DB Error: MySQL server has gone away

Stack Trace:

File: /var/www/html/lib/pkp/classes/site/SiteDAO.inc.php line 36
Function: DAO->retrieve("SELECT * FROM site")

File: /var/www/html/lib/pkp/classes/core/PKPRequest.inc.php line 515
Function: SiteDAO->getSite()

File: /var/www/html/classes/i18n/AppLocale.inc.php line 86
Function: PKPRequest->getSite()

File: /var/www/html/lib/pkp/classes/i18n/PKPLocale.inc.php line 109
Function: AppLocale->getLocale()

File: /var/www/html/lib/pkp/classes/core/Dispatcher.inc.php line 131
Function: PKPLocale->initialize()

File: /var/www/html/lib/pkp/classes/core/PKPApplication.inc.php line 178
Function: Dispatcher->dispatch(Object(Request))

File: /var/www/html/index.php line 69
Function: PKPApplication->execute()

DB Error: MySQL server has gone away

Stack Trace:

File: /var/www/html/lib/pkp/classes/session/SessionDAO.inc.php line 119
Function: DAO->update("UPDATE sessions SET user_id = ?, ip_address = ?, ...", Array(9))

File: /var/www/html/lib/pkp/classes/session/SessionManager.inc.php line 186
Function: SessionDAO->updateObject(Object(Session))

File: (unknown) line (unknown)
Function: SessionManager->write("odq0d0frvqt7m16ebsokpqu840", "")

File: (unknown) line (unknown)
Function: session_write_close()