Merge branch 'jv-deprecate-grpc-proxy' into 'master'

Add deprecation yaml for gRPC proxy compatibility

See merge request gitlab-org/gitlab!80283

data/deprecations/14-8-grpc-proxy.yml

+- name: "Support for gRPC-aware proxy deployed between Gitaly and rest of GitLab"
+  announcement_milestone: "14.8"  # The milestone when this feature was first announced as deprecated.
+  announcement_date: "2022-02-22"  # The date of the milestone release when this feature was first announced as deprecated. This should almost always be the 22nd of a month (YYYY-MM-22), unless you did an out of band blog post.
+  removal_milestone: "15.0"  # The milestone when this feature is planned to be removed
+  removal_date: 2022-05-22 # The date of the milestone release when this feature is planned to be removed. This should almost always be the 22nd of a month (YYYY-MM-22), unless you did an out of band blog post.
+  breaking_change: true  # If this deprecation is a breaking change, set this value to true
+  reporter: jacobvosmaer-gitlab  # GitLab username of the person reporting the deprecation
+  body: |  # Do not modify this line, instead modify the lines below.
+    Although not recommended or documented, it was possible to deploy a gRPC-aware proxy between Gitaly and
+    the rest of GitLab. For example, NGINX and Envoy. The ability to deploy a gRPC-aware proxy is
+    [deprecated](https://gitlab.com/gitlab-org/gitlab/-/issues/352517). If you currently use a gRPC-aware proxy for
+    Gitaly connections, you should change your proxy configuration to use TCP or TLS proxying (OSI layer 4) instead.
+
+    Gitaly Cluster became incompatible with gRPC-aware proxies in GitLab 13.12. Now all GitLab installations will be incompatible with
+    gRPC-aware proxies, even without Gitaly Cluster.
+
+    By sending some of our internal RPC traffic through a custom protocol (instead of gRPC) we
+    increase throughput and reduce Go garbage collection latency. For more information, see
+    the [relevant epic](https://gitlab.com/groups/gitlab-com/gl-infra/-/epics/463).
+# The following items are not published on the docs page, but may be used in the future.
+  stage:  # (optional - may be required in the future) String value of the stage that the feature was created in. e.g., Growth
+  tiers:  # (optional - may be required in the future) An array of tiers that the feature is available in currently.  e.g., [Free, Silver, Gold, Core, Premium, Ultimate]
+  issue_url:  # (optional) This is a link to the deprecation issue in GitLab
+  documentation_url:  # (optional) This is a link to the current documentation page
+  image_url:  # (optional) This is a link to a thumbnail image depicting the feature
+  video_url:  # (optional) Use the youtube thumbnail URL with the structure of https://img.youtube.com/vi/UNIQUEID/hqdefault.jpg

doc/update/deprecations.md

@@ -992,6 +992,28 @@ For more information, check the [summary section of the deprecation issue](https
 
 **Planned removal milestone: 15.0 (2022-05-22)**
 
+### Support for gRPC-aware proxy deployed between Gitaly and rest of GitLab
+
+WARNING:
+This feature will be changed or removed in 15.0
+as a [breaking change](https://docs.gitlab.com/ee/development/contributing/#breaking-changes).
+Before updating GitLab, review the details carefully to determine if you need to make any
+changes to your code, settings, or workflow.
+
+Although not recommended or documented, it was possible to deploy a gRPC-aware proxy between Gitaly and
+the rest of GitLab. For example, NGINX and Envoy. The ability to deploy a gRPC-aware proxy is
+[deprecated](https://gitlab.com/gitlab-org/gitlab/-/issues/352517). If you currently use a gRPC-aware proxy for
+Gitaly connections, you should change your proxy configuration to use TCP or TLS proxying (OSI layer 4) instead.
+
+Gitaly Cluster became incompatible with gRPC-aware proxies in GitLab 13.12. Now all GitLab installations will be incompatible with
+gRPC-aware proxies, even without Gitaly Cluster.
+
+By sending some of our internal RPC traffic through a custom protocol (instead of gRPC) we
+increase throughput and reduce Go garbage collection latency. For more information, see
+the [relevant epic](https://gitlab.com/groups/gitlab-com/gl-infra/-/epics/463).
+
+**Planned removal milestone: 15.0 (2022-05-22)**
+
 ### Test coverage project CI/CD setting
 
 WARNING: