Support Jump hashing algorithm for metric load balancing

[trinitronx]

Once the amount of metrics fed into graphite becomes large enough, it seems that the consistent hashring algorithm does not balance very effectively across the number of carbon-cache hosts. There is an open issue on the official graphite-carbon repo detailing some user stories and data regarding the hash ring and disk space allocation across carbon nodes. Additionally, there had been a Jump hashing algorithm written in Golang that appeared to fix the issue. Not sure what the implications on the rest of graphite components would be if implemented in the relay, but since it's in Golang as carbon-relay-ng is, I thought I'd mention it.

Original issue is here: graphite-project/carbon#485
Jump hash code is here: https://github.com/dgryski/go-shardedkv/blob/475ce8b591f975aec7fb84640ac244d6bd3d7860/choosers/jump/jump.go#L27

[Dieterbe]

Yeah at booking their stack also switched to jmp for this reason. I'll gladly accept a PR for this especially when it's compatible with other jump hashing implementations in other graphite tools

[Dieterbe]

AFAIK carbon still hasn't solved this. But gorelka is another tool that has (background)