http: use intrusive lists in ConnectionsList

Every HTTP message was performing multiple erase and insert operations
on two std::set instances ordered by a mutating key, showing up as ~2%
of CPU cycles in a hello-world server profile due to red-black tree
rebalancing and node allocations.
Replace both sets with intrusive doubly-linked lists. Membership in the
list of all connections no longer changes per message, and updating the
active connections list is now O(1) with no allocations. Appending to
the tail keeps the active list ordered by last_message_start_ because
uv_hrtime() is monotonic.
Signed-off-by: Matteo Collina <hello@matteocollina.com>
PR-URL: #65296
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: mcollina

src/node_http_parser.cc

@@ -246,55 +246,63 @@ struct StringPtr {
 size_t size_ = 0;
 };
 
-structParserComparator {
-booloperator()(const Parser* lhs, const Parser* rhs) const;
+// Intrusive doubly-linked list node, linked to itself when not in a list.
+structParserListNode {
+ ParserListNode* prev = this;
+ ParserListNode* next = this;
+
+ParserListNode() = default;
+~ParserListNode() { Remove(); }
+
+ParserListNode(const ParserListNode&) = delete;
+ ParserListNode& operator=(const ParserListNode&) = delete;
+
+voidRemove() {
+ prev->next = next;
+ next->prev = prev;
+ prev = this;
+ next = this;
+ }
 };
 
 classConnectionsList : publicBaseObject {
 public:
-staticvoidNew(const FunctionCallbackInfo<Value>& args);
+staticvoidNew(const FunctionCallbackInfo<Value>& args);
 
-staticvoidAll(const FunctionCallbackInfo<Value>& args);
+staticvoidAll(const FunctionCallbackInfo<Value>& args);
 
-staticvoidIdle(const FunctionCallbackInfo<Value>& args);
+staticvoidIdle(const FunctionCallbackInfo<Value>& args);
 
-staticvoidActive(const FunctionCallbackInfo<Value>& args);
+staticvoidActive(const FunctionCallbackInfo<Value>& args);
 
-staticvoidExpired(const FunctionCallbackInfo<Value>& args);
+staticvoidExpired(const FunctionCallbackInfo<Value>& args);
 
-voidPush(Parser* parser) {
- all_connections_.insert(parser);
- }
+inlinevoidPush(Parser* parser);
 
-voidPop(Parser* parser) {
- all_connections_.erase(parser);
- }
+inlinevoidPop(Parser* parser);
 
-voidPushActive(Parser* parser) {
- active_connections_.insert(parser);
- }
+inlinevoidPushActive(Parser* parser);
 
-voidPopActive(Parser* parser) {
- active_connections_.erase(parser);
- }
+inlinevoidPopActive(Parser* parser);
 
-SET_NO_MEMORY_INFO()
-SET_MEMORY_INFO_NAME(ConnectionsList)
-SET_SELF_SIZE(ConnectionsList)
+SET_NO_MEMORY_INFO()
+SET_MEMORY_INFO_NAME(ConnectionsList)
+SET_SELF_SIZE(ConnectionsList)
 
 private:
-ConnectionsList(Environment* env, Local<Object> object)
+ConnectionsList(Environment* env, Local<Object> object)
  : BaseObject(env, object) {
-MakeWeak();
-}
+MakeWeak();
+ }
 
- std::set<Parser*, ParserComparator> all_connections_;
- std::set<Parser*, ParserComparator> active_connections_;
+// active_connections_ is ordered by last_message_start_, as parsers are
+// appended right after it is assigned from the monotonic uv_hrtime().
+ ParserListNode all_connections_;
+ ParserListNode active_connections_;
 };
 
 classParser : publicAsyncWrap, publicStreamListener {
 friendclassConnectionsList;
-friendstructParserComparator;
 
 public:
 Parser(BindingData* binding_data, Local<Object> wrap)
@@ -308,13 +316,6 @@ class Parser : public AsyncWrap, public StreamListener {
  SET_SELF_SIZE(Parser)
 
  int on_message_begin() {
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
-if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
- connectionsList_->PopActive(this);
- }
-
  num_fields_ = num_values_ = 0;
  headers_completed_ = false;
  chunk_extensions_nread_ = 0;
@@ -326,7 +327,6 @@ class Parser : public AsyncWrap, public StreamListener {
  max_header_pairs_ = -1;
 
 if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
  connectionsList_->PushActive(this);
  }
 
@@ -345,7 +345,6 @@ class Parser : public AsyncWrap, public StreamListener {
 return0;
  }
 
-
 inton_url(constchar* at, size_t length) {
 int rv = TrackHeader(length);
 if (rv != 0) {
@@ -544,19 +543,12 @@ class Parser : public AsyncWrap, public StreamListener {
 inton_message_complete() {
  HandleScope scope(env()->isolate());
 
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
 if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
  connectionsList_->PopActive(this);
  }
 
  last_message_start_ = 0;
 
-if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
- }
-
 if (num_fields_)
 Flush(); // Flush trailing HTTP headers.
 
@@ -742,8 +734,6 @@ class Parser : public AsyncWrap, public StreamListener {
 // server.timeout is left to the default value of zero.
  parser->last_message_start_ = uv_hrtime();
 
-// Important: Push into the lists AFTER setting the last_message_start_
-// otherwise std::set.erase will fail later.
  parser->connectionsList_->Push(parser);
  parser->connectionsList_->PushActive(parser);
  } else {
@@ -1122,6 +1112,8 @@ class Parser : public AsyncWrap, public StreamListener {
 uint64_t max_http_header_size_;
 uint64_t last_message_start_;
  ConnectionsList* connectionsList_;
+ ParserListNode all_node_;
+ ParserListNode active_node_;
 
  BaseObjectPtr<BindingData> binding_data_;
 
@@ -1149,18 +1141,34 @@ class Parser : public AsyncWrap, public StreamListener {
 staticconstllhttp_settings_t settings;
 };
 
-boolParserComparator::operator()(const Parser* lhs, const Parser* rhs) const {
-if (lhs->last_message_start_ == 0 && rhs->last_message_start_ == 0) {
-// When both parsers are idle, guarantee strict order by
-// comparing pointers as ints.
-return lhs < rhs;
- } elseif (lhs->last_message_start_ == 0) {
-returntrue;
- } elseif (rhs->last_message_start_ == 0) {
-returnfalse;
- }
+namespace {
+
+// Append `node` at the tail of the list headed by `head`, unlinking it from
+// any list it is currently in.
+voidListPushBack(ParserListNode* head, ParserListNode* node) {
+ node->Remove();
+ node->prev = head->prev;
+ node->next = head;
+ head->prev->next = node;
+ head->prev = node;
+}
+
+} // anonymous namespace
 
-return lhs->last_message_start_ < rhs->last_message_start_;
+voidConnectionsList::Push(Parser* parser) {
+ListPushBack(&all_connections_, &parser->all_node_);
+}
+
+voidConnectionsList::Pop(Parser* parser) {
+ parser->all_node_.Remove();
+}
+
+voidConnectionsList::PushActive(Parser* parser) {
+ListPushBack(&active_connections_, &parser->active_node_);
+}
+
+voidConnectionsList::PopActive(Parser* parser) {
+ parser->active_node_.Remove();
 }
 
 voidConnectionsList::New(const FunctionCallbackInfo<Value>& args) {
@@ -1178,8 +1186,10 @@ void ConnectionsList::All(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1195,8 +1205,10 @@ void ConnectionsList::Idle(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
 if (parser->last_message_start_ == 0 || !parser->received_data_) {
  result.emplace_back(parser->object());
  }
@@ -1214,8 +1226,10 @@ void ConnectionsList::Active(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->active_connections_.size());
-for (auto parser : list->active_connections_) {
+for (ParserListNode* node = list->active_connections_.next;
+ node != &list->active_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1259,14 +1273,11 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
 return args.GetReturnValue().Set(Array::New(isolate, 0));
  }
 
-auto iter = list->active_connections_.begin();
-auto end = list->active_connections_.end();
-
  LocalVector<Value> result(isolate);
-result.reserve(list->active_connections_.size());
-while (iter != end) {
- Parser* parser = *iter;
-iter++;
+ParserListNode* node = list->active_connections_.next;
+while (node != &list->active_connections_) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
+node = node->next;
 
 // Check for expiration.
 if (
@@ -1278,7 +1289,7 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
  ) {
  result.emplace_back(parser->object());
 
-list->active_connections_.erase(parser);
+parser->active_node_.Remove();
  }
  }
 

src/node_http_parser.cc

@@ -246,55 +246,63 @@ struct StringPtr {
 size_t size_ = 0;
 };
 
-structParserComparator {
-booloperator()(const Parser* lhs, const Parser* rhs) const;
+// Intrusive doubly-linked list node, linked to itself when not in a list.
+structParserListNode {
+ ParserListNode* prev = this;
+ ParserListNode* next = this;
+
+ParserListNode() = default;
+~ParserListNode() { Remove(); }
+
+ParserListNode(const ParserListNode&) = delete;
+ ParserListNode& operator=(const ParserListNode&) = delete;
+
+voidRemove() {
+ prev->next = next;
+ next->prev = prev;
+ prev = this;
+ next = this;
+ }
 };
 
 classConnectionsList : publicBaseObject {
 public:
-staticvoidNew(const FunctionCallbackInfo<Value>& args);
+staticvoidNew(const FunctionCallbackInfo<Value>& args);
 
-staticvoidAll(const FunctionCallbackInfo<Value>& args);
+staticvoidAll(const FunctionCallbackInfo<Value>& args);
 
-staticvoidIdle(const FunctionCallbackInfo<Value>& args);
+staticvoidIdle(const FunctionCallbackInfo<Value>& args);
 
-staticvoidActive(const FunctionCallbackInfo<Value>& args);
+staticvoidActive(const FunctionCallbackInfo<Value>& args);
 
-staticvoidExpired(const FunctionCallbackInfo<Value>& args);
+staticvoidExpired(const FunctionCallbackInfo<Value>& args);
 
-voidPush(Parser* parser) {
- all_connections_.insert(parser);
- }
+inlinevoidPush(Parser* parser);
 
-voidPop(Parser* parser) {
- all_connections_.erase(parser);
- }
+inlinevoidPop(Parser* parser);
 
-voidPushActive(Parser* parser) {
- active_connections_.insert(parser);
- }
+inlinevoidPushActive(Parser* parser);
 
-voidPopActive(Parser* parser) {
- active_connections_.erase(parser);
- }
+inlinevoidPopActive(Parser* parser);
 
-SET_NO_MEMORY_INFO()
-SET_MEMORY_INFO_NAME(ConnectionsList)
-SET_SELF_SIZE(ConnectionsList)
+SET_NO_MEMORY_INFO()
+SET_MEMORY_INFO_NAME(ConnectionsList)
+SET_SELF_SIZE(ConnectionsList)
 
 private:
-ConnectionsList(Environment* env, Local<Object> object)
+ConnectionsList(Environment* env, Local<Object> object)
  : BaseObject(env, object) {
-MakeWeak();
-}
+MakeWeak();
+ }
 
- std::set<Parser*, ParserComparator> all_connections_;
- std::set<Parser*, ParserComparator> active_connections_;
+// active_connections_ is ordered by last_message_start_, as parsers are
+// appended right after it is assigned from the monotonic uv_hrtime().
+ ParserListNode all_connections_;
+ ParserListNode active_connections_;
 };
 
 classParser : publicAsyncWrap, publicStreamListener {
 friendclassConnectionsList;
-friendstructParserComparator;
 
 public:
 Parser(BindingData* binding_data, Local<Object> wrap)
@@ -308,13 +316,6 @@ class Parser : public AsyncWrap, public StreamListener {
  SET_SELF_SIZE(Parser)
 
  int on_message_begin() {
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
-if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
- connectionsList_->PopActive(this);
- }
-
  num_fields_ = num_values_ = 0;
  headers_completed_ = false;
  chunk_extensions_nread_ = 0;
@@ -326,7 +327,6 @@ class Parser : public AsyncWrap, public StreamListener {
  max_header_pairs_ = -1;
 
 if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
  connectionsList_->PushActive(this);
  }
 
@@ -345,7 +345,6 @@ class Parser : public AsyncWrap, public StreamListener {
 return0;
  }
 
-
 inton_url(constchar* at, size_t length) {
 int rv = TrackHeader(length);
 if (rv != 0) {
@@ -544,19 +543,12 @@ class Parser : public AsyncWrap, public StreamListener {
 inton_message_complete() {
  HandleScope scope(env()->isolate());
 
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
 if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
  connectionsList_->PopActive(this);
  }
 
  last_message_start_ = 0;
 
-if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
- }
-
 if (num_fields_)
 Flush(); // Flush trailing HTTP headers.
 
@@ -742,8 +734,6 @@ class Parser : public AsyncWrap, public StreamListener {
 // server.timeout is left to the default value of zero.
  parser->last_message_start_ = uv_hrtime();
 
-// Important: Push into the lists AFTER setting the last_message_start_
-// otherwise std::set.erase will fail later.
  parser->connectionsList_->Push(parser);
  parser->connectionsList_->PushActive(parser);
  } else {
@@ -1122,6 +1112,8 @@ class Parser : public AsyncWrap, public StreamListener {
 uint64_t max_http_header_size_;
 uint64_t last_message_start_;
  ConnectionsList* connectionsList_;
+ ParserListNode all_node_;
+ ParserListNode active_node_;
 
  BaseObjectPtr<BindingData> binding_data_;
 
@@ -1149,18 +1141,34 @@ class Parser : public AsyncWrap, public StreamListener {
 staticconstllhttp_settings_t settings;
 };
 
-boolParserComparator::operator()(const Parser* lhs, const Parser* rhs) const {
-if (lhs->last_message_start_ == 0 && rhs->last_message_start_ == 0) {
-// When both parsers are idle, guarantee strict order by
-// comparing pointers as ints.
-return lhs < rhs;
- } elseif (lhs->last_message_start_ == 0) {
-returntrue;
- } elseif (rhs->last_message_start_ == 0) {
-returnfalse;
- }
+namespace {
+
+// Append `node` at the tail of the list headed by `head`, unlinking it from
+// any list it is currently in.
+voidListPushBack(ParserListNode* head, ParserListNode* node) {
+ node->Remove();
+ node->prev = head->prev;
+ node->next = head;
+ head->prev->next = node;
+ head->prev = node;
+}
+
+} // anonymous namespace
 
-return lhs->last_message_start_ < rhs->last_message_start_;
+voidConnectionsList::Push(Parser* parser) {
+ListPushBack(&all_connections_, &parser->all_node_);
+}
+
+voidConnectionsList::Pop(Parser* parser) {
+ parser->all_node_.Remove();
+}
+
+voidConnectionsList::PushActive(Parser* parser) {
+ListPushBack(&active_connections_, &parser->active_node_);
+}
+
+voidConnectionsList::PopActive(Parser* parser) {
+ parser->active_node_.Remove();
 }
 
 voidConnectionsList::New(const FunctionCallbackInfo<Value>& args) {
@@ -1178,8 +1186,10 @@ void ConnectionsList::All(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1195,8 +1205,10 @@ void ConnectionsList::Idle(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
 if (parser->last_message_start_ == 0 || !parser->received_data_) {
  result.emplace_back(parser->object());
  }
@@ -1214,8 +1226,10 @@ void ConnectionsList::Active(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->active_connections_.size());
-for (auto parser : list->active_connections_) {
+for (ParserListNode* node = list->active_connections_.next;
+ node != &list->active_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1259,14 +1273,11 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
 return args.GetReturnValue().Set(Array::New(isolate, 0));
  }
 
-auto iter = list->active_connections_.begin();
-auto end = list->active_connections_.end();
-
  LocalVector<Value> result(isolate);
-result.reserve(list->active_connections_.size());
-while (iter != end) {
- Parser* parser = *iter;
-iter++;
+ParserListNode* node = list->active_connections_.next;
+while (node != &list->active_connections_) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
+node = node->next;
 
 // Check for expiration.
 if (
@@ -1278,7 +1289,7 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
  ) {
  result.emplace_back(parser->object());
 
-list->active_connections_.erase(parser);
+parser->active_node_.Remove();
  }
  }
 

src/node_http_parser.cc

@@ -246,55 +246,63 @@ struct StringPtr {
 size_t size_ = 0;
 };
 
-structParserComparator {
-booloperator()(const Parser* lhs, const Parser* rhs) const;
+// Intrusive doubly-linked list node, linked to itself when not in a list.
+structParserListNode {
+ ParserListNode* prev = this;
+ ParserListNode* next = this;
+
+ParserListNode() = default;
+~ParserListNode() { Remove(); }
+
+ParserListNode(const ParserListNode&) = delete;
+ ParserListNode& operator=(const ParserListNode&) = delete;
+
+voidRemove() {
+ prev->next = next;
+ next->prev = prev;
+ prev = this;
+ next = this;
+ }
 };
 
 classConnectionsList : publicBaseObject {
 public:
-staticvoidNew(const FunctionCallbackInfo<Value>& args);
+staticvoidNew(const FunctionCallbackInfo<Value>& args);
 
-staticvoidAll(const FunctionCallbackInfo<Value>& args);
+staticvoidAll(const FunctionCallbackInfo<Value>& args);
 
-staticvoidIdle(const FunctionCallbackInfo<Value>& args);
+staticvoidIdle(const FunctionCallbackInfo<Value>& args);
 
-staticvoidActive(const FunctionCallbackInfo<Value>& args);
+staticvoidActive(const FunctionCallbackInfo<Value>& args);
 
-staticvoidExpired(const FunctionCallbackInfo<Value>& args);
+staticvoidExpired(const FunctionCallbackInfo<Value>& args);
 
-voidPush(Parser* parser) {
- all_connections_.insert(parser);
- }
+inlinevoidPush(Parser* parser);
 
-voidPop(Parser* parser) {
- all_connections_.erase(parser);
- }
+inlinevoidPop(Parser* parser);
 
-voidPushActive(Parser* parser) {
- active_connections_.insert(parser);
- }
+inlinevoidPushActive(Parser* parser);
 
-voidPopActive(Parser* parser) {
- active_connections_.erase(parser);
- }
+inlinevoidPopActive(Parser* parser);
 
-SET_NO_MEMORY_INFO()
-SET_MEMORY_INFO_NAME(ConnectionsList)
-SET_SELF_SIZE(ConnectionsList)
+SET_NO_MEMORY_INFO()
+SET_MEMORY_INFO_NAME(ConnectionsList)
+SET_SELF_SIZE(ConnectionsList)
 
 private:
-ConnectionsList(Environment* env, Local<Object> object)
+ConnectionsList(Environment* env, Local<Object> object)
  : BaseObject(env, object) {
-MakeWeak();
-}
+MakeWeak();
+ }
 
- std::set<Parser*, ParserComparator> all_connections_;
- std::set<Parser*, ParserComparator> active_connections_;
+// active_connections_ is ordered by last_message_start_, as parsers are
+// appended right after it is assigned from the monotonic uv_hrtime().
+ ParserListNode all_connections_;
+ ParserListNode active_connections_;
 };
 
 classParser : publicAsyncWrap, publicStreamListener {
 friendclassConnectionsList;
-friendstructParserComparator;
 
 public:
 Parser(BindingData* binding_data, Local<Object> wrap)
@@ -308,13 +316,6 @@ class Parser : public AsyncWrap, public StreamListener {
  SET_SELF_SIZE(Parser)
 
  int on_message_begin() {
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
-if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
- connectionsList_->PopActive(this);
- }
-
  num_fields_ = num_values_ = 0;
  headers_completed_ = false;
  chunk_extensions_nread_ = 0;
@@ -326,7 +327,6 @@ class Parser : public AsyncWrap, public StreamListener {
  max_header_pairs_ = -1;
 
 if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
  connectionsList_->PushActive(this);
  }
 
@@ -345,7 +345,6 @@ class Parser : public AsyncWrap, public StreamListener {
 return0;
  }
 
-
 inton_url(constchar* at, size_t length) {
 int rv = TrackHeader(length);
 if (rv != 0) {
@@ -544,19 +543,12 @@ class Parser : public AsyncWrap, public StreamListener {
 inton_message_complete() {
  HandleScope scope(env()->isolate());
 
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
 if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
  connectionsList_->PopActive(this);
  }
 
  last_message_start_ = 0;
 
-if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
- }
-
 if (num_fields_)
 Flush(); // Flush trailing HTTP headers.
 
@@ -742,8 +734,6 @@ class Parser : public AsyncWrap, public StreamListener {
 // server.timeout is left to the default value of zero.
  parser->last_message_start_ = uv_hrtime();
 
-// Important: Push into the lists AFTER setting the last_message_start_
-// otherwise std::set.erase will fail later.
  parser->connectionsList_->Push(parser);
  parser->connectionsList_->PushActive(parser);
  } else {
@@ -1122,6 +1112,8 @@ class Parser : public AsyncWrap, public StreamListener {
 uint64_t max_http_header_size_;
 uint64_t last_message_start_;
  ConnectionsList* connectionsList_;
+ ParserListNode all_node_;
+ ParserListNode active_node_;
 
  BaseObjectPtr<BindingData> binding_data_;
 
@@ -1149,18 +1141,34 @@ class Parser : public AsyncWrap, public StreamListener {
 staticconstllhttp_settings_t settings;
 };
 
-boolParserComparator::operator()(const Parser* lhs, const Parser* rhs) const {
-if (lhs->last_message_start_ == 0 && rhs->last_message_start_ == 0) {
-// When both parsers are idle, guarantee strict order by
-// comparing pointers as ints.
-return lhs < rhs;
- } elseif (lhs->last_message_start_ == 0) {
-returntrue;
- } elseif (rhs->last_message_start_ == 0) {
-returnfalse;
- }
+namespace {
+
+// Append `node` at the tail of the list headed by `head`, unlinking it from
+// any list it is currently in.
+voidListPushBack(ParserListNode* head, ParserListNode* node) {
+ node->Remove();
+ node->prev = head->prev;
+ node->next = head;
+ head->prev->next = node;
+ head->prev = node;
+}
+
+} // anonymous namespace
 
-return lhs->last_message_start_ < rhs->last_message_start_;
+voidConnectionsList::Push(Parser* parser) {
+ListPushBack(&all_connections_, &parser->all_node_);
+}
+
+voidConnectionsList::Pop(Parser* parser) {
+ parser->all_node_.Remove();
+}
+
+voidConnectionsList::PushActive(Parser* parser) {
+ListPushBack(&active_connections_, &parser->active_node_);
+}
+
+voidConnectionsList::PopActive(Parser* parser) {
+ parser->active_node_.Remove();
 }
 
 voidConnectionsList::New(const FunctionCallbackInfo<Value>& args) {
@@ -1178,8 +1186,10 @@ void ConnectionsList::All(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1195,8 +1205,10 @@ void ConnectionsList::Idle(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
 if (parser->last_message_start_ == 0 || !parser->received_data_) {
  result.emplace_back(parser->object());
  }
@@ -1214,8 +1226,10 @@ void ConnectionsList::Active(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->active_connections_.size());
-for (auto parser : list->active_connections_) {
+for (ParserListNode* node = list->active_connections_.next;
+ node != &list->active_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1259,14 +1273,11 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
 return args.GetReturnValue().Set(Array::New(isolate, 0));
  }
 
-auto iter = list->active_connections_.begin();
-auto end = list->active_connections_.end();
-
  LocalVector<Value> result(isolate);
-result.reserve(list->active_connections_.size());
-while (iter != end) {
- Parser* parser = *iter;
-iter++;
+ParserListNode* node = list->active_connections_.next;
+while (node != &list->active_connections_) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
+node = node->next;
 
 // Check for expiration.
 if (
@@ -1278,7 +1289,7 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
  ) {
  result.emplace_back(parser->object());
 
-list->active_connections_.erase(parser);
+parser->active_node_.Remove();
  }
  }
 

src/node_http_parser.cc

@@ -246,55 +246,63 @@ struct StringPtr {
 size_t size_ = 0;
 };
 
-structParserComparator {
-booloperator()(const Parser* lhs, const Parser* rhs) const;
+// Intrusive doubly-linked list node, linked to itself when not in a list.
+structParserListNode {
+ ParserListNode* prev = this;
+ ParserListNode* next = this;
+
+ParserListNode() = default;
+~ParserListNode() { Remove(); }
+
+ParserListNode(const ParserListNode&) = delete;
+ ParserListNode& operator=(const ParserListNode&) = delete;
+
+voidRemove() {
+ prev->next = next;
+ next->prev = prev;
+ prev = this;
+ next = this;
+ }
 };
 
 classConnectionsList : publicBaseObject {
 public:
-staticvoidNew(const FunctionCallbackInfo<Value>& args);
+staticvoidNew(const FunctionCallbackInfo<Value>& args);
 
-staticvoidAll(const FunctionCallbackInfo<Value>& args);
+staticvoidAll(const FunctionCallbackInfo<Value>& args);
 
-staticvoidIdle(const FunctionCallbackInfo<Value>& args);
+staticvoidIdle(const FunctionCallbackInfo<Value>& args);
 
-staticvoidActive(const FunctionCallbackInfo<Value>& args);
+staticvoidActive(const FunctionCallbackInfo<Value>& args);
 
-staticvoidExpired(const FunctionCallbackInfo<Value>& args);
+staticvoidExpired(const FunctionCallbackInfo<Value>& args);
 
-voidPush(Parser* parser) {
- all_connections_.insert(parser);
- }
+inlinevoidPush(Parser* parser);
 
-voidPop(Parser* parser) {
- all_connections_.erase(parser);
- }
+inlinevoidPop(Parser* parser);
 
-voidPushActive(Parser* parser) {
- active_connections_.insert(parser);
- }
+inlinevoidPushActive(Parser* parser);
 
-voidPopActive(Parser* parser) {
- active_connections_.erase(parser);
- }
+inlinevoidPopActive(Parser* parser);
 
-SET_NO_MEMORY_INFO()
-SET_MEMORY_INFO_NAME(ConnectionsList)
-SET_SELF_SIZE(ConnectionsList)
+SET_NO_MEMORY_INFO()
+SET_MEMORY_INFO_NAME(ConnectionsList)
+SET_SELF_SIZE(ConnectionsList)
 
 private:
-ConnectionsList(Environment* env, Local<Object> object)
+ConnectionsList(Environment* env, Local<Object> object)
  : BaseObject(env, object) {
-MakeWeak();
-}
+MakeWeak();
+ }
 
- std::set<Parser*, ParserComparator> all_connections_;
- std::set<Parser*, ParserComparator> active_connections_;
+// active_connections_ is ordered by last_message_start_, as parsers are
+// appended right after it is assigned from the monotonic uv_hrtime().
+ ParserListNode all_connections_;
+ ParserListNode active_connections_;
 };
 
 classParser : publicAsyncWrap, publicStreamListener {
 friendclassConnectionsList;
-friendstructParserComparator;
 
 public:
 Parser(BindingData* binding_data, Local<Object> wrap)
@@ -308,13 +316,6 @@ class Parser : public AsyncWrap, public StreamListener {
  SET_SELF_SIZE(Parser)
 
  int on_message_begin() {
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
-if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
- connectionsList_->PopActive(this);
- }
-
  num_fields_ = num_values_ = 0;
  headers_completed_ = false;
  chunk_extensions_nread_ = 0;
@@ -326,7 +327,6 @@ class Parser : public AsyncWrap, public StreamListener {
  max_header_pairs_ = -1;
 
 if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
  connectionsList_->PushActive(this);
  }
 
@@ -345,7 +345,6 @@ class Parser : public AsyncWrap, public StreamListener {
 return0;
  }
 
-
 inton_url(constchar* at, size_t length) {
 int rv = TrackHeader(length);
 if (rv != 0) {
@@ -544,19 +543,12 @@ class Parser : public AsyncWrap, public StreamListener {
 inton_message_complete() {
  HandleScope scope(env()->isolate());
 
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
 if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
  connectionsList_->PopActive(this);
  }
 
  last_message_start_ = 0;
 
-if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
- }
-
 if (num_fields_)
 Flush(); // Flush trailing HTTP headers.
 
@@ -742,8 +734,6 @@ class Parser : public AsyncWrap, public StreamListener {
 // server.timeout is left to the default value of zero.
  parser->last_message_start_ = uv_hrtime();
 
-// Important: Push into the lists AFTER setting the last_message_start_
-// otherwise std::set.erase will fail later.
  parser->connectionsList_->Push(parser);
  parser->connectionsList_->PushActive(parser);
  } else {
@@ -1122,6 +1112,8 @@ class Parser : public AsyncWrap, public StreamListener {
 uint64_t max_http_header_size_;
 uint64_t last_message_start_;
  ConnectionsList* connectionsList_;
+ ParserListNode all_node_;
+ ParserListNode active_node_;
 
  BaseObjectPtr<BindingData> binding_data_;
 
@@ -1149,18 +1141,34 @@ class Parser : public AsyncWrap, public StreamListener {
 staticconstllhttp_settings_t settings;
 };
 
-boolParserComparator::operator()(const Parser* lhs, const Parser* rhs) const {
-if (lhs->last_message_start_ == 0 && rhs->last_message_start_ == 0) {
-// When both parsers are idle, guarantee strict order by
-// comparing pointers as ints.
-return lhs < rhs;
- } elseif (lhs->last_message_start_ == 0) {
-returntrue;
- } elseif (rhs->last_message_start_ == 0) {
-returnfalse;
- }
+namespace {
+
+// Append `node` at the tail of the list headed by `head`, unlinking it from
+// any list it is currently in.
+voidListPushBack(ParserListNode* head, ParserListNode* node) {
+ node->Remove();
+ node->prev = head->prev;
+ node->next = head;
+ head->prev->next = node;
+ head->prev = node;
+}
+
+} // anonymous namespace
 
-return lhs->last_message_start_ < rhs->last_message_start_;
+voidConnectionsList::Push(Parser* parser) {
+ListPushBack(&all_connections_, &parser->all_node_);
+}
+
+voidConnectionsList::Pop(Parser* parser) {
+ parser->all_node_.Remove();
+}
+
+voidConnectionsList::PushActive(Parser* parser) {
+ListPushBack(&active_connections_, &parser->active_node_);
+}
+
+voidConnectionsList::PopActive(Parser* parser) {
+ parser->active_node_.Remove();
 }
 
 voidConnectionsList::New(const FunctionCallbackInfo<Value>& args) {
@@ -1178,8 +1186,10 @@ void ConnectionsList::All(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1195,8 +1205,10 @@ void ConnectionsList::Idle(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
 if (parser->last_message_start_ == 0 || !parser->received_data_) {
  result.emplace_back(parser->object());
  }
@@ -1214,8 +1226,10 @@ void ConnectionsList::Active(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->active_connections_.size());
-for (auto parser : list->active_connections_) {
+for (ParserListNode* node = list->active_connections_.next;
+ node != &list->active_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1259,14 +1273,11 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
 return args.GetReturnValue().Set(Array::New(isolate, 0));
  }
 
-auto iter = list->active_connections_.begin();
-auto end = list->active_connections_.end();
-
  LocalVector<Value> result(isolate);
-result.reserve(list->active_connections_.size());
-while (iter != end) {
- Parser* parser = *iter;
-iter++;
+ParserListNode* node = list->active_connections_.next;
+while (node != &list->active_connections_) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
+node = node->next;
 
 // Check for expiration.
 if (
@@ -1278,7 +1289,7 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
  ) {
  result.emplace_back(parser->object());
 
-list->active_connections_.erase(parser);
+parser->active_node_.Remove();
  }
  }
 

src/node_http_parser.cc

@@ -246,55 +246,63 @@ struct StringPtr {
 size_t size_ = 0;
 };
 
-structParserComparator {
-booloperator()(const Parser* lhs, const Parser* rhs) const;
+// Intrusive doubly-linked list node, linked to itself when not in a list.
+structParserListNode {
+ ParserListNode* prev = this;
+ ParserListNode* next = this;
+
+ParserListNode() = default;
+~ParserListNode() { Remove(); }
+
+ParserListNode(const ParserListNode&) = delete;
+ ParserListNode& operator=(const ParserListNode&) = delete;
+
+voidRemove() {
+ prev->next = next;
+ next->prev = prev;
+ prev = this;
+ next = this;
+ }
 };
 
 classConnectionsList : publicBaseObject {
 public:
-staticvoidNew(const FunctionCallbackInfo<Value>& args);
+staticvoidNew(const FunctionCallbackInfo<Value>& args);
 
-staticvoidAll(const FunctionCallbackInfo<Value>& args);
+staticvoidAll(const FunctionCallbackInfo<Value>& args);
 
-staticvoidIdle(const FunctionCallbackInfo<Value>& args);
+staticvoidIdle(const FunctionCallbackInfo<Value>& args);
 
-staticvoidActive(const FunctionCallbackInfo<Value>& args);
+staticvoidActive(const FunctionCallbackInfo<Value>& args);
 
-staticvoidExpired(const FunctionCallbackInfo<Value>& args);
+staticvoidExpired(const FunctionCallbackInfo<Value>& args);
 
-voidPush(Parser* parser) {
- all_connections_.insert(parser);
- }
+inlinevoidPush(Parser* parser);
 
-voidPop(Parser* parser) {
- all_connections_.erase(parser);
- }
+inlinevoidPop(Parser* parser);
 
-voidPushActive(Parser* parser) {
- active_connections_.insert(parser);
- }
+inlinevoidPushActive(Parser* parser);
 
-voidPopActive(Parser* parser) {
- active_connections_.erase(parser);
- }
+inlinevoidPopActive(Parser* parser);
 
-SET_NO_MEMORY_INFO()
-SET_MEMORY_INFO_NAME(ConnectionsList)
-SET_SELF_SIZE(ConnectionsList)
+SET_NO_MEMORY_INFO()
+SET_MEMORY_INFO_NAME(ConnectionsList)
+SET_SELF_SIZE(ConnectionsList)
 
 private:
-ConnectionsList(Environment* env, Local<Object> object)
+ConnectionsList(Environment* env, Local<Object> object)
  : BaseObject(env, object) {
-MakeWeak();
-}
+MakeWeak();
+ }
 
- std::set<Parser*, ParserComparator> all_connections_;
- std::set<Parser*, ParserComparator> active_connections_;
+// active_connections_ is ordered by last_message_start_, as parsers are
+// appended right after it is assigned from the monotonic uv_hrtime().
+ ParserListNode all_connections_;
+ ParserListNode active_connections_;
 };
 
 classParser : publicAsyncWrap, publicStreamListener {
 friendclassConnectionsList;
-friendstructParserComparator;
 
 public:
 Parser(BindingData* binding_data, Local<Object> wrap)
@@ -308,13 +316,6 @@ class Parser : public AsyncWrap, public StreamListener {
  SET_SELF_SIZE(Parser)
 
  int on_message_begin() {
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
-if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
- connectionsList_->PopActive(this);
- }
-
  num_fields_ = num_values_ = 0;
  headers_completed_ = false;
  chunk_extensions_nread_ = 0;
@@ -326,7 +327,6 @@ class Parser : public AsyncWrap, public StreamListener {
  max_header_pairs_ = -1;
 
 if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
  connectionsList_->PushActive(this);
  }
 
@@ -345,7 +345,6 @@ class Parser : public AsyncWrap, public StreamListener {
 return0;
  }
 
-
 inton_url(constchar* at, size_t length) {
 int rv = TrackHeader(length);
 if (rv != 0) {
@@ -544,19 +543,12 @@ class Parser : public AsyncWrap, public StreamListener {
 inton_message_complete() {
  HandleScope scope(env()->isolate());
 
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
 if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
  connectionsList_->PopActive(this);
  }
 
  last_message_start_ = 0;
 
-if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
- }
-
 if (num_fields_)
 Flush(); // Flush trailing HTTP headers.
 
@@ -742,8 +734,6 @@ class Parser : public AsyncWrap, public StreamListener {
 // server.timeout is left to the default value of zero.
  parser->last_message_start_ = uv_hrtime();
 
-// Important: Push into the lists AFTER setting the last_message_start_
-// otherwise std::set.erase will fail later.
  parser->connectionsList_->Push(parser);
  parser->connectionsList_->PushActive(parser);
  } else {
@@ -1122,6 +1112,8 @@ class Parser : public AsyncWrap, public StreamListener {
 uint64_t max_http_header_size_;
 uint64_t last_message_start_;
  ConnectionsList* connectionsList_;
+ ParserListNode all_node_;
+ ParserListNode active_node_;
 
  BaseObjectPtr<BindingData> binding_data_;
 
@@ -1149,18 +1141,34 @@ class Parser : public AsyncWrap, public StreamListener {
 staticconstllhttp_settings_t settings;
 };
 
-boolParserComparator::operator()(const Parser* lhs, const Parser* rhs) const {
-if (lhs->last_message_start_ == 0 && rhs->last_message_start_ == 0) {
-// When both parsers are idle, guarantee strict order by
-// comparing pointers as ints.
-return lhs < rhs;
- } elseif (lhs->last_message_start_ == 0) {
-returntrue;
- } elseif (rhs->last_message_start_ == 0) {
-returnfalse;
- }
+namespace {
+
+// Append `node` at the tail of the list headed by `head`, unlinking it from
+// any list it is currently in.
+voidListPushBack(ParserListNode* head, ParserListNode* node) {
+ node->Remove();
+ node->prev = head->prev;
+ node->next = head;
+ head->prev->next = node;
+ head->prev = node;
+}
+
+} // anonymous namespace
 
-return lhs->last_message_start_ < rhs->last_message_start_;
+voidConnectionsList::Push(Parser* parser) {
+ListPushBack(&all_connections_, &parser->all_node_);
+}
+
+voidConnectionsList::Pop(Parser* parser) {
+ parser->all_node_.Remove();
+}
+
+voidConnectionsList::PushActive(Parser* parser) {
+ListPushBack(&active_connections_, &parser->active_node_);
+}
+
+voidConnectionsList::PopActive(Parser* parser) {
+ parser->active_node_.Remove();
 }
 
 voidConnectionsList::New(const FunctionCallbackInfo<Value>& args) {
@@ -1178,8 +1186,10 @@ void ConnectionsList::All(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1195,8 +1205,10 @@ void ConnectionsList::Idle(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
 if (parser->last_message_start_ == 0 || !parser->received_data_) {
  result.emplace_back(parser->object());
  }
@@ -1214,8 +1226,10 @@ void ConnectionsList::Active(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->active_connections_.size());
-for (auto parser : list->active_connections_) {
+for (ParserListNode* node = list->active_connections_.next;
+ node != &list->active_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1259,14 +1273,11 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
 return args.GetReturnValue().Set(Array::New(isolate, 0));
  }
 
-auto iter = list->active_connections_.begin();
-auto end = list->active_connections_.end();
-
  LocalVector<Value> result(isolate);
-result.reserve(list->active_connections_.size());
-while (iter != end) {
- Parser* parser = *iter;
-iter++;
+ParserListNode* node = list->active_connections_.next;
+while (node != &list->active_connections_) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
+node = node->next;
 
 // Check for expiration.
 if (
@@ -1278,7 +1289,7 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
  ) {
  result.emplace_back(parser->object());
 
-list->active_connections_.erase(parser);
+parser->active_node_.Remove();
  }
  }
 

src/node_http_parser.cc

@@ -246,55 +246,63 @@ struct StringPtr {
 size_t size_ = 0;
 };
 
-structParserComparator {
-booloperator()(const Parser* lhs, const Parser* rhs) const;
+// Intrusive doubly-linked list node, linked to itself when not in a list.
+structParserListNode {
+ ParserListNode* prev = this;
+ ParserListNode* next = this;
+
+ParserListNode() = default;
+~ParserListNode() { Remove(); }
+
+ParserListNode(const ParserListNode&) = delete;
+ ParserListNode& operator=(const ParserListNode&) = delete;
+
+voidRemove() {
+ prev->next = next;
+ next->prev = prev;
+ prev = this;
+ next = this;
+ }
 };
 
 classConnectionsList : publicBaseObject {
 public:
-staticvoidNew(const FunctionCallbackInfo<Value>& args);
+staticvoidNew(const FunctionCallbackInfo<Value>& args);
 
-staticvoidAll(const FunctionCallbackInfo<Value>& args);
+staticvoidAll(const FunctionCallbackInfo<Value>& args);
 
-staticvoidIdle(const FunctionCallbackInfo<Value>& args);
+staticvoidIdle(const FunctionCallbackInfo<Value>& args);
 
-staticvoidActive(const FunctionCallbackInfo<Value>& args);
+staticvoidActive(const FunctionCallbackInfo<Value>& args);
 
-staticvoidExpired(const FunctionCallbackInfo<Value>& args);
+staticvoidExpired(const FunctionCallbackInfo<Value>& args);
 
-voidPush(Parser* parser) {
- all_connections_.insert(parser);
- }
+inlinevoidPush(Parser* parser);
 
-voidPop(Parser* parser) {
- all_connections_.erase(parser);
- }
+inlinevoidPop(Parser* parser);
 
-voidPushActive(Parser* parser) {
- active_connections_.insert(parser);
- }
+inlinevoidPushActive(Parser* parser);
 
-voidPopActive(Parser* parser) {
- active_connections_.erase(parser);
- }
+inlinevoidPopActive(Parser* parser);
 
-SET_NO_MEMORY_INFO()
-SET_MEMORY_INFO_NAME(ConnectionsList)
-SET_SELF_SIZE(ConnectionsList)
+SET_NO_MEMORY_INFO()
+SET_MEMORY_INFO_NAME(ConnectionsList)
+SET_SELF_SIZE(ConnectionsList)
 
 private:
-ConnectionsList(Environment* env, Local<Object> object)
+ConnectionsList(Environment* env, Local<Object> object)
  : BaseObject(env, object) {
-MakeWeak();
-}
+MakeWeak();
+ }
 
- std::set<Parser*, ParserComparator> all_connections_;
- std::set<Parser*, ParserComparator> active_connections_;
+// active_connections_ is ordered by last_message_start_, as parsers are
+// appended right after it is assigned from the monotonic uv_hrtime().
+ ParserListNode all_connections_;
+ ParserListNode active_connections_;
 };
 
 classParser : publicAsyncWrap, publicStreamListener {
 friendclassConnectionsList;
-friendstructParserComparator;
 
 public:
 Parser(BindingData* binding_data, Local<Object> wrap)
@@ -308,13 +316,6 @@ class Parser : public AsyncWrap, public StreamListener {
  SET_SELF_SIZE(Parser)
 
  int on_message_begin() {
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
-if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
- connectionsList_->PopActive(this);
- }
-
  num_fields_ = num_values_ = 0;
  headers_completed_ = false;
  chunk_extensions_nread_ = 0;
@@ -326,7 +327,6 @@ class Parser : public AsyncWrap, public StreamListener {
  max_header_pairs_ = -1;
 
 if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
  connectionsList_->PushActive(this);
  }
 
@@ -345,7 +345,6 @@ class Parser : public AsyncWrap, public StreamListener {
 return0;
  }
 
-
 inton_url(constchar* at, size_t length) {
 int rv = TrackHeader(length);
 if (rv != 0) {
@@ -544,19 +543,12 @@ class Parser : public AsyncWrap, public StreamListener {
 inton_message_complete() {
  HandleScope scope(env()->isolate());
 
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
 if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
  connectionsList_->PopActive(this);
  }
 
  last_message_start_ = 0;
 
-if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
- }
-
 if (num_fields_)
 Flush(); // Flush trailing HTTP headers.
 
@@ -742,8 +734,6 @@ class Parser : public AsyncWrap, public StreamListener {
 // server.timeout is left to the default value of zero.
  parser->last_message_start_ = uv_hrtime();
 
-// Important: Push into the lists AFTER setting the last_message_start_
-// otherwise std::set.erase will fail later.
  parser->connectionsList_->Push(parser);
  parser->connectionsList_->PushActive(parser);
  } else {
@@ -1122,6 +1112,8 @@ class Parser : public AsyncWrap, public StreamListener {
 uint64_t max_http_header_size_;
 uint64_t last_message_start_;
  ConnectionsList* connectionsList_;
+ ParserListNode all_node_;
+ ParserListNode active_node_;
 
  BaseObjectPtr<BindingData> binding_data_;
 
@@ -1149,18 +1141,34 @@ class Parser : public AsyncWrap, public StreamListener {
 staticconstllhttp_settings_t settings;
 };
 
-boolParserComparator::operator()(const Parser* lhs, const Parser* rhs) const {
-if (lhs->last_message_start_ == 0 && rhs->last_message_start_ == 0) {
-// When both parsers are idle, guarantee strict order by
-// comparing pointers as ints.
-return lhs < rhs;
- } elseif (lhs->last_message_start_ == 0) {
-returntrue;
- } elseif (rhs->last_message_start_ == 0) {
-returnfalse;
- }
+namespace {
+
+// Append `node` at the tail of the list headed by `head`, unlinking it from
+// any list it is currently in.
+voidListPushBack(ParserListNode* head, ParserListNode* node) {
+ node->Remove();
+ node->prev = head->prev;
+ node->next = head;
+ head->prev->next = node;
+ head->prev = node;
+}
+
+} // anonymous namespace
 
-return lhs->last_message_start_ < rhs->last_message_start_;
+voidConnectionsList::Push(Parser* parser) {
+ListPushBack(&all_connections_, &parser->all_node_);
+}
+
+voidConnectionsList::Pop(Parser* parser) {
+ parser->all_node_.Remove();
+}
+
+voidConnectionsList::PushActive(Parser* parser) {
+ListPushBack(&active_connections_, &parser->active_node_);
+}
+
+voidConnectionsList::PopActive(Parser* parser) {
+ parser->active_node_.Remove();
 }
 
 voidConnectionsList::New(const FunctionCallbackInfo<Value>& args) {
@@ -1178,8 +1186,10 @@ void ConnectionsList::All(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1195,8 +1205,10 @@ void ConnectionsList::Idle(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
 if (parser->last_message_start_ == 0 || !parser->received_data_) {
  result.emplace_back(parser->object());
  }
@@ -1214,8 +1226,10 @@ void ConnectionsList::Active(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->active_connections_.size());
-for (auto parser : list->active_connections_) {
+for (ParserListNode* node = list->active_connections_.next;
+ node != &list->active_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1259,14 +1273,11 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
 return args.GetReturnValue().Set(Array::New(isolate, 0));
  }
 
-auto iter = list->active_connections_.begin();
-auto end = list->active_connections_.end();
-
  LocalVector<Value> result(isolate);
-result.reserve(list->active_connections_.size());
-while (iter != end) {
- Parser* parser = *iter;
-iter++;
+ParserListNode* node = list->active_connections_.next;
+while (node != &list->active_connections_) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
+node = node->next;
 
 // Check for expiration.
 if (
@@ -1278,7 +1289,7 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
  ) {
  result.emplace_back(parser->object());
 
-list->active_connections_.erase(parser);
+parser->active_node_.Remove();
  }
  }
 

src/node_http_parser.cc

@@ -246,55 +246,63 @@ struct StringPtr {
 size_t size_ = 0;
 };
 
-structParserComparator {
-booloperator()(const Parser* lhs, const Parser* rhs) const;
+// Intrusive doubly-linked list node, linked to itself when not in a list.
+structParserListNode {
+ ParserListNode* prev = this;
+ ParserListNode* next = this;
+
+ParserListNode() = default;
+~ParserListNode() { Remove(); }
+
+ParserListNode(const ParserListNode&) = delete;
+ ParserListNode& operator=(const ParserListNode&) = delete;
+
+voidRemove() {
+ prev->next = next;
+ next->prev = prev;
+ prev = this;
+ next = this;
+ }
 };
 
 classConnectionsList : publicBaseObject {
 public:
-staticvoidNew(const FunctionCallbackInfo<Value>& args);
+staticvoidNew(const FunctionCallbackInfo<Value>& args);
 
-staticvoidAll(const FunctionCallbackInfo<Value>& args);
+staticvoidAll(const FunctionCallbackInfo<Value>& args);
 
-staticvoidIdle(const FunctionCallbackInfo<Value>& args);
+staticvoidIdle(const FunctionCallbackInfo<Value>& args);
 
-staticvoidActive(const FunctionCallbackInfo<Value>& args);
+staticvoidActive(const FunctionCallbackInfo<Value>& args);
 
-staticvoidExpired(const FunctionCallbackInfo<Value>& args);
+staticvoidExpired(const FunctionCallbackInfo<Value>& args);
 
-voidPush(Parser* parser) {
- all_connections_.insert(parser);
- }
+inlinevoidPush(Parser* parser);
 
-voidPop(Parser* parser) {
- all_connections_.erase(parser);
- }
+inlinevoidPop(Parser* parser);
 
-voidPushActive(Parser* parser) {
- active_connections_.insert(parser);
- }
+inlinevoidPushActive(Parser* parser);
 
-voidPopActive(Parser* parser) {
- active_connections_.erase(parser);
- }
+inlinevoidPopActive(Parser* parser);
 
-SET_NO_MEMORY_INFO()
-SET_MEMORY_INFO_NAME(ConnectionsList)
-SET_SELF_SIZE(ConnectionsList)
+SET_NO_MEMORY_INFO()
+SET_MEMORY_INFO_NAME(ConnectionsList)
+SET_SELF_SIZE(ConnectionsList)
 
 private:
-ConnectionsList(Environment* env, Local<Object> object)
+ConnectionsList(Environment* env, Local<Object> object)
  : BaseObject(env, object) {
-MakeWeak();
-}
+MakeWeak();
+ }
 
- std::set<Parser*, ParserComparator> all_connections_;
- std::set<Parser*, ParserComparator> active_connections_;
+// active_connections_ is ordered by last_message_start_, as parsers are
+// appended right after it is assigned from the monotonic uv_hrtime().
+ ParserListNode all_connections_;
+ ParserListNode active_connections_;
 };
 
 classParser : publicAsyncWrap, publicStreamListener {
 friendclassConnectionsList;
-friendstructParserComparator;
 
 public:
 Parser(BindingData* binding_data, Local<Object> wrap)
@@ -308,13 +316,6 @@ class Parser : public AsyncWrap, public StreamListener {
  SET_SELF_SIZE(Parser)
 
  int on_message_begin() {
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
-if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
- connectionsList_->PopActive(this);
- }
-
  num_fields_ = num_values_ = 0;
  headers_completed_ = false;
  chunk_extensions_nread_ = 0;
@@ -326,7 +327,6 @@ class Parser : public AsyncWrap, public StreamListener {
  max_header_pairs_ = -1;
 
 if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
  connectionsList_->PushActive(this);
  }
 
@@ -345,7 +345,6 @@ class Parser : public AsyncWrap, public StreamListener {
 return0;
  }
 
-
 inton_url(constchar* at, size_t length) {
 int rv = TrackHeader(length);
 if (rv != 0) {
@@ -544,19 +543,12 @@ class Parser : public AsyncWrap, public StreamListener {
 inton_message_complete() {
  HandleScope scope(env()->isolate());
 
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
 if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
  connectionsList_->PopActive(this);
  }
 
  last_message_start_ = 0;
 
-if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
- }
-
 if (num_fields_)
 Flush(); // Flush trailing HTTP headers.
 
@@ -742,8 +734,6 @@ class Parser : public AsyncWrap, public StreamListener {
 // server.timeout is left to the default value of zero.
  parser->last_message_start_ = uv_hrtime();
 
-// Important: Push into the lists AFTER setting the last_message_start_
-// otherwise std::set.erase will fail later.
  parser->connectionsList_->Push(parser);
  parser->connectionsList_->PushActive(parser);
  } else {
@@ -1122,6 +1112,8 @@ class Parser : public AsyncWrap, public StreamListener {
 uint64_t max_http_header_size_;
 uint64_t last_message_start_;
  ConnectionsList* connectionsList_;
+ ParserListNode all_node_;
+ ParserListNode active_node_;
 
  BaseObjectPtr<BindingData> binding_data_;
 
@@ -1149,18 +1141,34 @@ class Parser : public AsyncWrap, public StreamListener {
 staticconstllhttp_settings_t settings;
 };
 
-boolParserComparator::operator()(const Parser* lhs, const Parser* rhs) const {
-if (lhs->last_message_start_ == 0 && rhs->last_message_start_ == 0) {
-// When both parsers are idle, guarantee strict order by
-// comparing pointers as ints.
-return lhs < rhs;
- } elseif (lhs->last_message_start_ == 0) {
-returntrue;
- } elseif (rhs->last_message_start_ == 0) {
-returnfalse;
- }
+namespace {
+
+// Append `node` at the tail of the list headed by `head`, unlinking it from
+// any list it is currently in.
+voidListPushBack(ParserListNode* head, ParserListNode* node) {
+ node->Remove();
+ node->prev = head->prev;
+ node->next = head;
+ head->prev->next = node;
+ head->prev = node;
+}
+
+} // anonymous namespace
 
-return lhs->last_message_start_ < rhs->last_message_start_;
+voidConnectionsList::Push(Parser* parser) {
+ListPushBack(&all_connections_, &parser->all_node_);
+}
+
+voidConnectionsList::Pop(Parser* parser) {
+ parser->all_node_.Remove();
+}
+
+voidConnectionsList::PushActive(Parser* parser) {
+ListPushBack(&active_connections_, &parser->active_node_);
+}
+
+voidConnectionsList::PopActive(Parser* parser) {
+ parser->active_node_.Remove();
 }
 
 voidConnectionsList::New(const FunctionCallbackInfo<Value>& args) {
@@ -1178,8 +1186,10 @@ void ConnectionsList::All(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1195,8 +1205,10 @@ void ConnectionsList::Idle(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
 if (parser->last_message_start_ == 0 || !parser->received_data_) {
  result.emplace_back(parser->object());
  }
@@ -1214,8 +1226,10 @@ void ConnectionsList::Active(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->active_connections_.size());
-for (auto parser : list->active_connections_) {
+for (ParserListNode* node = list->active_connections_.next;
+ node != &list->active_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1259,14 +1273,11 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
 return args.GetReturnValue().Set(Array::New(isolate, 0));
  }
 
-auto iter = list->active_connections_.begin();
-auto end = list->active_connections_.end();
-
  LocalVector<Value> result(isolate);
-result.reserve(list->active_connections_.size());
-while (iter != end) {
- Parser* parser = *iter;
-iter++;
+ParserListNode* node = list->active_connections_.next;
+while (node != &list->active_connections_) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
+node = node->next;
 
 // Check for expiration.
 if (
@@ -1278,7 +1289,7 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
  ) {
  result.emplace_back(parser->object());
 
-list->active_connections_.erase(parser);
+parser->active_node_.Remove();
  }
  }
 

src/node_http_parser.cc

@@ -246,55 +246,63 @@ struct StringPtr {
 size_t size_ = 0;
 };
 
-structParserComparator {
-booloperator()(const Parser* lhs, const Parser* rhs) const;
+// Intrusive doubly-linked list node, linked to itself when not in a list.
+structParserListNode {
+ ParserListNode* prev = this;
+ ParserListNode* next = this;
+
+ParserListNode() = default;
+~ParserListNode() { Remove(); }
+
+ParserListNode(const ParserListNode&) = delete;
+ ParserListNode& operator=(const ParserListNode&) = delete;
+
+voidRemove() {
+ prev->next = next;
+ next->prev = prev;
+ prev = this;
+ next = this;
+ }
 };
 
 classConnectionsList : publicBaseObject {
 public:
-staticvoidNew(const FunctionCallbackInfo<Value>& args);
+staticvoidNew(const FunctionCallbackInfo<Value>& args);
 
-staticvoidAll(const FunctionCallbackInfo<Value>& args);
+staticvoidAll(const FunctionCallbackInfo<Value>& args);
 
-staticvoidIdle(const FunctionCallbackInfo<Value>& args);
+staticvoidIdle(const FunctionCallbackInfo<Value>& args);
 
-staticvoidActive(const FunctionCallbackInfo<Value>& args);
+staticvoidActive(const FunctionCallbackInfo<Value>& args);
 
-staticvoidExpired(const FunctionCallbackInfo<Value>& args);
+staticvoidExpired(const FunctionCallbackInfo<Value>& args);
 
-voidPush(Parser* parser) {
- all_connections_.insert(parser);
- }
+inlinevoidPush(Parser* parser);
 
-voidPop(Parser* parser) {
- all_connections_.erase(parser);
- }
+inlinevoidPop(Parser* parser);
 
-voidPushActive(Parser* parser) {
- active_connections_.insert(parser);
- }
+inlinevoidPushActive(Parser* parser);
 
-voidPopActive(Parser* parser) {
- active_connections_.erase(parser);
- }
+inlinevoidPopActive(Parser* parser);
 
-SET_NO_MEMORY_INFO()
-SET_MEMORY_INFO_NAME(ConnectionsList)
-SET_SELF_SIZE(ConnectionsList)
+SET_NO_MEMORY_INFO()
+SET_MEMORY_INFO_NAME(ConnectionsList)
+SET_SELF_SIZE(ConnectionsList)
 
 private:
-ConnectionsList(Environment* env, Local<Object> object)
+ConnectionsList(Environment* env, Local<Object> object)
  : BaseObject(env, object) {
-MakeWeak();
-}
+MakeWeak();
+ }
 
- std::set<Parser*, ParserComparator> all_connections_;
- std::set<Parser*, ParserComparator> active_connections_;
+// active_connections_ is ordered by last_message_start_, as parsers are
+// appended right after it is assigned from the monotonic uv_hrtime().
+ ParserListNode all_connections_;
+ ParserListNode active_connections_;
 };
 
 classParser : publicAsyncWrap, publicStreamListener {
 friendclassConnectionsList;
-friendstructParserComparator;
 
 public:
 Parser(BindingData* binding_data, Local<Object> wrap)
@@ -308,13 +316,6 @@ class Parser : public AsyncWrap, public StreamListener {
  SET_SELF_SIZE(Parser)
 
  int on_message_begin() {
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
-if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
- connectionsList_->PopActive(this);
- }
-
  num_fields_ = num_values_ = 0;
  headers_completed_ = false;
  chunk_extensions_nread_ = 0;
@@ -326,7 +327,6 @@ class Parser : public AsyncWrap, public StreamListener {
  max_header_pairs_ = -1;
 
 if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
  connectionsList_->PushActive(this);
  }
 
@@ -345,7 +345,6 @@ class Parser : public AsyncWrap, public StreamListener {
 return0;
  }
 
-
 inton_url(constchar* at, size_t length) {
 int rv = TrackHeader(length);
 if (rv != 0) {
@@ -544,19 +543,12 @@ class Parser : public AsyncWrap, public StreamListener {
 inton_message_complete() {
  HandleScope scope(env()->isolate());
 
-// Important: Pop from the lists BEFORE resetting the last_message_start_
-// otherwise std::set.erase will fail.
 if (connectionsList_ != nullptr) {
- connectionsList_->Pop(this);
  connectionsList_->PopActive(this);
  }
 
  last_message_start_ = 0;
 
-if (connectionsList_ != nullptr) {
- connectionsList_->Push(this);
- }
-
 if (num_fields_)
 Flush(); // Flush trailing HTTP headers.
 
@@ -742,8 +734,6 @@ class Parser : public AsyncWrap, public StreamListener {
 // server.timeout is left to the default value of zero.
  parser->last_message_start_ = uv_hrtime();
 
-// Important: Push into the lists AFTER setting the last_message_start_
-// otherwise std::set.erase will fail later.
  parser->connectionsList_->Push(parser);
  parser->connectionsList_->PushActive(parser);
  } else {
@@ -1122,6 +1112,8 @@ class Parser : public AsyncWrap, public StreamListener {
 uint64_t max_http_header_size_;
 uint64_t last_message_start_;
  ConnectionsList* connectionsList_;
+ ParserListNode all_node_;
+ ParserListNode active_node_;
 
  BaseObjectPtr<BindingData> binding_data_;
 
@@ -1149,18 +1141,34 @@ class Parser : public AsyncWrap, public StreamListener {
 staticconstllhttp_settings_t settings;
 };
 
-boolParserComparator::operator()(const Parser* lhs, const Parser* rhs) const {
-if (lhs->last_message_start_ == 0 && rhs->last_message_start_ == 0) {
-// When both parsers are idle, guarantee strict order by
-// comparing pointers as ints.
-return lhs < rhs;
- } elseif (lhs->last_message_start_ == 0) {
-returntrue;
- } elseif (rhs->last_message_start_ == 0) {
-returnfalse;
- }
+namespace {
+
+// Append `node` at the tail of the list headed by `head`, unlinking it from
+// any list it is currently in.
+voidListPushBack(ParserListNode* head, ParserListNode* node) {
+ node->Remove();
+ node->prev = head->prev;
+ node->next = head;
+ head->prev->next = node;
+ head->prev = node;
+}
+
+} // anonymous namespace
 
-return lhs->last_message_start_ < rhs->last_message_start_;
+voidConnectionsList::Push(Parser* parser) {
+ListPushBack(&all_connections_, &parser->all_node_);
+}
+
+voidConnectionsList::Pop(Parser* parser) {
+ parser->all_node_.Remove();
+}
+
+voidConnectionsList::PushActive(Parser* parser) {
+ListPushBack(&active_connections_, &parser->active_node_);
+}
+
+voidConnectionsList::PopActive(Parser* parser) {
+ parser->active_node_.Remove();
 }
 
 voidConnectionsList::New(const FunctionCallbackInfo<Value>& args) {
@@ -1178,8 +1186,10 @@ void ConnectionsList::All(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1195,8 +1205,10 @@ void ConnectionsList::Idle(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->all_connections_.size());
-for (auto parser : list->all_connections_) {
+for (ParserListNode* node = list->all_connections_.next;
+ node != &list->all_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::all_node_, node);
 if (parser->last_message_start_ == 0 || !parser->received_data_) {
  result.emplace_back(parser->object());
  }
@@ -1214,8 +1226,10 @@ void ConnectionsList::Active(const FunctionCallbackInfo<Value>& args) {
 ASSIGN_OR_RETURN_UNWRAP(&list, args.This());
 
  LocalVector<Value> result(isolate);
- result.reserve(list->active_connections_.size());
-for (auto parser : list->active_connections_) {
+for (ParserListNode* node = list->active_connections_.next;
+ node != &list->active_connections_;
+ node = node->next) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
  result.emplace_back(parser->object());
  }
 
@@ -1259,14 +1273,11 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
 return args.GetReturnValue().Set(Array::New(isolate, 0));
  }
 
-auto iter = list->active_connections_.begin();
-auto end = list->active_connections_.end();
-
  LocalVector<Value> result(isolate);
-result.reserve(list->active_connections_.size());
-while (iter != end) {
- Parser* parser = *iter;
-iter++;
+ParserListNode* node = list->active_connections_.next;
+while (node != &list->active_connections_) {
+ Parser* parser = ContainerOf(&Parser::active_node_, node);
+node = node->next;
 
 // Check for expiration.
 if (
@@ -1278,7 +1289,7 @@ void ConnectionsList::Expired(const FunctionCallbackInfo<Value>& args) {
  ) {
  result.emplace_back(parser->object());
 
-list->active_connections_.erase(parser);
+parser->active_node_.Remove();
  }
  }