From 1736ad82643c0b55027626f330dff9af1519f04b Mon Sep 17 00:00:00 2001
From: Craig Cavalier <craigcav@gmail.com>
Date: Mon, 26 Oct 2015 14:40:56 -0700
Subject: [PATCH] zlib: only apply drain listener if given callback

When stream.flush() is called without a callback, an empty listener is
being added. Since flush may be called multiple times to push SSE's
down to the client, multiple noop listeners are being added. This in
turn causes the memory leak detected message.

PR-URL: https://github.com/nodejs/node/pull/3534
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
---
 lib/zlib.js | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/lib/zlib.js b/lib/zlib.js
index 996d1116ee7..3e6f7b18763 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -444,10 +444,9 @@ Zlib.prototype.flush = function(kind, callback) {
     if (callback)
       this.once('end', callback);
   } else if (ws.needDrain) {
-    var self = this;
-    this.once('drain', function() {
-      self.flush(kind, callback);
-    });
+    if (callback) {
+      this.once('drain', () => this.flush(kind, callback));
+    }
   } else {
     this._flushFlag = kind;
     this.write(new Buffer(0), '', callback);