diff --git a/server/controllers/WebSocketController.js b/server/controllers/WebSocketController.js
index 5cafd99..c02b9ee 100644
--- a/server/controllers/WebSocketController.js
+++ b/server/controllers/WebSocketController.js
@@ -1,6 +1,8 @@
 const WebSocket = require ('ws');
 const _ = require('lodash');
 
+const WorkerState = require('../core/WorkerState');//singleton
+const WebWorker = require('../core/WebWorker');//singleton
 const log = new (require('../core/AppLogger'))().log;//singleton
 //const utils = require('../core/utils');
 
@@ -12,6 +14,9 @@ class WebSocketController {
         this.config = config;
         this.isDevelopment = (config.branch == 'development');
 
+        this.workerState = new WorkerState();
+        this.webWorker = new WebWorker(config);
+
         this.wss = wss;
 
         wss.on('connection', (ws) => {
@@ -59,6 +64,8 @@ class WebSocketController {
                     await this.test(req, ws); break;
                 case 'get-config':
                     await this.getConfig(req, ws); break;
+                case 'get-worker-state':
+                    await this.getWorkerState(req, ws); break;
 
                 default:
                     throw new Error(`Action not found: ${req.action}`);
@@ -100,6 +107,14 @@ class WebSocketController {
         }
     }
 
+    async getWorkerState(req, ws) {
+        if (!req.workerId)
+            throw new Error(`key 'workerId' is empty`);
+
+        const state = this.workerState.getState(req.workerId);
+        this.send((state ? state : {}), req, ws);
+    }
+
 }
 
 module.exports = WebSocketController;
diff --git a/server/core/DbCreator.js b/server/core/DbCreator.js
new file mode 100644
index 0000000..e69de29
diff --git a/server/core/WebWorker.js b/server/core/WebWorker.js
new file mode 100644
index 0000000..fd5b98c
--- /dev/null
+++ b/server/core/WebWorker.js
@@ -0,0 +1,50 @@
+const WorkerState = require('./WorkerState');
+
+//server states:
+const ssNormal = 'normal';
+const ssDbLoading = 'db_loading';
+
+//singleton
+let instance = null;
+
+class WebWorker {
+    constructor(config) {
+        if (!instance) {
+            this.config = config;
+            this.workerState = new WorkerState();
+            
+            this.wState = this.workerState.getControl('server_state');
+            this.myState = '';
+
+            this.loadOrCreateDb();//no await
+
+            instance = this;
+        }
+
+        return instance;
+    }
+
+    checkMyState() {
+        if (this.myState != ssNormal)
+            throw new Error('server_busy');
+    }
+
+    setMyState(newState) {
+        this.myState = newState;
+        this.wState.set({state: newState});
+    }
+
+    async loadOrCreateDb() {
+        this.setMyState(ssDbLoading);
+
+        try {
+            //
+        } catch (e) {
+            //
+        } finally {
+            this.setMyState(ssNormal);
+        }
+    }
+}
+
+module.exports = WebWorker;
\ No newline at end of file
diff --git a/server/core/WorkerState.js b/server/core/WorkerState.js
new file mode 100644
index 0000000..3daf333
--- /dev/null
+++ b/server/core/WorkerState.js
@@ -0,0 +1,62 @@
+const utils = require('./utils');
+
+const cleanInterval = 3600; //sec
+const cleanAfterLastModified = cleanInterval - 60; //sec
+
+let instance = null;
+
+//singleton
+class WorkerState {
+    constructor() {
+        if (!instance) {
+            this.states = {};
+            this.cleanStates();
+            instance = this;
+        }
+
+        return instance;
+    }
+
+    generateWorkerId() {
+        return utils.randomHexString(20);
+    }
+
+    getControl(workerId) {
+        return {
+            set: state => this.setState(workerId, state),
+            finish: state => this.finishState(workerId, state),
+            get: () => this.getState(workerId),
+        };
+    }
+
+    setState(workerId, state) {
+        this.states[workerId] = Object.assign({}, this.states[workerId], state, {
+            workerId, 
+            lastModified: Date.now()
+        });
+    }
+
+    finishState(workerId, state) {
+        this.states[workerId] = Object.assign({}, this.states[workerId], state, {
+            workerId,
+            state: 'finish',
+            lastModified: Date.now()
+        });
+    }
+
+    getState(workerId) {
+        return this.states[workerId];
+    }
+
+    cleanStates() {
+        const now = Date.now();
+        for (let workerID in this.states) {
+            if ((now - this.states[workerID].lastModified) >= cleanAfterLastModified*1000) {
+                delete this.states[workerID];
+            }
+        }
+        setTimeout(this.cleanStates.bind(this), cleanInterval*1000);
+    }
+}
+
+module.exports = WorkerState;
\ No newline at end of file