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ASP.NET Core built-in Blazor (Components) metrics

This article describes the built-in Blazor (Components) metrics for ASP.NET Core produced using the System.Diagnostics.Metrics API. These metrics cover Razor component route changes and browser events, component lifecycle events, and server-side Blazor circuits. They're available in ASP.NET Core 10.0 or later.

For an overview of all built-in metrics reference pages and how to read this reference, see ASP.NET Core built-in metrics. For information on how to collect, report, enrich, and test with ASP.NET Core metrics, see ASP.NET Core metrics.

Microsoft.AspNetCore.Components

The Microsoft.AspNetCore.Components metrics report information on Razor component route changes and browser events:

Metric: aspnetcore.components.navigation

Name Instrument Type Unit (UCUM) Description
aspnetcore.components.navigation Counter {route} Tracks the total number of route changes in the app.
Attribute Type Description Examples Presence
aspnetcore.components.type string Component navigated to. TestComponent Always
aspnetcore.components.route string The component's route. /test-route Always
error.type string The full name of exception type. System.InvalidOperationException; Contoso.MyException If an exception is thrown.

Usage: How many different Blazor pages did users visit?

Metric: aspnetcore.components.event_handler

Name Instrument Type Unit (UCUM) Description
aspnetcore.components.event_handler Histogram s Measures the duration of processing browser events, including business logic of the component, excluding the duration of child component event handling.
Attribute Type Description Examples Presence
aspnetcore.components.type string Component type handling the event. TestComponent Always
aspnetcore.components.method string C# method handling the event. OnClick Always
aspnetcore.components.attribute.name string Component attribute name handling the event. onclick Always
error.type string The full name of exception type. System.InvalidOperationException; Contoso.MyException If an exception is thrown.

Usage:

  • Which component's click event handler is slow?
  • Which buttons are selected often?

Microsoft.AspNetCore.Components.Lifecycle

The Microsoft.AspNetCore.Components.Lifecycle metrics report information on Razor component lifecycle events:

Metric: aspnetcore.components.update_parameters

Name Instrument Type Unit (UCUM) Description
aspnetcore.components.update_parameters Histogram s Measures the duration of processing component parameters, including business logic.
Attribute Type Description Examples Presence
aspnetcore.components.type string Component type handling the event. TestComponent Always
error.type string The full name of exception type. System.InvalidOperationException; Contoso.MyException If an exception is thrown.

Usage:

  • Which components are slow to update?
  • Which components are updated often?

Metric: aspnetcore.components.render_diff

Name Instrument Type Unit (UCUM) Description
aspnetcore.components.render_diff Histogram s Tracks the duration of rendering batches.
Attribute Type Description Examples Presence
aspnetcore.components.diff.length int The length of the render diff/size of the batch (bucketed). 50 Always
error.type string The full name of exception type. System.InvalidOperationException; Contoso.MyException If an exception is thrown.

Usage:

  • Is server rendering slow?
  • Do I render diffs that are too large? (network bandwidth, DOM update)

Microsoft.AspNetCore.Components.Server.Circuits

The Microsoft.AspNetCore.Components.Server.Circuits metrics report information on server-side Blazor circuits in Blazor Server and Blazor Web Apps:

Metric: aspnetcore.components.circuit.active

Name Instrument Type Unit (UCUM) Description
aspnetcore.components.circuit.active UpDownCounter {circuit} Shows the number of active circuits currently in memory.

Usage: How much memory does the session state hold?

Metric: aspnetcore.components.circuit.connected

Name Instrument Type Unit (UCUM) Description
aspnetcore.components.circuit.connected UpDownCounter {circuit} Tracks the number of circuits connected to clients.

Usage: How many SignalR connections are open?

Metric: aspnetcore.components.circuit.duration

Name Instrument Type Unit (UCUM) Description
aspnetcore.components.circuit.duration Histogram s Measures circuit lifetime duration and provides total circuit count.

Usage:

  • How many sessions processed?
  • How long do users keep the session/tab open?

See also

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