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Split ASP.NET Core built-in metrics reference into topic-focused pages (#37421)
* Initial plan * Split built-in metrics page into focused topic pages Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com> * Apply suggestion from @wadepickett * Apply suggestions from code review Co-authored-by: Wade Pickett <wpickett@microsoft.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> * Document aspnetcore.authorization.attempts metric Add information about authorization attempts metric in ASP.NET Core. * Apply suggestion from @wadepickett * Apply suggestions from code review Co-authored-by: Wade Pickett <wpickett@microsoft.com> * Apply suggestions from code review Co-authored-by: Wade Pickett <wpickett@microsoft.com> * Apply suggestion from @wadepickett * Apply suggestions from code review Co-authored-by: Wade Pickett <wpickett@microsoft.com> * Apply suggestions from code review Co-authored-by: Wade Pickett <wpickett@microsoft.com> * Address outstanding metrics review feedback Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com> --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com> Co-authored-by: Wade Pickett <wpickett@microsoft.com> Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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‎aspnetcore/fundamentals/servers/kestrel/security-considerations.md‎

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These metrics integrate with OpenTelemetry, `dotnet-counters`, Prometheus exporters, and Azure Monitor. For full setup guidance, see:
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- [ASP.NET Core metrics overview](xref:log-mon/metrics/metrics)
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- [Kestrel built-in metrics reference](/aspnet/core/log-mon/metrics/built-in#microsoftaspnetcoreserverkestrel)
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- [Kestrel built-in metrics reference](xref:log-mon/metrics/built-in-http#microsoftaspnetcoreserverkestrel)
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### TLS-over-HTTP detection
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‎aspnetcore/log-mon/metrics/built-in-components.md‎

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---
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title: ASP.NET Core built-in Blazor (Components) metrics
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ai-usage: ai-assisted
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author: guardrex
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description: Learn about built-in Blazor (Components) metrics for ASP.NET Core apps, including component, lifecycle, and server circuit metrics.
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monikerRange: '>= aspnetcore-10.0'
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ms.author: wpickett
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ms.date: 08/05/2026
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ms.topic: reference
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uid: log-mon/metrics/built-in-components
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---
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# ASP.NET Core built-in Blazor (Components) metrics
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This article describes the built-in Blazor (Components) metrics for ASP.NET Core produced using the <xref:System.Diagnostics.Metrics?displayProperty=nameWithType> 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.
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For an overview of all built-in metrics reference pages and how to read this reference, see <xref:log-mon/metrics/built-in>. For information on how to collect, report, enrich, and test with ASP.NET Core metrics, see <xref:log-mon/metrics/metrics>.
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## `Microsoft.AspNetCore.Components`
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The `Microsoft.AspNetCore.Components` metrics report information on Razor component route changes and browser events:
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* [`aspnetcore.components.navigation`](#metric-aspnetcorecomponentsnavigation)
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* [`aspnetcore.components.event_handler`](#metric-aspnetcorecomponentsevent_handler)
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### Metric: `aspnetcore.components.navigation`
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Name | Instrument Type | Unit (UCUM) | Description
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--- | --- | --- | ---
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`aspnetcore.components.navigation`<!--](https://opentelemetry.io/docs/specs/semconv/dotnet/dotnet-http-metrics/#metric-aspnetcorecomponentsnavigation)--> | Counter | `{route}` | Tracks the total number of route changes in the app.
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Attribute | Type | Description | Examples | Presence
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--- | --- | --- | --- | ---
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`aspnetcore.components.type` | string | Component navigated to. | `TestComponent` | Always
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`aspnetcore.components.route` | string | The component's route. | `/test-route` | Always
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`error.type` | string | The full name of exception type. | `System.InvalidOperationException`; `Contoso.MyException` | If an exception is thrown.
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Usage: How many different Blazor pages did users visit?
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### Metric: `aspnetcore.components.event_handler`
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Name | Instrument Type | Unit (UCUM) | Description
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--- | --- | --- | ---
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`aspnetcore.components.event_handler`<!--](https://opentelemetry.io/docs/specs/semconv/dotnet/dotnet-http-metrics/#metric-aspnetcorecomponentsevent_handler)--> | Histogram | `s` | Measures the duration of processing browser events, including business logic of the component, excluding the duration of child component event handling.
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Attribute | Type | Description | Examples | Presence
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--- | --- | --- | --- | ---
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`aspnetcore.components.type` | string | Component type handling the event. | `TestComponent` | Always
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`aspnetcore.components.method` | string | C# method handling the event. | `OnClick` | Always
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`aspnetcore.components.attribute.name` | string | Component attribute name handling the event. | `onclick` | Always
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`error.type` | string | The full name of exception type. | `System.InvalidOperationException`; `Contoso.MyException` | If an exception is thrown.
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Usage:
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* Which component's click event handler is slow?
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* Which buttons are selected often?
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## `Microsoft.AspNetCore.Components.Lifecycle`
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The `Microsoft.AspNetCore.Components.Lifecycle` metrics report information on Razor component lifecycle events:
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* [`aspnetcore.components.update_parameters`](#metric-aspnetcorecomponentsupdate_parameters)
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* [`aspnetcore.components.render_diff`](#metric-aspnetcorecomponentsrender_diff)
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### Metric: `aspnetcore.components.update_parameters`
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Name | Instrument Type | Unit (UCUM) | Description
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--- | --- | --- | ---
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`aspnetcore.components.update_parameters`<!--](https://opentelemetry.io/docs/specs/semconv/dotnet/dotnet-http-metrics/#metric-aspnetcorecomponentsupdate_parameters)--> | Histogram | `s` | Measures the duration of processing component parameters, including business logic.
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Attribute | Type | Description | Examples | Presence
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--- | --- | --- | --- | ---
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`aspnetcore.components.type` | string | Component type handling the event. | `TestComponent` | Always
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`error.type` | string | The full name of exception type. | `System.InvalidOperationException`; `Contoso.MyException` | If an exception is thrown.
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Usage:
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* Which components are slow to update?
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* Which components are updated often?
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### Metric: `aspnetcore.components.render_diff`
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Name | Instrument Type | Unit (UCUM) | Description
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--- | --- | --- | ---
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`aspnetcore.components.render_diff`<!--](https://opentelemetry.io/docs/specs/semconv/dotnet/dotnet-http-metrics/#metric-aspnetcorecomponentsrender_diff)--> | Histogram | `s` | Tracks the duration of rendering batches.
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Attribute | Type | Description | Examples | Presence
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--- | --- | --- | --- | ---
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`aspnetcore.components.diff.length` | int | The length of the render diff/size of the batch (bucketed). | 50 | Always
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`error.type` | string | The full name of exception type. | `System.InvalidOperationException`; `Contoso.MyException` | If an exception is thrown.
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Usage:
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* Is server rendering slow?
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* Do I render diffs that are too large? (network bandwidth, DOM update)
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## `Microsoft.AspNetCore.Components.Server.Circuits`
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The `Microsoft.AspNetCore.Components.Server.Circuits` metrics report information on server-side Blazor circuits in Blazor Server and Blazor Web Apps:
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* [`aspnetcore.components.circuit.active`](#metric-aspnetcorecomponentscircuitactive)
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* [`aspnetcore.components.circuit.connected`](#metric-aspnetcorecomponentscircuitconnected)
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* [`aspnetcore.components.circuit.duration`](#metric-aspnetcorecomponentscircuitduration)
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### Metric: `aspnetcore.components.circuit.active`
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Name | Instrument Type | Unit (UCUM) | Description
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--- | --- | --- | ---
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`aspnetcore.components.circuit.active`<!--](https://opentelemetry.io/docs/specs/semconv/dotnet/dotnet-http-metrics/#metric-aspnetcorecomponentscircuitactive)--> | UpDownCounter | `{circuit}` | Shows the number of active circuits currently in memory.
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Usage: How much memory does the session state hold?
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### Metric: `aspnetcore.components.circuit.connected`
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Name | Instrument Type | Unit (UCUM) | Description
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--- | --- | --- | ---
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`aspnetcore.components.circuit.connected`<!--](https://opentelemetry.io/docs/specs/semconv/dotnet/dotnet-http-metrics/#metric-aspnetcorecomponentscircuitconnected)--> | UpDownCounter | `{circuit}` | Tracks the number of circuits connected to clients.
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Usage: How many SignalR connections are open?
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### Metric: `aspnetcore.components.circuit.duration`
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Name | Instrument Type | Unit (UCUM) | Description
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--- | --- | --- | ---
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`aspnetcore.components.circuit.duration`<!--](https://opentelemetry.io/docs/specs/semconv/dotnet/dotnet-http-metrics/#metric-aspnetcorecomponentscircuitduration)--> | Histogram | `s` | Measures circuit lifetime duration and provides total circuit count.
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Usage:
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* How many sessions processed?
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* How long do users keep the session/tab open?
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## See also
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* <xref:log-mon/metrics/built-in>
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* <xref:log-mon/metrics/built-in-http>
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* <xref:log-mon/metrics/built-in-diagnostics>
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* <xref:log-mon/metrics/built-in-security>
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* <xref:log-mon/metrics/metrics>

‎aspnetcore/log-mon/metrics/built-in-diagnostics.md‎

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---
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title: ASP.NET Core built-in diagnostics metrics
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ai-usage: ai-assisted
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author: guardrex
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description: Learn about built-in diagnostics metrics for ASP.NET Core apps, reported by the error handling middleware.
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ms.author: wpickett
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ms.date: 08/05/2026
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ms.topic: reference
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uid: log-mon/metrics/built-in-diagnostics
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---
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# ASP.NET Core built-in diagnostics metrics
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This article describes the built-in diagnostics metrics for ASP.NET Core produced using the <xref:System.Diagnostics.Metrics?displayProperty=nameWithType> API. These metrics report diagnostics information from the ASP.NET Core error handling middleware.
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For an overview of all built-in metrics reference pages and how to read this reference, see <xref:log-mon/metrics/built-in>. For information on how to collect, report, enrich, and test with ASP.NET Core metrics, see <xref:log-mon/metrics/metrics>.
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## `Microsoft.AspNetCore.Diagnostics`
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The `Microsoft.AspNetCore.Diagnostics` metrics report diagnostics information from [ASP.NET Core error handling middleware](/aspnet/core/fundamentals/error-handling):
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* [`aspnetcore.diagnostics.exceptions`](#metric-aspnetcorediagnosticsexceptions)
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### Metric: `aspnetcore.diagnostics.exceptions`
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Name | Instrument Type | Unit (UCUM) | Description
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--- | --- | --- | ---
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[`aspnetcore.diagnostics.exceptions`](https://opentelemetry.io/docs/specs/semconv/dotnet/dotnet-aspnetcore-metrics/#metric-aspnetcorediagnosticsexceptions) | Counter | `{exception}` | Number of exceptions caught by exception handling middleware.
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Attribute | Type | Description | Examples | Presence
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--- | --- | --- | --- | ---
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`aspnetcore.diagnostics.exception.result` | string | ASP.NET Core exception middleware handling result. | `handled`; `unhandled` | Always
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`aspnetcore.diagnostics.handler.type` | string | Full type name of the [`IExceptionHandler`](/dotnet/api/microsoft.aspnetcore.diagnostics.iexceptionhandler) implementation that handled the exception. | `Contoso.MyHandler` | If the exception was handled by this handler.
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`exception.type` | string | The full name of exception type. | `System.OperationCanceledException`; `Contoso.MyException` | Always
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## See also
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* <xref:log-mon/metrics/built-in>
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* <xref:log-mon/metrics/built-in-http>
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* <xref:log-mon/metrics/built-in-components>
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* <xref:log-mon/metrics/built-in-security>
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* <xref:log-mon/metrics/metrics>

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