feat: disable perMessageDeflate by default

The WebSocket permessage-deflate extension, while useful is some cases,
adds some extra memory overhead for each WebSocket connection, and
results in huge memory usage in production deployments.

It will now be disabled by default.

Backported from master: 078527a

README.md

@@ -239,7 +239,7 @@ to a single process.
       - `allowUpgrades` (`Boolean`): whether to allow transport upgrades
         (`true`)
       - `perMessageDeflate` (`Object|Boolean`): parameters of the WebSocket permessage-deflate extension
-        (see [ws module](https://github.com/einaros/ws) api docs). Set to `false` to disable. (`true`)
+        (see [ws module](https://github.com/einaros/ws) api docs). Set to `true` to enable. (`false`)
         - `threshold` (`Number`): data is compressed only if the byte size is above this value (`1024`)
       - `httpCompression` (`Object|Boolean`): parameters of the http compression for the polling transports
         (see [zlib](http://nodejs.org/api/zlib.html#zlib_options) api docs). Set to `false` to disable. (`true`)

lib/server.js

@@ -47,7 +47,7 @@ function Server (opts) {
   this.cookie = false !== opts.cookie ? (opts.cookie || 'io') : false;
   this.cookiePath = false !== opts.cookiePath ? (opts.cookiePath || '/') : false;
   this.cookieHttpOnly = false !== opts.cookieHttpOnly;
-  this.perMessageDeflate = false !== opts.perMessageDeflate ? (opts.perMessageDeflate || true) : false;
+  this.perMessageDeflate = opts.perMessageDeflate || false;
   this.httpCompression = false !== opts.httpCompression ? (opts.httpCompression || {}) : false;
   this.initialPacket = opts.initialPacket;
 

test/server.js

@@ -2503,7 +2503,7 @@ describe('server', function () {
     });
 
     it('should not compress when the byte size is below threshold', function (done) {
-      var engine = listen({ transports: ['websocket'] }, function (port) {
+      var engine = listen({ transports: ['websocket'], perMessageDeflate: true }, function (port) {
         engine.on('connection', function (conn) {
           var socket = conn.transport.socket;
           var send = socket.send;