Finch.Pool.Strategy.Hash (Finch v0.22.0)
View SourceSelects a pool worker by hashing a key, so the same key always maps to the same worker.
Useful for connection affinity: e.g. team IDs, session tokens, or any scenario where routing the same logical entity to the same connection is beneficial.
This strategy takes a key and selects a worker using :erlang.phash2/2.
This ensures that tasks classified under the same key will be delivered to the same worker,
which is useful to classify events by key and work on them sequentially on the worker,
distributing different keys across different workers.
If no key is given, it uses self() when constructing a state.
Example
key = Finch.Pool.Strategy.Hash.new()
Finch.request(req, MyFinch, pool_strategy: {Finch.Pool.Strategy.Hash, key})
## equivalent to the above
Finch.request(req, MyFinch, pool_strategy: {Finch.Pool.Strategy.Hash, self()})
key = Finch.Pool.Strategy.Hash.new(tenant_id)
Finch.request(req, MyFinch, pool_strategy: {Finch.Pool.Strategy.Hash, key})
## equivalent to the above
Finch.request(req, MyFinch, pool_strategy: {Finch.Pool.Strategy.Hash, tenant_id})