DB Error: MySQL server has gone away

Stack Trace:

File: /var/www/html/lib/pkp/classes/session/SessionDAO.inc.php line 31
Function: DAO->retrieve("SELECT * FROM sessions WHERE session_id = ?", Array(1))

File: /var/www/html/lib/pkp/classes/session/SessionManager.inc.php line 160
Function: SessionDAO->getSession("cic7elji1a7istb4oi29hfu1e1")

File: (unknown) line (unknown)
Function: SessionManager->read("cic7elji1a7istb4oi29hfu1e1")

File: /var/www/html/lib/pkp/classes/session/SessionManager.inc.php line 60
Function: session_start()

File: /var/www/html/lib/pkp/classes/session/SessionManager.inc.php line 121
Function: SessionManager->SessionManager(Object(SessionDAO), Object(Request))

File: /var/www/html/classes/security/Validation.inc.php line 273
Function: SessionManager->getManager()

File: /var/www/html/lib/pkp/classes/core/PKPPageRouter.inc.php line 65
Function: Validation->isLoggedIn()

File: /var/www/html/lib/pkp/classes/core/Dispatcher.inc.php line 114
Function: PKPPageRouter->isCacheable(Object(Request))

File: /var/www/html/lib/pkp/classes/core/PKPApplication.inc.php line 170
Function: Dispatcher->dispatch(Object(Request))

File: /var/www/html/index.php line 65
Function: PKPApplication->execute()