Omeka has encountered an error

Zend_Db_Adapter_Mysqli_Exception

Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (111)

exception 'Zend_Db_Adapter_Mysqli_Exception' with message 'Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (111)' in /var/www/clinton_omeka/application/libraries/Zend/Db/Adapter/Mysqli.php:340
Stack trace:
#0 /var/www/clinton_omeka/application/libraries/Zend/Db/Adapter/Abstract.php(316): Zend_Db_Adapter_Mysqli->_connect()
#1 /var/www/clinton_omeka/application/libraries/Omeka/Db.php(87): Zend_Db_Adapter_Abstract->getConnection()
#2 /var/www/clinton_omeka/application/libraries/Omeka/Db/Table.php(648): Omeka_Db->__call('query', Array)
#3 /var/www/clinton_omeka/application/libraries/Omeka/Db/Table.php(648): Omeka_Db->query(Object(Omeka_Db_Select), Array)
#4 /var/www/clinton_omeka/application/libraries/Omeka/Db/Table.php(281): Omeka_Db_Table->fetchObjects(Object(Omeka_Db_Select))
#5 /var/www/clinton_omeka/plugins/SimplePages/helpers/SimplePageFunctions.php(34): Omeka_Db_Table->findBy(Array)
#6 /var/www/clinton_omeka/plugins/SimplePages/SimplePagesPlugin.php(293): simple_pages_get_links_for_children_pages(0, 0, 'order', true)
#7 [internal function]: SimplePagesPlugin->filterPublicNavigationMain(Array)
#8 /var/www/clinton_omeka/application/libraries/Omeka/Plugin/Broker.php(273): call_user_func(Array, Array)
#9 /var/www/clinton_omeka/application/libraries/globals.php(324): Omeka_Plugin_Broker->applyFilters('public_navigati...', Array, Array)
#10 /var/www/clinton_omeka/application/libraries/Omeka/Navigation.php(164): apply_filters('public_navigati...', Array)
#11 /var/www/clinton_omeka/application/libraries/Omeka/Navigation.php(294): Omeka_Navigation::createNavigationFromFilter('public_navigati...')
#12 /var/www/clinton_omeka/application/libraries/globals.php(2763): Omeka_Navigation->addPagesFromFilter('public_navigati...')
#13 /var/www/clinton_omeka/themes/ThanksRoy/common/header.php(138): public_nav_main(Array)
#14 /var/www/clinton_omeka/application/libraries/Omeka/View.php(117): include('/var/www/clinto...')
#15 /var/www/clinton_omeka/application/libraries/Zend/View/Abstract.php(888): Omeka_View->_run('/var/www/clinto...')
#16 /var/www/clinton_omeka/application/libraries/Zend/View/Helper/Partial.php(109): Zend_View_Abstract->render('common/header.p...')
#17 [internal function]: Zend_View_Helper_Partial->partial('common/header.p...', Array)
#18 /var/www/clinton_omeka/application/libraries/Zend/View/Abstract.php(350): call_user_func_array(Array, Array)
#19 /var/www/clinton_omeka/application/libraries/globals.php(1661): Zend_View_Abstract->__call('partial', Array)
#20 /var/www/clinton_omeka/application/libraries/globals.php(1661): Omeka_View->partial('common/header.p...', Array)
#21 /var/www/clinton_omeka/application/libraries/globals.php(1675): common('header', Array)
#22 /var/www/clinton_omeka/application/views/scripts/items/search.php(4): head(Array)
#23 /var/www/clinton_omeka/application/libraries/Omeka/View.php(117): include('/var/www/clinto...')
#24 /var/www/clinton_omeka/application/libraries/Zend/View/Abstract.php(888): Omeka_View->_run('/var/www/clinto...')
#25 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(912): Zend_View_Abstract->render('items/search.ph...')
#26 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(933): Zend_Controller_Action_Helper_ViewRenderer->renderScript('items/search.ph...', NULL)
#27 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(972): Zend_Controller_Action_Helper_ViewRenderer->render()
#28 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/HelperBroker.php(277): Zend_Controller_Action_Helper_ViewRenderer->postDispatch()
#29 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action.php(527): Zend_Controller_Action_HelperBroker->notifyPostDispatch()
#30 /var/www/clinton_omeka/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('searchAction')
#31 /var/www/clinton_omeka/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#32 /var/www/clinton_omeka/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(105): Zend_Controller_Front->dispatch()
#33 /var/www/clinton_omeka/application/libraries/Zend/Application.php(384): Zend_Application_Bootstrap_Bootstrap->run()
#34 /var/www/clinton_omeka/application/libraries/Omeka/Application.php(77): Zend_Application->run()
#35 /var/www/clinton_omeka/index.php(23): Omeka_Application->run()
#36 {main}