Azure Functions App Settings

Understanding App Settings in Azure Functions

Azure Functions allow you to configure your function apps using application settings. These settings are crucial for managing configuration values, connection strings, and other parameters that your functions need to operate correctly. They provide a secure and flexible way to customize your function app's behavior without modifying your code.

Key Concepts

Configuration: App settings act as environment variables that can be accessed within your function code.
Security: Sensitive information like API keys and connection strings should be stored in app settings rather than hardcoded in your application.
Portability: You can easily update settings for different environments (development, staging, production) without redeploying your code.
Scalability: App settings are managed at the function app level, ensuring consistent configuration across all instances.

Accessing App Settings

You can access app settings in your function code using platform-specific methods. Here are examples for common languages:

C#


// Using IConfiguration in .NET Core/5+
var connectionString = _configuration["MyConnectionString"];

// Using ConfigurationManager (older .NET Framework)
// var settingValue = System.Configuration.ConfigurationManager.AppSettings["MySetting"];

JavaScript/TypeScript (Node.js)


// Accessing process.env in Node.js
const apiKey = process.env.MyApiKey;

Python


import os

# Accessing environment variables
connection_string = os.environ.get('CosmosDbConnectionString')

PowerShell


# Accessing environment variables
$storageAccountName = $env:StorageAccountName

Managing App Settings

You can manage app settings through the Azure portal, Azure CLI, or ARM templates.

Azure Portal

Navigate to your Function App in the Azure portal.
Under "Settings", select "Configuration".
Go to the "Application settings" tab.
Click "New application setting" to add a new key-value pair.
Click "Save" to apply your changes.

Azure CLI

To add or update an app setting using Azure CLI:


az functionapp config appsettings set --name <YourFunctionAppName> --resource-group <YourResourceGroupName> --settings MySetting=MyValue OtherSetting=AnotherValue

To delete an app setting:


az functionapp config appsettings delete --name <YourFunctionAppName> --resource-group <YourResourceGroupName> --setting-names MySetting

Important Note:

Changes to application settings often require your function app to restart. While Azure handles this automatically for many scenarios, be aware that a brief interruption might occur. For critical applications, consider deployment strategies that minimize downtime.

Common Use Cases

Connection Strings: Storing connection strings for databases (e.g., Azure SQL, Cosmos DB), storage accounts, or other services.
API Keys: Managing API keys for external services your functions integrate with.
Service Endpoints: Specifying URLs or endpoints for dependent services.
Feature Flags: Controlling the behavior of certain features dynamically.
Application-Specific Configurations: Any configuration parameter that needs to be managed outside of your code.

Best Practices

Use Key Vault for Secrets: For highly sensitive information like passwords or certificates, integrate Azure Key Vault with your app settings. This provides enhanced security and management.
Naming Conventions: Use consistent and descriptive names for your app settings (e.g., COSMOSDB_CONNECTION_STRING, SENDGRID_API_KEY).
Environment-Specific Settings: Leverage deployment slots or different function apps for distinct environments (dev, staging, prod) and manage their settings independently.
Avoid Hardcoding: Never hardcode secrets or configuration values directly in your function code.

Example: Storing a Database Connection String

Azure Portal:

Under "Configuration" -> "Application settings", add a new setting:

Name: DatabaseConnectionString
Value: Server=tcp:yourserver.database.windows.net,1433;Database=yourdatabase;User ID=youruser;Password=yourpassword;Encrypt=True;TrustServerCertificate=False;Connection Timeout=30;

Function Code (C#):


public static class MyFunction {
    [FunctionName("GetData")]
    public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequest req,
        ILogger log)
    {
        string connectionString = Environment.GetEnvironmentVariable("DatabaseConnectionString");

        // Use the connectionString to connect to your database
        // ...

        return new OkObjectResult("Data fetched successfully!");
    }
}