AWS Lambda In Action Chapter2

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Chapter 2. Your first Lambda function

This chapter covers

Creating your first AWS Lambda function

Understanding function configurations and settings

easy to use with the AWS command-line interface (CLI), or one of the AWS software development kits (SDKs) that can run on a server, in a browser, or in a mobile

client.

2.1. Creating a new function

Any good programming book should start with the “Hello World” example. But with AWS Lambda you don’t have standalone applications, but functions that take

an input (event) and can optionally provide a result (when called synchronously).

Let’s start with a slightly more complex task: a function that’s looking into the event for a name to “greet” and returns “Hello <name>!” If no name is provided in the

event, then the function should return a more generic “Hello World!”

Tip

You need an AWS account to follow the examples in this book. With a new AWS account, the Free Tier covers all the examples in this book with no cost to you. For

more information on the AWS Free Tier and how to create a new AWS account, please visit http://aws.amazon.com/free/.

Figure 2.1. With AWS Lambda you can create a new function using one of the provided blueprints, but for your first function you’ll start from scratch.

You can then choose a trigger for the new function (figure 2.2). A trigger is a source of events that will execute the function, providing the event an input. You have

multiple options for the trigger; a few of them will be used by the examples you’ll build while reading this book.

Figure 2.2. You can choose a trigger during the creation of a new function. Triggers invoke a Lambda function when certain events happen.

For example, you can choose the Amazon API Gateway to have a Web API calling a function, or AWS IoT, to build a serverless back end for an Internet of Things

(IoT) platform connecting devices with AWS. You’ll directly invoke this function and don’t need a trigger for now. Select “Next.”

You can now create a new AWS Lambda function (figure 2.3). For the name of the function, type “greetingsOnDemand”.

Figure 2.3. Configuring a new AWS Lambda function, starting with a name and a description, the runtime to use, and the code to execute

Note

Descriptions can also be read through AWS APIs, and having conventions in the content of the description—for example, describing the expected input/output—

can help in implementing automated “discovery” for your functions.

Using the AWS Lambda web console, you can provide the code for your function in three different ways:

Edit code inline, straight from the web browser

Upload a zip file from your local environment

Upload a zip file from Amazon S3

You can include custom libraries or modules that your code depends on in the zip file. In part 3 you’ll see that uploading functions via Amazon S3 can be an

interesting feature for implementing automatic deployments and continuous integration with AWS Lambda.

As the runtime for your function, you can choose Node.js 4.3 or Python 2.7. Examples of both are provided in this chapter; choose the language you prefer for your

back end deployment.