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# frozen_string_literal: true
# Released under the MIT License.
# Copyright, 2021-2025, by Samuel Williams.
require_relative "../support"
module IO::Event
# @namespace
module Debug
# Enforces the selector interface and delegates operations to a wrapped selector instance.
#
# You can enable this in the default selector by setting the `IO_EVENT_DEBUG_SELECTOR` environment variable. In addition, you can log all selector operations to a file by setting the `IO_EVENT_DEBUG_SELECTOR_LOG` environment variable. This is useful for debugging and understanding the behavior of the event loop.
class Selector
# Wrap the given selector with debugging.
#
# @parameter selector [Selector] The selector to wrap.
# @parameter env [Hash] The environment to read configuration from.
def self.wrap(selector, env = ENV)
log = nil
if log_path = env["IO_EVENT_DEBUG_SELECTOR_LOG"]
log = File.open(log_path, "w")
end
return self.new(selector, log: log)
end
# Initialize the debug selector with the given selector and optional log.
#
# @parameter selector [Selector] The selector to wrap.
# @parameter log [IO] The log to write debug messages to.
def initialize(selector, log: nil)
@selector = selector
@readable = {}
@writable = {}
@priority = {}
unless Fiber.current == selector.loop
Kernel::raise "Selector must be initialized on event loop fiber!"
end
@log = log
end
# The idle duration of the underlying selector.
#
# @returns [Numeric] The idle duration.
def idle_duration
@selector.idle_duration
end
# The current time.
#
# @returns [Numeric] The current time.
def now
Process.clock_gettime(Process::CLOCK_MONOTONIC)
end
# Log the given message.
#
# @asynchronous Will block the calling fiber and the entire event loop.
def log(message)
return unless @log
Fiber.blocking do
@log.puts("T+%10.1f; %s" % [now, message])
end
end
# Wakeup the the selector.
def wakeup
@selector.wakeup
end
# Close the selector.
def close
log("Closing selector")
if @selector.nil?
Kernel::raise "Selector already closed!"
end
@selector.close
@selector = nil
end
# Transfer from the calling fiber to the selector.
def transfer
log("Transfering to event loop")
@selector.transfer
end
# Resume the given fiber with the given arguments.
def resume(*arguments)
log("Resuming fiber with #{arguments.inspect}")
@selector.resume(*arguments)
end
# Yield to the selector.
def yield
log("Yielding to event loop")
@selector.yield
end
# Push the given fiber to the selector ready list, such that it will be resumed on the next call to {select}.
#
# @parameter fiber [Fiber] The fiber that is ready.
def push(fiber)
log("Pushing fiber #{fiber.inspect} to ready list")
@selector.push(fiber)
end
# Raise the given exception on the given fiber.
#
# @parameter fiber [Fiber] The fiber to raise the exception on.
# @parameter arguments [Array] The arguments to use when raising the exception.
def raise(fiber, *arguments, **options)
log("Raising exception on fiber #{fiber.inspect} with #{arguments.inspect}")
@selector.raise(fiber, *arguments, **options)
end
# Check if the selector is ready.
#
# @returns [Boolean] Whether the selector is ready.
def ready?
@selector.ready?
end
# Wait for the given process, forwarded to the underlying selector.
def process_wait(*arguments)
log("Waiting for process with #{arguments.inspect}")
@selector.process_wait(*arguments)
end
# Wait for the given IO, forwarded to the underlying selector.
def io_wait(fiber, io, events)
log("Waiting for IO #{io.inspect} for events #{events.inspect}")
@selector.io_wait(fiber, io, events)
end
# Read from the given IO, forwarded to the underlying selector.
def io_read(fiber, io, buffer, length, offset = 0)
log("Reading from IO #{io.inspect} with buffer #{buffer}; length #{length} offset #{offset}")
@selector.io_read(fiber, io, buffer, length, offset)
end
# Write to the given IO, forwarded to the underlying selector.
def io_write(fiber, io, buffer, length, offset = 0)
log("Writing to IO #{io.inspect} with buffer #{buffer}; length #{length} offset #{offset}")
@selector.io_write(fiber, io, buffer, length, offset)
end
# Forward the given method to the underlying selector.
def respond_to?(name, include_private = false)
@selector.respond_to?(name, include_private)
end
# Select for the given duration, forwarded to the underlying selector.
def select(duration = nil)
log("Selecting for #{duration.inspect}")
unless Fiber.current == @selector.loop
Kernel::raise "Selector must be run on event loop fiber!"
end
@selector.select(duration)
end
end
end
end
|
