From: Brian Candler <b.candler@...>
Date: 2010-12-25T01:13:22+09:00
Subject: Re: Secure Timeout

Martin Boese wrote in post #970440:
> I am looking for a secure way to Timeout a block of code. I noticed that
> 'timeout' (part of ruby) doesn't work if the script is busy in a certain
> function. For example:
>
>   require 'timeout'
>
>   Timeout.timeout(5) do
>      Dir["/**/**"]
>   end
>
> ... does NOT break after 5 seconds on my system. In fact not even
> sending TERM works until Dir[] is finished. I see this also happening on
> other functions, not just Dir[].
>
> Is it possible to implement a timeout function that can't fail? Any
> ideas how?

Ruby's timeout library uses threads, and threads in ruby 1.8 are 
cooperative. So if ruby is stuck in a system call, then the timeout 
can't fire until it returns.

So I'd suggest you fork a child to do the work (see IO.popen), and read 
the data from the child. If it hasn't returned a complete reply within 5 
seconds then the parent can kill it. Alternatively, poll it with 
waitpid(.., Process::WNOHANG) to see if it has terminated.

Regards,

Brian.

-- 
Posted via http://www.ruby-forum.com/.