ruby-grape / grape / 35590159799

98%

master: 99%

Pull #2978

github

Add Ractor mode

A Grape API is defined and compiled in the main Ractor -- a non-main one
cannot write a class instance variable at all, and that is where the DSL
keeps everything -- so the only shape this can take is: define, compile,
freeze, then serve from as many Ractors as the application wants.

Grape.ractor! turns the mode on, before the API classes load, because it
decides how a route block becomes a method: Ruby refuses to call a method
defined from an unshareable Proc from another Ractor, so in this mode the
blocks are isolated as they are read, and one that captures something
unshareable says so as its class loads. It needs Ruby 4.0 or later, and
says so rather than leaving an API half-frozen: 3.3 and 3.4 cannot make a
Method shareable, and an API is full of them -- every endpoint holds its
route block as one, and dry-types builds its coercers out of them.

MyAPI.finalize! then compiles the API, makes the whole graph behind it
shareable, and settles the process-wide state a request reads: Grape's
own configuration (read once per setting first, or dry-configurable's
memoization would write to a frozen Hash), the tables and options Rack,
ActiveSupport, Builder and the json gem fill as they load, and a snapshot
of the grape translations, since I18n keeps its configuration in class
variables that a non-main Ractor may not read at all. Instrumentation is
skipped in this mode for the same reason.

What it gives up is in the README: instrumentation, per-request locale,
file uploads (Ruby's own Tempfile is a Delegator, whose methods cannot be
called from a non-main Ractor) and reloading.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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