Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I have a script that runs on a server and performs some reporting and maintenance functions. I would like to ensure that there are always n instances of the script running. If an instance terminates unexpectedly I would like to start another instance to replace it. I will be doing this on Linux. What is the "right" way to accomplish this?

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Re: Keep n instances running
by BrowserUk (Patriarch) on Jun 20, 2012 at 02:10 UTC

    Parallel::ForkManager could probably do that with half a dozen lines if you insist on using Perl; but isn't that a perfect use for inetd?

    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.

    The start of some sanity?
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Re: Keep n instances running
by Anonymous Monk on Jun 20, 2012 at 02:16 UTC
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Re: Keep n instances running
by tweetiepooh (Hermit) on Jun 20, 2012 at 14:48 UTC

    When ever I need to keep a job running I use a sub shell type structure

    #!(bash|ksh|sh)
<set up environment>
(while true
do
<perl script>
# brief delay to ensure everything is shutdown
sleep 60
done) &

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    The subshell itself is backgrounded rather than just the Perl script.

    I'm sure this can be adapted to starting up n copies of <perl script> maybe a little loop that will fire up multiple subshells. Note I'm not a BASH expert 

    #!(bash|ksh|sh)
<set up environment>
for I in {1..n};
do
   (while true
      do
      <perl script> $I
      # brief delay to ensure everything is shutdown
      sleep 60
    done) &;
done

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