diff --git a/lib/history.js b/lib/history.js
index bdc922d..4a3bbe1 100644
--- a/lib/history.js
+++ b/lib/history.js
@@ -2,7 +2,6 @@
 //external modules
 var async = require('async');
 var moment = require('moment');
-var childProcess = require('child_process');
 
 //core
 var config = require("./config.js");
@@ -10,9 +9,6 @@ var logger = require("./logger.js");
 var response = require("./response.js");
 var models = require("./models");
 
-// workers
-var historyUpdater = require("./workers/historyUpdater");
-
 //public
 var History = {
     historyGet: historyGet,
@@ -24,51 +20,50 @@ var History = {
 
 var caches = {};
 //update when the history is dirty
-var updaterIsBusy = false;
 var updater = setInterval(function () {
-    if (updaterIsBusy) return;
     var deleted = [];
-    var _caches = {};
-    Object.keys(caches).forEach(function (key) {
+    async.each(Object.keys(caches), function (key, callback) {
         var cache = caches[key];
         if (cache.isDirty) {
-            _caches[key] = cache.history;
-            cache.isDirty = false;
+            if (config.debug) logger.info("history updater found dirty history: " + key);
+            var history = parseHistoryToArray(cache.history);
+            finishUpdateHistory(key, history, function (err, count) {
+                if (err) return callback(err, null);
+                if (!count) return callback(null, null);
+                cache.isDirty = false;
+                cache.updateAt = Date.now();
+                return callback(null, null);
+            });
         } else {
             if (moment().isAfter(moment(cache.updateAt).add(5, 'minutes'))) {
                 deleted.push(key);
             }
+            return callback(null, null);
         }
+    }, function (err) {
+        if (err) return logger.error('history updater error', err);
     });
     // delete specified caches
     for (var i = 0, l = deleted.length; i < l; i++) {
         caches[deleted[i]].history = {};
         delete caches[deleted[i]];
     }
-    if (Object.keys(_caches).length <= 0) return;
-    updaterIsBusy = true;
-    var worker = childProcess.fork("./lib/workers/historyUpdater.js");
-    if (config.debug) logger.info('history updater worker process started');
-    worker.send({
-        msg: 'update history',
-        caches: _caches
-    });
-    worker.on('message', function (data) {
-        if (!data || !data.msg || !data.userid) return;
-        var cache = caches[data.userid];
-        if (!cache) return;
-        switch(data.msg) {
-            case 'check':
-                cache.updateAt = Date.now();
-                break;
-        }
-    });
-    worker.on('close', function (code) {
-        updaterIsBusy = false;
-        if (config.debug) logger.info('history updater worker process exited with code ' + code);
-    });
 }, 1000);
 
+function finishUpdateHistory(userid, history, callback) {
+    models.User.update({
+        history: JSON.stringify(history)
+    }, {
+        where: {
+            id: userid
+        }
+    }).then(function (count) {
+        return callback(null, count);
+    }).catch(function (err) {
+        return callback(err, null);
+    });
+}
+
 function isReady() {
     var dirtyCount = 0;
     async.each(Object.keys(caches), function (key, callback) {
@@ -106,7 +101,7 @@ function getHistory(userid, callback) {
 }
 
 function setHistory(userid, history) {
-    if (Array.isArray(history)) history = historyUpdater.parseHistoryToObject(history);
+    if (Array.isArray(history)) history = parseHistoryToObject(history);
     if (!caches[userid]) {
         caches[userid] = {
             history: {},
@@ -135,13 +130,31 @@ function updateHistory(userid, noteId, document) {
     }
 }
 
+function parseHistoryToArray(history) {
+    var _history = [];
+    Object.keys(history).forEach(function (key) {
+        var item = history[key];
+        _history.push(item);
+    });
+    return _history;
+}
+
+function parseHistoryToObject(history) {
+    var _history = {};
+    for (var i = 0, l = history.length; i < l; i++) {
+        var item = history[i];
+        _history[item.id] = item;
+    }
+    return _history;
+}
+
 function historyGet(req, res) {
     if (req.isAuthenticated()) {
         getHistory(req.user.id, function (err, history) {
             if (err) return response.errorInternalError(res);
             if (!history) return response.errorNotFound(res);
             res.send({
-                history: historyUpdater.parseHistoryToArray(history)
+                history: parseHistoryToArray(history)
             });
         });
     } else {
diff --git a/lib/workers/historyUpdater.js b/lib/workers/historyUpdater.js
deleted file mode 100644
index df80e92..0000000
--- a/lib/workers/historyUpdater.js
+++ /dev/null
@@ -1,66 +0,0 @@
-// external modules
-var async = require('async');
-
-// core
-var config = require("../config.js");
-var logger = require("../logger.js");
-var models = require("../models");
-
-process.on('message', function (data) {
-    if (!data || !data.msg || data.msg !== 'update history' || !data.caches) return process.exit();
-    var caches = data.caches;
-    async.each(Object.keys(caches), function (key, callback) {
-        var cache = caches[key];
-        if (config.debug) logger.info("history updater found dirty history: " + key);
-        var history = parseHistoryToArray(cache);
-        finishUpdateHistory(key, history, function (err, count) {
-            if (err) return callback(err, null);
-            if (!count) return callback(null, null);
-            process.send({
-                msg: 'check',
-                userid: key
-            });
-            return callback(null, null);
-        });
-    }, function (err) {
-        if (err) logger.error('history updater error', err);
-        process.exit();
-    });
-});
-
-function finishUpdateHistory(userid, history, callback) {
-    models.User.update({
-        history: JSON.stringify(history)
-    }, {
-        where: {
-            id: userid
-        }
-    }).then(function (count) {
-        return callback(null, count);
-    }).catch(function (err) {
-        return callback(err, null);
-    });
-}
-
-function parseHistoryToArray(history) {
-    var _history = [];
-    Object.keys(history).forEach(function (key) {
-        var item = history[key];
-        _history.push(item);
-    });
-    return _history;
-}
-
-function parseHistoryToObject(history) {
-    var _history = {};
-    for (var i = 0, l = history.length; i < l; i++) {
-        var item = history[i];
-        _history[item.id] = item;
-    }
-    return _history;
-}
-
-module.exports = {
-    parseHistoryToArray: parseHistoryToArray,
-    parseHistoryToObject: parseHistoryToObject
-};
\ No newline at end of file