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Configure Azure Monitor OpenTelemetry

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This article covers configuration settings for the Azure Monitor OpenTelemetry distro.

Connection string

A connection string in Application Insights defines the target location for sending telemetry data.

Use one of the following three ways to configure the connection string:

  • Add UseAzureMonitor() to your program.cs file:

    var builder = WebApplication.CreateBuilder(args);

// Add the OpenTelemetry telemetry service to the application.
// This service will collect and send telemetry data to Azure Monitor.
builder.Services.AddOpenTelemetry().UseAzureMonitor(options => {
    options.ConnectionString = "<Your Connection String>";
});

var app = builder.Build();

app.Run();

  • Set an environment variable.

    APPLICATIONINSIGHTS_CONNECTION_STRING=<Your Connection String>

  • Add the following section to your appsettings.json config file.

    {
  "AzureMonitor": {
      "ConnectionString": "<Your Connection String>"
  }
}

Note

If you set the connection string in more than one place, we adhere to the following precedence:

  1. Code
  2. Environment Variable
  3. Configuration File

Set the Cloud Role Name and the Cloud Role Instance

For supported languages, the Azure Monitor OpenTelemetry Distro automatically detects the resource context and provides default values for the Cloud Role Name and the Cloud Role Instance properties of your component. However, you might want to override the default values to something that makes sense to your team. The cloud role name value appears on the Application Map as the name underneath a node.

Set the Cloud Role Name and the Cloud Role Instance via Resource attributes. Cloud Role Name uses service.namespace and service.name attributes, although it falls back to service.name if service.namespace isn't set. Cloud Role Instance uses the service.instance.id attribute value. For information on standard attributes for resources, see OpenTelemetry Semantic Conventions.

// Setting role name and role instance

// Create a dictionary of resource attributes.
var resourceAttributes = new Dictionary<string, object> {
    { "service.name", "my-service" },
    { "service.namespace", "my-namespace" },
    { "service.instance.id", "my-instance" }};

// Create a new ASP.NET Core web application builder.
var builder = WebApplication.CreateBuilder(args);

// Add the OpenTelemetry telemetry service to the application.
// This service will collect and send telemetry data to Azure Monitor.
builder.Services.AddOpenTelemetry()
    .UseAzureMonitor()
    // Configure the ResourceBuilder to add the custom resource attributes to all signals.
    // Custom resource attributes should be added AFTER AzureMonitor to override the default ResourceDetectors.
    .ConfigureResource(resourceBuilder => resourceBuilder.AddAttributes(_testResourceAttributes));

// Build the ASP.NET Core web application.
var app = builder.Build();

// Start the ASP.NET Core web application.
app.Run();

Enable Sampling

You might want to enable sampling to reduce your data ingestion volume, which reduces your cost. Azure Monitor provides a custom fixed-rate sampler that populates events with a sampling ratio, which Application Insights converts to ItemCount. The fixed-rate sampler ensures accurate experiences and event counts. The sampler is designed to preserve your traces across services, and it's interoperable with older Application Insights Software Development Kits (SDKs). For more information, see Learn More about sampling.

Note

Metrics and Logs are unaffected by sampling.

The sampler expects a sample rate of between 0 and 1 inclusive. A rate of 0.1 means approximately 10% of your traces are sent.

// Create a new ASP.NET Core web application builder.
var builder = WebApplication.CreateBuilder(args);

// Add the OpenTelemetry telemetry service to the application.
// This service will collect and send telemetry data to Azure Monitor.
builder.Services.AddOpenTelemetry().UseAzureMonitor(options =>
{
    // Set the sampling ratio to 10%. This means that 10% of all traces will be sampled and sent to Azure Monitor.
    options.SamplingRatio = 0.1F;
});

// Build the ASP.NET Core web application.
var app = builder.Build();

// Start the ASP.NET Core web application.
app.Run();

Tip

When using fixed-rate/percentage sampling and you aren't sure what to set the sampling rate as, start at 5% (i.e., 0.05 sampling ratio) and adjust the rate based on the accuracy of the operations shown in the failures and performance panes. A higher rate generally results in higher accuracy. However, ANY sampling will affect accuracy so we recommend alerting on OpenTelemetry metrics, which are unaffected by sampling.

Live metrics

Live metrics provides a real-time analytics dashboard for insight into application activity and performance.

Important

See the Supplemental Terms of Use for Microsoft Azure Previews for legal terms that apply to Azure features that are in beta, preview, or otherwise not yet released into general availability.

This feature is enabled by default.

Users can disable Live Metrics when configuring the Distro.

builder.Services.AddOpenTelemetry().UseAzureMonitor(options => {
	// Disable the Live Metrics feature.
    options.EnableLiveMetrics = false;
});

Enable Microsoft Entra ID (formerly Azure AD) authentication

You might want to enable Microsoft Entra authentication for a more secure connection to Azure, which prevents unauthorized telemetry from being ingested into your subscription.

We support the credential classes provided by Azure Identity.

  • We recommend DefaultAzureCredential for local development.
  • We recommend ManagedIdentityCredential for system-assigned and user-assigned managed identities.
    • For system-assigned, use the default constructor without parameters.
    • For user-assigned, provide the client ID to the constructor.
  • We recommend ClientSecretCredential for service principals.
    • Provide the tenant ID, client ID, and client secret to the constructor.

  1. Install the latest Azure.Identity package:

    dotnet add package Azure.Identity

  2. Provide the desired credential class:

    // Create a new ASP.NET Core web application builder.    
var builder = WebApplication.CreateBuilder(args);

// Add the OpenTelemetry telemetry service to the application.
// This service will collect and send telemetry data to Azure Monitor.
builder.Services.AddOpenTelemetry().UseAzureMonitor(options => {
    // Set the Azure Monitor credential to the DefaultAzureCredential.
    // This credential will use the Azure identity of the current user or
    // the service principal that the application is running as to authenticate
    // to Azure Monitor.
    options.Credential = new DefaultAzureCredential();
});

// Build the ASP.NET Core web application.
var app = builder.Build();

// Start the ASP.NET Core web application.
app.Run();

Offline Storage and Automatic Retries

To improve reliability and resiliency, Azure Monitor OpenTelemetry-based offerings write to offline/local storage by default when an application loses its connection with Application Insights. It saves the application telemetry to disk and periodically tries to send it again for up to 48 hours. In high-load applications, telemetry is occasionally dropped for two reasons. First, when the allowable time is exceeded, and second, when the maximum file size is exceeded or the SDK doesn't have an opportunity to clear out the file. If we need to choose, the product saves more recent events over old ones. Learn More

The Distro package includes the AzureMonitorExporter, which by default uses one of the following locations for offline storage (listed in order of precedence):

  • Windows
    • %LOCALAPPDATA%\Microsoft\AzureMonitor
    • %TEMP%\Microsoft\AzureMonitor
  • Non-Windows
    • %TMPDIR%/Microsoft/AzureMonitor
    • /var/tmp/Microsoft/AzureMonitor
    • /tmp/Microsoft/AzureMonitor

To override the default directory, you should set AzureMonitorOptions.StorageDirectory.

// Create a new ASP.NET Core web application builder.
var builder = WebApplication.CreateBuilder(args);

// Add the OpenTelemetry telemetry service to the application.
// This service will collect and send telemetry data to Azure Monitor.
builder.Services.AddOpenTelemetry().UseAzureMonitor(options =>
{
    // Set the Azure Monitor storage directory to "C:\\SomeDirectory".
    // This is the directory where the OpenTelemetry SDK will store any telemetry data that cannot be sent to Azure Monitor immediately.
    options.StorageDirectory = "C:\\SomeDirectory";
});

// Build the ASP.NET Core web application.
var app = builder.Build();

// Start the ASP.NET Core web application.
app.Run();

To disable this feature, you should set AzureMonitorOptions.DisableOfflineStorage = true.

Enable the OTLP Exporter

You might want to enable the OpenTelemetry Protocol (OTLP) Exporter alongside the Azure Monitor Exporter to send your telemetry to two locations.

Note

The OTLP Exporter is shown for convenience only. We don't officially support the OTLP Exporter or any components or third-party experiences downstream of it.

  1. Install the OpenTelemetry.Exporter.OpenTelemetryProtocol package in your project.

    dotnet add package OpenTelemetry.Exporter.OpenTelemetryProtocol

  2. Add the following code snippet. This example assumes you have an OpenTelemetry Collector with an OTLP receiver running. For details, see the example on GitHub.

    // Create a new ASP.NET Core web application builder.
var builder = WebApplication.CreateBuilder(args);

// Add the OpenTelemetry telemetry service to the application.
// This service will collect and send telemetry data to Azure Monitor.
builder.Services.AddOpenTelemetry().UseAzureMonitor();

// Add the OpenTelemetry OTLP exporter to the application.
// This exporter will send telemetry data to an OTLP receiver, such as Prometheus
builder.Services.AddOpenTelemetry().WithTracing(builder => builder.AddOtlpExporter());
builder.Services.AddOpenTelemetry().WithMetrics(builder => builder.AddOtlpExporter());

// Build the ASP.NET Core web application.
var app = builder.Build();

// Start the ASP.NET Core web application.
app.Run();

OpenTelemetry configurations

The following OpenTelemetry configurations can be accessed through environment variables while using the Azure Monitor OpenTelemetry Distros.

Environment variable Description
APPLICATIONINSIGHTS_CONNECTION_STRING Set it to the connection string for your Application Insights resource.
APPLICATIONINSIGHTS_STATSBEAT_DISABLED Set it to true to opt out of internal metrics collection.
OTEL_RESOURCE_ATTRIBUTES Key-value pairs to be used as resource attributes. For more information about resource attributes, see the Resource SDK specification.
OTEL_SERVICE_NAME Sets the value of the service.name resource attribute. If service.name is also provided in OTEL_RESOURCE_ATTRIBUTES, then OTEL_SERVICE_NAME takes precedence.

Redact URL Query Strings

To redact URL query strings, turn off query string collection. We recommend this setting if you call Azure storage using a SAS token.

When using the Azure.Monitor.OpenTelemetry.AspNetCore distro package, both the ASP.NET Core and HttpClient Instrumentation libraries are included. Our distro package sets Query String Redaction off by default.

To change this behavior, you must set an environment variable to either "true" or "false".

  • ASP.NET Core Instrumentation: OTEL_DOTNET_EXPERIMENTAL_ASPNETCORE_DISABLE_URL_QUERY_REDACTION Query String Redaction is disabled by default. To enable, set this environment variable to "false".
  • Http Client Instrumentation: OTEL_DOTNET_EXPERIMENTAL_HTTPCLIENT_DISABLE_URL_QUERY_REDACTION Query String Redaction is disabled by default. To enable, set this environment variable to "false".