net,src: refactor writeQueueSize tracking

Currently, writeQueueSize is never used in C++ and barely used
within JS. Instead of constantly updating the value on the JS
object, create a getter that will retrieve the most up-to-date
value from C++.

For the vast majority of cases though, create a new prop on
Socket.prototype[kLastWriteQueueSize] using a Symbol. Use this
to track the current write size, entirely in JS land.

PR-URL: nodejs/node#17650
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/_tls_wrap.js

@@ -460,11 +460,6 @@ TLSSocket.prototype._init = function(socket, wrap) {
   var options = this._tlsOptions;
   var ssl = this._handle;
 
-  // lib/net.js expect this value to be non-zero if write hasn't been flushed
-  // immediately. After the handshake is done this will represent the actual
-  // write queue size
-  ssl.writeQueueSize = 1;
-
   this.server = options.server;
 
   // For clients, we will always have either a given ca list or be using

lib/net.js

@@ -48,6 +48,8 @@ const { nextTick } = require('internal/process/next_tick');
 const errors = require('internal/errors');
 const dns = require('dns');
 
+const kLastWriteQueueSize = Symbol('lastWriteQueueSize');
+
 // `cluster` is only used by `listenInCluster` so for startup performance
 // reasons it's lazy loaded.
 var cluster = null;
@@ -198,6 +200,7 @@ function Socket(options) {
   this._handle = null;
   this._parent = null;
   this._host = null;
+  this[kLastWriteQueueSize] = 0;
 
   if (typeof options === 'number')
     options = { fd: options }; // Legacy interface.
@@ -398,12 +401,14 @@ Socket.prototype.setTimeout = function(msecs, callback) {
 
 
 Socket.prototype._onTimeout = function() {
-  if (this._handle) {
-    // `.prevWriteQueueSize` !== `.updateWriteQueueSize()` means there is
+  const handle = this._handle;
+  const lastWriteQueueSize = this[kLastWriteQueueSize];
+  if (lastWriteQueueSize > 0 && handle) {
+    // `lastWriteQueueSize !== writeQueueSize` means there is
     // an active write in progress, so we suppress the timeout.
-    const prevWriteQueueSize = this._handle.writeQueueSize;
-    if (prevWriteQueueSize > 0 &&
-        prevWriteQueueSize !== this._handle.updateWriteQueueSize()) {
+    const writeQueueSize = handle.writeQueueSize;
+    if (lastWriteQueueSize !== writeQueueSize) {
+      this[kLastWriteQueueSize] = writeQueueSize;
       this._unrefTimer();
       return;
     }
@@ -473,7 +478,7 @@ Object.defineProperty(Socket.prototype, 'readyState', {
 Object.defineProperty(Socket.prototype, 'bufferSize', {
   get: function() {
     if (this._handle) {
-      return this._handle.writeQueueSize + this.writableLength;
+      return this[kLastWriteQueueSize] + this.writableLength;
     }
   }
 });
@@ -764,12 +769,13 @@ Socket.prototype._writeGeneric = function(writev, data, encoding, cb) {
 
   this._bytesDispatched += req.bytes;
 
-  // If it was entirely flushed, we can write some more right now.
-  // However, if more is left in the queue, then wait until that clears.
-  if (req.async && this._handle.writeQueueSize !== 0)
-    req.cb = cb;
-  else
+  if (!req.async) {
     cb();
+    return;
+  }
+
+  req.cb = cb;
+  this[kLastWriteQueueSize] = req.bytes;
 };
 
 
@@ -853,6 +859,9 @@ function afterWrite(status, handle, req, err) {
   if (self !== process.stderr && self !== process.stdout)
     debug('afterWrite', status);
 
+  if (req.async)
+    self[kLastWriteQueueSize] = 0;
+
   // callback may come after call to destroy.
   if (self.destroyed) {
     debug('afterWrite destroyed');
@@ -872,7 +881,7 @@ function afterWrite(status, handle, req, err) {
     debug('afterWrite call cb');
 
   if (req.cb)
-    req.cb.call(self);
+    req.cb.call(undefined);
 }
 
 

src/pipe_wrap.cc

@@ -165,7 +165,6 @@ PipeWrap::PipeWrap(Environment* env,
   int r = uv_pipe_init(env->event_loop(), &handle_, ipc);
   CHECK_EQ(r, 0);  // How do we proxy this error up to javascript?
                    // Suggestion: uv_pipe_init() returns void.
-  UpdateWriteQueueSize();
 }
 
 

src/stream_base.cc

@@ -193,7 +193,8 @@ int StreamBase::Writev(const FunctionCallbackInfo<Value>& args) {
   }
 
   err = DoWrite(req_wrap, buf_list, count, nullptr);
-  req_wrap_obj->Set(env->async(), True(env->isolate()));
+  if (HasWriteQueue())
+    req_wrap_obj->Set(env->async(), True(env->isolate()));
 
   if (err)
     req_wrap->Dispose();
@@ -249,7 +250,8 @@ int StreamBase::WriteBuffer(const FunctionCallbackInfo<Value>& args) {
   req_wrap = WriteWrap::New(env, req_wrap_obj, this);
 
   err = DoWrite(req_wrap, bufs, count, nullptr);
-  req_wrap_obj->Set(env->async(), True(env->isolate()));
+  if (HasWriteQueue())
+    req_wrap_obj->Set(env->async(), True(env->isolate()));
   req_wrap_obj->Set(env->buffer_string(), args[1]);
 
   if (err)
@@ -373,7 +375,8 @@ int StreamBase::WriteString(const FunctionCallbackInfo<Value>& args) {
         reinterpret_cast<uv_stream_t*>(send_handle));
   }
 
-  req_wrap_obj->Set(env->async(), True(env->isolate()));
+  if (HasWriteQueue())
+    req_wrap_obj->Set(env->async(), True(env->isolate()));
 
   if (err)
     req_wrap->Dispose();
@@ -467,6 +470,10 @@ int StreamResource::DoTryWrite(uv_buf_t** bufs, size_t* count) {
   return 0;
 }
 
+bool StreamResource::HasWriteQueue() {
+  return true;
+}
+
 
 const char* StreamResource::Error() const {
   return nullptr;

src/stream_base.h

@@ -162,6 +162,7 @@ class StreamResource {
                       uv_buf_t* bufs,
                       size_t count,
                       uv_stream_t* send_handle) = 0;
+  virtual bool HasWriteQueue();
   virtual const char* Error() const;
   virtual void ClearError();
 

src/stream_wrap.cc

@@ -40,13 +40,15 @@
 namespace node {
 
 using v8::Context;
+using v8::DontDelete;
 using v8::EscapableHandleScope;
 using v8::FunctionCallbackInfo;
 using v8::FunctionTemplate;
 using v8::HandleScope;
-using v8::Integer;
 using v8::Local;
 using v8::Object;
+using v8::ReadOnly;
+using v8::Signature;
 using v8::Value;
 
 
@@ -99,7 +101,16 @@ LibuvStreamWrap::LibuvStreamWrap(Environment* env,
 void LibuvStreamWrap::AddMethods(Environment* env,
                                  v8::Local<v8::FunctionTemplate> target,
                                  int flags) {
-  env->SetProtoMethod(target, "updateWriteQueueSize", UpdateWriteQueueSize);
+  Local<FunctionTemplate> get_write_queue_size =
+      FunctionTemplate::New(env->isolate(),
+                            GetWriteQueueSize,
+                            env->as_external(),
+                            Signature::New(env->isolate(), target));
+  target->PrototypeTemplate()->SetAccessorProperty(
+      env->write_queue_size_string(),
+      get_write_queue_size,
+      Local<FunctionTemplate>(),
+      static_cast<PropertyAttribute>(ReadOnly | DontDelete));
   env->SetProtoMethod(target, "setBlocking", SetBlocking);
   StreamBase::AddMethods<LibuvStreamWrap>(env, target, flags);
 }
@@ -135,17 +146,6 @@ bool LibuvStreamWrap::IsIPCPipe() {
 }
 
 
-uint32_t LibuvStreamWrap::UpdateWriteQueueSize() {
-  HandleScope scope(env()->isolate());
-  uint32_t write_queue_size = stream()->write_queue_size;
-  object()->Set(env()->context(),
-                env()->write_queue_size_string(),
-                Integer::NewFromUnsigned(env()->isolate(),
-                                         write_queue_size)).FromJust();
-  return write_queue_size;
-}
-
-
 int LibuvStreamWrap::ReadStart() {
   return uv_read_start(stream(), OnAlloc, OnRead);
 }
@@ -267,13 +267,18 @@ void LibuvStreamWrap::OnRead(uv_stream_t* handle,
 }
 
 
-void LibuvStreamWrap::UpdateWriteQueueSize(
-    const FunctionCallbackInfo<Value>& args) {
+void LibuvStreamWrap::GetWriteQueueSize(
+    const FunctionCallbackInfo<Value>& info) {
   LibuvStreamWrap* wrap;
-  ASSIGN_OR_RETURN_UNWRAP(&wrap, args.Holder());
+  ASSIGN_OR_RETURN_UNWRAP(&wrap, info.This());
+
+  if (wrap->stream() == nullptr) {
+    info.GetReturnValue().Set(0);
+    return;
+  }
 
-  uint32_t write_queue_size = wrap->UpdateWriteQueueSize();
-  args.GetReturnValue().Set(write_queue_size);
+  uint32_t write_queue_size = wrap->stream()->write_queue_size;
+  info.GetReturnValue().Set(write_queue_size);
 }
 
 
@@ -370,12 +375,16 @@ int LibuvStreamWrap::DoWrite(WriteWrap* w,
   }
 
   w->Dispatched();
-  UpdateWriteQueueSize();
 
   return r;
 }
 
 
+bool LibuvStreamWrap::HasWriteQueue() {
+  return stream()->write_queue_size > 0;
+}
+
+
 void LibuvStreamWrap::AfterUvWrite(uv_write_t* req, int status) {
   WriteWrap* req_wrap = WriteWrap::from_req(req);
   CHECK_NE(req_wrap, nullptr);
@@ -387,7 +396,6 @@ void LibuvStreamWrap::AfterUvWrite(uv_write_t* req, int status) {
 
 void LibuvStreamWrap::AfterWrite(WriteWrap* w, int status) {
   StreamBase::AfterWrite(w, status);
-  UpdateWriteQueueSize();
 }
 
 }  // namespace node

src/stream_wrap.h

@@ -55,6 +55,7 @@ class LibuvStreamWrap : public HandleWrap, public StreamBase {
               uv_buf_t* bufs,
               size_t count,
               uv_stream_t* send_handle) override;
+  bool HasWriteQueue() override;
 
   inline uv_stream_t* stream() const {
     return stream_;
@@ -83,15 +84,14 @@ class LibuvStreamWrap : public HandleWrap, public StreamBase {
   }
 
   AsyncWrap* GetAsyncWrap() override;
-  uint32_t UpdateWriteQueueSize();
 
   static void AddMethods(Environment* env,
                          v8::Local<v8::FunctionTemplate> target,
                          int flags = StreamBase::kFlagNone);
 
  private:
-  static void UpdateWriteQueueSize(
-      const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void GetWriteQueueSize(
+      const v8::FunctionCallbackInfo<v8::Value>& info);
   static void SetBlocking(const v8::FunctionCallbackInfo<v8::Value>& args);
 
   // Callbacks for libuv

src/tcp_wrap.cc

@@ -169,7 +169,6 @@ TCPWrap::TCPWrap(Environment* env, Local<Object> object, ProviderType provider)
   int r = uv_tcp_init(env->event_loop(), &handle_);
   CHECK_EQ(r, 0);  // How do we proxy this error up to javascript?
                    // Suggestion: uv_tcp_init() returns void.
-  UpdateWriteQueueSize();
 }
 
 

src/tls_wrap.cc

@@ -35,14 +35,16 @@ namespace node {
 using crypto::SecureContext;
 using crypto::SSLWrap;
 using v8::Context;
+using v8::DontDelete;
 using v8::EscapableHandleScope;
 using v8::Exception;
 using v8::Function;
 using v8::FunctionCallbackInfo;
 using v8::FunctionTemplate;
-using v8::Integer;
 using v8::Local;
 using v8::Object;
+using v8::ReadOnly;
+using v8::Signature;
 using v8::String;
 using v8::Value;
 
@@ -309,7 +311,6 @@ void TLSWrap::EncOut() {
 
   // No data to write
   if (BIO_pending(enc_out_) == 0) {
-    UpdateWriteQueueSize();
     if (clear_in_->Length() == 0)
       InvokeQueued(0);
     return;
@@ -555,17 +556,6 @@ bool TLSWrap::IsClosing() {
 }
 
 
-uint32_t TLSWrap::UpdateWriteQueueSize(uint32_t write_queue_size) {
-  HandleScope scope(env()->isolate());
-  if (write_queue_size == 0)
-    write_queue_size = BIO_pending(enc_out_);
-  object()->Set(env()->context(),
-                env()->write_queue_size_string(),
-                Integer::NewFromUnsigned(env()->isolate(),
-                                         write_queue_size)).FromJust();
-  return write_queue_size;
-}
-
 
 int TLSWrap::ReadStart() {
   if (stream_ != nullptr)
@@ -612,9 +602,6 @@ int TLSWrap::DoWrite(WriteWrap* w,
     // However, if there is any data that should be written to the socket,
     // the callback should not be invoked immediately
     if (BIO_pending(enc_out_) == 0) {
-      // net.js expects writeQueueSize to be > 0 if the write isn't
-      // immediately flushed
-      UpdateWriteQueueSize(1);
       return stream_->DoWrite(w, bufs, count, send_handle);
     }
   }
@@ -666,7 +653,6 @@ int TLSWrap::DoWrite(WriteWrap* w,
 
   // Try writing data immediately
   EncOut();
-  UpdateWriteQueueSize();
 
   return 0;
 }
@@ -938,12 +924,17 @@ int TLSWrap::SelectSNIContextCallback(SSL* s, int* ad, void* arg) {
 #endif  // SSL_CTRL_SET_TLSEXT_SERVERNAME_CB
 
 
-void TLSWrap::UpdateWriteQueueSize(const FunctionCallbackInfo<Value>& args) {
+void TLSWrap::GetWriteQueueSize(const FunctionCallbackInfo<Value>& info) {
   TLSWrap* wrap;
-  ASSIGN_OR_RETURN_UNWRAP(&wrap, args.Holder());
+  ASSIGN_OR_RETURN_UNWRAP(&wrap, info.This());
 
-  uint32_t write_queue_size = wrap->UpdateWriteQueueSize();
-  args.GetReturnValue().Set(write_queue_size);
+  if (wrap->clear_in_ == nullptr) {
+    info.GetReturnValue().Set(0);
+    return;
+  }
+
+  uint32_t write_queue_size = BIO_pending(wrap->enc_out_);
+  info.GetReturnValue().Set(write_queue_size);
 }
 
 
@@ -966,14 +957,24 @@ void TLSWrap::Initialize(Local<Object> target,
   t->InstanceTemplate()->SetInternalFieldCount(1);
   t->SetClassName(tlsWrapString);
 
+  Local<FunctionTemplate> get_write_queue_size =
+      FunctionTemplate::New(env->isolate(),
+                            GetWriteQueueSize,
+                            env->as_external(),
+                            Signature::New(env->isolate(), t));
+  t->PrototypeTemplate()->SetAccessorProperty(
+      env->write_queue_size_string(),
+      get_write_queue_size,
+      Local<FunctionTemplate>(),
+      static_cast<PropertyAttribute>(ReadOnly | DontDelete));
+
   AsyncWrap::AddWrapMethods(env, t, AsyncWrap::kFlagHasReset);
   env->SetProtoMethod(t, "receive", Receive);
   env->SetProtoMethod(t, "start", Start);
   env->SetProtoMethod(t, "setVerifyMode", SetVerifyMode);
   env->SetProtoMethod(t, "enableSessionCallbacks", EnableSessionCallbacks);
   env->SetProtoMethod(t, "destroySSL", DestroySSL);
   env->SetProtoMethod(t, "enableCertCb", EnableCertCb);
-  env->SetProtoMethod(t, "updateWriteQueueSize", UpdateWriteQueueSize);
 
   StreamBase::AddMethods<TLSWrap>(env, t, StreamBase::kFlagHasWritev);
   SSLWrap<TLSWrap>::AddMethods(env, t);