I am reading about load balancing.
I understand the idea that load balancers transfer the load among several slave servers of any given app. However very few literature that I can find talks about what happens when the load balancers themselves start struggling with the huge amount of requests, to the point that the "simple" task of load balancing (distribute requests among slaves) becomes an impossible undertaking.
Take for example this picture where you see 3 Load Balancers (LB) and some slave servers.
Figure 1: Clients know one IP to which they connect, one load balancer is behind that IP and will have to handle all those requests, thus that first load balancer is the bottleneck (and the internet connection).
What happens when the first load balancer starts struggling? If I add a new load balancer to side with the first one, I must add even another one so that the clients only need to know one IP. So the dilema continues: I still have only one load balancer receiving all my requests...!
Figure 2: I added one load balancer, but for having clients to know just one IP I had to add another one to centralize the incoming connections, thus ending up with the same bottleneck.
Moreover, my internet connection will also reach its limit of clients it can handle so I probably will want to have my load balancers in remote places to avoid flooding my internet connection. However if I distribute my load balancers, and want to keep my clients knowing just one single IP they have to connect, I still need to have one central load balancer behind that IP carrying all the traffic once again...
How do real world companies like Google and Facebook handle these issues? Can this be done without giving the clients multiple IPs and expect them to choose one at random avoiding every client to connect to the same load balancer, thus flooding us?