Add optional support for the fiber-profiler gem. (#376)

Author: ioquatix

.github/workflows/test-coverage.yaml

@@ -27,8 +27,15 @@ jobs:
             ruby: "3.3"
             selector: EPoll
           - os: ubuntu
-            ruby: "3.3"
+            ruby: "3.4"
+            selector: EPoll
+          - os: ubuntu
+            ruby: "3.4"
             selector: URing
+          - os: ubuntu
+            ruby: "3.4"
+            selector: URing
+            fiber_profile_capture: "true"
           - os: ubuntu
             ruby: "head"
             selector: URing
@@ -37,6 +44,9 @@ jobs:
             selector: URing
             worker_pool: "true"
 
+    env:
+      FIBER_PROFILER_CAPTURE: ${{matrix.fiber_profile_capture}}
+    
     steps:
     - uses: actions/checkout@v4
     - uses: ruby/setup-ruby-pkgs@v1
@@ -51,13 +61,14 @@ jobs:
       env:
         IO_EVENT_SELECTOR: ${{matrix.selector}}
         ASYNC_SCHEDULER_DEFAULT_WORKER_POOL: ${{matrix.worker_pool}}
+        FIBER_PROFILER_CAPTURE: ${{matrix.fiber_profile_capture}}
       run: bundle exec bake test
 
     - uses: actions/upload-artifact@v4
       with:
         include-hidden-files: true
         if-no-files-found: error
-        name: coverage-${{matrix.os}}-${{matrix.ruby}}-${{matrix.selector}}-${{matrix.worker_pool}}
+        name: coverage-${{matrix.os}}-${{matrix.ruby}}-${{matrix.selector}}-${{matrix.worker_pool}}-${{matrix.fiber_profile_capture}}
         path: .covered.db
 
   validate:

async.gemspec

@@ -27,7 +27,7 @@ Gem::Specification.new do |spec|
 
 	spec.add_dependency "console", "~> 1.29"
 	spec.add_dependency "fiber-annotation"
-	spec.add_dependency "io-event", "~> 1.7"
+	spec.add_dependency "io-event", "~> 1.9"
 	spec.add_dependency "traces", "~> 0.15"
 	spec.add_dependency "metrics", "~> 0.12"
 end

gems.rb

@@ -11,6 +11,11 @@
 
 # gem "io-event", git: "https://github.com/socketry/io-event.git"
 
+# In order to capture both code paths in coverage, we need to optionally load this gem:
+if ENV["FIBER_PROFILER_CAPTURE"] == "true"
+	gem "fiber-profiler"
+end
+
 group :maintenance, optional: true do
 	gem "bake-gem"
 	gem "bake-modernize"

lib/async/scheduler.rb

@@ -15,6 +15,14 @@
 require "resolv"
 
 module Async
+	begin
+		require "fiber/profiler"
+		Profiler = Fiber::Profiler
+	rescue LoadError
+		# Fiber::Profiler is not available.
+		Profiler = nil
+	end
+	
 	# Handles scheduling of fibers. Implements the fiber scheduler interface.
 	class Scheduler < Node
 		DEFAULT_WORKER_POOL = ENV.fetch("ASYNC_SCHEDULER_DEFAULT_WORKER_POOL", nil).then do |value|
@@ -42,10 +50,12 @@ def self.supported?
 		# @public Since *Async v1*.
 		# @parameter parent [Node | Nil] The parent node to use for task hierarchy.
 		# @parameter selector [IO::Event::Selector] The selector to use for event handling.
-		def initialize(parent = nil, selector: nil, worker_pool: DEFAULT_WORKER_POOL)
+		def initialize(parent = nil, selector: nil, profiler: Profiler&.default, worker_pool: DEFAULT_WORKER_POOL)
 			super(parent)
 
 			@selector = selector || ::IO::Event::Selector.new(Fiber.current)
+			@profiler = profiler
+			
 			@interrupted = false
 
 			@blocked = 0
@@ -492,13 +502,19 @@ def stop
 		def run(...)
 			Kernel.raise ClosedError if @selector.nil?
 
-			initial_task = self.async(...) if block_given?
-			
-			self.run_loop do
-				run_once
+			begin
+				@profiler&.start
+				
+				initial_task = self.async(...) if block_given?
+				
+				self.run_loop do
+					run_once
+				end
+				
+				return initial_task
+			ensure
+				@profiler&.stop
 			end
-			
-			return initial_task
 		end
 
 		# Start an asynchronous task within the specified reactor. The task will be executed until the first blocking call, at which point it will yield and and this method will return.

test/io.rb

@@ -45,12 +45,14 @@
 		it "can write with timeout" do
 			skip_unless_constant_defined(:TimeoutError, IO)
 
+			big = "x" * 1024 * 1024
+			
 			input, output = IO.pipe
 			output.timeout = 0.001
 
 			expect do
 				while true
-					output.write("Hello")
+					output.write(big)
 				end
 			end.to raise_exception(::IO::TimeoutError)
 		end