Control timeout of system process in Rails

Question

I am launching casperJS scripts from my controller as this:

output = `casperjs #{path_to_file} '#{url}#'`

And sometimes, for several reasons the casperjs script might hang, or might take a long time. I am wondering if there is anyway I can set a timeout in my controller to just kill the process and control it. Is that possible?

usha · Accepted Answer · 2013-10-24T18:29:49.270

1

require 'timeout'
Timeout.timeout(<seconds>) do
   output = `casperjs #{path_to_file} '#{url}#'`
end

This will raise a Timeout::Error exception if the script doesn't finish within the given time

Edit(to kill the process after timeout)

require 'timeout'
pipe_cmd_in, pipe_cmd_out = IO.pipe
pid = Process.spawn("casperjs #{path_to_file} '#{url}#'", :out => pipe_cmd_out, :err => pipe_cmd_out)
Timeout.timeout(<seconds>) do
   Process.wait(pid)
   pipe_cmd_out.close
   output = pipe_cmd_in.read;
end
rescue Timeout::Error
   Process.kill('TERM', pid)
end

Have a look at the teminator gem as well. It will help if you have many system calls to deal with

edited Oct 24 '13 at 18:29

answered Oct 23 '13 at 20:13

usha

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But do I need to kill the script? If so, how? Or it's already killed by the Timeout? – Hommer Smith Oct 23 '13 at 21:51
Vimsha, I assume that the process.wait(pid) is supposed to be Process.wait(pid), right? Also, shouldn't it have a begin somewhere? – Hommer Smith Oct 23 '13 at 22:57
I have another problem with this approach.. I need to store what the script returns into a variable (output). How can I do that with spawn? – Hommer Smith Oct 23 '13 at 23:02
Vimsha, this line: process.wait(pid) -- why is process not uppercase? Process? – Hommer Smith Oct 24 '13 at 17:18
It should be uppercase. – usha Oct 24 '13 at 18:30
Vimsha, I also think a begin is missing. – Hommer Smith Oct 24 '13 at 23:51

Control timeout of system process in Rails

1 Answers1