app/code/community/Nexcessnet/Turpentine/Model/Observer/Esi.php
public function setCustomerGroupCookie($eventObject) {
        $customer = $eventObject->getCustomer();
        $cookie = Mage::getSingleton('core/cookie');
        if (Mage::getStoreConfig('persistent/options/enabled')) {
            $cookie->set('customer_group', $customer->getGroupId(), Mage::getStoreConfig('persistent/options/lifetime'));
        } else {
            $cookie->set('customer_group', $customer->getGroupId());
        }
    }
public function setCustomerGroupCookie($eventObject) {
        $customer = $eventObject->getCustomer();
        $cookie = Mage::getSingleton('core/cookie');
        if (Mage::getStoreConfig('persistent/options/enabled')) {
            $cookie->set('customer_group', $customer->getGroupId(), Mage::getStoreConfig('persistent/options/lifetime'));
        } else {
            $cookie->set('customer_group', $customer->getGroupId());
        }
    }
public function setCustomerGroupCookie ( $ eventObject ) { $ customer = $ eventObject -> getCustomer ( ) ; $ cookie = Mage :: getSingleton ( 'core/cookie' ) ; if ( Mage :: getStoreConfig ( 'persistent/options/enabled' ) ) { $ cookie -> set ( 'customer_group' , $ customer -> getGroupId ( ) , Mage :: getStoreConfig ( 'persistent/options/lifetime' ) ) ; } else { $ cookie -> set ( 'customer_group' , $ customer -> getGroupId ( ) ) ; } }
Set a cookie with the customer group id when customer logs in

Events: customer_login

@param Varien_Object $eventObject
@return null
Set a cookie with the customer group id when customer logs in