Change network.peer.address to opt-in on http.client.open_connections (related to #3279)

.chloggen/http-peer-address-opt-in.yaml

@@ -0,0 +1,28 @@
+# Use this changelog template to create an entry for release notes.
+#
+# If your change doesn't affect end users you should instead start
+# your pull request title with [chore] or use the "Skip Changelog" label.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the area of concern in the attributes-registry, (e.g. http, cloud, db)
+component: http
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Change `network.peer.address` attribute requirement level from Recommended to Opt-In on the `http.client.open_connections` metric.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+# The values here must be integers.
+issues: [3279]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  `network.peer.address` is typically high-cardinality (one time series per remote IP).
+  On `http.client.open_connections` (an UpDownCounter, always exported with cumulative
+  temporality) this caused unbounded growth of metric streams over the lifetime of the
+  process, exhausting SDK cardinality limits and collapsing useful low-cardinality
+  attributes (e.g. `url.scheme`) into the overflow bucket. Operators that need this
+  attribute can still opt-in.

docs/http/http-metrics.md

@@ -951,8 +951,8 @@ This metric is optional.
 | [`http.connection.state`](/docs/registry/attributes/http.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Required` | string | State of the HTTP connection in the HTTP connection pool. | `active`; `idle` |
 | [`server.address`](/docs/registry/attributes/server.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Required` | string | Server domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [1] | `example.com`; `10.1.2.80`; `/tmp/my.sock` |
 | [`server.port`](/docs/registry/attributes/server.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Required` | int | Server port number. [2] | `80`; `8080`; `443` |
-| [`network.peer.address`](/docs/registry/attributes/network.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Recommended` | string | Peer address of the network connection - IP address or Unix domain socket name. | `10.1.2.80`; `/tmp/my.sock` |
 | [`network.protocol.version`](/docs/registry/attributes/network.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Recommended` | string | The actual version of the protocol used for network communication. [3] | `1.1`; `2` |
+| [`network.peer.address`](/docs/registry/attributes/network.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Opt-In` | string | Peer address of the network connection - IP address or Unix domain socket name. | `10.1.2.80`; `/tmp/my.sock` |
 | [`url.scheme`](/docs/registry/attributes/url.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Opt-In` | string | The [URI scheme](https://www.rfc-editor.org/rfc/rfc3986#section-3.1) component identifying the used protocol. | `http`; `https` |
 
 **[1] `server.address`:** 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.

model/http/metrics.yaml

@@ -177,7 +177,7 @@ groups:
       - ref: http.connection.state
         requirement_level: required
       - ref: network.peer.address
-        requirement_level: recommended
+        requirement_level: opt_in
       - ref: network.protocol.version
         requirement_level: recommended
       - ref: server.address