Merge pull request #8851 from gyuho/doc-doc

*: highlight gRPC metrics change in v3.1

CHANGELOG.md

@@ -326,6 +326,11 @@ See [upgrade 3.1](https://github.com/coreos/etcd/blob/master/Documentation/upgra
 
 ### Changed
 
+- Deprecated following gRPC metrics in favor of [go-grpc-prometheus](https://github.com/grpc-ecosystem/go-grpc-prometheus):
+  - `etcd_grpc_requests_total`
+  - `etcd_grpc_requests_failed_total`
+  - `etcd_grpc_active_streams`
+  - `etcd_grpc_unary_requests_duration_seconds`
 - etcd uses default route IP if advertise URL is not given
 - Cluster rejects removing members if quorum will be lost
 - SRV records (e.g., infra1.example.com) must match the discovery domain (i.e., example.com) if no custom certificate authority is given

Documentation/upgrades/upgrade_3_1.md

@@ -8,6 +8,15 @@ Before [starting an upgrade](#upgrade-procedure), read through the rest of this
 
 ### Upgrade checklists
 
+#### Monitoring
+
+Following metrics from v3.0.x have been deprecated in favor of [go-grpc-prometheus](https://github.com/grpc-ecosystem/go-grpc-prometheus):
+
+- `etcd_grpc_requests_total`
+- `etcd_grpc_requests_failed_total`
+- `etcd_grpc_active_streams`
+- `etcd_grpc_unary_requests_duration_seconds`
+
 #### Upgrade requirements
 
 To upgrade an existing etcd deployment to 3.1, the running cluster must be 3.0 or greater. If it's before 3.0, please [upgrade to 3.0](upgrade_3_0.md) before upgrading to 3.1.