Change user_agent.original from recommended to opt-in on HTTP client spans

CHANGELOG.md

@@ -32,6 +32,8 @@ release.
   ([#409](https://github.com/open-telemetry/semantic-conventions/pull/409))
 - Remove `url.path` default value.
   ([#462](https://github.com/open-telemetry/semantic-conventions/pull/462))
+- Change `user_agent.original` from recommended to opt-in on HTTP client spans.
+  ([#468](https://github.com/open-telemetry/semantic-conventions/pull/468))
 
 ### Features
 

docs/http/http-spans.md

@@ -129,7 +129,6 @@ sections below.
 | [`network.protocol.name`](../attributes-registry/network.md) | string | [OSI application layer](https://osi-model.com/application-layer/) or non-OSI equivalent. [6] | `http`; `spdy` | Opt-In |
 | [`network.protocol.version`](../attributes-registry/network.md) | string | Version of the protocol specified in `network.protocol.name`. [7] | `1.0`; `1.1`; `2`; `3` | Recommended |
 | [`network.transport`](../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). [8] | `tcp`; `udp` | Opt-In |
-| [`user_agent.original`](../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` | Recommended |
 
 **[1]:** If the request fails with an error before response status code was sent or received,
 `error.type` SHOULD be set to exception type (its fully-qualified class name, if applicable)
@@ -237,6 +236,7 @@ For an HTTP client span, `SpanKind` MUST be `Client`.
 | [`server.address`](../general/attributes.md) | string | Host identifier of the ["URI origin"](https://www.rfc-editor.org/rfc/rfc9110.html#name-uri-origin) HTTP request is sent to. [2] | `example.com`; `10.1.2.80`; `/tmp/my.sock` | Required |
 | [`server.port`](../general/attributes.md) | int | Port identifier of the ["URI origin"](https://www.rfc-editor.org/rfc/rfc9110.html#name-uri-origin) HTTP request is sent to. [3] | `80`; `8080`; `443` | Conditionally Required: [4] |
 | [`url.full`](../attributes-registry/url.md) | string | Absolute URL describing a network resource according to [RFC3986](https://www.rfc-editor.org/rfc/rfc3986) [5] | `https://www.foo.bar/search?q=OpenTelemetry#SemConv`; `//localhost` | Required |
+| [`user_agent.original`](../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` | Opt-In |
 
 **[1]:** The resend count SHOULD be updated each time an HTTP request gets resent by the client, regardless of what was the cause of the resending (e.g. redirection, authorization failure, 503 Server Unavailable, network issues, or any other).
 
@@ -354,6 +354,7 @@ For an HTTP server span, `SpanKind` MUST be `Server`.
 | [`url.path`](../attributes-registry/url.md) | string | The [URI path](https://www.rfc-editor.org/rfc/rfc3986#section-3.3) component | `/search` | Required |
 | [`url.query`](../attributes-registry/url.md) | string | The [URI query](https://www.rfc-editor.org/rfc/rfc3986#section-3.4) component [7] | `q=OpenTelemetry` | Conditionally Required: If and only if one was received/sent. |
 | [`url.scheme`](../attributes-registry/url.md) | string | The [URI scheme](https://www.rfc-editor.org/rfc/rfc3986#section-3.1) component identifying the used protocol. [8] | `http`; `https` | Required |
+| [`user_agent.original`](../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` | Recommended |
 
 **[1]:** The IP address of the original client behind all proxies, if known (e.g. from [Forwarded](https://developer.mozilla.org/docs/Web/HTTP/Headers/Forwarded), [X-Forwarded-For](https://developer.mozilla.org/docs/Web/HTTP/Headers/X-Forwarded-For), or a similar header). Otherwise, the immediate client peer address.
 

model/trace/http.yaml

@@ -24,7 +24,6 @@ groups:
         note: >
           Generally `tcp` for `HTTP/1.0`, `HTTP/1.1`, and `HTTP/2`. Generally `udp` for `HTTP/3`.
           Other obscure implementations are possible.
-      - ref: user_agent.original
 
   - id: trace.http.client
     type: span
@@ -48,6 +47,8 @@ groups:
       - ref: url.full
         sampling_relevant: true
         requirement_level: required
+      - ref: user_agent.original
+        requirement_level: opt_in
 
   - id: trace.http.server
     type: span
@@ -89,3 +90,4 @@ groups:
         sampling_relevant: true
       - ref: url.scheme
         sampling_relevant: true
+      - ref: user_agent.original