ASP.NET Core metrics
This article describes the metrics built-in for ASP.NET Core produced using the System.Diagnostics.Metrics API. For a listing of metrics based on the older EventCounters API, see here.
Tip
For more information about how to collect, report, enrich, and test ASP.NET Core metrics, see Using ASP.NET Core metrics.
Microsoft.AspNetCore.Hosting
The Microsoft.AspNetCore.Hosting
metrics report high-level information about HTTP requests received by ASP.NET Core:
Metric: http.server.request.duration
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
http.server.request.duration |
Histogram | s |
Measures the duration of inbound HTTP requests. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
http.route |
string | The matched route. | {controller}/{action}/{id?} |
If it's available. |
error.type |
string | Describes a class of error the operation ended with. | timeout ; name_resolution_error ; 500 |
If request has ended with an error. |
http.request.method |
string | HTTP request method. | GET ; POST ; HEAD |
Always |
http.response.status_code |
int | HTTP response status code. | 200 |
If one was sent. |
network.protocol.version |
string | Version of the protocol specified in network.protocol.name . |
3.1.1 |
Always |
url.scheme |
string | The URI scheme component identifying the used protocol. | http ; https |
Always |
aspnetcore.request.is_unhandled |
Boolean | True when the request wasn't handled by the application pipeline. | true |
If the request was unhandled. |
The time used to handle an inbound HTTP request as measured at the hosting layer of ASP.NET Core. The time measurement starts once the underlying web host has:
- Sufficiently parsed the HTTP request headers on the inbound network stream to identify the new request.
- Initialized the context data structures such as the HttpContext.
The time ends when:
- The ASP.NET Core handler pipeline is finished executing.
- All response data has been sent.
- The context data structures for the request are being disposed.
When using OpenTelemetry, the default buckets for this metric are set to [ 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10 ].
Available starting in: .NET 8.0.
Metric: http.server.active_requests
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
http.server.active_requests |
UpDownCounter | {request} |
Measures the number of concurrent HTTP requests that are currently in-flight. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
http.request.method |
string | HTTP request method. [1] | GET ; POST ; HEAD |
Always |
url.scheme |
string | The URI scheme component identifying the used protocol. | http ; https |
Always |
Available starting in: .NET 8.0.
Microsoft.AspNetCore.Routing
The Microsoft.AspNetCore.Routing
metrics report information about routing HTTP requests to ASP.NET Core endpoints:
Metric: aspnetcore.routing.match_attempts
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.routing.match_attempts |
Counter | {match_attempt} |
Number of requests that were attempted to be matched to an endpoint. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.routing.match_status |
string | Match result | success ; failure |
Always |
aspnetcore.routing.is_fallback_route |
boolean | A value that indicates whether the matched route is a fallback route. | True |
If a route was successfully matched. |
http.route |
string | The matched route | {controller}/{action}/{id?} |
If a route was successfully matched. |
Available starting in: .NET 8.0.
Microsoft.AspNetCore.Diagnostics
The Microsoft.AspNetCore.Diagnostics
metrics report diagnostics information from ASP.NET Core error handling middleware:
Metric: aspnetcore.diagnostics.exceptions
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.diagnostics.exceptions |
Counter | {exception} |
Number of exceptions caught by exception handling middleware. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.diagnostics.exception.result |
string | ASP.NET Core exception middleware handling result | handled ; unhandled |
Always |
aspnetcore.diagnostics.handler.type |
string | Full type name of the IExceptionHandler implementation that handled the exception. |
Contoso.MyHandler |
If the exception was handled by this handler. |
exception.type |
string | The full name of exception type. | System.OperationCanceledException ; Contoso.MyException |
Always |
Available starting in: .NET 8.0.
Microsoft.AspNetCore.RateLimiting
The Microsoft.AspNetCore.RateLimiting
metrics report rate limiting information from ASP.NET Core rate-limiting middleware:
aspnetcore.rate_limiting.active_request_leases
aspnetcore.rate_limiting.request_lease.duration
aspnetcore.rate_limiting.queued_requests
aspnetcore.rate_limiting.request.time_in_queue
aspnetcore.rate_limiting.requests
Metric: aspnetcore.rate_limiting.active_request_leases
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.rate_limiting.active_request_leases |
UpDownCounter | {request} |
Number of requests that are currently active on the server that hold a rate limiting lease. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.rate_limiting.policy |
string | Rate limiting policy name. | fixed ; sliding ; token |
If the matched endpoint for the request had a rate-limiting policy. |
Available starting in: .NET 8.0.
Metric: aspnetcore.rate_limiting.request_lease.duration
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.rate_limiting.request_lease.duration |
Histogram | s |
The duration of the rate limiting lease held by requests on the server. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.rate_limiting.policy |
string | Rate limiting policy name. | fixed ; sliding ; token |
If the matched endpoint for the request had a rate-limiting policy. |
Available starting in: .NET 8.0.
Metric: aspnetcore.rate_limiting.queued_requests
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.rate_limiting.queued_requests |
UpDownCounter | {request} |
Number of requests that are currently queued waiting to acquire a rate limiting lease. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.rate_limiting.policy |
string | Rate limiting policy name. | fixed ; sliding ; token |
If the matched endpoint for the request had a rate-limiting policy. |
Available starting in: .NET 8.0.
Metric: aspnetcore.rate_limiting.request.time_in_queue
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.rate_limiting.request.time_in_queue |
Histogram | s |
The time a request spent in a queue waiting to acquire a rate limiting lease. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.rate_limiting.policy |
string | Rate limiting policy name. | fixed ; sliding ; token |
If the matched endpoint for the request had a rate-limiting policy. |
aspnetcore.rate_limiting.result |
string | The rate limiting result shows whether lease was acquired or contains a rejection reason. | acquired ; request_canceled |
Always |
Available starting in: .NET 8.0.
Metric: aspnetcore.rate_limiting.requests
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.rate_limiting.requests |
Counter | {request} |
Number of requests that tried to acquire a rate limiting lease. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.rate_limiting.policy |
string | Rate limiting policy name. | fixed ; sliding ; token |
If the matched endpoint for the request had a rate-limiting policy. |
aspnetcore.rate_limiting.result |
string | The rate limiting result shows whether lease was acquired or contains a rejection reason. | acquired ; request_canceled |
Always |
Available starting in: .NET 8.0.
Microsoft.AspNetCore.HeaderParsing
The Microsoft.AspNetCore.HeaderParsing
metrics report information about ASP.NET Core header parsing:
Metric: aspnetcore.header_parsing.parse_errors
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.header_parsing.parse_errors |
Counter | {parse_error} |
Number of errors that occurred when parsing HTTP request headers. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.header_parsing.header.name |
string | The header name. | Content-Type |
Always |
error.type |
string | The error message. | Unable to parse media type value. |
Always |
Available starting in: .NET 8.0.
Metric: aspnetcore.header_parsing.cache_accesses
The metric is emitted only for HTTP request header parsers that support caching.
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
aspnetcore.header_parsing.cache_accesses |
Counter | {cache_access} |
Number of times a cache storing parsed header values was accessed. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
aspnetcore.header_parsing.header.name |
string | The header name. | Content-Type |
Always |
aspnetcore.header_parsing.cache_access.type |
string | A value indicating whether the header's value was found in the cache or not. | Hit ; Miss |
Always |
Available starting in: .NET 8.0.
Microsoft.AspNetCore.Server.Kestrel
The Microsoft.AspNetCore.Server.Kestrel
metrics report HTTP connection information from ASP.NET Core Kestrel web server:
kestrel.active_connections
kestrel.connection.duration
kestrel.rejected_connections
kestrel.queued_connections
kestrel.queued_requests
kestrel.upgraded_connections
kestrel.tls_handshake.duration
kestrel.active_tls_handshakes
Metric: kestrel.active_connections
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
kestrel.active_connections |
UpDownCounter | {connection} |
Number of connections that are currently active on the server. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
network.transport |
string | OSI transport layer or inter-process communication method. | tcp ; unix |
Always |
network.type |
string | OSI network layer or non-OSI equivalent. | ipv4 ; ipv6 |
If the transport is tcp or udp . |
server.address |
string | Server address domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. | example.com |
Always |
server.port |
int | Server port number | 80 ; 8080 ; 443 |
If the transport is tcp or udp . |
Available starting in: .NET 8.0.
Metric: kestrel.connection.duration
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
kestrel.connection.duration |
Histogram | s |
The duration of connections on the server. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
error.type |
string | The full name of exception type. | System.OperationCanceledException ; Contoso.MyException |
If an exception was thrown. |
network.protocol.name |
string | OSI application layer or non-OSI equivalent. | http ; web_sockets |
Always |
network.protocol.version |
string | Version of the protocol specified in network.protocol.name . |
1.1 ; 2 |
Always |
network.transport |
string | OSI transport layer or inter-process communication method. | tcp ; unix |
Always |
network.type |
string | OSI network layer or non-OSI equivalent. | ipv4 ; ipv6 |
If the transport is tcp or udp . |
server.address |
string | Server address domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. | example.com |
Always |
server.port |
int | Server port number | 80 ; 8080 ; 443 |
If the transport is tcp or udp . |
tls.protocol.version |
string | TLS protocol version. | 1.2 ; 1.3 |
If the connection is secured with TLS. |
As this metric is tracking the connection duration, and ideally http connections are used for multiple requests, the buckets should be longer than those used for request durations. For example, using [ 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 30, 60, 120, 300] provides an upper bucket of 5 mins.
Available starting in: .NET 8.0.
Metric: kestrel.rejected_connections
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
kestrel.rejected_connections |
Counter | {connection} |
Number of connections rejected by the server. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
network.transport |
string | OSI transport layer or inter-process communication method. | tcp ; unix |
Always |
network.type |
string | OSI network layer or non-OSI equivalent. | ipv4 ; ipv6 |
If the transport is tcp or udp . |
server.address |
string | Server address domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. | example.com |
Always |
server.port |
int | Server port number | 80 ; 8080 ; 443 |
If the transport is tcp or udp . |
Connections are rejected when the currently active count exceeds the value configured with MaxConcurrentConnections
.
Available starting in: .NET 8.0.
Metric: kestrel.queued_connections
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
kestrel.queued_connections |
UpDownCounter | {connection} |
Number of connections that are currently queued and are waiting to start. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
network.transport |
string | OSI transport layer or inter-process communication method. | tcp ; unix |
Always |
network.transport |
string | OSI network layer or non-OSI equivalent. | ipv4 ; ipv6 |
If the transport is tcp or udp . |
server.address |
string | Server address domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. | example.com |
Always |
server.port |
int | Server port number | 80 ; 8080 ; 443 |
If the transport is tcp or udp . |
Available starting in: .NET 8.0.
Metric: kestrel.queued_requests
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
kestrel.queued_requests |
UpDownCounter | {request} |
Number of HTTP requests on multiplexed connections (HTTP/2 and HTTP/3) that are currently queued and are waiting to start. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
network.protocol.name |
string | OSI application layer or non-OSI equivalent. | http ; web_sockets |
Always |
network.protocol.version |
string | Version of the protocol specified in network.protocol.name . |
1.1 ; 2 |
Always |
network.transport |
string | OSI transport layer or inter-process communication method. | tcp ; unix |
Always |
network.transport |
string | OSI network layer or non-OSI equivalent. | ipv4 ; ipv6 |
If the transport is tcp or udp . |
server.address |
string | Server address domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. | example.com |
Always |
server.port |
int | Server port number | 80 ; 8080 ; 443 |
If the transport is tcp or udp . |
Available starting in: .NET 8.0.
Metric: kestrel.upgraded_connections
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
kestrel.upgraded_connections |
UpDownCounter | {connection} |
Number of connections that are currently upgraded (WebSockets). |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
network.transport |
string | OSI transport layer or inter-process communication method. | tcp ; unix |
Always |
network.transport |
string | OSI network layer or non-OSI equivalent. | ipv4 ; ipv6 |
If the transport is tcp or udp . |
server.address |
string | Server address domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. | example.com |
Always |
server.port |
int | Server port number | 80 ; 8080 ; 443 |
If the transport is tcp or udp . |
The counter only tracks HTTP/1.1 connections.
Available starting in: .NET 8.0.
Metric: kestrel.tls_handshake.duration
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
kestrel.tls_handshake.duration |
Histogram | s |
The duration of TLS handshakes on the server. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
error.type |
string | The full name of exception type. | System.OperationCanceledException ; Contoso.MyException |
If an exception was thrown. |
network.transport |
string | OSI transport layer or inter-process communication method. | tcp ; unix |
Always |
network.transport |
string | OSI network layer or non-OSI equivalent. | ipv4 ; ipv6 |
If the transport is tcp or udp . |
server.address |
string | Server address domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. | example.com |
Always |
server.port |
int | Server port number | 80 ; 8080 ; 443 |
If the transport is tcp or udp . |
tls.protocol.version |
string | TLS protocol version. | 1.2 ; 1.3 |
If the connection is secured with TLS. |
When using OpenTelemetry, the default buckets for this metic are set to [ 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10 ].
Available starting in: .NET 8.0.
Metric: kestrel.active_tls_handshakes
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
kestrel.active_tls_handshakes |
UpDownCounter | {handshake} |
Number of TLS handshakes that are currently in progress on the server. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
network.transport |
string | OSI transport layer or inter-process communication method. | tcp ; unix |
Always |
network.transport |
string | OSI network layer or non-OSI equivalent. | ipv4 ; ipv6 |
If the transport is tcp or udp . |
server.address |
string | Server address domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. | example.com |
Always |
server.port |
int | Server port number | 80 ; 8080 ; 443 |
If the transport is tcp or udp . |
Available starting in: .NET 8.0.
Microsoft.AspNetCore.Http.Connections
The Microsoft.AspNetCore.Http.Connections
metrics report connection information from ASP.NET Core SignalR:
Metric: signalr.server.connection.duration
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
signalr.server.connection.duration |
Histogram | s |
The duration of connections on the server. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
signalr.connection.status |
string | SignalR HTTP connection closure status. | app_shutdown ; timeout |
Always |
signalr.transport |
string | SignalR transport type | web_sockets ; long_polling |
Always |
Available starting in: .NET 8.0.
Value | Description |
---|---|
normal_closure |
The connection was closed normally. |
timeout |
The connection was closed due to a timeout. |
app_shutdown |
The connection was closed because the app is shutting down. |
signalr.transport
is one of the following:
Value | Protocol |
---|---|
server_sent_events |
server-sent events |
long_polling |
Long Polling |
web_sockets |
WebSocket |
As this metric is tracking the connection duration, and ideally SignalR connections are durable, the buckets should be longer than those used for request durations. For example, using [0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 30, 60, 120, 300] provides an upper bucket of 5 mins.
Available starting in: .NET 8.0.
Metric: signalr.server.active_connections
Name | Instrument Type | Unit (UCUM) | Description |
---|---|---|---|
signalr.server.active_connections |
UpDownCounter | {connection} |
Number of connections that are currently active on the server. |
Attribute | Type | Description | Examples | Presence |
---|---|---|---|---|
signalr.connection.status |
string | SignalR HTTP connection closure status. | app_shutdown ; timeout |
Always |
signalr.transport |
string | SignalR transport type | web_sockets ; long_polling |
Always |
Available starting in: .NET 8.0.
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