Class: Hydra::Pipe

Inherits:
Object
  • Object
show all
Includes:
MessagingIO
Defined in:
lib/hydra/pipe.rb

Overview

Read and write between two processes via pipes. For example:

@pipe = Hydra::Pipe.new
@child = Process.fork do
  @pipe.identify_as_child
  puts "A message from my parent:\n#{@pipe.gets.text}"
  @pipe.close
end
@pipe.identify_as_parent
@pipe.write Hydra::Messages::TestMessage.new(:text => "Hello!")
@pipe.close

Note that the TestMessage class is only available in tests, and not in Hydra by default.

When the process forks, the pipe is copied. When a pipe is identified as a parent or child, it is choosing which ends of the pipe to use.

A pipe is actually two pipes:

Parent  == Pipe 1 ==> Child
Parent <== Pipe 2 ==  Child

It’s like if you had two cardboard tubes and you were using them to drop balls with messages in them between processes. One tube is for sending from parent to child, and the other tube is for sending from child to parent.

Instance Method Summary collapse

Methods included from MessagingIO

#close, #gets, #write

Constructor Details

#initialize ⇒ Pipe

Creates a new uninitialized pipe pair.



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# File 'lib/hydra/pipe.rb', line 34

def initialize
  @child_read, @parent_write = IO.pipe
  @parent_read, @child_write = IO.pipe
end

Instance Method Details

#identify_as_child ⇒ Object

Identify this side of the pipe as the child.



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# File 'lib/hydra/pipe.rb', line 40

def identify_as_child
  @parent_write.close
  @parent_read.close
  @reader = @child_read
  @writer = @child_write
end

#identify_as_parent ⇒ Object

Identify this side of the pipe as the parent



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# File 'lib/hydra/pipe.rb', line 48

def identify_as_parent
  @child_write.close
  @child_read.close
  @reader = @parent_read
  @writer = @parent_write
end

#inspect ⇒ Object

Output pipe nicely



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# File 'lib/hydra/pipe.rb', line 56

def inspect
  "#<#{self.class} @reader=#{@reader.to_s}, @writer=#{@writer.to_s}>"
end