From: Daniel Berger <djberg96@...>
Date: 2009-08-13T18:14:49+09:00
Subject: Re: How to make net-ping thread safe?

Laurent Julliard wrote:
> Hi,
> 
> I'm using the excellent net-ping gem (v 1.2.2 on Ruby 1.8.6 Linux box) 
> from Daniel Berger to ping a number of machines on a local area network.
> 
> I recently refactored my code to use threads and I'm having troubles 
> with Net::Ping::ICMP. I'm trying to ping several machines, each one in a 
> separate thread and I'm seing strange things like when one machine is on 
> all three machines are reported on (although two are off). When I run my 
> program with one thread only the on/off state shows as expected.
> 
> So I'm wondering if the Net::Ping::ICMP#ping method is thread safe? 
> Daniel said he made no attempt to make sure that the code is and 
> usggested that I post this question here.
> 
> The code for the method Net::Ping::ICMP#ping is here:
> http://www.koders.com/ruby/fidE6256BC790B8AD197544CE26287B5C7D3200E4C8.aspx?s=icmp#L5 
> 
> 
> (line 61)
> 
> Here is also a simplified version of my own code:
> 
> -----------------------------------------------
> 
> require 'rubygems'
> require 'net/ping/icmp'
> 
> WORK_STATIONS = ['192.168.1.1', '192.168.1.2', '192.168.1.3']
> threads = []
> ping_objects = []
> 
> WORK_STATIONS.each do |ip|
>   ping_objects << Net::Ping::ICMP.new(ip)
>   threads << Thread.new(ip, ping_objects.last) do |ip, p|
>     puts "Monitoring #{ip}..."
>     loop do
>       puts "#{ip} is #{p.ping ? 'on' : 'off'}"
>       sleep 2
>     end
>   end
> end
> 
> threads.each { |th| th.join }

Very late reply here.

Odd. When I ran nearly identical code it worked as expected. However, 
when applied Joel's patch it didn't work right - it reported all hosts 
as off. Not sure why.

That was on OS X 10.4.9 with Ruby 1.8.6-368 btw.

Regards,

Dan