Load reporting service documentation (#10962)

Signed-off-by: kathan24 <kshah@lyft.com>

Mirrored from https://github.com/envoyproxy/envoy @ 570f7ac553e64206193d64952bf8d4a72b76e49c

envoy/config/endpoint/v3/load_report.proto

@@ -17,11 +17,11 @@ option java_outer_classname = "LoadReportProto";
 option java_multiple_files = true;
 option (udpa.annotations.file_status).package_version_status = ACTIVE;
 
-// These are stats Envoy reports to GLB every so often. Report frequency is
-// defined by
+// [#protodoc-title: Load Report]
+
+// These are stats Envoy reports to the management server at a frequency defined by
 // :ref:`LoadStatsResponse.load_reporting_interval<envoy_api_field_service.load_stats.v3.LoadStatsResponse.load_reporting_interval>`.
 // Stats per upstream region/zone and optionally per subzone.
-// [#not-implemented-hide:] Not configuration. TBD how to doc proto APIs.
 // [#next-free-field: 9]
 message UpstreamLocalityStats {
   option (udpa.annotations.versioning).previous_message_type =
@@ -60,7 +60,6 @@ message UpstreamLocalityStats {
   uint32 priority = 6;
 }
 
-// [#not-implemented-hide:] Not configuration. TBD how to doc proto APIs.
 // [#next-free-field: 8]
 message UpstreamEndpointStats {
   option (udpa.annotations.versioning).previous_message_type =
@@ -103,7 +102,6 @@ message UpstreamEndpointStats {
   repeated EndpointLoadMetricStats load_metric_stats = 5;
 }
 
-// [#not-implemented-hide:] Not configuration. TBD how to doc proto APIs.
 message EndpointLoadMetricStats {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.api.v2.endpoint.EndpointLoadMetricStats";
@@ -121,7 +119,6 @@ message EndpointLoadMetricStats {
 
 // Per cluster load stats. Envoy reports these stats a management server in a
 // :ref:`LoadStatsRequest<envoy_api_msg_service.load_stats.v3.LoadStatsRequest>`
-// [#not-implemented-hide:] Not configuration. TBD how to doc proto APIs.
 // Next ID: 7
 // [#next-free-field: 7]
 message ClusterStats {

envoy/service/load_stats/v3/lrs.proto

@@ -17,7 +17,15 @@ option java_multiple_files = true;
 option java_generic_services = true;
 option (udpa.annotations.file_status).package_version_status = ACTIVE;
 
-// [#protodoc-title: Load reporting service]
+// [#protodoc-title: Load Reporting service (LRS)]
+
+// Load Reporting Service is an Envoy API to emit load reports. Envoy will initiate a bi-directional
+// stream with a management server. Upon connecting, the management server can send a
+// :ref:`LoadStatsResponse <envoy_api_msg_service.load_stats.v3.LoadStatsResponse>` to a node it is
+// interested in getting the load reports for. Envoy in this node will start sending
+// :ref:`LoadStatsRequest <envoy_api_msg_service.load_stats.v3.LoadStatsRequest>`. This is done periodically
+// based on the :ref:`load reporting interval <envoy_api_field_service.load_stats.v3.LoadStatsResponse.load_reporting_interval>`
+// For details, take a look at the :ref:`Load Reporting Service sandbox example <install_sandboxes_load_reporting_service>`.
 
 service LoadReportingService {
   // Advanced API to allow for multi-dimensional load balancing by remote
@@ -53,7 +61,6 @@ service LoadReportingService {
 }
 
 // A load report Envoy sends to the management server.
-// [#not-implemented-hide:] Not configuration. TBD how to doc proto APIs.
 message LoadStatsRequest {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.service.load_stats.v2.LoadStatsRequest";
@@ -67,7 +74,6 @@ message LoadStatsRequest {
 
 // The management server sends envoy a LoadStatsResponse with all clusters it
 // is interested in learning load stats about.
-// [#not-implemented-hide:] Not configuration. TBD how to doc proto APIs.
 message LoadStatsResponse {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.service.load_stats.v2.LoadStatsResponse";
@@ -82,6 +88,7 @@ message LoadStatsResponse {
   bool send_all_clusters = 4;
 
   // The minimum interval of time to collect stats over. This is only a minimum for two reasons:
+  //
   // 1. There may be some delay from when the timer fires until stats sampling occurs.
   // 2. For clusters that were already feature in the previous *LoadStatsResponse*, any traffic
   //    that is observed in between the corresponding previous *LoadStatsRequest* and this