Add optional name resolver for per-process cache redirection#436
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Add optional name resolver for per-process cache redirection#436pinetops wants to merge 1 commit into
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Every cache call funnels through `Overseer.lookup/1` to map a cache name to its state. There is currently no supported way to redirect that resolution based on the calling process, which forces test-isolation libraries (e.g. for `async: true` tests) to runtime-patch Cachex's bytecode to give each test its own cache. Add an opt-in `:name_resolver` — a `(atom -> atom)` function consulted at the single resolution chokepoint via `Overseer.resolve_name/1`. It defaults to the identity function, so there is no behaviour change and no measurable overhead unless configured. When set, a name can be transparently routed to a different cache (e.g. a per-test cache derived from the process dictionary or `$callers`), enabling sandboxing without forking or patching Cachex. Resolution is non-recursive (the resolver's result is the ETS key), and a resolver returning nil falls back to the original name.
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…on coupling Ecto/Mimic/Mox have first-class per-process hooks; Cachex and FunWithFlags don't, so sandbox_case patches their compiled modules at runtime (test env only) to route to isolated ETS storage. Document this mechanism, the tested version ranges (Cachex 4.1.x, FWF 1.13.x), and the graceful-degradation behavior (probe shape, warn + skip on mismatch rather than crash). Note the upstream direction: whitfin/cachex#436 (a per-process name resolver) and the no-patch FunWithFlags alternative (custom Store.Persistent adapter + cache disabled). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Motivation
Every public
Cachex.*call funnels throughCachex.Services.Overseer.lookup/1, which maps a cache name to its cache state via a single ETS read. There's currently no supported way to influence that resolution based on the calling process.This matters for test isolation. A library that wants to give each
async: truetest its own isolated cache (so concurrent tests don't share state through a globally-named cache) has no hook to do so.What this does
Adds an opt-in
:name_resolverconsulted at the single resolution chokepoint, via a newOverseer.resolve_name/1:The resolver is a
(atom -> atom)function.lookup/1's atom clause passes the name through it before the ETS read, so a name can be transparently routed to a different registered cache — e.g. a per-test cache derived from the process dictionary or$callers.:name_resolveris unset, behaviour is unchanged and there's no measurable overhead (oneApplication.get_envreturningnil).nilfalls back to the original name.This lets test-isolation (and similar per-process routing) work against vanilla Cachex, no fork or bytecode patching..