Bug Report or Feature Request (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request

Repro steps.

Sometimes the config.json gets suddenly cleared, causing the system to stop working.

Desired functionality.

The problem could be caused by concurrent write of the config file.

1. Syncronize the call to write method
2. Create backup file (config.json.bkup) before each write. Load this file on startup if config.json fails.