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/models/Table/Collection.php(77): Omeka_Db->__call('fetchPairs', Array)
#3 /var/www/clinton_omeka/application/models/Table/Collection.php(77): Omeka_Db->fetchPairs(Object(Omeka_Db_Select))
#4 /var/www/clinton_omeka/application/libraries/globals.php(1614): Table_Collection->findPairsForSelectForm(Array)
#5 /var/www/clinton_omeka/application/views/scripts/items/search-form.php(127): get_table_options('Collection', NULL, Array)
#6 /var/www/clinton_omeka/application/libraries/Omeka/View.php(117): include('/var/www/clinto...')
#7 /var/www/clinton_omeka/application/libraries/Zend/View/Abstract.php(888): Omeka_View->_run('/var/www/clinto...')
#8 /var/www/clinton_omeka/application/libraries/Zend/View/Helper/Partial.php(109): Zend_View_Abstract->render('items/search-fo...')
#9 [internal function]: Zend_View_Helper_Partial->partial('items/search-fo...', Array)
#10 /var/www/clinton_omeka/application/libraries/Zend/View/Abstract.php(350): call_user_func_array(Array, Array)
#11 /var/www/clinton_omeka/application/views/scripts/items/search.php(15): Zend_View_Abstract->__call('partial', Array)
#12 /var/www/clinton_omeka/application/views/scripts/items/search.php(15): Omeka_View->partial('items/search-fo...', Array)
#13 /var/www/clinton_omeka/application/libraries/Omeka/View.php(117): include('/var/www/clinto...')
#14 /var/www/clinton_omeka/application/libraries/Zend/View/Abstract.php(888): Omeka_View->_run('/var/www/clinto...')
#15 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(912): Zend_View_Abstract->render('items/search.ph...')
#16 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(933): Zend_Controller_Action_Helper_ViewRenderer->renderScript('items/search.ph...', NULL)
#17 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(972): Zend_Controller_Action_Helper_ViewRenderer->render()
#18 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/HelperBroker.php(277): Zend_Controller_Action_Helper_ViewRenderer->postDispatch()
#19 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action.php(527): Zend_Controller_Action_HelperBroker->notifyPostDispatch()
#20 /var/www/clinton_omeka/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('searchAction')
#21 /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))
#22 /var/www/clinton_omeka/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(105): Zend_Controller_Front->dispatch()
#23 /var/www/clinton_omeka/application/libraries/Zend/Application.php(384): Zend_Application_Bootstrap_Bootstrap->run()
#24 /var/www/clinton_omeka/application/libraries/Omeka/Application.php(77): Zend_Application->run()
#25 /var/www/clinton_omeka/index.php(23): Omeka_Application->run()
#26 {main}