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(670): Omeka_Db->__call('fetchRow', Array)
#3 /var/www/clinton_omeka/application/libraries/Omeka/Db/Table.php(670): Omeka_Db->fetchRow(Object(Omeka_Db_Select), Array)
#4 /var/www/clinton_omeka/application/libraries/Omeka/Db/Table.php(429): Omeka_Db_Table->fetchObject(Object(Omeka_Db_Select), Array)
#5 /var/www/clinton_omeka/plugins/SolrSearch/models/SolrSearchFieldTable.php(76): Omeka_Db_Table->findBySql('slug=?', Array, true)
#6 /var/www/clinton_omeka/plugins/SolrSearch/helpers/SolrSearch_Helpers_Facet.php(132): SolrSearchFieldTable->findBySlug('tag')
#7 /var/www/clinton_omeka/plugins/SolrSearch/views/shared/results/index.php(43): SolrSearch_Helpers_Facet::keyToLabel('tag')
#8 /var/www/clinton_omeka/application/libraries/Omeka/View.php(117): include('/var/www/clinto...')
#9 /var/www/clinton_omeka/application/libraries/Zend/View/Abstract.php(888): Omeka_View->_run('/var/www/clinto...')
#10 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(912): Zend_View_Abstract->render('results/index.p...')
#11 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(933): Zend_Controller_Action_Helper_ViewRenderer->renderScript('results/index.p...', NULL)
#12 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(972): Zend_Controller_Action_Helper_ViewRenderer->render()
#13 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action/HelperBroker.php(277): Zend_Controller_Action_Helper_ViewRenderer->postDispatch()
#14 /var/www/clinton_omeka/application/libraries/Zend/Controller/Action.php(527): Zend_Controller_Action_HelperBroker->notifyPostDispatch()
#15 /var/www/clinton_omeka/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('indexAction')
#16 /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))
#17 /var/www/clinton_omeka/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(105): Zend_Controller_Front->dispatch()
#18 /var/www/clinton_omeka/application/libraries/Zend/Application.php(384): Zend_Application_Bootstrap_Bootstrap->run()
#19 /var/www/clinton_omeka/application/libraries/Omeka/Application.php(77): Zend_Application->run()
#20 /var/www/clinton_omeka/index.php(23): Omeka_Application->run()
#21 {main}