Class: NIO::Selector

Inherits:
Object
  • Object
show all
Defined in:
lib/nio/selector.rb,
ext/nio4r/selector.c

Overview

Selectors monitor IO objects for events of interest

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(backend = :ruby) ⇒ Object

Instance methods


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# File 'lib/nio/selector.rb', line 31

def initialize(backend = :ruby)
  raise ArgumentError, "unsupported backend: #{backend}" unless [:ruby, nil].include?(backend)

  @selectables = {}
  @lock = Mutex.new

  # Other threads can wake up a selector
  @wakeup, @waker = IO.pipe
  @closed = false
end

Class Method Details

.backends ⇒ Object

Class methods


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# File 'lib/nio/selector.rb', line 26

def self.backends
  [:ruby]
end

Instance Method Details

#backend ⇒ Object

Return a symbol representing the backend I/O multiplexing mechanism used. Supported backends are:

  • :ruby - pure Ruby (i.e IO.select)

  • :java - Java NIO on JRuby

  • :epoll - libev w\ Linux epoll

  • :poll - libev w\ POSIX poll

  • :kqueue - libev w\ BSD kqueue

  • :select - libev w\ SysV select

  • :port - libev w\ I/O completion ports

  • :linuxaio - libev w\ Linux AIO io_submit (experimental)

  • :io_uring - libev w\ Linux io_uring (experimental)

  • :unknown - libev w\ unknown backend


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# File 'lib/nio/selector.rb', line 54

def backend
  :ruby
end

#close ⇒ Object

Close this selector and free its resources


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# File 'lib/nio/selector.rb', line 161

def close
  @lock.synchronize do
    return if @closed

    begin
      @wakeup.close
    rescue IOError
    end

    begin
      @waker.close
    rescue IOError
    end

    @closed = true
  end
end

#closed? ⇒ Boolean

Is this selector closed?

Returns:

  • (Boolean) 

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# File 'lib/nio/selector.rb', line 180

def closed?
  @closed
end

#deregister(io) ⇒ Object

Deregister the given IO object from the selector


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# File 'lib/nio/selector.rb', line 82

def deregister(io)
  @lock.synchronize do
    monitor = @selectables.delete IO.try_convert(io)
    monitor.close(false) if monitor && !monitor.closed?
    monitor
  end
end

#empty? ⇒ Boolean

Returns:

  • (Boolean) 

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# File 'ext/nio4r/selector.c', line 44

def empty?
  @selectables.empty?
end

#register(io, interest) ⇒ Object

Register interest in an IO object with the selector for the given types of events. Valid event types for interest are:

  • :r - is the IO readable?

  • :w - is the IO writeable?

  • :rw - is the IO either readable or writeable?


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# File 'lib/nio/selector.rb', line 63

def register(io, interest)
  unless defined?(::OpenSSL) && io.is_a?(::OpenSSL::SSL::SSLSocket)
    io = IO.try_convert(io)
  end

  @lock.synchronize do
    raise IOError, "selector is closed" if closed?

    monitor = @selectables[io]
    raise ArgumentError, "already registered as #{monitor.interests.inspect}" if monitor

    monitor = Monitor.new(io, interest, self)
    @selectables[monitor.io] = monitor

    monitor
  end
end

#registered?(io) ⇒ Boolean

Is the given IO object registered with the selector?

Returns:

  • (Boolean) 

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# File 'lib/nio/selector.rb', line 91

def registered?(io)
  @lock.synchronize { @selectables.key? io }
end

#select(timeout = nil) ⇒ Object

Select which monitors are ready


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# File 'lib/nio/selector.rb', line 96

def select(timeout = nil)
  selected_monitors = Set.new

  @lock.synchronize do
    readers = [@wakeup]
    writers = []

    @selectables.each do |io, monitor|
      readers << io if monitor.interests == :r || monitor.interests == :rw
      writers << io if monitor.interests == :w || monitor.interests == :rw
      monitor.readiness = nil
    end

    ready_readers, ready_writers = Kernel.select(readers, writers, [], timeout)
    return unless ready_readers # timeout

    ready_readers.each do |io|
      if io == @wakeup
        # Clear all wakeup signals we've received by reading them
        # Wakeups should have level triggered behavior
        @wakeup.read(@wakeup.stat.size)
      else
        monitor = @selectables[io]
        monitor.readiness = :r
        selected_monitors << monitor
      end
    end

    ready_writers.each do |io|
      monitor = @selectables[io]
      monitor.readiness = monitor.readiness == :r ? :rw : :w
      selected_monitors << monitor
    end
  end

  if block_given?
    selected_monitors.each { |m| yield m }
    selected_monitors.size
  else
    selected_monitors.to_a
  end
end

#wakeup ⇒ Object

Wake up a thread that’s in the middle of selecting on this selector, if any such thread exists.

Invoking this method more than once between two successive select calls has the same effect as invoking it just once. In other words, it provides level-triggered behavior.


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# File 'lib/nio/selector.rb', line 145

def wakeup
  # Send the selector a signal in the form of writing data to a pipe
  begin
    @waker.write_nonblock "\0"
  rescue IO::WaitWritable
    # This indicates the wakeup pipe is full, which means the other thread
    # has already received many wakeup calls, but not processed them yet.
    # The other thread will completely drain this pipe when it wakes up,
    # so it's ok to ignore this exception if it occurs: we know the other
    # thread has already been signaled to wake up
  end

  nil
end