net: track bytesWritten in C++ land

Move tracking of `socket.bytesWritten` to C++ land.

This makes it easier to provide this functionality for all
`StreamBase` instances, and in particular should keep working
when they have been 'consumed' in C++ in some way (e.g. for
the network sockets that are underlying to TLS or HTTP2 streams).

Also, this parallels `socket.bytesRead` a lot more now.

PR-URL: https://github.com/nodejs/node/pull/19551
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/net.js

@@ -32,7 +32,7 @@ function makeSyncWrite(fd) {
     if (enc !== 'buffer')
       chunk = Buffer.from(chunk, enc);
 
-    this._bytesDispatched += chunk.length;
+    this._handle.bytesWritten += chunk.length;
 
     const ctx = {};
     writeBuffer(fd, chunk, 0, chunk.length, null, undefined, ctx);

lib/net.js

@@ -206,7 +206,6 @@ function normalizeArgs(args) {
 // called when creating new Socket, or when re-using a closed Socket
 function initSocketHandle(self) {
   self._undestroy();
-  self._bytesDispatched = 0;
   self._sockname = null;
 
   // Handle creation may be deferred to bind() or connect() time.
@@ -222,7 +221,8 @@ function initSocketHandle(self) {
 }
 
 
-const BYTES_READ = Symbol('bytesRead');
+const kBytesRead = Symbol('kBytesRead');
+const kBytesWritten = Symbol('kBytesWritten');
 
 
 function Socket(options) {
@@ -278,6 +278,11 @@ function Socket(options) {
 
       this._writev = null;
       this._write = makeSyncWrite(fd);
+      // makeSyncWrite adjusts this value like the original handle would, so
+      // we need to let it do that by turning it into a writable, own property.
+      Object.defineProperty(this._handle, 'bytesWritten', {
+        value: 0, writable: true
+      });
     }
   } else {
     // these will be set once there is a connection
@@ -316,7 +321,8 @@ function Socket(options) {
   this._server = null;
 
   // Used after `.destroy()`
-  this[BYTES_READ] = 0;
+  this[kBytesRead] = 0;
+  this[kBytesWritten] = 0;
 }
 util.inherits(Socket, stream.Duplex);
 
@@ -588,8 +594,9 @@ Socket.prototype._destroy = function(exception, cb) {
     if (this !== process.stderr)
       debug('close handle');
     var isException = exception ? true : false;
-    // `bytesRead` should be accessible after `.destroy()`
-    this[BYTES_READ] = this._handle.bytesRead;
+    // `bytesRead` and `kBytesWritten` should be accessible after `.destroy()`
+    this[kBytesRead] = this._handle.bytesRead;
+    this[kBytesWritten] = this._handle.bytesWritten;
 
     this._handle.close(() => {
       debug('emit close');
@@ -689,7 +696,7 @@ function protoGetter(name, callback) {
 }
 
 protoGetter('bytesRead', function bytesRead() {
-  return this._handle ? this._handle.bytesRead : this[BYTES_READ];
+  return this._handle ? this._handle.bytesRead : this[kBytesRead];
 });
 
 protoGetter('remoteAddress', function remoteAddress() {
@@ -761,8 +768,6 @@ Socket.prototype._writeGeneric = function(writev, data, encoding, cb) {
   // Bail out if handle.write* returned an error
   if (ret) return ret;
 
-  this._bytesDispatched += req.bytes;
-
   if (!req.async) {
     cb();
     return;
@@ -782,6 +787,13 @@ Socket.prototype._write = function(data, encoding, cb) {
   this._writeGeneric(false, data, encoding, cb);
 };
 
+
+// Legacy alias. Having this is probably being overly cautious, but it doesn't
+// really hurt anyone either. This can probably be removed safely if desired.
+protoGetter('_bytesDispatched', function _bytesDispatched() {
+  return this._handle ? this._handle.bytesWritten : this[kBytesWritten];
+});
+
 protoGetter('bytesWritten', function bytesWritten() {
   var bytes = this._bytesDispatched;
   const state = this._writableState;

src/env.h

@@ -117,6 +117,7 @@ struct PackageConfig {
   V(bytes_string, "bytes")                                                    \
   V(bytes_parsed_string, "bytesParsed")                                       \
   V(bytes_read_string, "bytesRead")                                           \
+  V(bytes_written_string, "bytesWritten")                                     \
   V(cached_data_string, "cachedData")                                         \
   V(cached_data_produced_string, "cachedDataProduced")                        \
   V(cached_data_rejected_string, "cachedDataRejected")                        \

src/stream_base-inl.h

@@ -193,6 +193,10 @@ inline StreamWriteResult StreamBase::Write(
     v8::Local<v8::Object> req_wrap_obj) {
   Environment* env = stream_env();
   int err;
+
+  for (size_t i = 0; i < count; ++i)
+    bytes_written_ += bufs[i].len;
+
   if (send_handle == nullptr) {
     err = DoTryWrite(&bufs, &count);
     if (err != 0 || count == 0) {
@@ -301,6 +305,12 @@ void StreamBase::AddMethods(Environment* env,
                             env->as_external(),
                             signature);
 
+  Local<FunctionTemplate> get_bytes_written_templ =
+      FunctionTemplate::New(env->isolate(),
+                            GetBytesWritten<Base>,
+                            env->as_external(),
+                            signature);
+
   t->PrototypeTemplate()->SetAccessorProperty(env->fd_string(),
                                               get_fd_templ,
                                               Local<FunctionTemplate>(),
@@ -316,6 +326,11 @@ void StreamBase::AddMethods(Environment* env,
                                               Local<FunctionTemplate>(),
                                               attributes);
 
+  t->PrototypeTemplate()->SetAccessorProperty(env->bytes_written_string(),
+                                              get_bytes_written_templ,
+                                              Local<FunctionTemplate>(),
+                                              attributes);
+
   env->SetProtoMethod(t, "readStart", JSMethod<Base, &StreamBase::ReadStartJS>);
   env->SetProtoMethod(t, "readStop", JSMethod<Base, &StreamBase::ReadStopJS>);
   if ((flags & kFlagNoShutdown) == 0)
@@ -357,7 +372,6 @@ void StreamBase::GetFD(const FunctionCallbackInfo<Value>& args) {
 
 template <class Base>
 void StreamBase::GetBytesRead(const FunctionCallbackInfo<Value>& args) {
-  // The handle instance hasn't been set. So no bytes could have been read.
   Base* handle;
   ASSIGN_OR_RETURN_UNWRAP(&handle,
                           args.This(),
@@ -368,6 +382,18 @@ void StreamBase::GetBytesRead(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(static_cast<double>(wrap->bytes_read_));
 }
 
+template <class Base>
+void StreamBase::GetBytesWritten(const FunctionCallbackInfo<Value>& args) {
+  Base* handle;
+  ASSIGN_OR_RETURN_UNWRAP(&handle,
+                          args.This(),
+                          args.GetReturnValue().Set(0));
+
+  StreamBase* wrap = static_cast<StreamBase*>(handle);
+  // uint64_t -> double. 53bits is enough for all real cases.
+  args.GetReturnValue().Set(static_cast<double>(wrap->bytes_written_));
+}
+
 template <class Base>
 void StreamBase::GetExternal(const FunctionCallbackInfo<Value>& args) {
   Base* handle;

src/stream_base.cc

@@ -243,6 +243,7 @@ int StreamBase::WriteString(const FunctionCallbackInfo<Value>& args) {
     uv_buf_t* bufs = &buf;
     size_t count = 1;
     err = DoTryWrite(&bufs, &count);
+    bytes_written_ += data_size;
 
     // Immediate failure or success
     if (err != 0 || count == 0) {

src/stream_base.h

@@ -247,6 +247,7 @@ class StreamResource {
 
   StreamListener* listener_ = nullptr;
   uint64_t bytes_read_ = 0;
+  uint64_t bytes_written_ = 0;
 
   friend class StreamListener;
 };
@@ -324,6 +325,9 @@ class StreamBase : public StreamResource {
   template <class Base>
   static void GetBytesRead(const v8::FunctionCallbackInfo<v8::Value>& args);
 
+  template <class Base>
+  static void GetBytesWritten(const v8::FunctionCallbackInfo<v8::Value>& args);
+
   template <class Base,
             int (StreamBase::*Method)(
       const v8::FunctionCallbackInfo<v8::Value>& args)>