Magento migration error - dbModel read resource does not implement Zend_Db_Adapter_Abstract

Question

After migrated a Magento(CE 1.9.1) website from Apache server to Nginx server, i am getting error in frontend: dbModel read resource does not implement Zend_Db_Adapter_Abstract

But admin panel is working fine.

#0 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Model/Resource/Db/Collection/Abstract.php(134): Varien_Data_Collection_Db->setConnection(false)
#1 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Model/Config.php(1348): Mage_Core_Model_Resource_Db_Collection_Abstract->__construct(Array)
#2 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Model/Config.php(1380): Mage_Core_Model_Config->getModelInstance('wordpress_resou...', Array)
#3 /var/www/vhosts/example.com/htdocs/app/Mage.php(491): Mage_Core_Model_Config->getResourceModelInstance('wordpress/post_...', Array)
#4 /var/www/vhosts/example.com/htdocs/app/design/frontend/bloonaway/default/template/page/home.phtml(197): Mage::getResourceModel('wordpress/post_...')
#5 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Template.php(241): include('/var/www/vhosts...')
#6 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/bloona...')
#7 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#8 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Template->_toHtml()
#9 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml()
#10 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Text_List->_toHtml()
#11 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Abstract.php(637): Mage_Core_Block_Abstract->toHtml()
#12 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Abstract.php(581): Mage_Core_Block_Abstract->_getChildHtml('content', true)
#13 /var/www/vhosts/example.com/htdocs/app/design/frontend/bloonaway/default/template/page/1column.phtml(116): Mage_Core_Block_Abstract->getChildHtml('content')
#14 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Template.php(241): include('/var/www/vhosts...')
#15 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/bloona...')
#16 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#17 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Template->_toHtml()
#18 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Model/Layout.php(555): Mage_Core_Block_Abstract->toHtml()
#19 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Controller/Varien/Action.php(390): Mage_Core_Model_Layout->getOutput()
#20 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Cms/Helper/Page.php(137): Mage_Core_Controller_Varien_Action->renderLayout()
#21 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Cms/Helper/Page.php(52): Mage_Cms_Helper_Page->_renderPage(Object(Mage_Cms_IndexController), 'home')
#22 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Cms/controllers/IndexController.php(45): Mage_Cms_Helper_Page->renderPage(Object(Mage_Cms_IndexController), 'home')
#23 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Cms_IndexController->indexAction()
#24 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action->dispatch('index')
#25 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#26 /var/www/vhosts/example.com/htdocs/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#27 /var/www/vhosts/example.com/htdocs/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#28 /var/www/vhosts/example.com/htdocs/index.php(91): Mage::run('', 'store')
#29 {main}

I have tried all solutions provided in other similar threads but no luck.

I tried below following to fix this.

1. Cleared all caches from the var/cache folder.
2. Deleted all session from var/session folder.
3. Given 777 file permission recursively to the entire application.
4. Changed the DB setting in local.xml
5. I have disabled all local modules also using local.xml <disable_local_modules>true</disable_local_modules>

How to fix this. Thanks.

Answer 1

I traced this same error to an event dispatcher which lead me to Fishpig_Wordpress_Model_Sitemap_Sitemap. My staging website could not connect to my Wordpress DB which somehow related to this error. I disabled Fishpig in my staging environment which resolved this issue.

In the class I mentioned, Fishpig has this snarky comment:

/**
 * Magento, if you're listening, you should have already added
 * the 2 variables below to this model (and every model!!)
 */

The two variables mentioned are...

protected $_eventPrefix = 'sitemap_sitemap';
protected $_eventObject = 'sitemap';

Removing these two variables will resolve the issue. However, since this works in my production, I restored them and simply disabled the module on staging only via the module configuration.

Answer 2

I got the same error when I am trying to upgrade a store.

How I avoid this issue, Backup all 3rd Party extension module XML files (from app/etc/modules) and then remove these files from app/etc/modules.

With this, above error is gone. I installed Magento and then add extensions files back. All things worked as expected.

Hope this will help you.