Fix a few memory leaks; add /gc console command

3 memory leaks were fixed
  - ipThrottle (due to the periodic cleaner clearing the wrong object...)
  - ipCount (shouldn't have leaked very much, but removing obsolete data is good practice)
  - lastguestlogin (again, shouldn't leak much, but should be cleared periodically anyways)
A new console command (i.e. from the terminal running node) was added: /gc
  - If the process is invoked as node --expose-gc index.js, /gc allows you to manually invoke the garbage collector

lib/io/ioserver.js

@@ -12,7 +12,6 @@ var CONNECT_RATE = {
     sustained: 0.1
 };
 
-// Keep track of rate limiting by IP
 var ipThrottle = {};
 // Keep track of number of connections per IP
 var ipCount = {};
@@ -80,6 +79,10 @@ function handleConnection(sock) {
 
     sock.on("disconnect", function () {
         ipCount[ip]--;
+        if (ipCount[ip] === 0) {
+            /* Clear out unnecessary counters to save memory */
+            delete ipCount[ip];
+        }
     });
 
     if (!(ip in ipCount)) {
@@ -139,3 +142,21 @@ module.exports = {
         }
     }
 };
+
+/* Clean out old rate limiters */
+setInterval(function () {
+    for (var ip in ipThrottle) {
+        if (ipThrottle[ip].lastTime < Date.now() - 60 * 1000) {
+            var obj = ipThrottle[ip];
+            /* Not strictly necessary, but seems to help the GC out a bit */
+            for (var key in obj) {
+                delete obj[key];
+            }
+            delete ipThrottle[ip];
+        }
+    }
+
+    if (Config.get("aggressive-gc") && global && global.gc) {
+        global.gc();
+    }
+}, 5 * 60 * 1000);