Configuring Logging for Isolated Azure Functions

Logging is a critical aspect of monitoring and troubleshooting your Azure Functions. In isolated Azure Functions, logging can be configured using the appsettings.json file and the logging services provided by the .NET SDK. This article will guide you through setting up logging for isolated Azure Functions.

Step 1: Create or Update appsettings.json

First, ensure that your Azure Functions project has an appsettings.json file. This file is used to configure various settings, including logging levels.

Example appsettings.json:

{

  "Logging": {

    "LogLevel": {

      "Default": "Information",

      "Function": "Information",

      "Microsoft": "Warning"

    }

  },

  "ApplicationInsights": {

    "ConnectionString": "InstrumentationKey=your-instrumentation-key;IngestionEndpoint=https://<region>.in.applicationinsights.azure.com/"

  }

}

In this example:

• The LogLevel section defines the minimum log level for different categories. You can adjust these as needed:

  • Default applies to all categories.

  • Function applies to the Azure Functions logs.

  • Microsoft applies to logs from Microsoft libraries.

• The ApplicationInsights section configures Application Insights for telemetry. Replace your-instrumentation-key and <region> with your actual Application Insights instrumentation key and region.

Step 2: Modify Program.cs

Next, configure logging in your Program.cs file. This is where you set up the host builder and configure services.

Example Program.cs:

using Microsoft.Extensions.Configuration;

using Microsoft.Extensions.Hosting;

using Microsoft.Extensions.Logging;

using Microsoft.ApplicationInsights.Extensibility;

using Microsoft.ApplicationInsights.WorkerService;





public class Program

{

    public static void Main(string[] args)

    {

        var host = new HostBuilder()

            .ConfigureAppConfiguration((hostingContext, config) =>

            {

                config.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)

                      .AddEnvironmentVariables();

            })

            .ConfigureFunctionsWorkerDefaults()

            .ConfigureLogging((context, logging) =>

            {

                var configuration = context.Configuration.GetSection("Logging");

                logging.ClearProviders();

                logging.AddConsole();

                logging.AddApplicationInsights();





                // Apply logging configuration from appsettings.json

                logging.AddConfiguration(configuration);

            })

            .ConfigureServices((context, services) =>

            {

                services.AddApplicationInsightsTelemetryWorkerService(

                    options => options.ConnectionString = context.Configuration["ApplicationInsights:ConnectionString"]);

            })

            .Build();





        host.Run();

    }

}

Explanation:

• ConfigureAppConfiguration: Adds the appsettings.json and environment variables to the configuration.

• ConfigureFunctionsWorkerDefaults: Configures default settings for Azure Functions.

• ConfigureLogging: Sets up logging providers and configurations:

  • Clears existing providers.

  • Adds console logging.

  • Adds Application Insights logging.

  • Applies logging configuration from appsettings.json.

• ConfigureServices: Adds Application Insights telemetry services using the connection string from appsettings.json.

Step 3: Deploy and Monitor

Once you have configured your logging, deploy your Azure Functions to Azure. You can monitor your logs in the Azure portal under Monitor > Logs and in your Application Insights resource.

No ConnectionString

If you prefer not to specify the ConnectionString in your configuration files, you can rely on environment variables or Azure-managed service identities to automatically configure Application Insights.

Using Environment Variables:

1. Set the APPLICATIONINSIGHTS_CONNECTION_STRING environment variable in your Azure Function App settings.

In Azure Portal:

• Navigate to your Azure Function App.

• Go to Configuration under the Settings section.

• Click on New application setting.

• Add the key APPLICATIONINSIGHTS_CONNECTION_STRING and set its value to your Application Insights connection string.

Example Program.cs Without ConnectionString:

In this scenario, you don't need to set the connection string in your appsettings.json or Program.cs. The SDK will automatically pick up the environment variable.

using Microsoft.Extensions.Configuration;

using Microsoft.Extensions.Hosting;

using Microsoft.Extensions.Logging;

using Microsoft.ApplicationInsights.Extensibility;

using Microsoft.ApplicationInsights.WorkerService;





public class Program

{

    public static void Main(string[] args)

    {

        var host = new HostBuilder()

            .ConfigureAppConfiguration((hostingContext, config) =>

            {

                config.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)

                      .AddEnvironmentVariables();

            })

            .ConfigureFunctionsWorkerDefaults()

            .ConfigureLogging((context, logging) =>

            {

                var configuration = context.Configuration.GetSection("Logging");

                logging.ClearProviders();

                logging.AddConsole();

                logging.AddApplicationInsights();





                // Apply logging configuration from appsettings.json

                logging.AddConfiguration(configuration);

            })

            .ConfigureServices((context, services) =>

            {

                // No need to explicitly set the connection string here

                services.AddApplicationInsightsTelemetryWorkerService();

            })

            .Build();





        host.Run();

    }

}

Explanation:

• The ApplicationInsightsTelemetryWorkerService will automatically use the APPLICATIONINSIGHTS_CONNECTION_STRING environment variable if it is set in the Azure Function App settings.

Additional Tips:

• Local Development: Ensure you have the correct settings in local.settings.json for local development. You can set the APPLICATIONINSIGHTS_CONNECTION_STRING environment variable in your development environment as well.

• Environment Variables: Use environment variables for sensitive information like the Application Insights connection string.

• Log Levels: Adjust log levels in appsettings.json to control the verbosity of logs.

Example local.settings.json for Local Development:

{

  "IsEncrypted": false,

  "Values": {

    "AzureWebJobsStorage": "UseDevelopmentStorage=true",

    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",

    "APPLICATIONINSIGHTS_CONNECTION_STRING": "your-connection-string"

  },

  "Logging": {

    "LogLevel": {

      "Default": "Debug",

      "Function": "Debug",

      "Microsoft": "Information"

    }

  }

}

Conclusion

Configuring logging for isolated Azure Functions involves setting up your appsettings.json for logging levels and Application Insights, modifying your Program.cs to configure logging services, and deploying your function app. If you prefer not to include the connection string in your configuration files, you can leverage environment variables to securely manage your Application Insights configuration. This setup allows you to effectively monitor and troubleshoot your functions using the Azure portal and Application Insights.