Introduce IO::Event::WorkerPool for blocking_operation_wait.

[samuel-williams-shopify]

This implements a thread-based worker pool that integrates with Ruby's experimental fiber scheduler blocking_operation_wait hook to handle blocking operations asynchronously. The WorkerPool uses feature detection to support the new rb_fiber_scheduler_blocking_operation_* functions introduced in recent Ruby versions, providing a promise-based interface for submitting work to a thread pool without blocking the event loop. For example, when blocking operations like large IO::Buffer.copy calls (>1MiB) release the GVL, fiber schedulers can delegate them to the worker pool, allowing the main thread to continue processing other fibers.

Types of Changes

• New feature.

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[Copilot]

Pull Request Overview

This PR adds a thread‐based IO::Event::WorkerPool and integrates it into a test fiber scheduler via Ruby’s blocking_operation_wait hook, enabling non‐blocking execution of GVL‐releasing operations.

• Introduces IO::Event::WorkerPool C extension and registers it in Init_IO_Event
• Adds IO::Event::TestScheduler fixture to delegate blocking operations to the worker pool
• Adds tests for pool construction, stats, and integration with large IO::Buffer.copy operations

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/io/event/worker_pool.rb	New tests for pool instantiation, stats API, and scheduler integration
fixtures/io/event/test_scheduler.rb	Defines IO::Event::TestScheduler to route blocking ops to WorkerPool
ext/io/event/worker_pool.h	Declares the Init_IO_Event_WorkerPool initializer
ext/io/event/fiber.c	Changed visibility of IO_Event_Fiber_current from static to global
ext/io/event/event.c	Calls Init_IO_Event_WorkerPool to register the extension
ext/extconf.rb	Adds worker_pool.c to the build list and feature detection for blocking hooks

Comments suppressed due to low confidence (4)

test/io/event/worker_pool.rb:11

• [nitpick] Consider adding unit tests for WorkerPool#call to verify that submitted tasks execute and that the returned promise resolves or rejects correctly.

describe IO::Event::WorkerPool do

ext/extconf.rb:26

• The build list includes "io/event/worker_pool.c" but that source file isn't committed. This will break compilation; ensure the .c implementation is present or remove it from $srcs.

$srcs = ["io/event/event.c", "io/event/time.c", "io/event/fiber.c", "io/event/worker_pool.c", "io/event/selector/selector.c"]

test/io/event/worker_pool.rb:7

• The test requires io/event/test_scheduler, but the fixture file lives under fixtures/.... Consider using require_relative or adjusting $LOAD_PATH so the test can load the scheduler definition.

require "io/event/test_scheduler"

ext/io/event/fiber.c:38

• [nitpick] IO_Event_Fiber_current was made a global symbol by removing static. Unless it needs external linkage, restore static to limit symbol exposure.

VALUE IO_Event_Fiber_current(void) {

[trevorturk]

This is very exciting to see! 👀