Semantic conventions for HTTP client and server metrics emitted by .NET

Status: Stable

This article defines semantic conventions for HTTP metrics emitted by .NET components and runtime.

HTTP client

All Http client metrics are reported by the System.Net.Http meter.

Metric: http.client.request.duration

Client request duration measures the time it takes to receive response headers and doesn’t include time to read the response body.

This metric follows the common http.client.request.duration definition.

Notes:

• Meter name is System.Net.Http
• Metric added in .NET 8.0
• When the error.type attribute is reported, it contains one of HTTP Request errors in snake_case, a full exception type, or a string representation of received status code.
• network.protocol.name is not reported and should always be assumed to match http.
• server.port is not reported when it matches a default one for provided scheme (443 for https and 80 for http)
• url.scheme is always reported.

Metric: http.client.open_connections

[1]: Meter name: System.Net.Http; Added in: .NET 8.0

[1]: HTTP 1.0 and 1.1 requests share connections in the connection pool and are both reported as version 1.1. So, the network.protocol.version value reported on connection metrics is different than the one reported on request-level metrics or spans for HTTP 1.0 requests.

[2]: If an HTTP client request is explicitly made to an IP address, e.g. http://x.x.x.x:8080, then server.address SHOULD be the IP address x.x.x.x. A DNS lookup SHOULD NOT be used.

[3]: When observed from the client side, and when communicating through an intermediary, server.port SHOULD represent the server port behind any intermediaries, for example proxies, if it’s available.

[4]: If not the default (80 for http scheme, 443 for https).

http.connection.state MUST be one of the following:

Metric: http.client.connection.duration

this metric SHOULD be specified with ExplicitBucketBoundaries of [ 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 30, 60, 120, 300 ].

[1]: Meter name: System.Net.Http; Added in: .NET 8.0

[1]: HTTP 1.0 and 1.1 requests share connections in the connection pool and are both reported as version 1.1. So, the network.protocol.version value reported on connection metrics is different than the one reported on request-level metrics or spans for HTTP 1.0 requests.

[2]: If an HTTP client request is explicitly made to an IP address, e.g. http://x.x.x.x:8080, then server.address SHOULD be the IP address x.x.x.x. A DNS lookup SHOULD NOT be used.

[3]: When observed from the client side, and when communicating through an intermediary, server.port SHOULD represent the server port behind any intermediaries, for example proxies, if it’s available.

[4]: If not the default (80 for http scheme, 443 for https).

Metric: http.client.request.time_in_queue

this metric SHOULD be specified with ExplicitBucketBoundaries of [ 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 ].

[1]: Meter name: System.Net.Http; Added in: .NET 8.0

[1]: HTTP request method value is one of the “known” methods listed in RFC9110 and the PATCH method defined in RFC5789. If the HTTP request method isn’t known, it sets the http.request.method attribute to _OTHER. It’s not possible at the moment to override the list of known HTTP methods.

[2]: HTTP 1.0 and 1.1 requests share connections in the connection pool and are both reported as version 1.1. So, the network.protocol.version value reported on connection metrics is different than the one reported on request-level metrics or spans for HTTP 1.0 requests.

[3]: If an HTTP client request is explicitly made to an IP address, e.g. http://x.x.x.x:8080, then server.address SHOULD be the IP address x.x.x.x. A DNS lookup SHOULD NOT be used.

[4]: When observed from the client side, and when communicating through an intermediary, server.port SHOULD represent the server port behind any intermediaries, for example proxies, if it’s available.

[5]: If not the default (80 for http scheme, 443 for https).

http.request.method has the following list of well-known values. If one of them applies, then the respective value MUST be used, otherwise a custom value MAY be used.

Metric: http.client.active_requests

[1]: Meter name: System.Net.Http; Added in: .NET 8.0

[1]: HTTP request method value is one of the “known” methods listed in RFC9110 and the PATCH method defined in RFC5789. If the HTTP request method isn’t known, it sets the http.request.method attribute to _OTHER. It’s not possible at the moment to override the list of known HTTP methods.

[2]: If an HTTP client request is explicitly made to an IP address, e.g. http://x.x.x.x:8080, then server.address SHOULD be the IP address x.x.x.x. A DNS lookup SHOULD NOT be used.

[3]: When observed from the client side, and when communicating through an intermediary, server.port SHOULD represent the server port behind any intermediaries, for example proxies, if it’s available.

[4]: If not the default (80 for http scheme, 443 for https).

http.request.method has the following list of well-known values. If one of them applies, then the respective value MUST be used, otherwise a custom value MAY be used.

HTTP server

All HTTP server metrics are reported by the Microsoft.AspNetCore.Hosting meter.

Metric: http.server.request.duration

Measures time to last byte. This metric follows the common http.server.request.duration definition.

Notes:

• Meter name is Microsoft.AspNetCore.Hosting

• Metric added in ASP.NET Core 8.0

• Opt-in server.address and server.port attributes are not reported

• Additional attributes:

  • The aspnetcore.request.is_unhandled boolean attribute is reported when the request was not handled by the application pipeline. It’s skipped otherwise.

Metric: http.server.active_requests

Measures the number of HTTP requests that are currently active on the server. This metric follows the common http.server.active_requests definition.

Notes:

• Meter name is Microsoft.AspNetCore.Hosting
• Opt-in server.address and server.port attributes are not reported
• Metric added in ASP.NET Core 8.0