programming Lambda functions with Node.js. We are going to take a closer look at the function handler, and in particular its arguments, that is:

• Event objects
• Context objects
• Callback objects

Open thehandler.js file and delete the code that's in the function body. One way to learn about the event and context object would be to log them out on the console:

'use strict';
module.exports.hello = (event, context, callback) => {
    console.log('event is', event);
};

Let's see what this gives us.

I am invoking the function locally to see what the output is with the function name set ashello:

sls invoke local -f hello
event is

Ok, my event, apparently, is null. Let's see what the context is, as shown next:

module.exports.hello = (event, context, callback) =&gt...

In the previous section, we learned about programming Lambda function handlers. Now, let's explore testing and debugging.

Here, we are going to look at three different testing and debugging approaches:

• Using the Serverless framework
• Using Postman for testing our API
• Using the AWS Management Console

Let's go back to ourhandler.js file from the previous section. There are a couple things that should be changed. The response method should be changed back to something that our API can work with.

Give it abody property with astringify JSON content, as shown here:

body: JSON.stringify({

And, in the JSON content, get back the event in the remaining time from the context, and then, instead of returning an error, we will return the response:

'use strict';
module.exports.hello = (event, context, callback) => {
    let remainingTime...

In this chapter, we learned how to use the Serverless framework to create and test Lambda functions and APIs, and we tried out different approaches for API testing, Lambda testing, and debugging. Now, we have all the things necessary to build a real application, so in the next chapter, that's what we are going to do, by building a serverless application.