server: lazy-load memcache module

Don't require that the memcache module is installed if metrics_enabled=false.

server/js/main.js

@@ -13,7 +13,7 @@ function main(config) {
         worlds = [],
         lastTotalPlayers = 0,
         checkPopulationInterval = setInterval(function() {
-            if(metrics.isReady) {
+            if(metrics && metrics.isReady) {
                 metrics.getTotalPlayers(function(totalPlayers) {
                     if(totalPlayers !== lastTotalPlayers) {
                         lastTotalPlayers = totalPlayers;
@@ -44,7 +44,7 @@ function main(config) {
                 }
             };
 
-        if(config.metrics_enabled) {
+        if(metrics) {
             metrics.getOpenWorldCount(function(open_world_count) {
                 // choose the least populated world among open worlds
                 world = _.min(_.first(worlds, open_world_count), function(w) { return w.playerCount; });
@@ -78,8 +78,7 @@ function main(config) {
         var world = new WorldServer('world'+ (i+1), config.nb_players_per_world, server);
         world.run(config.map_filepath);
         worlds.push(world);
-
-        if(config.metrics_enabled) {
+        if(metrics) {
             world.onPlayerAdded(onPopulationChange);
             world.onPlayerRemoved(onPopulationChange);
         }

server/js/metrics.js

@@ -1,14 +1,13 @@
 
 var cls = require("./lib/class"),
-    _ = require("underscore"),
-    memcache = require("memcache");
+    _ = require("underscore");
 
 module.exports = Metrics = Class.extend({
     init: function(config) {
         var self = this;
 
         this.config = config;
-        this.client = new memcache.Client(config.memcached_port, config.memcached_host),
+        this.client = new require("memcache").Client(config.memcached_port, config.memcached_host),
         this.client.connect();
         this.isReady = false;
 
@@ -73,4 +72,4 @@ module.exports = Metrics = Class.extend({
             callback(result);
         });
     }
-});
+});