RPC: Clarify how to populate server.address and server.port when using client-side load balancing or service discovery

.chloggen/grpc-server-port-url.yaml

@@ -0,0 +1,7 @@
+change_type: enhancement
+component: rpc
+note: >
+  Clarify how to populate `server.address` and `server.port` when using
+  client-side load balancing or service discovery.
+
+issues: [3258, 3317]

docs/rpc/dubbo.md

@@ -48,7 +48,7 @@ for the details on which values classify as errors.
 | [`rpc.response.status_code`](/docs/registry/attributes/rpc.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Required` | string | The string representation of the Dubbo response status code returned by the server or generated by the client. [2] | `OK`; `DEADLINE_EXCEEDED`; `SERVER_ERROR` |
 | [`error.type`](/docs/registry/attributes/error.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Conditionally Required` If and only if the operation failed. | string | Describes a class of error the operation ended with. [3] | `DEADLINE_EXCEEDED`; `java.net.UnknownHostException`; `-32602` |
 | [`rpc.method_original`](/docs/registry/attributes/rpc.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Conditionally Required` If and only if it's different than `rpc.method`. | string | The original name of the method used by the client. | `com.myservice.EchoService/catchAll`; `com.myservice.EchoService/unknownMethod`; `InvalidMethod` |
-| [`server.address`](/docs/registry/attributes/server.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Conditionally Required` If available. | string | RPC server [host name](https://grpc.github.io/grpc/core/md_doc_naming.html). [4] | `192.168.1.100`; `api.example.com` |
+| [`server.address`](/docs/registry/attributes/server.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Conditionally Required` If available. | string | A string identifying a group of RPC server instances request is sent to. [4] | `192.168.1.100`; `api.example.com` |
 | [`server.port`](/docs/registry/attributes/server.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Conditionally Required` [5] | int | Server port number. [6] | `20880`; `50051` |
 | [`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. [7] | `10.1.2.80`; `/tmp/my.sock` |
 | [`network.peer.port`](/docs/registry/attributes/network.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Recommended` If `network.peer.address` is set. | int | Peer port number of the network connection. | `65123` |
@@ -188,7 +188,7 @@ for the details on which values classify as errors.
 | [`error.type`](/docs/registry/attributes/error.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Conditionally Required` If and only if the operation failed. | string | Describes a class of error the operation ended with. [2] | `DEADLINE_EXCEEDED`; `java.net.UnknownHostException`; `-32602` |
 | [`rpc.method`](/docs/registry/attributes/rpc.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Conditionally Required` if available. | string | The fully-qualified logical name of the method from the RPC interface perspective. [3] | `com.example.ExampleService/exampleMethod`; `EchoService/Echo`; `_OTHER` |
 | [`rpc.method_original`](/docs/registry/attributes/rpc.md) | ![Development](https://img.shields.io/badge/-development-blue) | `Conditionally Required` If and only if it's different than `rpc.method`. | string | The original name of the method used by the client. | `com.myservice.EchoService/catchAll`; `com.myservice.EchoService/unknownMethod`; `InvalidMethod` |
-| [`server.address`](/docs/registry/attributes/server.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Conditionally Required` If available. | string | RPC server [host name](https://grpc.github.io/grpc/core/md_doc_naming.html). [4] | `example.com`; `10.1.2.80`; `/tmp/my.sock` |
+| [`server.address`](/docs/registry/attributes/server.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Conditionally Required` If available. | string | A string identifying a group of RPC server instances request is sent to. [4] | `example.com`; `10.1.2.80`; `/tmp/my.sock` |
 | [`server.port`](/docs/registry/attributes/server.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Conditionally Required` [5] | int | Server port number. [6] | `80`; `8080`; `443` |
 | [`client.address`](/docs/registry/attributes/client.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Recommended` | string | Client address - domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [7] | `client.example.com`; `10.1.2.80`; `/tmp/my.sock` |
 | [`client.port`](/docs/registry/attributes/client.md) | ![Stable](https://img.shields.io/badge/-stable-lightgreen) | `Recommended` | int | Client port number. [8] | `65123` |
@@ -256,7 +256,9 @@ The `code.function.name` attribute may be used to record the fully-qualified
 method actually executing the call on the server side, or the
 RPC client stub method on the client side.
 
-**[4] `server.address`:** May contain server IP address, DNS name, or local socket name. When host component is an IP address, instrumentations SHOULD NOT do a reverse proxy lookup to obtain DNS name and SHOULD set `server.address` to the IP address provided in the host component.
+**[4] `server.address`:** May contain a DNS name, an endpoint and path in the service registry, local socket name or an IP address.
+Semantic conventions for individual RPC systems SHOULD document how to populate this attribute.
+When address is an IP address, instrumentations SHOULD NOT do a reverse DNS lookup to obtain a DNS name and SHOULD set `server.address` to the provided IP address.
 
 **[5] `server.port`:** if `server.address` is set and if the port is supported by the network transport used for communication.