ETS-backed kura_pool implementation. Hands out opaque connection refs from an ETS-tracked free list. Useful for:

• Conformance tests against the kura_pool behaviour without docker.
• Unit tests of code that needs to lease/return connections but does not actually need to run SQL.
• A worked example for authors of new pool impls (the second impl is what proves a behaviour is real).

This pool does NOT speak any database protocol. The conn() value returned from checkout/2 is an opaque reference that callers can match on in tests but cannot pass to pgo or any other driver.

Pool layout

Each pool owns one ETS table, named after the pool atom. The table holds two rows:

• {available, [ref()]} — free connection refs.
• {checked_out, #{ref() => pid()}} — leased refs and their owner.

pool_size from start_pool/2 opts determines how many refs are pre-generated. Defaults to 1.

Example

{ok, _Pid} = kura_pool_ets:start_pool(my_test_pool, #{pool_size => 4}),
{ok, Conn, Token} = kura_pool_ets:checkout(my_test_pool, #{}),
%% ... use Conn ...
ok = kura_pool_ets:checkin(my_test_pool, Token),
ok = kura_pool_ets:stop_pool(my_test_pool).