Edge Functions

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Azion Edge Functions allow you to create event-driven, serverless applications, at the edge of the network, closer to users.

With Edge Functions, you can perform serverless functions in response to events on Edge Nodes of our network. Without requiring or having to manage servers.

You can use functions to handle HTTP in the following Request and Response phases:

  • As soon as a user’s requests are received in the Edge Node (Viewer Request)
  • Before the Azion Edge Node forwards the Request to the Origin (Origin Request)
  • As soon as the Edge Node gets the response from the Origin (Origin Response)
  • Before the Azion Edge Node forwards the response to the user (Viewer Response)

You can also generate Responses without necessarily having to forward the request to the origin.

Using Edge Functions written in Lua and JavaScript on Azion’s Edge Computing platform, you can create a variety of solutions, for example:

  • Inspect cookies to rewrite URLs to different versions of a site for A/B testing.
  • Send different objects to your users based on the User-Agent header, which contains information about the device that submitted the request. For example, you can send images in different resolutions to users based on their devices.
  • Inspect headers or authorized tokens, inserting a corresponding header and allowing access control before forwarding a request to the origin.
  • Add, delete, and modify headers and rewrite the URL path to direct users to different cache objects.
  • Generate new HTTP responses to do things like redirect unauthenticated users to login pages, or create and deliver static webpages right from the edge.

See more ways to use Edge Functions in Use Cases.

  1. How do they work?
  2. How to use?
  3. Hands-on
  4. Support Documentation

1. How do they work?

Create your custom functions or use any of the existing ones provided by azion, both for Edge Application or Edge Firewall. The languages currently supported by the platform are Lua and JavaScript.

Edge Functions run during the handling of the request, and the Azion Edge Computing Platform provides a Rules Engine model that can trigger the execution of the Edge Functions code according to the handling phases.

The language-specific Runtime provides a programming interface for interacting and manipulating Request and Response objects to implement the necessary logic.

When instantiating an Edge Function, you can enter parameters that will be passed on to the function, in JSON format, through arguments. You can also define and run tests online to validate its construction.

Edge Functions are performed directly on Azion Edges infrastructure. To use them, they just need to be associated to a Behavior in the Rules Engine. Thus, when a request meets the criteria defined in the Rule Engine rules, the Edge Function will be triggered.

2. How to use?

Write your own custom functions or use any of the ready-to-use ones provided by Azion or Independent Software Vendors. Using Real-Time Manager, in the Libraries, you can create Edge Functions and maintain a repository of functions that can be used in the Edge Application or Edge Firewall. Consult the Runtime API according to the Runtime chosen for writing the Edge Function.

Create Edge Functions

Use the Runtime API of your preferred language to write Edge Functions.

Using the JavaScript Runtime Environment, Edge Functions written by the user go directly into effect without undergoing an internal review because the code runs on limited to isolated resources.

The Edge Functions that use code written in Lua do undergo thorough a review by our software engineers before going into effect. Our goal is to ensure the security and correct use of the Edge Computing platform. We review your code according to the following criteria:

  • Use of any global variables that are not allowed. Due to the multi-tenant environment, the Edge Function Lua code should avoid using global variables and shared memory
  • blocking HTTP calls. Every call to an external service must use the HTTP protocol through asynchronous APIs so that the process is not blocked
  • The Code or Lib must also pass the luacheck tests.

For more details of each Runtime API and code samples, see the documentation for Runtime APIs.

Edge Functions Instances

According to its initiator type, before associating an execution trigger with Edge Function, it must be instantiated in Edge Application or Edge Firewall. With the Edge Functions module enabled, you can instantiate your Edge Functions for later use in a Rules Engine Rule, through the Functions tab.

To learn more about Edge Functions Instances, access the Edge Application and Edge Firewall documentation.

Edge Functions Metrics

We provide real-time information about the performance of your Edge Functions, through Real-Time Metrics.

To access the graphs, follow these steps:

  1. Access the Real-Time Manager and enter the Data Services menu and select Real-Time Metrics, then click Edge Functions.
  2. View information such as the number of invocations per instance of Edge Function.

Read more about Real-Time Metrics.

4. Hands-On Step by step guide to creating an Edge Function

To see your Edge Function in effectively operation you just need to write, instantiate and associate it with a Behavior Run Function, using a Rule in the Rules Engine:

  1. Access the Real-Time Manager and enter the Libraries menu, select Edge Functions.

  2. Add a new edge function by clicking the Add Function button.

  3. In Language, select JavaScript.

    async function handleRequest(request) {
     return new Response("Hello World!",
    addEventListener("fetch", event => {
  4. Access an Edge Application and Enable the Edge Functions Module,

  5. On the Rules Engine tab, create or edit a Rule and in the Behavior section, in the field Then, select “Run Function” and associate it to the desired Edge Function.

  6. Example of response when running the Behavior Run Function:

    Hello World!
  7. Use Real-Time Metrics to track metrics such as, for example, the number of invocations of Edge Functions instances.

4. Support Documentation

Didn’t find what you were looking for? Open a support ticket.