admission control: add rps_threshold & max_rejection_probability (#16742)

Signed-off-by: gaoweiwen <whereisgww@outlook.com>

Mirrored from https://github.com/envoyproxy/envoy @ ce1882cad8fa8ddf0cf88f7b36037edb657e5067

envoy/extensions/filters/http/admission_control/v3alpha/admission_control.proto

@@ -19,7 +19,7 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 // [#protodoc-title: Admission Control]
 // [#extension: envoy.filters.http.admission_control]
 
-// [#next-free-field: 6]
+// [#next-free-field: 8]
 message AdmissionControl {
   // Default method of specifying what constitutes a successful request. All status codes that
   // indicate a successful request must be explicitly specified if not relying on the default
@@ -91,4 +91,13 @@ message AdmissionControl {
   // below this threshold, rejection probability will increase. Any success rate above the threshold
   // results in a rejection probability of 0. Defaults to 95%.
   config.core.v3.RuntimePercent sr_threshold = 5;
+
+  // If the average RPS of the sampling window is below this threshold, the request
+  // will not be rejected, even if the success rate is lower than sr_threshold.
+  // Defaults to 0.
+  config.core.v3.RuntimeUInt32 rps_threshold = 6;
+
+  // The probability of rejection will never exceed this value, even if the failure rate is rising.
+  // Defaults to 80%.
+  config.core.v3.RuntimePercent max_rejection_probability = 7;
 }