net,stream: add isPaused, don't read() when paused

net Sockets were calling read(0) to start reading, without
checking to see if they were paused first. This would result
in paused Socket objects keeping the event loop alive.

Fixes #8200

Reviewed-by: Trevor Norris <trev.norris@gmail.com>

doc/api/stream.markdown

@@ -310,6 +310,24 @@ readable.on('data', function(chunk) {
 })
 ```
 
+#### readable.isPaused()
+
+* Return: `Boolean`
+
+This method returns whether or not the `readable` has been **explicitly**
+paused by client code (using `readable.pause()` without a corresponding
+`readable.resume()`).
+
+```javascript
+var readable = new stream.Readable
+
+readable.isPaused() // === false
+readable.pause()
+readable.isPaused() // === true
+readable.resume()
+readable.isPaused() // === false
+```
+
 #### readable.pipe(destination, [options])
 
 * `destination` {[Writable][] Stream} The destination for writing data

lib/_stream_readable.js

@@ -131,6 +131,10 @@ Readable.prototype.unshift = function(chunk) {
   return readableAddChunk(this, state, chunk, '', true);
 };
 
+Readable.prototype.isPaused = function() {
+  return this._readableState.flowing === false;
+};
+
 function readableAddChunk(stream, state, chunk, encoding, addToFront) {
   var er = chunkInvalid(state, chunk);
   if (er) {

lib/net.js

@@ -970,7 +970,7 @@ function afterConnect(status, handle, req, readable, writable) {
 
     // start the first read, or get an immediate EOF.
     // this doesn't actually consume any bytes, because len=0.
-    if (readable)
+    if (readable && !self.isPaused())
       self.read(0);
 
   } else {

test/simple/test-net-connect-paused-connection.js

@@ -0,0 +1,35 @@
+// Copyright Joyent, Inc. and other Node contributors.
+
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var assert = require('assert');
+var common = require('../common');
+
+var net = require('net');
+
+net.createServer(function(conn) {
+  conn.unref();
+}).listen(8124).unref();
+
+net.connect(8124, 'localhost').pause();
+
+setTimeout(function() {
+  assert.fail('expected to exit');
+}, 1000).unref();

test/simple/test-stream-ispaused.js

@@ -0,0 +1,44 @@
+// Copyright Joyent, Inc. and other Node contributors.
+
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var assert = require('assert');
+var common = require('../common');
+
+var stream = require('stream');
+
+var readable = new stream.Readable;
+
+// _read is a noop, here.
+readable._read = Function();
+
+// default state of a stream is not "paused"
+assert.ok(!readable.isPaused());
+
+// make the stream start flowing...
+readable.on('data', Function());
+
+// still not paused.
+assert.ok(!readable.isPaused());
+
+readable.pause();
+assert.ok(readable.isPaused());
+readable.resume();
+assert.ok(!readable.isPaused());