Magento – Fix Product URL Key Sporadically Being Set to Blank

You can do this by using catalog_product_save_befoe event .Here details below

code MageStack_24869.xml of app\etc\modules\

<?xml version="1.0" ?>
<config>
    <modules>
    <MageStack_24869>
        <codePool>local</codePool>
        <active>true</active>
    </MageStack_24869>
    </modules>
</config>

And config.xml path app\code\local\MageStack\24869\etc\ and code is

<?xml version="1.0"?>
<config>
  <modules>
    <MageStack_24869>
      <version>0.1.0</version>
    </MageStack_24869>
  </modules>
    <global>
        <models>
            <mageStack24869>
                <class>MageStack_24869_Model</class>
            </mageStack24869>
        </models>
  </global>
    <global>
        <events>
            <catalog_product_save_before>
                <observers>
                    <mageStack24869>
                        <type>singleton</type>
                        <class>mageStack24869/observer</class>
                        <method>updateurl</method>
                    </mageStack24869>
                </observers>
            </catalog_product_save_before>
        </events>
    </global>       
</config> 

Also Observer.php code path (app\code\local\MageStack\24869\Model)

<?php
class MageStack_24869_Model_Observer{
    public function updateurl($observer){
        //Mage::log('My log entry', null, 'mylogfile.log');
        if($observer->getEvent()->getProduct()){
            $Product=$observer->getEvent()->getProduct();
            $Url='';
            if(!is_null($Product->getData('country_of_manufacture'))):
            $Url=$Url.$Product->getAttributeText('country_of_manufacture').'-';
            endif;
            if(!is_null($Product->getData('sku'))):
            $Url=$Url.$Product->getData('sku').'-';
            endif;
            if(!is_null($Product->getData('name'))):
            $Url=$Url.$Product->getData('name');
            endif;
            //Mage::log('My log entry'.$Url, null, 'mylogfile.log');
            $Product->setData('url_key',$Url);      

        }
    }
}

Also you can do using below code

https://stackoverflow.com/questions/23987445/how-to-customize-product-url

I assumed this could be the reason of the get productUrl and i found the solution, which is:

instead of getProductUrl use getUrlPath()