[add] down ping delay

srv/src/slackManager.js

@@ -1,6 +1,8 @@
 
 const Slack = require('./slack.js').Slack
     ,INACTIVE_DELAY = 120000
+    ,PING_DELAY = 600000
+;
 
 function SlackManager() {
     this.cache = require('memory-cache');
@@ -13,7 +15,7 @@ setInterval(function() {
     keys.forEach(function(instKey) {
         instance.cache.get(instKey).ping();
     });
-}, 60000);
+}, PING_DELAY);
 
 SlackManager.prototype.getScope = function() {
     return [