router: add ability to shadow a request to multiple clusters (#9164)

Signed-off-by: Derek Argueta <dereka@pinterest.com>

Mirrored from https://github.com/envoyproxy/envoy @ 9b68a2b7dc03eeb809af65d3596521eccdab0cdf

envoy/api/v2/route/route.proto

@@ -517,7 +517,7 @@ message CorsPolicy {
   core.RuntimeFractionalPercent shadow_enabled = 10;
 }
 
-// [#next-free-field: 30]
+// [#next-free-field: 31]
 message RouteAction {
   enum ClusterNotFoundResponseCode {
     // HTTP status code - 503 Service Unavailable.
@@ -810,7 +810,14 @@ message RouteAction {
   RetryPolicy retry_policy = 9;
 
   // Indicates that the route has a request mirroring policy.
-  RequestMirrorPolicy request_mirror_policy = 10;
+  //
+  // .. attention::
+  //   This field has been deprecated in favor of `request_mirror_policies` which supports one or
+  //   more mirroring policies.
+  RequestMirrorPolicy request_mirror_policy = 10 [deprecated = true];
+
+  // Indicates that the route has request mirroring policies.
+  repeated RequestMirrorPolicy request_mirror_policies = 30;
 
   // Optionally specifies the :ref:`routing priority <arch_overview_http_routing_priority>`.
   core.RoutingPriority priority = 11 [(validate.rules).enum = {defined_only: true}];

envoy/api/v3alpha/route/route.proto

@@ -487,7 +487,7 @@ message CorsPolicy {
   core.RuntimeFractionalPercent shadow_enabled = 10;
 }
 
-// [#next-free-field: 30]
+// [#next-free-field: 31]
 message RouteAction {
   option (udpa.annotations.versioning).previous_message_type = "envoy.api.v2.route.RouteAction";
 
@@ -661,7 +661,9 @@ message RouteAction {
     google.protobuf.BoolValue enabled = 2;
   }
 
-  reserved 12, 18, 19, 16, 22, 21;
+  reserved 12, 18, 19, 16, 22, 21, 10;
+
+  reserved "request_mirror_policy";
 
   oneof cluster_specifier {
     option (validate.required) = true;
@@ -792,8 +794,8 @@ message RouteAction {
   // (e.g.: policies are not merged, most internal one becomes the enforced policy).
   RetryPolicy retry_policy = 9;
 
-  // Indicates that the route has a request mirroring policy.
-  RequestMirrorPolicy request_mirror_policy = 10;
+  // Indicates that the route has request mirroring policies.
+  repeated RequestMirrorPolicy request_mirror_policies = 30;
 
   // Optionally specifies the :ref:`routing priority <arch_overview_http_routing_priority>`.
   core.RoutingPriority priority = 11 [(validate.rules).enum = {defined_only: true}];