Getting Started

This guide explains how to use io-event for non-blocking IO.

Installation

Add the gem to your project:

$ bundle add io-event

Core Concepts

io-event has several core concepts:

A module IO::Event::Selector implementation which provides the primitive operations for implementation an event loop.
A class IO::Event::Debug::Selector which adds extra validations and checks at the expense of performance. You should generally use this during tests.

Basic Event Loop

This example shows how to perform a blocking operation

require 'fiber'
require 'io/event'

selector = IO::Event::Selector.new(Fiber.current)
input, output = IO.pipe

writer = Fiber.new do
	output.write("Hello World")
	output.close
end

reader = Fiber.new do
	selector.io_wait(Fiber.current, input, IO::READABLE)
	pp read: input.read
end

# The reader will be blocked until the IO has data available:
reader.transfer

# Write some data to the pipe and close the writing end:
writer.transfer

selector.select(1)

# Results in:
# {:read=>"Hello World"}

Debugging

The class IO::Event::Debug::Selector class adds extra validations and checks at the expense of performance. It can also log all operations. You can use this by setting the following environment variables:

$ IO_EVENT_SELECTOR_DEBUG=y IO_EVENT_SELECTOR_DEBUG_LOG=/dev/stderr bundle exec ./my_script.rb

The format of the log is subject to change, but it may be useful for debugging.