gjsbrt / hashed-weighted-round-robin

Hashed weighted round robin is a load balancing algorithm that will distribute traffic between destinations based on a hash and weight of backends.

Heyo, I'm Gijsbert!

Nice to meet you. I am a passionate self-taught full stack developer from the Netherlands. I primarily work on DutchIS, have a look if you are interessted 😁.

hashed-weighted-round-robin's Issues

Nice work.

This all seems pretty sound, although I'm not sure round-robin is the best description - more like weighted-hash?

The problem that you could run into is when you need to add or remove backends from the pool (eg. when reconfigured or a backend fails health checks). This would change to the length of the array, which makes a drastic change to selections of backends, and would break the majority of connections.

This can be avoided by using a consistent hashing algorithm which results in only losing around 1/n-th of the connections when the pool changes. Rendezvous hasing or Maglev are two examples - I found the worked example from page 32 onwards in this description of Google's internal project to be quite easy to follow:

https://www.usenix.org/sites/default/files/conference/protected-files/nsdi16_slides_eisenbud.pdf