[server] Add new flat_hash_map structure for per-channel registered methods (#34612)

Protected by new experiment. Will be followed up by #34286.

BUILD

@@ -1487,6 +1487,7 @@ grpc_cc_library(
         "absl/container:inlined_vector",
         "absl/functional:any_invocable",
         "absl/functional:function_ref",
+        "absl/hash",
         "absl/meta:type_traits",
         "absl/status",
         "absl/status:statusor",

src/core/lib/experiments/experiments.cc

@@ -114,6 +114,9 @@ const char* const description_registered_method_lookup_in_transport =
     "Change registered method's lookup point to transport";
 const char* const additional_constraints_registered_method_lookup_in_transport =
     "{}";
+const char* const description_registered_methods_map =
+    "Use absl::flat_hash_map for registered methods.";
+const char* const additional_constraints_registered_methods_map = "{}";
 const char* const description_round_robin_delegate_to_pick_first =
     "Change round_robin code to delegate to pick_first as per dualstack "
     "backend design.";
@@ -245,6 +248,8 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"registered_method_lookup_in_transport",
      description_registered_method_lookup_in_transport,
      additional_constraints_registered_method_lookup_in_transport, true, true},
+    {"registered_methods_map", description_registered_methods_map,
+     additional_constraints_registered_methods_map, false, true},
     {"round_robin_delegate_to_pick_first",
      description_round_robin_delegate_to_pick_first,
      additional_constraints_round_robin_delegate_to_pick_first, true, true},
@@ -377,6 +382,9 @@ const char* const description_registered_method_lookup_in_transport =
     "Change registered method's lookup point to transport";
 const char* const additional_constraints_registered_method_lookup_in_transport =
     "{}";
+const char* const description_registered_methods_map =
+    "Use absl::flat_hash_map for registered methods.";
+const char* const additional_constraints_registered_methods_map = "{}";
 const char* const description_round_robin_delegate_to_pick_first =
     "Change round_robin code to delegate to pick_first as per dualstack "
     "backend design.";
@@ -508,6 +516,8 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"registered_method_lookup_in_transport",
      description_registered_method_lookup_in_transport,
      additional_constraints_registered_method_lookup_in_transport, true, true},
+    {"registered_methods_map", description_registered_methods_map,
+     additional_constraints_registered_methods_map, false, true},
     {"round_robin_delegate_to_pick_first",
      description_round_robin_delegate_to_pick_first,
      additional_constraints_round_robin_delegate_to_pick_first, true, true},
@@ -640,6 +650,9 @@ const char* const description_registered_method_lookup_in_transport =
     "Change registered method's lookup point to transport";
 const char* const additional_constraints_registered_method_lookup_in_transport =
     "{}";
+const char* const description_registered_methods_map =
+    "Use absl::flat_hash_map for registered methods.";
+const char* const additional_constraints_registered_methods_map = "{}";
 const char* const description_round_robin_delegate_to_pick_first =
     "Change round_robin code to delegate to pick_first as per dualstack "
     "backend design.";
@@ -771,6 +784,8 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"registered_method_lookup_in_transport",
      description_registered_method_lookup_in_transport,
      additional_constraints_registered_method_lookup_in_transport, true, true},
+    {"registered_methods_map", description_registered_methods_map,
+     additional_constraints_registered_methods_map, false, true},
     {"round_robin_delegate_to_pick_first",
      description_round_robin_delegate_to_pick_first,
      additional_constraints_round_robin_delegate_to_pick_first, true, true},

src/core/lib/experiments/experiments.h

@@ -102,6 +102,7 @@ inline bool IsPromiseBasedServerCallEnabled() { return false; }
 inline bool IsRedMaxConcurrentStreamsEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_REGISTERED_METHOD_LOOKUP_IN_TRANSPORT
 inline bool IsRegisteredMethodLookupInTransportEnabled() { return true; }
+inline bool IsRegisteredMethodsMapEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_ROUND_ROBIN_DELEGATE_TO_PICK_FIRST
 inline bool IsRoundRobinDelegateToPickFirstEnabled() { return true; }
 inline bool IsRstpitEnabled() { return false; }
@@ -173,6 +174,7 @@ inline bool IsPromiseBasedServerCallEnabled() { return false; }
 inline bool IsRedMaxConcurrentStreamsEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_REGISTERED_METHOD_LOOKUP_IN_TRANSPORT
 inline bool IsRegisteredMethodLookupInTransportEnabled() { return true; }
+inline bool IsRegisteredMethodsMapEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_ROUND_ROBIN_DELEGATE_TO_PICK_FIRST
 inline bool IsRoundRobinDelegateToPickFirstEnabled() { return true; }
 inline bool IsRstpitEnabled() { return false; }
@@ -244,6 +246,7 @@ inline bool IsPromiseBasedServerCallEnabled() { return false; }
 inline bool IsRedMaxConcurrentStreamsEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_REGISTERED_METHOD_LOOKUP_IN_TRANSPORT
 inline bool IsRegisteredMethodLookupInTransportEnabled() { return true; }
+inline bool IsRegisteredMethodsMapEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_ROUND_ROBIN_DELEGATE_TO_PICK_FIRST
 inline bool IsRoundRobinDelegateToPickFirstEnabled() { return true; }
 inline bool IsRstpitEnabled() { return false; }
@@ -298,6 +301,7 @@ enum ExperimentIds {
   kExperimentIdPromiseBasedServerCall,
   kExperimentIdRedMaxConcurrentStreams,
   kExperimentIdRegisteredMethodLookupInTransport,
+  kExperimentIdRegisteredMethodsMap,
   kExperimentIdRoundRobinDelegateToPickFirst,
   kExperimentIdRstpit,
   kExperimentIdScheduleCancellationOverWrite,
@@ -421,6 +425,10 @@ inline bool IsRedMaxConcurrentStreamsEnabled() {
 inline bool IsRegisteredMethodLookupInTransportEnabled() {
   return IsExperimentEnabled(kExperimentIdRegisteredMethodLookupInTransport);
 }
+#define GRPC_EXPERIMENT_IS_INCLUDED_REGISTERED_METHODS_MAP
+inline bool IsRegisteredMethodsMapEnabled() {
+  return IsExperimentEnabled(kExperimentIdRegisteredMethodsMap);
+}
 #define GRPC_EXPERIMENT_IS_INCLUDED_ROUND_ROBIN_DELEGATE_TO_PICK_FIRST
 inline bool IsRoundRobinDelegateToPickFirstEnabled() {
   return IsExperimentEnabled(kExperimentIdRoundRobinDelegateToPickFirst);

src/core/lib/experiments/experiments.yaml

@@ -199,6 +199,12 @@
   expiry: 2024/03/31
   owner: yashkt@google.com
   test_tags: ["surface_registered_method_lookup"]
+- name: registered_methods_map
+  description:
+    Use absl::flat_hash_map for registered methods.
+  expiry: 2024/01/31
+  owner: alishananda@google.com
+  test_tags: []
 - name: round_robin_delegate_to_pick_first
   description:
     Change round_robin code to delegate to pick_first as per dualstack

src/core/lib/experiments/rollouts.yaml

@@ -98,6 +98,8 @@
   default: false
 - name: registered_method_lookup_in_transport
   default: true
+- name: registered_methods_map
+  default: false
 - name: round_robin_delegate_to_pick_first
   default: true
 - name: rstpit

src/core/lib/surface/server.cc

@@ -32,6 +32,7 @@
 #include <vector>
 
 #include "absl/cleanup/cleanup.h"
+#include "absl/container/flat_hash_map.h"
 #include "absl/status/status.h"
 #include "absl/types/optional.h"
 #include "absl/types/variant.h"
@@ -40,6 +41,7 @@
 #include <grpc/grpc.h>
 #include <grpc/impl/channel_arg_names.h>
 #include <grpc/impl/connectivity_state.h>
+#include <grpc/slice.h>
 #include <grpc/status.h>
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>
@@ -825,6 +827,10 @@ Server::RegisteredMethod* Server::RegisterMethod(
     const char* method, const char* host,
     grpc_server_register_method_payload_handling payload_handling,
     uint32_t flags) {
+  if (IsRegisteredMethodsMapEnabled() && started_) {
+    Crash("Attempting to register method after server started");
+  }
+
   if (!method) {
     gpr_log(GPR_ERROR,
             "grpc_server_register_method method string cannot be NULL");
@@ -1132,7 +1138,7 @@ class Server::ChannelData::ConnectivityWatcher
 //
 
 Server::ChannelData::~ChannelData() {
-  registered_methods_.reset();
+  old_registered_methods_.reset();
   if (server_ != nullptr) {
     if (server_->channelz_node_ != nullptr && channelz_socket_uuid_ != 0) {
       server_->channelz_node_->RemoveChildSocket(channelz_socket_uuid_);
@@ -1160,27 +1166,27 @@ void Server::ChannelData::InitTransport(RefCountedPtr<Server> server,
   // Build a lookup table phrased in terms of mdstr's in this channels context
   // to quickly find registered methods.
   size_t num_registered_methods = server_->registered_methods_.size();
-  if (num_registered_methods > 0) {
+  if (!IsRegisteredMethodsMapEnabled() && num_registered_methods > 0) {
     uint32_t max_probes = 0;
     size_t slots = 2 * num_registered_methods;
-    registered_methods_ =
+    old_registered_methods_ =
         std::make_unique<std::vector<ChannelRegisteredMethod>>(slots);
     for (std::unique_ptr<RegisteredMethod>& rm : server_->registered_methods_) {
       Slice host;
       Slice method = Slice::FromExternalString(rm->method);
       const bool has_host = !rm->host.empty();
       if (has_host) {
-        host = Slice::FromExternalString(rm->host.c_str());
+        host = Slice::FromExternalString(rm->host);
       }
       uint32_t hash = MixHash32(has_host ? host.Hash() : 0, method.Hash());
       uint32_t probes = 0;
-      for (probes = 0; (*registered_methods_)[(hash + probes) % slots]
+      for (probes = 0; (*old_registered_methods_)[(hash + probes) % slots]
                            .server_registered_method != nullptr;
            probes++) {
       }
       if (probes > max_probes) max_probes = probes;
       ChannelRegisteredMethod* crm =
-          &(*registered_methods_)[(hash + probes) % slots];
+          &(*old_registered_methods_)[(hash + probes) % slots];
       crm->server_registered_method = rm.get();
       crm->flags = rm->flags;
       crm->has_host = has_host;
@@ -1191,6 +1197,15 @@ void Server::ChannelData::InitTransport(RefCountedPtr<Server> server,
     }
     GPR_ASSERT(slots <= UINT32_MAX);
     registered_method_max_probes_ = max_probes;
+  } else if (IsRegisteredMethodsMapEnabled()) {
+    for (std::unique_ptr<RegisteredMethod>& rm : server_->registered_methods_) {
+      auto key = std::make_pair(!rm->host.empty() ? rm->host : "", rm->method);
+      registered_methods_.emplace(
+          key, std::make_unique<ChannelRegisteredMethod>(
+                   rm.get(), rm->flags, /*has_host=*/!rm->host.empty(),
+                   Slice::FromExternalString(rm->method),
+                   Slice::FromExternalString(rm->host)));
+    }
   }
   // Publish channel.
   {
@@ -1216,13 +1231,13 @@ void Server::ChannelData::InitTransport(RefCountedPtr<Server> server,
 
 Server::ChannelRegisteredMethod* Server::ChannelData::GetRegisteredMethod(
     const grpc_slice& host, const grpc_slice& path) {
-  if (registered_methods_ == nullptr) return nullptr;
+  if (old_registered_methods_ == nullptr) return nullptr;
   // TODO(ctiller): unify these two searches
   // check for an exact match with host
   uint32_t hash = MixHash32(grpc_slice_hash(host), grpc_slice_hash(path));
   for (size_t i = 0; i <= registered_method_max_probes_; i++) {
-    ChannelRegisteredMethod* rm =
-        &(*registered_methods_)[(hash + i) % registered_methods_->size()];
+    ChannelRegisteredMethod* rm = &(
+        *old_registered_methods_)[(hash + i) % old_registered_methods_->size()];
     if (rm->server_registered_method == nullptr) break;
     if (!rm->has_host) continue;
     if (rm->host != host) continue;
@@ -1232,8 +1247,8 @@ Server::ChannelRegisteredMethod* Server::ChannelData::GetRegisteredMethod(
   // check for a wildcard method definition (no host set)
   hash = MixHash32(0, grpc_slice_hash(path));
   for (size_t i = 0; i <= registered_method_max_probes_; i++) {
-    ChannelRegisteredMethod* rm =
-        &(*registered_methods_)[(hash + i) % registered_methods_->size()];
+    ChannelRegisteredMethod* rm = &(
+        *old_registered_methods_)[(hash + i) % old_registered_methods_->size()];
     if (rm->server_registered_method == nullptr) break;
     if (rm->has_host) continue;
     if (rm->method != path) continue;
@@ -1242,6 +1257,22 @@ Server::ChannelRegisteredMethod* Server::ChannelData::GetRegisteredMethod(
   return nullptr;
 }
 
+Server::ChannelRegisteredMethod* Server::ChannelData::GetRegisteredMethod(
+    const absl::string_view& host, const absl::string_view& path) {
+  if (registered_methods_.empty()) return nullptr;
+  // check for an exact match with host
+  auto it = registered_methods_.find(std::make_pair(host, path));
+  if (it != registered_methods_.end()) {
+    return it->second.get();
+  }
+  // check for wildcard method definition (no host set)
+  it = registered_methods_.find(std::make_pair("", path));
+  if (it != registered_methods_.end()) {
+    return it->second.get();
+  }
+  return nullptr;
+}
+
 void Server::ChannelData::SetRegisteredMethodOnMetadata(
     void* arg, ServerMetadata* metadata) {
   auto* chand = static_cast<Server::ChannelData*>(arg);
@@ -1258,8 +1289,13 @@ void Server::ChannelData::SetRegisteredMethodOnMetadata(
     // Path not being set would result in an RPC error.
     return;
   }
-  ChannelRegisteredMethod* method =
-      chand->GetRegisteredMethod(authority->c_slice(), path->c_slice());
+  ChannelRegisteredMethod* method;
+  if (!IsRegisteredMethodsMapEnabled()) {
+    method = chand->GetRegisteredMethod(authority->c_slice(), path->c_slice());
+  } else {
+    method = chand->GetRegisteredMethod(authority->as_string_view(),
+                                        path->as_string_view());
+  }
   // insert in metadata
   metadata->Set(GrpcRegisteredMethod(), method);
 }
@@ -1336,7 +1372,12 @@ ArenaPromise<ServerMetadataHandle> Server::ChannelData::MakeCallPromise(
         call_args.client_initial_metadata->get(GrpcRegisteredMethod())
             .value_or(nullptr));
   } else {
-    rm = chand->GetRegisteredMethod(host_ptr->c_slice(), path->c_slice());
+    if (!IsRegisteredMethodsMapEnabled()) {
+      rm = chand->GetRegisteredMethod(host_ptr->c_slice(), path->c_slice());
+    } else {
+      rm = chand->GetRegisteredMethod(host_ptr->as_string_view(),
+                                      path->as_string_view());
+    }
   }
   ArenaPromise<absl::StatusOr<NextResult<MessageHandle>>>
       maybe_read_first_message([] { return NextResult<MessageHandle>(); });
@@ -1602,7 +1643,12 @@ void Server::CallData::StartNewRpc(grpc_call_element* elem) {
           recv_initial_metadata_->get(GrpcRegisteredMethod())
               .value_or(nullptr));
     } else {
-      rm = chand->GetRegisteredMethod(host_->c_slice(), path_->c_slice());
+      if (!IsRegisteredMethodsMapEnabled()) {
+        rm = chand->GetRegisteredMethod(host_->c_slice(), path_->c_slice());
+      } else {
+        rm = chand->GetRegisteredMethod(host_->as_string_view(),
+                                        path_->as_string_view());
+      }
     }
     if (rm != nullptr) {
       matcher_ = rm->server_registered_method->matcher.get();

src/core/lib/surface/server.h

@@ -31,7 +31,11 @@
 #include <vector>
 
 #include "absl/base/thread_annotations.h"
+#include "absl/container/flat_hash_map.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/hash/hash.h"
 #include "absl/status/statusor.h"
+#include "absl/strings/string_view.h"
 #include "absl/types/optional.h"
 
 #include <grpc/grpc.h>
@@ -202,6 +206,18 @@ class Server : public InternallyRefCounted<Server>,
   struct RequestedCall;
 
   struct ChannelRegisteredMethod {
+    ChannelRegisteredMethod() = default;
+    ChannelRegisteredMethod(RegisteredMethod* server_registered_method_arg,
+                            uint32_t flags_arg, bool has_host_arg,
+                            Slice method_arg, Slice host_arg)
+        : server_registered_method(server_registered_method_arg),
+          flags(flags_arg),
+          has_host(has_host_arg),
+          method(std::move(method_arg)),
+          host(std::move(host_arg)) {}
+
+    ~ChannelRegisteredMethod() = default;
+
     RegisteredMethod* server_registered_method = nullptr;
     uint32_t flags;
     bool has_host;
@@ -231,6 +247,9 @@ class Server : public InternallyRefCounted<Server>,
 
     ChannelRegisteredMethod* GetRegisteredMethod(const grpc_slice& host,
                                                  const grpc_slice& path);
+
+    ChannelRegisteredMethod* GetRegisteredMethod(const absl::string_view& host,
+                                                 const absl::string_view& path);
     // Filter vtable functions.
     static grpc_error_handle InitChannelElement(
         grpc_channel_element* elem, grpc_channel_element_args* args);
@@ -250,6 +269,17 @@ class Server : public InternallyRefCounted<Server>,
 
     static void FinishDestroy(void* arg, grpc_error_handle error);
 
+    struct StringViewStringViewPairHash
+        : absl::flat_hash_set<
+              std::pair<absl::string_view, absl::string_view>>::hasher {
+      using is_transparent = void;
+    };
+
+    struct StringViewStringViewPairEq
+        : std::equal_to<std::pair<absl::string_view, absl::string_view>> {
+      using is_transparent = void;
+    };
+
     RefCountedPtr<Server> server_;
     RefCountedPtr<Channel> channel_;
     // The index into Server::cqs_ of the CQ used as a starting point for
@@ -260,7 +290,14 @@ class Server : public InternallyRefCounted<Server>,
     // TODO(vjpai): Convert this to an STL map type as opposed to a direct
     // bucket implementation. (Consider performance impact, hash function to
     // use, etc.)
-    std::unique_ptr<std::vector<ChannelRegisteredMethod>> registered_methods_;
+    std::unique_ptr<std::vector<ChannelRegisteredMethod>>
+        old_registered_methods_;
+    // Map of registered methods.
+    absl::flat_hash_map<std::pair<std::string, std::string> /*host, method*/,
+                        std::unique_ptr<ChannelRegisteredMethod>,
+                        StringViewStringViewPairHash,
+                        StringViewStringViewPairEq>
+        registered_methods_;
     uint32_t registered_method_max_probes_;
     grpc_closure finish_destroy_channel_closure_;
     intptr_t channelz_socket_uuid_;