Suddenly the session on our live site stopped working. Do not know why this is happening.
Our site is hosted on AWS EC2 Linux
var and var/session folder exists and have permission 777
nothing there in exception.log or system.log
cache folder is cleared and have permission 777
Cannot login as customer, admin and add to cart not working
Best Answer
If you are using Google Chrome, you can right-click on the page, choose Inspect Element, then Resources tab, look for Cookies down the left-hand menu, and click on your domain name.
Under the domain name, the cookies that have been set for it will be displayed, along with path, expiry, etc. Very useful.
In your case, you are looking for the 'frontend' session cookie under 'name'. You can delete it, and refresh the page to see if Magento recreates it, in which case sessions are probs working. Hope that helps :)
PS: Magento uses sessions very heavily, if they're broken other things will be breaking all over the show as well.
Also follow bellow links
https://stackoverflow.com/questions/9891761/magento-customer-session-not-working
https://community.magento.com/t5/Programming-Questions/Magento-1-9-customer-and-cart-session-not-working/td-p/3540
I hope this will help you.