Lazily fill metadata map

4 files changed, 36 insertions, 13 deletions

diff --git a/include/grpcpp/impl/codegen/call.h b/include/grpcpp/impl/codegen/call.h
index a5e930aaa5..e94adada94 100644
--- a/include/grpcpp/impl/codegen/call.h
+++ b/include/grpcpp/impl/codegen/call.h
@@ -50,8 +50,6 @@ namespace internal {
 class Call;
 class CallHook;
 
-const char kBinaryErrorDetailsKey[] = "grpc-status-details-bin";
-
 // TODO(yangg) if the map is changed before we send, the pointers will be a
 // mess. Make sure it does not happen.
 inline grpc_metadata* FillMetadataArray(
@@ -531,7 +529,6 @@ class CallOpRecvInitialMetadata {
 
   void FinishOp(bool* status) {
     if (metadata_map_ == nullptr) return;
-    metadata_map_->FillMap();
     metadata_map_ = nullptr;
   }
 
@@ -566,13 +563,7 @@ class CallOpClientRecvStatus {
 
   void FinishOp(bool* status) {
     if (recv_status_ == nullptr) return;
-    metadata_map_->FillMap();
-    grpc::string binary_error_details;
-    auto iter = metadata_map_->map()->find(kBinaryErrorDetailsKey);
-    if (iter != metadata_map_->map()->end()) {
-      binary_error_details =
-          grpc::string(iter->second.begin(), iter->second.length());
-    }
+    grpc::string binary_error_details = metadata_map_->GetBinaryErrorDetails();
     *recv_status_ =
         Status(static_cast<StatusCode>(status_code_),
                GRPC_SLICE_IS_EMPTY(error_message_)
diff --git a/include/grpcpp/impl/codegen/client_context.h b/include/grpcpp/impl/codegen/client_context.h
index 9dda4c7fac..cf1d901888 100644
--- a/include/grpcpp/impl/codegen/client_context.h
+++ b/include/grpcpp/impl/codegen/client_context.h
@@ -202,6 +202,7 @@ class ClientContext {
   const std::multimap<grpc::string_ref, grpc::string_ref>&
   GetServerInitialMetadata() const {
     GPR_CODEGEN_ASSERT(initial_metadata_received_);
+    recv_initial_metadata_.FillMap();
     return *recv_initial_metadata_.map();
   }
 
@@ -214,6 +215,7 @@ class ClientContext {
   const std::multimap<grpc::string_ref, grpc::string_ref>&
   GetServerTrailingMetadata() const {
     // TODO(yangg) check finished
+    trailing_metadata_.FillMap();
     return *trailing_metadata_.map();
   }
 
@@ -425,8 +427,8 @@ class ClientContext {
   mutable std::shared_ptr<const AuthContext> auth_context_;
   struct census_context* census_context_;
   std::multimap<grpc::string, grpc::string> send_initial_metadata_;
-  internal::MetadataMap recv_initial_metadata_;
-  internal::MetadataMap trailing_metadata_;
+  mutable internal::MetadataMap recv_initial_metadata_;
+  mutable internal::MetadataMap trailing_metadata_;
 
   grpc_call* propagate_from_call_;
   PropagationOptions propagation_options_;
diff --git a/include/grpcpp/impl/codegen/metadata_map.h b/include/grpcpp/impl/codegen/metadata_map.h
index 0866539d88..6e0c2a9637 100644
--- a/include/grpcpp/impl/codegen/metadata_map.h
+++ b/include/grpcpp/impl/codegen/metadata_map.h
@@ -19,11 +19,15 @@
 #ifndef GRPCPP_IMPL_CODEGEN_METADATA_MAP_H
 #define GRPCPP_IMPL_CODEGEN_METADATA_MAP_H
 
+#include <grpc/slice.h>
 #include <grpcpp/impl/codegen/slice.h>
 
 namespace grpc {
 
 namespace internal {
+
+const char kBinaryErrorDetailsKey[] = "grpc-status-details-bin";
+
 class MetadataMap {
  public:
   MetadataMap() { memset(&arr_, 0, sizeof(arr_)); }
@@ -32,7 +36,31 @@ class MetadataMap {
     g_core_codegen_interface->grpc_metadata_array_destroy(&arr_);
   }
 
+  grpc::string GetBinaryErrorDetails() {
+    // if filled, extract from the multimap for O(log(n))
+    if (filled) {
+      auto iter = map_.find(kBinaryErrorDetailsKey);
+      if (iter != map_.end()) {
+        return grpc::string(iter->second.begin(), iter->second.length());
+      }
+    }
+    // if not yet filled, take the O(n) lookup to avoid allocating the
+    // multimap until it is requested.
+    else {
+      for (size_t i = 0; i < arr_.count; i++) {
+        if (grpc_slice_str_cmp(arr_.metadata[i].key, kBinaryErrorDetailsKey)) {
+          return grpc::string(reinterpret_cast<const char*>(
+                                  GRPC_SLICE_START_PTR(arr_.metadata[i].value)),
+                              GRPC_SLICE_LENGTH(arr_.metadata[i].value));
+        }
+      }
+    }
+    return grpc::string();
+  }
+
   void FillMap() {
+    if (filled) return;
+    filled = true;
     for (size_t i = 0; i < arr_.count; i++) {
       // TODO(yangg) handle duplicates?
       map_.insert(std::pair<grpc::string_ref, grpc::string_ref>(
@@ -48,6 +76,7 @@ class MetadataMap {
   grpc_metadata_array* arr() { return &arr_; }
 
  private:
+  bool filled = false;
   grpc_metadata_array arr_;
   std::multimap<grpc::string_ref, grpc::string_ref> map_;
 };
diff --git a/include/grpcpp/impl/codegen/server_context.h b/include/grpcpp/impl/codegen/server_context.h
index 6314364db6..506c51a5d9 100644
--- a/include/grpcpp/impl/codegen/server_context.h
+++ b/include/grpcpp/impl/codegen/server_context.h
@@ -169,6 +169,7 @@ class ServerContext {
   /// \return A multimap of initial metadata key-value pairs from the server.
   const std::multimap<grpc::string_ref, grpc::string_ref>& client_metadata()
       const {
+    client_metadata_.FillMap();
     return *client_metadata_.map();
   }
 
@@ -294,7 +295,7 @@ class ServerContext {
   CompletionQueue* cq_;
   bool sent_initial_metadata_;
   mutable std::shared_ptr<const AuthContext> auth_context_;
-  internal::MetadataMap client_metadata_;
+  mutable internal::MetadataMap client_metadata_;
   std::multimap<grpc::string, grpc::string> initial_metadata_;
   std::multimap<grpc::string, grpc::string> trailing_metadata_;