David Turner 39a3a950de Simplify rebalancer's weight function (#51632)
This commit inlines the `weightShardAdded` and `weightShardRemoved` methods
from the `BalancedShardsAllocator#WeightFunction` that respectively add and
subtract 1 (±ε) from the result of `weight`. It then follows up with a number
of simplifications that this inlining enables.

As a side-effect it also somewhat reduces the number of calls to canRebalance
and canAllocate during rebalancing when there are multiple shards of the same
index on a node that is heavier than average.
2020-01-31 14:40:23 +00:00
..