[chttp2] Re-enable overload protection experiment (#34770)

Seems like a small pause is needed for max_concurrent_streams to allow
things to settle out properly with this experiment.

bazel/experiments.bzl

@@ -39,7 +39,6 @@ EXPERIMENTS = {
             ],
             "flow_control_test": [
                 "multiping",
-                "overload_protection",
                 "peer_state_based_framing",
                 "red_max_concurrent_streams",
                 "rstpit",
@@ -89,6 +88,7 @@ EXPERIMENTS = {
                 "chttp2_batch_requests",
                 "chttp2_offload_on_rst_stream",
                 "lazier_stream_updates",
+                "overload_protection",
                 "write_size_cap",
                 "write_size_policy",
             ],
@@ -129,7 +129,6 @@ EXPERIMENTS = {
             ],
             "flow_control_test": [
                 "multiping",
-                "overload_protection",
                 "peer_state_based_framing",
                 "red_max_concurrent_streams",
                 "rstpit",
@@ -173,6 +172,7 @@ EXPERIMENTS = {
                 "chttp2_batch_requests",
                 "chttp2_offload_on_rst_stream",
                 "lazier_stream_updates",
+                "overload_protection",
                 "write_size_cap",
                 "write_size_policy",
             ],
@@ -224,7 +224,6 @@ EXPERIMENTS = {
             ],
             "flow_control_test": [
                 "multiping",
-                "overload_protection",
                 "peer_state_based_framing",
                 "red_max_concurrent_streams",
                 "rstpit",
@@ -271,6 +270,7 @@ EXPERIMENTS = {
                 "chttp2_batch_requests",
                 "chttp2_offload_on_rst_stream",
                 "lazier_stream_updates",
+                "overload_protection",
                 "write_size_cap",
                 "write_size_policy",
             ],

src/core/lib/experiments/experiments.cc

@@ -240,7 +240,7 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"multiping", description_multiping, additional_constraints_multiping,
      false, true},
     {"overload_protection", description_overload_protection,
-     additional_constraints_overload_protection, false, true},
+     additional_constraints_overload_protection, true, true},
     {"peer_state_based_framing", description_peer_state_based_framing,
      additional_constraints_peer_state_based_framing, false, true},
     {"pick_first_happy_eyeballs", description_pick_first_happy_eyeballs,
@@ -521,7 +521,7 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"multiping", description_multiping, additional_constraints_multiping,
      false, true},
     {"overload_protection", description_overload_protection,
-     additional_constraints_overload_protection, false, true},
+     additional_constraints_overload_protection, true, true},
     {"peer_state_based_framing", description_peer_state_based_framing,
      additional_constraints_peer_state_based_framing, false, true},
     {"pick_first_happy_eyeballs", description_pick_first_happy_eyeballs,
@@ -802,7 +802,7 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"multiping", description_multiping, additional_constraints_multiping,
      false, true},
     {"overload_protection", description_overload_protection,
-     additional_constraints_overload_protection, false, true},
+     additional_constraints_overload_protection, true, true},
     {"peer_state_based_framing", description_peer_state_based_framing,
      additional_constraints_peer_state_based_framing, false, true},
     {"pick_first_happy_eyeballs", description_pick_first_happy_eyeballs,

src/core/lib/experiments/experiments.h

@@ -91,7 +91,8 @@ inline bool IsMemoryPressureControllerEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_MONITORING_EXPERIMENT
 inline bool IsMonitoringExperimentEnabled() { return true; }
 inline bool IsMultipingEnabled() { return false; }
-inline bool IsOverloadProtectionEnabled() { return false; }
+#define GRPC_EXPERIMENT_IS_INCLUDED_OVERLOAD_PROTECTION
+inline bool IsOverloadProtectionEnabled() { return true; }
 inline bool IsPeerStateBasedFramingEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_PICK_FIRST_HAPPY_EYEBALLS
 inline bool IsPickFirstHappyEyeballsEnabled() { return true; }
@@ -166,7 +167,8 @@ inline bool IsMemoryPressureControllerEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_MONITORING_EXPERIMENT
 inline bool IsMonitoringExperimentEnabled() { return true; }
 inline bool IsMultipingEnabled() { return false; }
-inline bool IsOverloadProtectionEnabled() { return false; }
+#define GRPC_EXPERIMENT_IS_INCLUDED_OVERLOAD_PROTECTION
+inline bool IsOverloadProtectionEnabled() { return true; }
 inline bool IsPeerStateBasedFramingEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_PICK_FIRST_HAPPY_EYEBALLS
 inline bool IsPickFirstHappyEyeballsEnabled() { return true; }
@@ -240,7 +242,8 @@ inline bool IsMemoryPressureControllerEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_MONITORING_EXPERIMENT
 inline bool IsMonitoringExperimentEnabled() { return true; }
 inline bool IsMultipingEnabled() { return false; }
-inline bool IsOverloadProtectionEnabled() { return false; }
+#define GRPC_EXPERIMENT_IS_INCLUDED_OVERLOAD_PROTECTION
+inline bool IsOverloadProtectionEnabled() { return true; }
 inline bool IsPeerStateBasedFramingEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_PICK_FIRST_HAPPY_EYEBALLS
 inline bool IsPickFirstHappyEyeballsEnabled() { return true; }

src/core/lib/experiments/rollouts.yaml

@@ -89,7 +89,7 @@
 - name: monitoring_experiment
   default: true
 - name: overload_protection
-  default: false
+  default: true
 - name: peer_state_based_framing
   default: false
 - name: pick_first_happy_eyeballs

test/core/end2end/tests/max_concurrent_streams.cc

@@ -133,6 +133,11 @@ CORE_END2END_TEST(Http2SingleHopTest, MaxConcurrentStreams) {
   live_call = (live_call == 300) ? 400 : 300;
   Expect(live_call + 1, true);
   Step();
+  // Spin for a little: we expect to see no events now - and this time allows
+  // any overload protection machinery in the transport to settle (chttp2 tries
+  // to ensure calls are finished deleting before allowing more requests
+  // through).
+  Step();
   auto s2 = RequestCall(201);
   Expect(201, true);
   Step();