Fix flakiness of pipeflood test

test/sequential/sequential.status

@@ -7,7 +7,6 @@ prefix sequential
 [true] # This section applies to all platforms
 
 [$system==win32]
-test-http-pipeline-flood                        : PASS,FLAKY
 
 [$system==linux]
 test-vm-syntax-error-stderr                     : PASS,FLAKY

test/sequential/test-http-pipeline-flood.js

@@ -1,91 +1,98 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
+const common = require('../common');
+const assert = require('assert');
+
+// Here we are testing the HTTP server module's flood prevention mechanism.
+// When writeable.write returns false (ie the underlying send() indicated the
+// native buffer is full), the HTTP server cork()s the readable part of the
+// stream. This means that new requests will not be read (however request which
+// have already been read, but are awaiting processing will still be
+// processed).
+
+// Normally when the writable stream emits a 'drain' event, the server then
+// uncorks the readable stream, although we arent testing that part here.
 
 switch (process.argv[2]) {
   case undefined:
     return parent();
   case 'child':
     return child();
   default:
-    throw new Error('wtf');
+    throw new Error(`Unexpected value: ${process.argv[2]}`);
 }
 
 function parent() {
-  var http = require('http');
-  var bigResponse = new Buffer(10240).fill('x');
+  const http = require('http');
+  const bigResponse = new Buffer(10240).fill('x');
   var gotTimeout = false;
   var childClosed = false;
   var requests = 0;
   var connections = 0;
+  var backloggedReqs = 0;
 
-  var server = http.createServer(function(req, res) {
+  const server = http.createServer(function(req, res) {
     requests++;
     res.setHeader('content-length', bigResponse.length);
-    res.end(bigResponse);
+    if (!res.write(bigResponse)) {
+      if (backloggedReqs === 0) {
+        // Once the native buffer fills (ie write() returns false), the flood
+        // prevention should kick in.
+        // This means the stream should emit no more 'data' events. However we
+        // may still be asked to process more requests if they were read before
+        // the flood-prevention mechanism activated.
+        setImmediate(() => {
+          req.socket.on('data', () => common.fail('Unexpected data received'));
+        });
+      }
+      backloggedReqs++;
+    }
+    res.end();
   });
 
   server.on('connection', function(conn) {
     connections++;
   });
 
-  // kill the connection after a bit, verifying that the
-  // flood of requests was eventually halted.
-  server.setTimeout(200, function(conn) {
-    gotTimeout = true;
-    conn.destroy();
-  });
-
   server.listen(common.PORT, function() {
-    var spawn = require('child_process').spawn;
-    var args = [__filename, 'child'];
-    var child = spawn(process.execPath, args, { stdio: 'inherit' });
-    child.on('close', function(code) {
-      assert(!code);
+    const spawn = require('child_process').spawn;
+    const args = [__filename, 'child'];
+    const child = spawn(process.execPath, args, { stdio: 'inherit' });
+    child.on('close', function() {
       childClosed = true;
       server.close();
     });
+
+    server.setTimeout(common.platformTimeout(200), function(conn) {
+      gotTimeout = true;
+      child.kill();
+    });
   });
 
   process.on('exit', function() {
     assert(gotTimeout);
     assert(childClosed);
     assert.equal(connections, 1);
-    // The number of requests we end up processing before the outgoing
-    // connection backs up and requires a drain is implementation-dependent.
-    // We can safely assume is more than 250.
-    console.log('server got %d requests', requests);
-    assert(requests >= 250);
-    console.log('ok');
   });
 }
 
 function child() {
-  var net = require('net');
+  const net = require('net');
 
-  var gotEpipe = false;
-  var conn = net.connect({ port: common.PORT });
+  const conn = net.connect({ port: common.PORT });
 
   var req = 'GET / HTTP/1.1\r\nHost: localhost:' +
             common.PORT + '\r\nAccept: */*\r\n\r\n';
 
   req = new Array(10241).join(req);
 
   conn.on('connect', function() {
+    // Terminate child after flooding.
+    setTimeout(function() { conn.destroy(); }, common.platformTimeout(1000));
     write();
   });
 
   conn.on('drain', write);
 
-  conn.on('error', function(er) {
-    gotEpipe = true;
-  });
-
-  process.on('exit', function() {
-    assert(gotEpipe);
-    console.log('ok - child');
-  });
-
   function write() {
     while (false !== conn.write(req, 'ascii'));
   }