worker: improve MessagePort performance

lib/internal/per_context/messageport.js

@@ -0,0 +1,12 @@
+'use strict';
+class MessageEvent {
+  constructor(data, target) {
+    this.data = data;
+    this.target = target;
+  }
+}
+
+exports.emitMessage = function(data) {
+  if (typeof this.onmessage === 'function')
+    this.onmessage(new MessageEvent(data, this));
+};

node.gyp

@@ -37,6 +37,7 @@
       'lib/internal/bootstrap/switches/is_not_main_thread.js',
       'lib/internal/per_context/primordials.js',
       'lib/internal/per_context/domexception.js',
+      'lib/internal/per_context/messageport.js',
       'lib/async_hooks.js',
       'lib/assert.js',
       'lib/buffer.js',

src/api/environment.cc

@@ -482,6 +482,7 @@ bool InitializeContextForSnapshot(Local<Context> context) {
 
     static const char* context_files[] = {"internal/per_context/primordials",
                                           "internal/per_context/domexception",
+                                          "internal/per_context/messageport",
                                           nullptr};
 
     for (const char** module = context_files; *module != nullptr; module++) {

src/env.h

@@ -403,7 +403,6 @@ constexpr size_t kFsStatsBufferLength =
   V(http2stream_constructor_template, v8::ObjectTemplate)                      \
   V(http2ping_constructor_template, v8::ObjectTemplate)                        \
   V(libuv_stream_wrap_ctor_template, v8::FunctionTemplate)                     \
-  V(message_event_object_template, v8::ObjectTemplate)                         \
   V(message_port_constructor_template, v8::FunctionTemplate)                   \
   V(pipe_constructor_template, v8::FunctionTemplate)                           \
   V(promise_wrap_template, v8::ObjectTemplate)                                 \

src/node_messaging.cc

@@ -170,6 +170,20 @@ uint32_t Message::AddWASMModule(CompiledWasmModule&& mod) {
 
 namespace {
 
+MaybeLocal<Function> GetEmitMessageFunction(Local<Context> context) {
+  Isolate* isolate = context->GetIsolate();
+  Local<Object> per_context_bindings;
+  Local<Value> emit_message_val;
+  if (!GetPerContextExports(context).ToLocal(&per_context_bindings) ||
+      !per_context_bindings->Get(context,
+                                FIXED_ONE_BYTE_STRING(isolate, "emitMessage"))
+          .ToLocal(&emit_message_val)) {
+    return MaybeLocal<Function>();
+  }
+  CHECK(emit_message_val->IsFunction());
+  return emit_message_val.As<Function>();
+}
+
 MaybeLocal<Function> GetDOMException(Local<Context> context) {
   Isolate* isolate = context->GetIsolate();
   Local<Object> per_context_bindings;
@@ -471,20 +485,28 @@ MessagePort::MessagePort(Environment* env,
     MessagePort* channel = ContainerOf(&MessagePort::async_, handle);
     channel->OnMessage();
   };
+
   CHECK_EQ(uv_async_init(env->event_loop(),
                          &async_,
                          onmessage), 0);
-  async_.data = static_cast<void*>(this);
+  async_.data = nullptr;  // Reset later to indicate success of the constructor.
 
   Local<Value> fn;
   if (!wrap->Get(context, env->oninit_symbol()).ToLocal(&fn))
     return;
 
   if (fn->IsFunction()) {
     Local<Function> init = fn.As<Function>();
-    USE(init->Call(context, wrap, 0, nullptr));
+    if (init->Call(context, wrap, 0, nullptr).IsEmpty())
+      return;
   }
 
+  Local<Function> emit_message_fn;
+  if (!GetEmitMessageFunction(context).ToLocal(&emit_message_fn))
+    return;
+  emit_message_fn_.Reset(env->isolate(), emit_message_fn);
+
+  async_.data = static_cast<void*>(this);
   Debug(this, "Created message port");
 }
 
@@ -532,6 +554,11 @@ MessagePort* MessagePort::New(
     return nullptr;
   MessagePort* port = new MessagePort(env, context, instance);
   CHECK_NOT_NULL(port);
+  if (port->async_.data == nullptr) {
+    port->Close();
+    return nullptr;
+  }
+
   if (data) {
     port->Detach();
     port->data_ = std::move(data);
@@ -624,16 +651,8 @@ void MessagePort::OnMessage() {
       continue;
     }
 
-    Local<Object> event;
-    Local<Value> cb_args[1];
-    if (!env()->message_event_object_template()->NewInstance(context)
-            .ToLocal(&event) ||
-        event->Set(context, env()->data_string(), payload).IsNothing() ||
-        event->Set(context, env()->target_string(), object()).IsNothing() ||
-        (cb_args[0] = event, false) ||
-        MakeCallback(env()->onmessage_string(),
-                     arraysize(cb_args),
-                     cb_args).IsEmpty()) {
+    Local<Function> emit_message = PersistentToLocal::Strong(emit_message_fn_);
+    if (MakeCallback(emit_message, 1, &payload).IsEmpty()) {
       // Re-schedule OnMessage() execution in case of failure.
       if (data_)
         TriggerAsync();
@@ -902,6 +921,7 @@ void MessagePort::Entangle(MessagePort* a, MessagePortData* b) {
 
 void MessagePort::MemoryInfo(MemoryTracker* tracker) const {
   tracker->TrackField("data", data_);
+  tracker->TrackField("emit_message_fn", emit_message_fn_);
 }
 
 Local<FunctionTemplate> GetMessagePortConstructorTemplate(Environment* env) {
@@ -911,8 +931,6 @@ Local<FunctionTemplate> GetMessagePortConstructorTemplate(Environment* env) {
   if (!templ.IsEmpty())
     return templ;
 
-  Isolate* isolate = env->isolate();
-
   {
     Local<FunctionTemplate> m = env->NewFunctionTemplate(MessagePort::New);
     m->SetClassName(env->message_port_constructor_string());
@@ -923,13 +941,6 @@ Local<FunctionTemplate> GetMessagePortConstructorTemplate(Environment* env) {
     env->SetProtoMethod(m, "start", MessagePort::Start);
 
     env->set_message_port_constructor_template(m);
-
-    Local<FunctionTemplate> event_ctor = FunctionTemplate::New(isolate);
-    event_ctor->SetClassName(FIXED_ONE_BYTE_STRING(isolate, "MessageEvent"));
-    Local<ObjectTemplate> e = event_ctor->InstanceTemplate();
-    e->Set(env->data_string(), Null(isolate));
-    e->Set(env->target_string(), Null(isolate));
-    env->set_message_event_object_template(e);
   }
 
   return GetMessagePortConstructorTemplate(env);
@@ -948,7 +959,13 @@ static void MessageChannel(const FunctionCallbackInfo<Value>& args) {
   Context::Scope context_scope(context);
 
   MessagePort* port1 = MessagePort::New(env, context);
+  if (port1 == nullptr) return;
   MessagePort* port2 = MessagePort::New(env, context);
+  if (port2 == nullptr) {
+    port1->Close();
+    return;
+  }
+
   MessagePort::Entangle(port1, port2);
 
   args.This()->Set(context, env->port1_string(), port1->object())

src/node_messaging.h

@@ -205,6 +205,7 @@ class MessagePort : public HandleWrap {
   std::unique_ptr<MessagePortData> data_ = nullptr;
   bool receiving_messages_ = false;
   uv_async_t async_;
+  v8::Global<v8::Function> emit_message_fn_;
 
   friend class MessagePortData;
 };