Semantic Conventions for HTTP Metrics

Status: [Experimental, partial feature-freeze][DocumentStatus]

The conventions described in this section are HTTP specific. When HTTP operations occur, metric events about those operations will be generated and reported to provide insight into the operations. By adding HTTP attributes to metric events it allows for finely tuned filtering.

Disclaimer: These are initial HTTP metric instruments and attributes but more may be added in the future.

Warning Existing HTTP instrumentations that are using v1.20.0 of this document (or prior):

  • SHOULD NOT change the version of the HTTP or networking conventions that they emit until the HTTP semantic conventions are marked stable (HTTP stabilization will include stabilization of a core set of networking conventions which are also used in HTTP instrumentations). Conventions include, but are not limited to, attributes, metric and span names, and unit of measure.
  • SHOULD introduce an environment variable OTEL_SEMCONV_STABILITY_OPT_IN in the existing major version which is a comma-separated list of values. The only values defined so far are:
    • http - emit the new, stable HTTP and networking conventions, and stop emitting the old experimental HTTP and networking conventions that the instrumentation emitted previously.
    • http/dup - emit both the old and the stable HTTP and networking conventions, allowing for a seamless transition.
    • The default behavior (in the absence of one of these values) is to continue emitting whatever version of the old experimental HTTP and networking conventions the instrumentation was emitting previously.
    • Note: http/dup has higher precedence than http in case both values are present
  • SHOULD maintain (security patching at a minimum) the existing major version for at least six months after it starts emitting both sets of conventions.
  • SHOULD drop the environment variable in the next major version (stable next major version SHOULD NOT be released prior to October 1, 2023).

HTTP Server

Metric: http.server.request.duration

Status: [Experimental, Feature-freeze][DocumentStatus]

This metric is required.

When this metric is reported alongside an HTTP server span, the metric value SHOULD be the same as the HTTP server span 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
http.server.request.duration Histogram s Duration of HTTP server requests.
Attribute Type Description Examples Requirement Level
error.type string Describes a class of error the operation ended with. [1] timeout; name_resolution_error; 500 Conditionally Required: If request has ended with an error.
http.request.method string HTTP request method. [2] GET; POST; HEAD Required
http.response.status_code int HTTP response status code. 200 Conditionally Required: If and only if one was received/sent.
http.route string The matched route (path template in the format used by the respective server framework). See note below [3] /users/:userID?; {controller}/{action}/{id?} Conditionally Required: If and only if it’s available
network.protocol.name string OSI application layer or non-OSI equivalent. [4] http; spdy Recommended: if not default (http).
network.protocol.version string Version of the protocol specified in network.protocol.name. [5] 1.0; 1.1; 2; 3 Recommended
server.address string Name of the local HTTP server that received the request. [6] example.com; 10.1.2.80; /tmp/my.sock Opt-In
server.port int Port of the local HTTP server that received the request. [7] 80; 8080; 443 Opt-In
url.scheme string The URI scheme component identifying the used protocol. http; https Required

[1]: If the request fails with an error before response status code was sent or received, error.type SHOULD be set to exception type or a component-specific low cardinality error code.

If response status code was sent or received and status indicates an error according to HTTP span status definition, error.type SHOULD be set to the status code number (represented as a string), an exception type (if thrown) or a component-specific error code.

The error.type value SHOULD be predictable and SHOULD have low cardinality. Instrumentations SHOULD document the list of errors they report.

The cardinality of error.type within one instrumentation library SHOULD be low, but 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 request has completed successfully, instrumentations SHOULD NOT set error.type.

[2]: HTTP request method value SHOULD be “known” to the instrumentation. By default, this convention defines “known” methods as the ones listed in RFC9110 and the PATCH method defined in RFC5789.

If the HTTP request method is not known to instrumentation, it MUST set the http.request.method attribute to _OTHER.

If the HTTP instrumentation could end up converting valid HTTP request methods to _OTHER, then it MUST provide a way to override the list of known HTTP methods. If this override is done via environment variable, then the environment variable MUST be named OTEL_INSTRUMENTATION_HTTP_KNOWN_METHODS and support a comma-separated list of case-sensitive known HTTP methods (this list MUST be a full override of the default known method, it is not a list of known methods in addition to the defaults).

HTTP method names are case-sensitive and http.request.method attribute value MUST match a known HTTP method name exactly. Instrumentations for specific web frameworks that consider HTTP methods to be case insensitive, SHOULD populate a canonical equivalent. Tracing instrumentations that do so, MUST also set http.request.method_original to the original value.

[3]: 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.

[4]: The value SHOULD be normalized to lowercase.

[5]: network.protocol.version refers to the version of the protocol used and might be different from the protocol client’s version. If the HTTP client used has a version of 0.27.2, but sends HTTP version 1.1, this attribute should be set to 1.1.

[6]: Determined by using the first of the following that applies

  • The primary server name of the matched virtual host. MUST only include host identifier.
  • Host identifier of the request target if it’s sent in absolute-form.
  • Host identifier of the Host header

SHOULD NOT be set if only IP address is available and capturing name would require a reverse DNS lookup.

[7]: Determined by using the first of the following that applies

  • Port identifier of the primary server host of the matched virtual host.
  • Port identifier of the request target if it’s sent in absolute-form.
  • Port identifier of the Host header

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
_OTHER A fallback error value to be used when the instrumentation does not define a custom value for it.

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.

Value Description
CONNECT CONNECT method.
DELETE DELETE method.
GET GET method.
HEAD HEAD method.
OPTIONS OPTIONS method.
PATCH PATCH method.
POST POST method.
PUT PUT method.
TRACE TRACE method.
_OTHER Any HTTP method that the instrumentation has no prior knowledge of.

Metric: http.server.active_requests

Status: [Experimental][DocumentStatus]

This metric is optional.

Name Instrument Type Unit (UCUM) Description
http.server.active_requests UpDownCounter {request} Number of active HTTP server requests.
Attribute Type Description Examples Requirement Level
http.request.method string HTTP request method. [1] GET; POST; HEAD Required
server.address string Name of the local HTTP server that received the request. [2] example.com; 10.1.2.80; /tmp/my.sock Opt-In
server.port int Port of the local HTTP server that received the request. [3] 80; 8080; 443 Opt-In
url.scheme string The URI scheme component identifying the used protocol. http; https Required

[1]: HTTP request method value SHOULD be “known” to the instrumentation. By default, this convention defines “known” methods as the ones listed in RFC9110 and the PATCH method defined in RFC5789.

If the HTTP request method is not known to instrumentation, it MUST set the http.request.method attribute to _OTHER.

If the HTTP instrumentation could end up converting valid HTTP request methods to _OTHER, then it MUST provide a way to override the list of known HTTP methods. If this override is done via environment variable, then the environment variable MUST be named OTEL_INSTRUMENTATION_HTTP_KNOWN_METHODS and support a comma-separated list of case-sensitive known HTTP methods (this list MUST be a full override of the default known method, it is not a list of known methods in addition to the defaults).

HTTP method names are case-sensitive and http.request.method attribute value MUST match a known HTTP method name exactly. Instrumentations for specific web frameworks that consider HTTP methods to be case insensitive, SHOULD populate a canonical equivalent. Tracing instrumentations that do so, MUST also set http.request.method_original to the original value.

[2]: Determined by using the first of the following that applies

  • The primary server name of the matched virtual host. MUST only include host identifier.
  • Host identifier of the request target if it’s sent in absolute-form.
  • Host identifier of the Host header

SHOULD NOT be set if only IP address is available and capturing name would require a reverse DNS lookup.

[3]: Determined by using the first of the following that applies

  • Port identifier of the primary server host of the matched virtual host.
  • Port identifier of the request target if it’s sent in absolute-form.
  • Port identifier of the Host header

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.

Value Description
CONNECT CONNECT method.
DELETE DELETE method.
GET GET method.
HEAD HEAD method.
OPTIONS OPTIONS method.
PATCH PATCH method.
POST POST method.
PUT PUT method.
TRACE TRACE method.
_OTHER Any HTTP method that the instrumentation has no prior knowledge of.

Metric: http.server.request.body.size

Status: [Experimental][DocumentStatus]

This metric is optional.

Name Instrument Type Unit (UCUM) Description
http.server.request.body.size Histogram By Size of HTTP server request bodies. [1]

[1]: The size of the request payload body in bytes. This is the number of bytes transferred excluding headers and is often, but not always, present as the Content-Length header. For requests using transport encoding, this should be the compressed size.

Attribute Type Description Examples Requirement Level
error.type string Describes a class of error the operation ended with. [1] timeout; name_resolution_error; 500 Conditionally Required: If request has ended with an error.
http.request.method string HTTP request method. [2] GET; POST; HEAD Required
http.response.status_code int HTTP response status code. 200 Conditionally Required: If and only if one was received/sent.
http.route string The matched route (path template in the format used by the respective server framework). See note below [3] /users/:userID?; {controller}/{action}/{id?} Conditionally Required: If and only if it’s available
network.protocol.name string OSI application layer or non-OSI equivalent. [4] http; spdy Recommended: if not default (http).
network.protocol.version string Version of the protocol specified in network.protocol.name. [5] 1.0; 1.1; 2; 3 Recommended
server.address string Name of the local HTTP server that received the request. [6] example.com; 10.1.2.80; /tmp/my.sock Opt-In
server.port int Port of the local HTTP server that received the request. [7] 80; 8080; 443 Opt-In
url.scheme string The URI scheme component identifying the used protocol. http; https Required

[1]: If the request fails with an error before response status code was sent or received, error.type SHOULD be set to exception type or a component-specific low cardinality error code.

If response status code was sent or received and status indicates an error according to HTTP span status definition, error.type SHOULD be set to the status code number (represented as a string), an exception type (if thrown) or a component-specific error code.

The error.type value SHOULD be predictable and SHOULD have low cardinality. Instrumentations SHOULD document the list of errors they report.

The cardinality of error.type within one instrumentation library SHOULD be low, but 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 request has completed successfully, instrumentations SHOULD NOT set error.type.

[2]: HTTP request method value SHOULD be “known” to the instrumentation. By default, this convention defines “known” methods as the ones listed in RFC9110 and the PATCH method defined in RFC5789.

If the HTTP request method is not known to instrumentation, it MUST set the http.request.method attribute to _OTHER.

If the HTTP instrumentation could end up converting valid HTTP request methods to _OTHER, then it MUST provide a way to override the list of known HTTP methods. If this override is done via environment variable, then the environment variable MUST be named OTEL_INSTRUMENTATION_HTTP_KNOWN_METHODS and support a comma-separated list of case-sensitive known HTTP methods (this list MUST be a full override of the default known method, it is not a list of known methods in addition to the defaults).

HTTP method names are case-sensitive and http.request.method attribute value MUST match a known HTTP method name exactly. Instrumentations for specific web frameworks that consider HTTP methods to be case insensitive, SHOULD populate a canonical equivalent. Tracing instrumentations that do so, MUST also set http.request.method_original to the original value.

[3]: 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.

[4]: The value SHOULD be normalized to lowercase.

[5]: network.protocol.version refers to the version of the protocol used and might be different from the protocol client’s version. If the HTTP client used has a version of 0.27.2, but sends HTTP version 1.1, this attribute should be set to 1.1.

[6]: Determined by using the first of the following that applies

  • The primary server name of the matched virtual host. MUST only include host identifier.
  • Host identifier of the request target if it’s sent in absolute-form.
  • Host identifier of the Host header

SHOULD NOT be set if only IP address is available and capturing name would require a reverse DNS lookup.

[7]: Determined by using the first of the following that applies

  • Port identifier of the primary server host of the matched virtual host.
  • Port identifier of the request target if it’s sent in absolute-form.
  • Port identifier of the Host header

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
_OTHER A fallback error value to be used when the instrumentation does not define a custom value for it.

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.

Value Description
CONNECT CONNECT method.
DELETE DELETE method.
GET GET method.
HEAD HEAD method.
OPTIONS OPTIONS method.
PATCH PATCH method.
POST POST method.
PUT PUT method.
TRACE TRACE method.
_OTHER Any HTTP method that the instrumentation has no prior knowledge of.