From: "Christoffer Lernö" <lerno@...>
Date: 2007-10-15T04:51:10+09:00
Subject: Re: write_nonblock is blocking?


On 14 Oct 2007, at 18:14, Tanaka Akira wrote:

> In article <E8AB2CFA-FDAF-47B3-A0BE-4C089960C5CF@dragonascendant.com>,
>   Christoffer Lernö <lerno@dragonascendant.com> writes:
>
>> Could this be due to me running
>>
>> ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-darwin8.10.1] ?
>>
>> The funny thing was that only the socket returned by accept_nonblock
>> had this behaviour, that is
>
> I think it is a Mac OS X problem.
>
> Your example works without problem on GNU/Linux and FreeBSD
> box but not on Mac OS X.
>
> % cat z1.rb
> require 'socket'
> require 'fcntl'
> a = TCPServer.new(5000)
> socket = TCPSocket.new("localhost", 5000)
> other = a.accept
> p other.fcntl(Fcntl::F_GETFL) & Fcntl::O_NONBLOCK
> puts "Start Write"
> p other.write_nonblock("X" * 300000)
> puts "End Write"
> % ./ruby -v z1.rb
> ruby 1.8.6 (2007-03-13 patchlevel 0) [powerpc-darwin8.3.0]
> 0
> Start Write
> 81560
> End Write
>
> The IO returned from accept is not nonblocking mode.
> So write_nonblock makes it nonblocking mode at first.
>
> % cat z2.rb
> require 'socket'
> require 'fcntl'
> a = TCPServer.new(5000)
> socket = TCPSocket.new("localhost", 5000)
> other = a.accept_nonblock
> p other.fcntl(Fcntl::F_GETFL) & Fcntl::O_NONBLOCK
> puts "Start Write"
> p other.write_nonblock("X" * 300000)
> puts "End Write"
> % ./ruby -v z2.rb
> ruby 1.8.6 (2007-03-13 patchlevel 0) [powerpc-darwin8.3.0]
> 4
> Start Write
> ^Cz2.rb:8: Interrupt
>
> The IO returned from accept_nonblock seems nonblocking mode.
> So write_nonblock doesn't make it nonblocking mode.
> But actually it is not nonblocking mode, I think.

Yeah, that seems to be it.

This workaround in the ruby code gets around the problem:

require 'socket'
require 'fcntl'
a = TCPServer.new(5000)
socket = TCPSocket.new("localhost", 5000)
other = a.accept_nonblock
other.fcntl(Fcntl::F_SETFL, other.fcntl(Fcntl::F_GETFL) & ~ 
(Fcntl::O_NONBLOCK))
puts "Start Write"
other.write_nonblock("X" * 300000)
puts "End Write"


/C