Reduce per-request allocations on the request hot path#2696
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Reduce per-request allocations on the request hot path#2696ericproulx wants to merge 1 commit intomasterfrom
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A bundle of small, behavior-preserving cleanups that drop allocations
or chain walks from every request. Stable values (filter buckets,
versioner options, etc.) are computed once at compile/init and read via
`attr_reader`, instead of being re-resolved through nested hash lookups
on every request.
* `Endpoint#run`: precompute filter buckets (befores, before_validations,
after_validations, afters, finallies) and `:build_params_with` once
in `compile!`; replace the dynamic `define_method` accessor block
with `attr_reader`; remove a dead `header 'Allow', header['Allow']`
self-assignment.
* `Versioner::Base`: replace the two `define_method`-per-key blocks
(top-level and `version_options` keys) with `attr_reader` plus ivars
precomputed in `initialize`. Per-request `pattern`/`prefix`/`vendor`/
`strict`/etc. lookups now hit attr loads.
* `Request#make_params`: skip the `except(:version, :route_info)` hash
allocation in the common case where routing args contain only the
known keys.
* `Validators::Base#validate!`: lazy-allocate `array_errors`. Saves one
Array allocation per validator per request when validation succeeds.
* `InheritableValues#[]`: drop the per-call merge with `Hash#fetch`
plus a fallback block. Lookup is 1.55x faster microbenched, allocates
zero. Mostly helps boot/compile time (where ~30+ reads per endpoint
hit this).
* `Grape::API::Instance`: rename `ROOT_PREFIX_VERSIONING_KEY` to
`ROOT_PREFIX_VERSIONING_KEYS` (it holds 3 symbols), pair via `zip`
instead of `each_with_index` + manual indexing.
* `Validations::Types::CustomTypeCoercer#infer_coercion_method`:
guard-clause refactor of the nested if/else.
End-to-end, 3-run averaged on Ruby 4.0.3, arm64-darwin25, against
`/api/v1/hello` returning a small JSON object:
no-yjit yjit
master HEAD: 52,088 i/s 101,563 i/s
master + this PR: 57,433 i/s 107,982 i/s
+10.3% +6.3%
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
A bundle of small, behavior-preserving cleanups that reduce per-request allocations and method-dispatch chains on the request hot path. None change semantics — existing specs pass unchanged. The unifying pattern: stable values (filter buckets, versioner options, etc.) are computed once at compile/init time and read via
attr_reader, instead of being re-resolved through nested hash lookups on every request.Changes
Endpoint#run— precompute filter buckets (befores,before_validations,after_validations,afters,finallies) and:build_params_withonce incompile!; replace the dynamicdefine_methodaccessor block withattr_reader; remove a deadheader 'Allow', header['Allow']self-assignment.Versioner::Base— same shape: replace the twodefine_method-per-key blocks withattr_reader+ ivars precomputed ininitialize. Per-requestpattern/prefix/vendor/strict/etc. lookups now hit attr loads.Request#make_params— skip theexcept(:version, :route_info)hash allocation in the common case where routing args contain only the known keys.Validators::Base#validate!— lazy-allocatearray_errors. Saves one Array allocation per validator per request when validation succeeds.InheritableValues#[]— drop the per-call@inherited_values.merge(@new_values)and useHash#fetchwith a fallback block. 1.55x faster lookup, zero allocation. Mostly helps boot/compile time (where ~30+ reads per endpoint hit this).Grape::API::Instance— renameROOT_PREFIX_VERSIONING_KEY→ROOT_PREFIX_VERSIONING_KEYS(holds 3 symbols); pair withzipinstead ofeach_with_index+ manual indexing.Validations::Types::CustomTypeCoercer#infer_coercion_method— guard-clause refactor of nested if/else.Throughput impact
3-run averaged on Ruby 4.0.3, arm64-darwin25, against
/api/v1/helloreturning a small JSON object:The relative gain compresses under YJIT (10% → 6%) since the JIT was already specializing some of the hot-path indirection; the absolute gain stays at ~+6.4k req/s either way.
Test plan
bundle exec rspec— full suite green (2236 examples, 0 failures), no test changes needed.bundle exec rubocopon touched files — clean.🤖 Generated with Claude Code