Semantic Conventions for ASP.NET Core metrics

Status: Stable

This article defines semantic conventions for ASP.NET Core metrics.

Server

Routing

All routing metrics are reported by the Microsoft.AspNetCore.Routing meter.

Metric: aspnetcore.routing.match_attempts

Name	Instrument Type	Unit (UCUM)	Description	Stability
aspnetcore.routing.match_attempts	Counter	{match_attempt}	Number of requests that were attempted to be matched to an endpoint. [1]

[1]: Meter name: Microsoft.AspNetCore.Routing; Added in: ASP.NET Core 8.0

Attribute	Type	Description	Examples	Requirement Level	Stability
aspnetcore.routing.match_status	string	Match result - success or failure	success; failure	Required
aspnetcore.routing.is_fallback	boolean	A value that indicates whether the matched route is a fallback route.	true	Conditionally Required if and only if a route was successfully matched.
http.route	string	The matched route, that is, the path template in the format used by the respective server framework. [1]	/users/:userID?; {controller}/{action}/{id?}	Conditionally Required if and only if a route was successfully matched.

[1]: MUST NOT be populated when this is not supported by the HTTP server framework as the route attribute should have low-cardinality and the URI path can NOT substitute it. SHOULD include the application root if there is one.

aspnetcore.routing.match_status 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.

Value	Description	Stability
failure	Match failed
success	Match succeeded

Exceptions

Exceptions Metric is reported by the Microsoft.AspNetCore.Diagnostics meter.

Metric: aspnetcore.diagnostics.exceptions

Name	Instrument Type	Unit (UCUM)	Description	Stability
aspnetcore.diagnostics.exceptions	Counter	{exception}	Number of exceptions caught by exception handling middleware. [1]

[1]: Meter name: Microsoft.AspNetCore.Diagnostics; Added in: ASP.NET Core 8.0

Attribute	Type	Description	Examples	Requirement Level	Stability
aspnetcore.diagnostics.exception.result	string	ASP.NET Core exception middleware handling result	handled; unhandled	Required
error.type	string	The full name of exception type. [1]	System.OperationCanceledException; Contoso.MyException	Required
aspnetcore.diagnostics.handler.type	string	Full type name of the IExceptionHandler implementation that handled the exception.	Contoso.MyHandler	Conditionally Required [2]

[1]: The error.type SHOULD be predictable, and SHOULD have low cardinality.

When error.type is set to a type (e.g., an exception type), its canonical class name identifying the type within the artifact SHOULD be used.

Instrumentations SHOULD document the list of errors they report.

The cardinality of error.type within one instrumentation library SHOULD be low. Telemetry consumers that aggregate data from multiple instrumentation libraries and applications should be prepared for error.type to have high cardinality at query time when no additional filters are applied.

If the operation has completed successfully, instrumentations SHOULD NOT set error.type.

If a specific domain defines its own set of error identifiers (such as HTTP or gRPC status codes), it’s RECOMMENDED to:

• Use a domain-specific attribute
• Set error.type to capture all errors, regardless of whether they are defined within the domain-specific set or not.

[2]: if and only if the exception was handled by this handler.

aspnetcore.diagnostics.exception.result 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.

Value	Description	Stability
aborted	Exception handling didn’t run because the request was aborted.
handled	Exception was handled by the exception handling middleware.
skipped	Exception handling was skipped because the response had started.
unhandled	Exception was not handled by the exception handling middleware.

error.type 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.

Value	Description	Stability
_OTHER	A fallback error value to be used when the instrumentation doesn’t define a custom value.

Rate-limiting

All rate-limiting metrics are reported by the Microsoft.AspNetCore.RateLimiting meter.

Metric: aspnetcore.rate_limiting.active_request_leases

Name	Instrument Type	Unit (UCUM)	Description	Stability
aspnetcore.rate_limiting.active_request_leases	UpDownCounter	{request}	Number of requests that are currently active on the server that hold a rate limiting lease. [1]

[1]: Meter name: Microsoft.AspNetCore.RateLimiting; Added in: ASP.NET Core 8.0

Attribute	Type	Description	Examples	Requirement Level	Stability
aspnetcore.rate_limiting.policy	string	Rate limiting policy name.	fixed; sliding; token	Conditionally Required [1]

[1]: if the matched endpoint for the request had a rate-limiting policy.

Metric: aspnetcore.rate_limiting.request_lease.duration

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 ].

Name	Instrument Type	Unit (UCUM)	Description	Stability
aspnetcore.rate_limiting.request_lease.duration	Histogram	s	The duration of rate limiting lease held by requests on the server. [1]

[1]: Meter name: Microsoft.AspNetCore.RateLimiting; Added in: ASP.NET Core 8.0

Attribute	Type	Description	Examples	Requirement Level	Stability
aspnetcore.rate_limiting.policy	string	Rate limiting policy name.	fixed; sliding; token	Conditionally Required [1]

[1]: if the matched endpoint for the request had a rate-limiting policy.

Metric: aspnetcore.rate_limiting.queued_requests

Name	Instrument Type	Unit (UCUM)	Description	Stability
aspnetcore.rate_limiting.queued_requests	UpDownCounter	{request}	Number of requests that are currently queued, waiting to acquire a rate limiting lease. [1]

[1]: Meter name: Microsoft.AspNetCore.RateLimiting; Added in: ASP.NET Core 8.0

Attribute	Type	Description	Examples	Requirement Level	Stability
aspnetcore.rate_limiting.policy	string	Rate limiting policy name.	fixed; sliding; token	Conditionally Required [1]

[1]: if the matched endpoint for the request had a rate-limiting policy.

Metric: aspnetcore.rate_limiting.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 ].

Name	Instrument Type	Unit (UCUM)	Description	Stability
aspnetcore.rate_limiting.request.time_in_queue	Histogram	s	The time the request spent in a queue waiting to acquire a rate limiting lease. [1]

[1]: Meter name: Microsoft.AspNetCore.RateLimiting; Added in: ASP.NET Core 8.0

Attribute	Type	Description	Examples	Requirement Level	Stability
aspnetcore.rate_limiting.result	string	Rate-limiting result, shows whether the lease was acquired or contains a rejection reason	acquired; request_canceled	Required
aspnetcore.rate_limiting.policy	string	Rate limiting policy name.	fixed; sliding; token	Conditionally Required [1]

[1]: if the matched endpoint for the request had a rate-limiting policy.

aspnetcore.rate_limiting.result 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.

Value	Description	Stability
acquired	Lease was acquired
endpoint_limiter	Lease request was rejected by the endpoint limiter
global_limiter	Lease request was rejected by the global limiter
request_canceled	Lease request was canceled

Metric: aspnetcore.rate_limiting.requests

Name	Instrument Type	Unit (UCUM)	Description	Stability
aspnetcore.rate_limiting.requests	Counter	{request}	Number of requests that tried to acquire a rate limiting lease. [1]

[1]: Requests could be:

• Rejected by global or endpoint rate limiting policies
• Canceled while waiting for the lease.

Meter name: Microsoft.AspNetCore.RateLimiting; Added in: ASP.NET Core 8.0

Attribute	Type	Description	Examples	Requirement Level	Stability
aspnetcore.rate_limiting.result	string	Rate-limiting result, shows whether the lease was acquired or contains a rejection reason	acquired; request_canceled	Required
aspnetcore.rate_limiting.policy	string	Rate limiting policy name.	fixed; sliding; token	Conditionally Required [1]

[1]: if the matched endpoint for the request had a rate-limiting policy.

aspnetcore.rate_limiting.result 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.

Value	Description	Stability
acquired	Lease was acquired
endpoint_limiter	Lease request was rejected by the endpoint limiter
global_limiter	Lease request was rejected by the global limiter
request_canceled	Lease request was canceled