http: fix pipeline regression

Always check that socket still has the parser. It may be destroyed
interim, and we may end up with an uncaught exception.

Fix: #3508
PR-URL: nodejs-private/node-private#5
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/_http_server.js

@@ -372,7 +372,7 @@ function connectionListener(socket) {
       }
     }
 
-    if (socket._paused) {
+    if (socket._paused && socket.parser) {
       // onIncoming paused the socket, we should pause the parser as well
       debug('pause parser');
       socket.parser.pause();
@@ -411,7 +411,8 @@ function connectionListener(socket) {
     // If we previously paused, then start reading again.
     if (socket._paused) {
       socket._paused = false;
-      socket.parser.resume();
+      if (socket.parser)
+        socket.parser.resume();
       socket.resume();
     }
   }

test/parallel/test-http-pipeline-regr-3508.js

@@ -0,0 +1,57 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+const net = require('net');
+
+var once = false;
+var first = null;
+var second = null;
+
+const chunk = new Buffer(1024);
+chunk.fill('X');
+
+var size = 0;
+
+var more;
+var done;
+
+var server = http.createServer(function(req, res) {
+  if (!once)
+    server.close();
+  once = true;
+
+  if (first === null) {
+    first = res;
+    return;
+  }
+  if (second === null) {
+    second = res;
+    res.write(chunk);
+  } else {
+    res.end(chunk);
+  }
+  size += res.outputSize;
+  if (size <= req.socket._writableState.highWaterMark) {
+    more();
+    return;
+  }
+  done();
+}).on('upgrade', function(req, socket) {
+  second.end(chunk, function() {
+    socket.end();
+  });
+  first.end('hello');
+}).listen(common.PORT, function() {
+  var s = net.connect(common.PORT);
+  more = function() {
+    s.write('GET / HTTP/1.1\r\n\r\n');
+  };
+  done = function() {
+    s.write('GET / HTTP/1.1\r\n\r\n' +
+            'GET / HTTP/1.1\r\nConnection: upgrade\r\nUpgrade: ws\r\n\r\naaa');
+  };
+  more();
+  more();
+  s.resume();
+});