Async::IO

Async::IO provides builds on async and provides asynchronous wrappers for IO, Socket, and related classes.

Installation

Add this line to your application's Gemfile:

gem 'async-io'

And then execute:

$ bundle

Or install it yourself as:

$ gem install async-io

Usage

Basic echo server (from spec/async/io/echo_spec.rb):

require 'async/io'

def echo_server(endpoint)
    Async do |task|
        # This is a synchronous block within the current task:
        endpoint.accept do |client|
            # This is an asynchronous block within the current reactor:
            data = client.read(512)

            # This produces out-of-order responses.
            task.sleep(rand * 0.01)

            client.write(data.reverse)
        end
    end
end

def echo_client(endpoint, data)
    Async do |task|
        endpoint.connect do |peer|
            result = peer.write(data)

            message = peer.read(512)

            puts "Sent #{data}, got response: #{message}"
        end
    end
end

Async do
    endpoint = Async::IO::Endpoint.tcp('0.0.0.0', 9000)

    server = echo_server(endpoint)

    5.times.collect do |i|
        echo_client(endpoint, "Hello World #{i}")
    end.each(&:wait)

    server.stop
end

Timeouts

Timeouts add a temporal limit to the execution of your code. If the IO doesn't respond in time, it will fail. Timeouts are high level concerns and you generally shouldn't use them except at the very highest level of your program.

message = task.with_timeout(5) do
    begin
        peer.read(512)
    rescue Async::TimeoutError
        nil # The timeout was triggered.
    end
end

Any yield operation can cause a timeout to trigger. Non-async functions might not timeout because they are outside the scope of async.

Wrapper Timeouts

Asynchronous operations may block forever. You can assign a per-wrapper operation timeout duration. All asynchronous operations will be bounded by this timeout.

peer.timeout = 1
peer.read(512) # If this takes more than 1 second, Async::TimeoutError will be raised.

The benefit of this approach is that it applies to all operations. Typically, this would be configured by the user, and set to something pretty high, e.g. 120 seconds.

Reading Characters

This example shows how to read one character at a time as the user presses it on the keyboard, and echos it back out as uppercase:

require 'async'
require 'async/io/stream'
require 'io/console'

$stdin.raw!
$stdin.echo = false

Async do |task|
    stdin = Async::IO::Stream.new(
        Async::IO::Generic.new($stdin)
    )

    while character = stdin.read(1)
        $stdout.write character.upcase
    end
end

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

See Also

• async — Asynchronous event-driven reactor.
• async-process — Asynchronous process spawning/waiting.
• async-websocket — Asynchronous client and server websockets.
• async-dns — Asynchronous DNS resolver and server.
• async-rspec — Shared contexts for running async specs.
• rubydns — A easy to use Ruby DNS server.

License

Released under the MIT license.

Copyright, 2017, by Samuel G. D. Williams.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.