Refactor gun pooling and simplify adapter option insertion
This patch refactors gun pooling to use Elixir process registry and simplifies adapter option insertion.
Having the pool use process registry instead of a GenServer has a number of advantages:
- Simpler code: the initial implementation adds about half the lines of code it deletes
- Concurrency: unlike a GenServer, ETS-based registry can handle multiple checkout/checkin requests at the same time
- Precise and easy idle connection clousure: current proposal for closing idle connections in
the GenServer-based pool needs to filter through all connections once a minute and compare their
last active time with closing time. With Elixir process registry this can be done
by just using
Process.cancel_timerin the worker process.
- Lower memory footprint: In my tests
gun-memory-leakbranch uses about 290mb on peak load (250 connections) and 235mb on idle (5-10 connections). Registry-based pool uses 210mb on idle and 240mb on peak load
- Port pool-aware FollowRedirects middleware from !2440 (closed)
- Decide on what "pools" are supposed to be
- Fix tests
Add failure logging (maybe use