Semantic Conventions for HTTP Metrics

Status: Experimental, partial feature-freeze

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 attributes that they emit until the HTTP semantic conventions are marked stable (HTTP stabilization will include stabilization of a core set of networking attributes which are also used in HTTP instrumentations).
• 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 attributes, and stop emitting the old experimental HTTP and networking attributes that the instrumentation emitted previously.
  • http/dup - emit both the old and the stable HTTP and networking attributes, 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 attributes the instrumentation was emitting previously.
• SHOULD maintain (security patching at a minimum) the existing major version for at least six months after it starts emitting both sets of attributes.
• 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.duration

Status: Experimental, Feature-freeze

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, 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]: 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.

[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 and, except if reporting a metric, MUST set the exact method received in the request line as value of the http.request.method_original attribute.

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]: 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.

[4]: 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.

[5]: 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.

Metric: http.server.active_requests

Status: Experimental

This metric is optional.

[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 and, except if reporting a metric, MUST set the exact method received in the request line as value of the http.request.method_original attribute.

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.

Metric: http.server.request.size

Status: Experimental

This metric is optional.

[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.

[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 and, except if reporting a metric, MUST set the exact method received in the request line as value of the http.request.method_original attribute.

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]: 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.

[4]: 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.

[5]: 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.

Metric: http.server.response.size

Status: Experimental

This metric is optional.

[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.

[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 and, except if reporting a metric, MUST set the exact method received in the request line as value of the http.request.method_original attribute.

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]: 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.

[4]: 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.

[5]: 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.

HTTP Client

Metric: http.client.duration

Status: Experimental, Feature-freeze

This metric is required.

When this metric is reported alongside an HTTP client span, the metric value SHOULD be the same as the HTTP client span duration.

This metric SHOULD be specified with ExplicitBucketBoundaries of [ 0, 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]: 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 and, except if reporting a metric, MUST set the exact method received in the request line as value of the http.request.method_original attribute.

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]: 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.

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

• Host identifier of the request target if it’s sent in absolute-form
• Host identifier of the Host header

SHOULD NOT be set if capturing it would require an extra DNS lookup.

[4]: When request target is absolute URI, server.port MUST match URI port identifier, otherwise it MUST match Host header port identifier.

[5]: If not 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.request.size

Status: Experimental

This metric is optional.

[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 and, except if reporting a metric, MUST set the exact method received in the request line as value of the http.request.method_original attribute.

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]: 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.

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

• Host identifier of the request target if it’s sent in absolute-form
• Host identifier of the Host header

SHOULD NOT be set if capturing it would require an extra DNS lookup.

[4]: When request target is absolute URI, server.port MUST match URI port identifier, otherwise it MUST match Host header port identifier.

[5]: If not 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.response.size

Status: Experimental

This metric is optional.

[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 and, except if reporting a metric, MUST set the exact method received in the request line as value of the http.request.method_original attribute.

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]: 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.

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

• Host identifier of the request target if it’s sent in absolute-form
• Host identifier of the Host header

SHOULD NOT be set if capturing it would require an extra DNS lookup.

[4]: When request target is absolute URI, server.port MUST match URI port identifier, otherwise it MUST match Host header port identifier.

[5]: If not 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.