We plan to install multiple Apache servers instead of single Apache server since it is overloaded. My concern is: in one user session, the user may send 2 or more requests. How do multiple Apache servers to communicate each other for the same session?
For example, we have Apache Server A and Apache Server B. A and B process user shopping cart requests in turn, but connect to the same database. User William wants to buy a PC and a notebook (just like in Dell.com). He login to the PHP shopping cart. First he puts a PC into his shopping cart, this request is processed by Apache Server A. Then, in same session, he puts a notebook into his shopping cart, this request is processed by Apache Server B. How can Apache Server B knows user William has a PC in shopping cart so B can calculate the total price for a PC plus a notebook?
Thanks a lot.