Locality-aware load balancing(LALB) is an algorithm that can send requests to downstream servers with the lowest latency timely and automatically. The algorithm is originated from the DP system and is now added to brpc!
Problems that LALB can solve:
The most common algorithm to redirect requests is round-robin and random. The premise of these two methods is that the downstream servers and networks are similar. But in the current online environment, especially the hybrid environment, it is difficult to achieve because:
These problems have always been there, but are hidden by machine monitoring from hard-working OPs. There are also some attempts in the level of frameworks. For example, WeightedStrategy in UB redirects requests based on cpu usage of downstream machines and obviously it cannot solve the latency-related issues, or even cpu issues: since it is implemented as regularly reloading a list of weights, one can imagine that the update frequency cannot be high. A lot of requests may timeout when the load balancer reacts. And there is a math problem here: how to change cpu usage to weight.