add localfile recorder

lib/recorder.js

@@ -2,12 +2,41 @@
 var zlib      = require('zlib'),
     Datastore = require('nedb'), 
     util      = require("util"),
-    events    = require('events'),
-    db        = new Datastore(); //in-memory store
+    fs        = require("fs"),
+    events    = require('events');
 
-function Recorder(){
+//option.filename
+function Recorder(option){
     var self = this,
-        id   = 1;
+        id   = 1,
+        db;
+
+    option = option || {};
+    if(option.filename){
+
+        try{
+            if(fs.existsSync(option.filename)){
+                fs.writeFileSync(option.filename,""); //empty original file
+            }
+
+            db = new Datastore({
+                filename : option.filename,
+                autoload :true
+            });
+            db.persistence.setAutocompactionInterval(5001);
+            console.log("db file : " + option.filename);
+
+        }catch(e){
+            console.log(e);            
+            console.log("Failed to load on-disk db file. Will use in-meomory db instead.");
+            db = new Datastore();
+        }
+        
+    }else{
+        //in-memory db
+        db = new Datastore();
+    }
+
 
     self.recordBodyMap = []; // id - body 
 
@@ -64,6 +93,9 @@ function Recorder(){
     self.getSummaryList = function(cb){
         db.find({},cb);
     };
+
+
+    self.db = db;
 }
 
 util.inherits(Recorder, events.EventEmitter);