Functions quickstart

Create your first function in Azion Console, the Azion CLI, or the API, instantiate it on an application, and trigger it with a Rules Engine rule.

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This guide instructs you through running your first function on Azion. The steps take about 10 minutes.

  • Create a function that returns Hello World!.
  • Instantiate the function on an application.
  • Add a Rules Engine rule that runs the instance on the /hello-world URI.
  • Request that URI and read the response.

Three objects make a function run, and each one links to the next:

  1. The function holds the JavaScript code.
  2. The function instance binds the function to an application. It also carries the Args, a JSON object passed into the execution context.
  3. The Rules Engine rule selects the instance with the Run Function behavior. The rule sets the execution phase and the criteria that trigger it.

Creating a function does not execute it. An instance without a Rules Engine rule never runs.

The Azion Terraform provider manages the same three objects. For every interface that carries them, refer to Functions.

Prerequisites

Console

  • An Azion account. To create one, refer to How to create an account on Azion.
  • The Edit Functions permission on the account. It grants permission to create, edit, and remove functions, and it also requires the permission View Functions.
  • The Edit Applications permission on the account. The instance and the rule change an application, and this permission grants permission to edit, create, and remove applications. It also requires the permission View Applications. Refer to Teams Permissions.
  • An application. To create one, refer to Applications quickstart.
  • Access to Azion Console. To sign in, refer to Access Azion Console.

Create the function

The function holds the code that answers the request. This one returns the string Hello World!.

Console

To create the function in Azion Console:

Open the Functions page

Access Azion Console > Products Menu > Libraries > Functions.

Select + Function
Name the function

Enter a name for the function. For example: hello-world.

Paste the code in the Code tab

In the Code tab, paste the following code:

JavaScript
01export default {
02 async fetch(request, env, ctx) {
03 return new Response('Hello World!');
04 },
05};
Select Save

The function is saved and available to instantiate on an application.

To read the response of the function before it serves traffic, use Preview deployment. It runs the code in Azion Console without a deployment.

Instantiate the function on your application

An instance binds the function to one application, and one function can back several instances. Each path turns on the Functions module for the application, then creates the instance.

Console

To bind the function to an application in Azion Console:

Still in Azion Console, go to Products Menu > Build > Applications
Select the application that runs the function
In the Main Settings tab, turn on the Functions module
Select Save
Go to the Functions Instances tab
Select + Function Instance
Name the instance

Enter a name for the instance. For example: hello-world instance.

Select the function

Select the hello-world function.

Select Save

The new instance appears in the Functions Instances tab.

Add the rule that runs the function

An instance runs only when a Rules Engine rule selects it. This rule runs the instance on requests to /hello-world.

Console

To add the rule in Azion Console:

In the same application, go to the Rules Engine tab
Select + Rule
Name the rule

Enter a name for the rule. For example: Run hello-world.

Select Request Phase
Select the variable in the Criteria section

In the Criteria section, select the ${uri} variable.

Select is equal as the comparison operator
Enter the argument

Enter /hello-world as the argument.

In the Behaviors section, select Run Function
Select the instance you created
Select Save

The rule runs the instance on every request whose URI is /hello-world.

If Run Function is not in the Behaviors list, the application also needs the Application Accelerator module. Refer to Run Function is missing from the behaviors list for the fix.

New rules can take a few minutes to propagate. Wait before you request the URI.

Verify the response

Your application answers on a domain in the format xxxxxxxxx.map.azionedge.net. To set the domain for your application, refer to Add a custom domain to a workload.

To confirm that the function runs, request the URI set in the rule:

curl https://<your-azion-domain>/hello-world

The response body is the string the function returns:

Hello World!

The function now runs on every request that matches the rule criteria.

Next steps

How it worksThe invocation chain in detail, from the function to the request that triggers it.Function instancesPass Args to an instance in JSON.Environment variablesStore configuration and secrets outside the function code, then read each one by key at run time.JavaScript examplesFunction code to adapt for your own logic.Best practicesWhat each part of the handler does, and the design choices that keep an invocation inside its limits.Local developmentBuild and run the project on your own machine with the azion dev command.