Azure Functions API Documentation

Introduction to Azure Functions API

The Azure Functions API provides a robust set of endpoints for managing and interacting with your Azure Functions applications. You can use this API to automate deployment, monitor execution, configure settings, and even trigger your functions programmatically.

This documentation outlines the available API operations, authentication mechanisms, and best practices for integrating Azure Functions into your custom applications and workflows.

Why use the Azure Functions API?

Automation: Automate deployment pipelines, scaling operations, and configuration changes.
Integration: Seamlessly integrate Azure Functions with other services and applications.
Monitoring: Gain programmatic access to logs, metrics, and execution status for better observability.
Orchestration: Build complex workflows by programmatically triggering and managing function executions.

Getting Started

To use the Azure Functions API, you'll need to authenticate your requests. The primary methods are:

Azure AD (Microsoft Entra ID) Authentication: Recommended for most applications, providing secure and token-based access.
Function Keys: Simpler for direct function invocation, but less secure for management operations.

Refer to the Authentication section for detailed instructions.

Prerequisites

An Azure subscription.
An existing Azure Functions app.
Appropriate permissions within your Azure AD tenant if using Azure AD authentication.

API Reference

The Azure Functions API encompasses various resource providers, including:

Microsoft.Web: For managing Function Apps, deployments, and settings.
Microsoft.Insights: For accessing monitoring data and logs.

Authentication

Securely accessing the Azure Functions API is crucial. Here are the common authentication methods:

1. Azure AD (Microsoft Entra ID) Authentication

This is the recommended approach for programmatic access to manage Azure resources, including Function Apps. You'll need to register an application in Azure AD and obtain credentials (client ID, client secret or certificate).

Register an application in Azure AD.
Grant the application appropriate roles (e.g., "Contributor" or custom roles) on your Function App or Resource Group.
Obtain an OAuth 2.0 access token from Azure AD using your application's credentials.
Include the access token in the Authorization header of your API requests as a Bearer token:
```
Authorization: Bearer <your_access_token>
```

Example of acquiring an access token (using Azure CLI):

az account get-access-token --resource "https://management.azure.com/" --output tsv

2. Function Keys

Function keys are primarily used for invoking individual functions. They are less suitable for management operations due to security limitations.

To invoke a function using its key:

POST /api/MyFunctionName?code=YOUR_FUNCTION_KEY

You can retrieve function keys via the Azure Portal or programmatically using the Microsoft.Web API.

Key API Endpoints (Microsoft.Web Resource Provider)

GET /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Web/sites/{name}

Get details of a specific Function App.

POST /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Web/sites/{name}/start

Start a Function App.

POST /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Web/sites/{name}/stop

Stop a Function App.

GET /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Web/sites/{name}/functions

List all functions within a Function App.

POST /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Web/sites/{name}/functions/{functionName}/invoke

Invoke a specific function. This endpoint requires appropriate authentication (e.g., Function Key or Azure AD token with appropriate permissions).

GET /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Web/sites/{name}/logs/list

Retrieve application logs for a Function App.

Triggering Functions Programmatically

You can trigger functions in several ways using the API:

HTTP Trigger: For functions with an HTTP trigger, simply make an HTTP request to the function's URL. Include necessary authentication headers or query parameters (like Function Keys).
Other Triggers: For non-HTTP triggers (e.g., Queue, Blob, Timer), you can use the /invoke endpoint or specific management APIs provided by the relevant service integration. For example, to trigger a queue-based function, you might add a message to the associated Azure Queue Storage.

Managing Functions and Function Apps

Use the Microsoft.Web API endpoints to:

Create, update, and delete Function Apps.
Deploy code packages.
Configure application settings, connection strings, and authentication.
Manage deployment slots.

Key Concepts

Function App

A Function App is the container for your individual functions. It provides the execution context, scaling, and management features.

Triggers

Triggers define how a function is invoked. Common triggers include HTTP, Timer, Queue Storage, Blob Storage, and Event Hubs.

Bindings

Bindings simplify interaction with other Azure services. Input bindings provide data to your function, and output bindings send data from your function to another service.

Function Keys

Security tokens used to authenticate calls to HTTP-triggered functions. They can be master keys or function-specific keys.

Service Limits & Considerations

Be aware of Azure Functions service limits, such as:

Maximum execution time for consumption plans.
Maximum request/response payload size.
Concurrency limits.

Refer to the official Azure Functions documentation for the most up-to-date limits.

Important: Always use Azure AD (Microsoft Entra ID) authentication for managing Function Apps and sensitive operations. Function keys should primarily be used for invoking HTTP-triggered functions directly.

Troubleshooting

Common issues and how to address them:

Authentication Errors: Ensure your access tokens are valid and include the correct scopes. Verify Azure AD application permissions and role assignments.
Function Not Found: Double-check the function name and ensure it exists within the Function App.
Authorization Denied: Verify that the identity making the API call has the necessary permissions (e.g., Contributor role on the Function App).
Timeout Errors: Optimize your function logic or consider a different hosting plan (e.g., Premium or Dedicated) for longer-running operations.

Utilize Application Insights to diagnose runtime errors and performance bottlenecks.