Run a function on an application

Add the Rules Engine rule that runs a function instance on an application, from Azion Console or the Azion API, then verify the response.

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A function instance runs only when a Rules Engine rule selects it with the Run Function behavior. You add that rule from Azion Console or the Azion API. For a guided first run that creates the function, the instance, and the rule in one pass, refer to Functions quickstart.

Prerequisites

A pre-built function from Azion Marketplace replaces a function you write. The Azion - Hello World function is linked to your account and is ready to instantiate.

Add the rule that runs the function

The rule sets the execution phase, the criteria that trigger it, and the instance it runs. It then runs that instance on every request that matches the criteria. Azion Console and the Azion API create the same rule.

Add the rule in Azion Console

To add the rule from Azion Console:

Open the application

Access Azion Console > Applications > your application.

In the Rules Engine tab, select + Rule
Name the rule

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

Select Request Phase
In the Criteria section, select the URI variable

Select the ${uri} variable.

Select is equal as the comparison operator
Enter the URI that runs the function

Enter the URI as the argument. For example: /hello-world.

In the Behaviors section, select Run Function
Select the function instance
Select Save

The rule appears in the Rules Engine tab of the application. New rules can take a few minutes to propagate.

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.

Add the rule with the Azion API

Send a POST request to the request rules endpoint of the application. Replace [TOKEN VALUE] with your personal token, <application_id> with your application ID, and <edge_function_instance_id> with the ID of the function instance:

Shell
01curl --request POST \
02 --url https://api.azion.com/v4/workspace/applications/<application_id>/request_rules \
03 --header 'Accept: application/json' \
04 --header 'Authorization: Token [TOKEN VALUE]' \
05 --header 'Content-Type: application/json' \
06 --data {
07 "name": "Run Hello World",
08 "active": true,
09 "criteria": [
10 [
11 {
12 "conditional": "if",
13 "variable": "${uri}",
14 "operator": "is_equal",
15 "argument": "/hello-world"
16 }
17 ]
18 ],
19 "behaviors": [
20 {
21 "type": "run_function",
22 "attributes": { "value": <edge_function_instance_id> }
23 }
24 ],
25 "description": "Run function on /hello-world"
26}

The response returns the rule the application now carries:

JSON
01{
02 "state": "pending",
03 "data": {
04 "id": <rule_id>,
05 "name": "Run Hello World",
06 "active": true,
07 "criteria": [
08 [
09 {
10 "conditional": "if",
11 "variable": "${uri}",
12 "operator": "is_equal",
13 "argument": "/hello-world"
14 }
15 ]
16 ],
17 "behaviors": [
18 {
19 "type": "run_function",
20 "attributes": {
21 "value": <edge_function_instance_id>
22 }
23 }
24 ],
25 "description": "Run function on /hello-world",
26 "order": 0,
27 "last_editor": "your-email@example.com",
28 "last_modified": "2026-01-01T12:00:00.000000Z"
29 }
30}

The "state": "pending" value means the rule takes a few minutes to propagate. For every field of the rules endpoint, refer to Create an application rule.

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.

Wait for the rule to propagate, then request the URI set in the criteria:

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

The response body is the string the function returns. The hello-world function of the Functions quickstart answers:

Hello World!

A response that does not come from the function means the rule did not match the request, or the change has not propagated yet.

Next steps

Functions quickstartThe full path, from an empty account to a function that answers a request.Instantiate a function on an applicationCreate the instance this rule selects, and pass its Args in JSON.Create an application ruleThe criteria and behaviors a rule carries, beyond Run Function.Troubleshoot function execution and logsWhat to check when a function does not run, or returns an error.