redis filter: Add rate limit for redis client reconnection (#26502)

Adding a rate limiting for redis client reconnection rate to avoid reconnection storm on redis server

Risk Level: Low
Testing: Unit test, Manual test with redis

Fixes #26400

Signed-off-by: lgao <lgao@roblox.com>

Mirrored from https://github.com/envoyproxy/envoy @ dbec6f88d6d814829f1988d92e888cdc98c34fb1

envoy/extensions/filters/network/redis_proxy/v3/redis_proxy.proto

@@ -31,7 +31,7 @@ message RedisProxy {
       "envoy.config.filter.network.redis_proxy.v2.RedisProxy";
 
   // Redis connection pool settings.
-  // [#next-free-field: 10]
+  // [#next-free-field: 11]
   message ConnPoolSettings {
     option (udpa.annotations.versioning).previous_message_type =
         "envoy.config.filter.network.redis_proxy.v2.RedisProxy.ConnPoolSettings";
@@ -127,6 +127,11 @@ message RedisProxy {
 
     // Read policy. The default is to read from the primary.
     ReadPolicy read_policy = 7 [(validate.rules).enum = {defined_only: true}];
+
+    // Ops or connection timeout triggers reconnection to redis server which could result in reconnection
+    // storm to busy redis server. This config is a protection to rate limit reconnection rate.
+    // If not set, there will be no rate limiting on the reconnection.
+    ConnectionRateLimit connection_rate_limit = 10;
   }
 
   message PrefixRoutes {
@@ -221,6 +226,13 @@ message RedisProxy {
     repeated string commands = 4;
   }
 
+  // Configuration to limit reconnection rate to redis server to protect redis server
+  // from client reconnection storm.
+  message ConnectionRateLimit {
+    // Reconnection rate per sec. Rate limiting is implemented with TokenBucket.
+    uint32 connection_rate_limit_per_sec = 1;
+  }
+
   reserved 2;
 
   reserved "cluster";