Design a load balancer

Why load balancing: E.g. to handle million/billion users, we need to have 10000 servers. Thus we need to load balancing the requests uniformly distributed to our 'healthy' servers.

这里Bittiger 提供了一个讲硬件load balancer的视频。我总结了一下笔记。

1. Load balancing 算法： round robin, random, current connections count, response time.

2. Follow - on traffic (同一个request map到同一个server上。):

   1. long-lived TCP connection

      • keep track of open connections

   2. short-lived

      1. Source address affinity (not reliable)

      2. Deep packet Inspection (use cookie)

         • pros: reliable
         • cons: less through put (flow table.)

3. 原来F5就是卖负载均衡器得。L7型号得load balancer。 在6k吞吐量时候可以达到1000k的qps.就是所每个request小于6k的数据的话，一个load balancer就可以刚1million的qps了。感觉好厉害啊。