Load balancer ¶

A load balancer is a device sitting between clients and servers. Its main purpose is to ensure the charge is appropriately balanced between every server, to avoid overcooking servers.

They operate either at layer 4 (TCP, IP...) or at layer 7 (HTTP...).

➡️ There are hardware-based and software-based load balancers.

They commonly use algorithms such as round-robin (in turn), weighted round robin (is server busy?), least connections/response time...

There are periodic checks to ensure that servers are still available. If there is no response from a server, it's considered as down. When the server is "up" again, it notifies the load balancer.