redis: upstream client draining and temp host connection limit and cl… (#7104)

Signed-off-by: Mitch Sukalski <mitch.sukalski@workday.com>

Mirrored from https://github.com/envoyproxy/envoy @ 80a4ed73982936fe3a0ff08f697f18023c849ea9

envoy/config/filter/network/redis_proxy/v2/redis_proxy.proto

@@ -10,6 +10,7 @@ option go_package = "v2";
 import "envoy/api/v2/core/base.proto";
 
 import "google/protobuf/duration.proto";
+import "google/protobuf/wrappers.proto";
 
 import "validate/validate.proto";
 import "gogoproto/gogo.proto";
@@ -82,6 +83,13 @@ message RedisProxy {
     // If `max_buffer_size_before_flush` is set, but `buffer_flush_timeout` is not, the latter
     // defaults to 3ms.
     google.protobuf.Duration buffer_flush_timeout = 5 [(gogoproto.stdduration) = true];
+
+    // `max_upstream_unknown_connections` controls how many upstream connections to unknown hosts
+    // can be created at any given time by any given worker thread (see `enable_redirection` for
+    // more details). If the host is unknown and a connection cannot be created due to enforcing
+    // this limit, then redirection will fail and the original redirection error will be passed
+    // downstream unchanged. This limit defaults to 100.
+    google.protobuf.UInt32Value max_upstream_unknown_connections = 6;
   }
 
   // Network settings for the connection pool to the upstream clusters.