标签归档:sticky sessions

load balancing, affinity, persistence, sticky sessions: what you need to know

Synopsis

To ensure high availability and performance of Web applications, it is now common to use a load-balancer.
While some people uses layer 4 load-balancers, it can be sometime recommended to use layer 7 load-balancers to be more efficient with HTTP protocol.

NOTE: To understand better the difference between such load-balancers, please read the Load-Balancing FAQ.

A load-balancer in an infrastructure

The picture below shows how we usually install a load-balancer in an infrastructure:

This is a logical diagram. When working at layer 7 (aka Application layer), the load-balancer acts as a reverse proxy.
So, from a physical point of view, it can be plugged anywhere in the architecture:

  • in a DMZ
  • in the server LAN
  • as front of the servers, acting as the default gateway
  • far away in an other separated datacenter

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