Module subset 

Deterministic Subsetting load balancer

For very large clusters (1000+ backends), maintaining connections to all backends is expensive. Deterministic subsetting limits each proxy instance to a subset of backends while ensuring:

1. Each backend gets roughly equal traffic across all proxies
2. The subset is stable (same proxy always uses same subset)
3. Subset membership is deterministic (based on proxy ID)

The algorithm uses consistent hashing to assign backends to subsets, ensuring minimal disruption when backends are added or removed.

Reference: https://sre.google/sre-book/load-balancing-datacenter/

Structs

SubsetBalancer

Deterministic Subsetting load balancer

SubsetConfig

Configuration for Deterministic Subsetting

Enums

SubsetInnerAlgorithm

Inner algorithm for selecting within the subset