change metrics to emphasize experimental status of url.template

docs/http/http-metrics.md

@@ -21,6 +21,7 @@ operations. By adding HTTP attributes to metric events it allows for finely tune
   - [Metric: `http.server.response.body.size`](#metric-httpserverresponsebodysize)
 - [HTTP Client](#http-client)
   - [Metric: `http.client.request.duration`](#metric-httpclientrequestduration)
+    - [Experimental attributes](#experimental-attributes)
   - [Metric: `http.client.request.body.size`](#metric-httpclientrequestbodysize)
   - [Metric: `http.client.response.body.size`](#metric-httpclientresponsebodysize)
   - [Metric: `http.client.open_connections`](#metric-httpclientopen_connections)
@@ -449,7 +450,6 @@ 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
 | [`network.protocol.name`](/docs/attributes-registry/network.md) | string | [OSI application layer](https://osi-model.com/application-layer/) or non-OSI equivalent. [5] | `http`; `spdy` | `Conditionally Required` [6] | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`network.protocol.version`](/docs/attributes-registry/network.md) | string | The actual version of the protocol used for network communication. [7] | `1.0`; `1.1`; `2`; `3` | `Recommended` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`url.scheme`](/docs/attributes-registry/url.md) | string | The [URI scheme](https://www.rfc-editor.org/rfc/rfc3986#section-3.1) component identifying the used protocol. | `http`; `https` | `Opt-In` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
-| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [8] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 
 **[1]:** HTTP request method value SHOULD be "known" to the instrumentation.
 By default, this convention defines "known" methods as the ones listed in [RFC9110](https://www.rfc-editor.org/rfc/rfc9110.html#name-methods)
@@ -493,8 +493,6 @@ If the request has completed successfully, instrumentations SHOULD NOT set `erro
 
 **[7]:** If protocol version is subject to negotiation (for example using [ALPN](https://www.rfc-editor.org/rfc/rfc7301.html)), this attribute SHOULD be set to the negotiated version. If the actual protocol version is not known, this attribute SHOULD NOT be set.
 
-**[8]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
-
 `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 | Stability |
@@ -517,6 +515,20 @@ If the request has completed successfully, instrumentations SHOULD NOT set `erro
 | `_OTHER` | A fallback error value to be used when the instrumentation doesn't define a custom value. | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 <!-- endsemconv -->
 
+#### Experimental attributes
+
+**Status**: [Experimental][DocumentStatus]
+
+Instrumentations MAY allow users to enable additional experimental attributes.
+
+<!-- semconv attributes.http.client.experimental(full) -->
+| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
+|---|---|---|---|---|---|
+| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [1] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+
+**[1]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
+<!-- endsemconv -->
+
 ### Metric: `http.client.request.body.size`
 
 This metric is optional.
@@ -538,9 +550,9 @@ This metric is optional.
 | [`error.type`](/docs/attributes-registry/error.md) | string | Describes a class of error the operation ended with. [4] | `timeout`; `java.net.UnknownHostException`; `server_certificate_invalid`; `500` | `Conditionally Required` If request has ended with an error. | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`http.response.status_code`](/docs/attributes-registry/http.md) | int | [HTTP response status code](https://tools.ietf.org/html/rfc7231#section-6). | `200` | `Conditionally Required` If and only if one was received/sent. | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`network.protocol.name`](/docs/attributes-registry/network.md) | string | [OSI application layer](https://osi-model.com/application-layer/) or non-OSI equivalent. [5] | `http`; `spdy` | `Conditionally Required` [6] | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
-| [`network.protocol.version`](/docs/attributes-registry/network.md) | string | The actual version of the protocol used for network communication. [7] | `1.0`; `1.1`; `2`; `3` | `Recommended` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
+| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [7] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Conditionally Required` If available. | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+| [`network.protocol.version`](/docs/attributes-registry/network.md) | string | The actual version of the protocol used for network communication. [8] | `1.0`; `1.1`; `2`; `3` | `Recommended` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`url.scheme`](/docs/attributes-registry/url.md) | string | The [URI scheme](https://www.rfc-editor.org/rfc/rfc3986#section-3.1) component identifying the used protocol. | `http`; `https` | `Opt-In` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
-| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [8] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 
 **[1]:** HTTP request method value SHOULD be "known" to the instrumentation.
 By default, this convention defines "known" methods as the ones listed in [RFC9110](https://www.rfc-editor.org/rfc/rfc9110.html#name-methods)
@@ -582,9 +594,9 @@ If the request has completed successfully, instrumentations SHOULD NOT set `erro
 
 **[6]:** If not `http` and `network.protocol.version` is set.
 
-**[7]:** If protocol version is subject to negotiation (for example using [ALPN](https://www.rfc-editor.org/rfc/rfc7301.html)), this attribute SHOULD be set to the negotiated version. If the actual protocol version is not known, this attribute SHOULD NOT be set.
+**[7]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
 
-**[8]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
+**[8]:** If protocol version is subject to negotiation (for example using [ALPN](https://www.rfc-editor.org/rfc/rfc7301.html)), this attribute SHOULD be set to the negotiated version. If the actual protocol version is not known, this attribute SHOULD NOT be set.
 
 `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.
 
@@ -629,9 +641,9 @@ This metric is optional.
 | [`error.type`](/docs/attributes-registry/error.md) | string | Describes a class of error the operation ended with. [4] | `timeout`; `java.net.UnknownHostException`; `server_certificate_invalid`; `500` | `Conditionally Required` If request has ended with an error. | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`http.response.status_code`](/docs/attributes-registry/http.md) | int | [HTTP response status code](https://tools.ietf.org/html/rfc7231#section-6). | `200` | `Conditionally Required` If and only if one was received/sent. | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`network.protocol.name`](/docs/attributes-registry/network.md) | string | [OSI application layer](https://osi-model.com/application-layer/) or non-OSI equivalent. [5] | `http`; `spdy` | `Conditionally Required` [6] | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
-| [`network.protocol.version`](/docs/attributes-registry/network.md) | string | The actual version of the protocol used for network communication. [7] | `1.0`; `1.1`; `2`; `3` | `Recommended` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
+| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [7] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Conditionally Required` If available. | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+| [`network.protocol.version`](/docs/attributes-registry/network.md) | string | The actual version of the protocol used for network communication. [8] | `1.0`; `1.1`; `2`; `3` | `Recommended` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`url.scheme`](/docs/attributes-registry/url.md) | string | The [URI scheme](https://www.rfc-editor.org/rfc/rfc3986#section-3.1) component identifying the used protocol. | `http`; `https` | `Opt-In` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
-| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [8] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 
 **[1]:** HTTP request method value SHOULD be "known" to the instrumentation.
 By default, this convention defines "known" methods as the ones listed in [RFC9110](https://www.rfc-editor.org/rfc/rfc9110.html#name-methods)
@@ -673,9 +685,9 @@ If the request has completed successfully, instrumentations SHOULD NOT set `erro
 
 **[6]:** If not `http` and `network.protocol.version` is set.
 
-**[7]:** If protocol version is subject to negotiation (for example using [ALPN](https://www.rfc-editor.org/rfc/rfc7301.html)), this attribute SHOULD be set to the negotiated version. If the actual protocol version is not known, this attribute SHOULD NOT be set.
+**[7]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
 
-**[8]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
+**[8]:** If protocol version is subject to negotiation (for example using [ALPN](https://www.rfc-editor.org/rfc/rfc7301.html)), this attribute SHOULD be set to the negotiated version. If the actual protocol version is not known, this attribute SHOULD NOT be set.
 
 `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.
 
@@ -782,6 +794,7 @@ This metric is optional.
 | [`server.port`](/docs/attributes-registry/server.md) | int | Port identifier of the ["URI origin"](https://www.rfc-editor.org/rfc/rfc9110.html#name-uri-origin) HTTP request is sent to. [2] | `80`; `8080`; `443` | `Required` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`http.request.method`](/docs/attributes-registry/http.md) | string | HTTP request method. [3] | `GET`; `POST`; `HEAD` | `Recommended` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`url.scheme`](/docs/attributes-registry/url.md) | string | The [URI scheme](https://www.rfc-editor.org/rfc/rfc3986#section-3.1) component identifying the used protocol. | `http`; `https` | `Opt-In` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
+| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [4] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 
 **[1]:** When observed from the client side, and when communicating through an intermediary, `server.address` SHOULD represent the server address behind any intermediaries, for example proxies, if it's available.
 
@@ -802,6 +815,8 @@ HTTP method names are case-sensitive and `http.request.method` attribute value M
 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.
 
+**[4]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
+
 `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 | Stability |

docs/http/http-spans.md

@@ -141,7 +141,6 @@ For an HTTP client span, `SpanKind` MUST be `Client`.
 | [`http.response.header.<key>`](/docs/attributes-registry/http.md) | string[] | HTTP response headers, `<key>` being the normalized HTTP Header name (lowercase), the value being the header values. [12] | `http.response.header.content-type=["application/json"]`; `http.response.header.my-custom-header=["abc", "def"]` | `Opt-In` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`network.transport`](/docs/attributes-registry/network.md) | string | [OSI transport layer](https://osi-model.com/transport-layer/) or [inter-process communication method](https://wikipedia.org/wiki/Inter-process_communication). [13] | `tcp`; `udp` | `Opt-In` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 | [`url.scheme`](/docs/attributes-registry/url.md) | string | The [URI scheme](https://www.rfc-editor.org/rfc/rfc3986#section-3.1) component identifying the used protocol. | `http`; `https` | `Opt-In` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
-| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [14] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 | [`user_agent.original`](/docs/attributes-registry/user-agent.md) | string | Value of the [HTTP User-Agent](https://www.rfc-editor.org/rfc/rfc9110.html#field.user-agent) header sent by the client. | `CERN-LineMode/2.15 libwww/2.17b3`; `Mozilla/5.0 (iPhone; CPU iPhone OS 14_7_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.1.2 Mobile/15E148 Safari/604.1`; `YourApp/1.0.0 grpc-java-okhttp/1.27.2` | `Opt-In` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 
 **[1]:** HTTP request method value SHOULD be "known" to the instrumentation.
@@ -204,8 +203,6 @@ The attribute value MUST consist of either multiple header values as an array of
 
 **[13]:** Generally `tcp` for `HTTP/1.0`, `HTTP/1.1`, and `HTTP/2`. Generally `udp` for `HTTP/3`. Other obscure implementations are possible.
 
-**[14]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
-
 The following attributes can be important for making sampling decisions and SHOULD be provided **at span creation time** (if provided at all):
 
 * [`http.request.method`](/docs/attributes-registry/http.md)
@@ -257,6 +254,9 @@ Instrumentations MAY allow users to enable additional experimental attributes.
 | [`http.request.size`](/docs/attributes-registry/http.md) | int | The total size of the request in bytes. This should be the total number of bytes sent over the wire, including the request line (HTTP/1.1), framing (HTTP/2 and HTTP/3), headers, and request body if any. | `1437` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 | [`http.response.body.size`](/docs/attributes-registry/http.md) | int | The size of the response payload body in bytes. This is the number of bytes transferred excluding headers and is often, but not always, present as the [Content-Length](https://www.rfc-editor.org/rfc/rfc9110.html#field.content-length) header. For requests using transport encoding, this should be the compressed size. | `3495` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 | [`http.response.size`](/docs/attributes-registry/http.md) | int | The total size of the response in bytes. This should be the total number of bytes sent over the wire, including the status line (HTTP/1.1), framing (HTTP/2 and HTTP/3), headers, and response body and trailers if any. | `1437` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+| [`url.template`](/docs/attributes-registry/url.md) | string | The low-cardinality template of an [absolute path reference](https://www.rfc-editor.org/rfc/rfc3986#section-4.2). [1] | `/users/{id}`; `/users/:id`; `/users?id={id}` | `Opt-In` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+
+**[1]:** The `url.template` MUST have low cardinality. It is not usually available on HTTP clients, but may be known by the application or specialized HTTP instrumentation.
 <!-- endsemconv -->
 
 ### HTTP client span duration

model/http-common.yaml

@@ -55,6 +55,11 @@ groups:
       - ref: url.scheme
         requirement_level: opt_in
         examples: ["http", "https"]
+
+  - id: attributes.http.client.experimental
+    type: attribute_group
+    brief: "Experimental HTTP attributes."
+    attributes:
       - ref: url.template
         requirement_level: opt_in
         note: >