http: fix stalled pipeline bug (v3.x backport)

Original commit ab03635:

  This is a two-part fix:

  - Fix pending data notification in `OutgoingMessage` to notify server
    about flushed data too
  - Fix pause/resume behavior for the consumed socket. `resume` event is
    emitted on a next tick, and `socket._paused` can already be `true` at
    this time. Pause the socket again to avoid PAUSED error on parser.

  Fix: nodejs#3332
  PR-URL: nodejs#3342
  Reviewed-By: James M Snell <jasnell@gmail.com>
  Reviewed-By: Trevor Norris <trev.norris@gmail.com>

lib/_http_outgoing.js

@@ -124,7 +124,7 @@ OutgoingMessage.prototype._send = function(data, encoding, callback) {
       this.outputEncodings.unshift('binary');
       this.outputCallbacks.unshift(null);
       this.outputSize += this._header.length;
-      if (this._onPendingData !== null)
+      if (typeof this._onPendingData === 'function')
         this._onPendingData(this._header.length);
     }
     this._headerSent = true;
@@ -147,20 +147,7 @@ OutgoingMessage.prototype._writeRaw = function(data, encoding, callback) {
     // There might be pending data in the this.output buffer.
     var outputLength = this.output.length;
     if (outputLength > 0) {
-      var output = this.output;
-      var outputEncodings = this.outputEncodings;
-      var outputCallbacks = this.outputCallbacks;
-      for (var i = 0; i < outputLength; i++) {
-        connection.write(output[i], outputEncodings[i],
-                         outputCallbacks[i]);
-      }
-
-      this.output = [];
-      this.outputEncodings = [];
-      this.outputCallbacks = [];
-      if (this._onPendingData !== null)
-        this._onPendingData(-this.outputSize);
-      this.outputSize = 0;
+      this._flushOutput(connection);
     } else if (data.length === 0) {
       if (typeof callback === 'function')
         process.nextTick(callback);
@@ -185,7 +172,7 @@ OutgoingMessage.prototype._buffer = function(data, encoding, callback) {
   this.outputEncodings.push(encoding);
   this.outputCallbacks.push(callback);
   this.outputSize += data.length;
-  if (this._onPendingData !== null)
+  if (typeof this._onPendingData === 'function')
     this._onPendingData(data.length);
   return false;
 };
@@ -618,24 +605,11 @@ OutgoingMessage.prototype._finish = function() {
 // to attempt to flush any pending messages out to the socket.
 OutgoingMessage.prototype._flush = function() {
   var socket = this.socket;
-  var outputLength, ret;
+  var ret;
 
   if (socket && socket.writable) {
     // There might be remaining data in this.output; write it out
-    outputLength = this.output.length;
-    if (outputLength > 0) {
-      var output = this.output;
-      var outputEncodings = this.outputEncodings;
-      var outputCallbacks = this.outputCallbacks;
-      for (var i = 0; i < outputLength; i++) {
-        ret = socket.write(output[i], outputEncodings[i],
-                           outputCallbacks[i]);
-      }
-
-      this.output = [];
-      this.outputEncodings = [];
-      this.outputCallbacks = [];
-    }
+    ret = this._flushOutput(socket);
 
     if (this.finished) {
       // This is a queue to the server or client to bring in the next this.
@@ -647,6 +621,32 @@ OutgoingMessage.prototype._flush = function() {
   }
 };
 
+OutgoingMessage.prototype._flushOutput = function _flushOutput(socket) {
+  var ret;
+  var outputLength = this.output.length;
+  if (outputLength <= 0)
+    return ret;
+
+  var output = this.output;
+  var outputEncodings = this.outputEncodings;
+  var outputCallbacks = this.outputCallbacks;
+  socket.cork();
+  for (var i = 0; i < outputLength; i++) {
+    ret = socket.write(output[i], outputEncodings[i],
+                       outputCallbacks[i]);
+  }
+  socket.uncork();
+
+  this.output = [];
+  this.outputEncodings = [];
+  this.outputCallbacks = [];
+  if (typeof this._onPendingData === 'function')
+    this._onPendingData(-this.outputSize);
+  this.outputSize = 0;
+
+  return ret;
+};
+
 
 OutgoingMessage.prototype.flushHeaders = function() {
   if (!this._header) {

test/parallel/test-http-pipeline-regr-3332.js

@@ -0,0 +1,41 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+const net = require('net');
+
+const big = new Buffer(16 * 1024);
+big.fill('A');
+
+const COUNT = 1e4;
+
+var received = 0;
+
+var client;
+const server = http.createServer(function(req, res) {
+  res.end(big, function() {
+    if (++received === COUNT) {
+      server.close();
+      client.end();
+    }
+  });
+}).listen(common.PORT, function() {
+  var req = new Array(COUNT + 1).join('GET / HTTP/1.1\r\n\r\n');
+  client = net.connect(common.PORT, function() {
+    client.write(req);
+  });
+
+  // Just let the test terminate instead of hanging
+  client.on('close', function() {
+    if (received !== COUNT)
+      server.close();
+  });
+  client.resume();
+});
+
+process.on('exit', function() {
+  // The server should pause connection on pipeline flood, but it shoul still
+  // resume it and finish processing the requests, when its output queue will
+  // be empty again.
+  assert.equal(received, COUNT);
+});