Re: Creating a 'load simulator' by calling Perl Programs - or Forking?
- From: pgodfrin <pgodfrin@xxxxxxxxx>
- Date: Fri, 4 Apr 2008 06:15:55 -0700 (PDT)
On Apr 4, 1:44 am, sheinr...@xxxxxxxxxxx wrote:
On Apr 4, 6:12 am, pgodfrin <pgodf...@xxxxxxxxx> wrote:
On Apr 3, 4:22 pm, xhos...@xxxxxxxxx wrote:
pgodfrin <pgodf...@xxxxxxxxx> wrote:
...
Question #1: What is the proper way to execute the perl programs?
You gave two examples, sequentially and in parallel. Which one is
appropriate depends on what kind of load you want to simulate, which in
turn depends on why are you are doing the simulation.
Question #2: Is there a way to echo to the screen that the wait() is
happening and provide some indication of progress?
To clarify this question, I had originally tried:
do {$x=wait; print ".";} until $x==-1;
Thinking I would get a period printed during the loop. (silly me -
wait only comes back when a child process dies...).
So you do get a period printed, once per child-exit. This is what I would
want to do, anyway, but I seem to be in a philosophical minority in this
regard (I hate progress indicators that merely indicate that the system
clock is ticking, and nothing about the actual progress of the actual
program.) I'm not sure what you originally thought it might do instead.
Periods to be printed as fast as Perl possible can print them?
Of course if this is much to complicated a way to so a simulated load,
then so be it - just a plain old fork and wait works fine... And I
could always remove the /dev/null and actually see the called programs
output, which will tell me that it's still running... But I was
curious if there is a more elegant or at least interesting way of
doing this?
If the waiting program is still running, and is still waiting, then the
program it is waiting on must still be running. What other possibilities
are there?
If you really want the "time has not come to a halt" thing, then
something like this:
perl -le '$|=1; fork or do {sleep 4*$_; exit} foreach (1..3); \
$SIG{ALRM}=sub{print "."; alarm 1}; alarm 1; \
do {$x=wait; print "$x";} until $x==-1; \
alarm 0'
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20287
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20288
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20289
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Xho
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Hi Xho,
As always - good points. I am looking to load up the system, so a
parallel simulation seems to be the best approach. And frankly, the
period printing was just a way to see that indeed something was
happening, but clearly and wholly unnecessary - although I did get a
chuckle over the time halting comment...
And anyway 'watch ps u' in anotehr session celarly shows me the
processes still running.
But - the question still remains - what's the best way to call other
perl programs? Exec, system or something else?
pg
Hi pg,
a module that I've written couple of months ago was for that very
purpose.
Basically your script will have to instantiate an PreforkAgent, tell
it how many children to beget (degree of parallelization) and provide
it with a couple of callbacks as means of communication.
These callback routines may provide any task, execute it as you like
and perform evaluation of results and logging.
The module's initial purpose was it to generate as much load on a
remote system as the local server would allow. You can however, setup
a small number of children and even delay the task assignments without
interfering with the former tasks.
Children will live and be re-used until the job-queue is depleted.
You might download the module fromhttp://www.atablis.com/temp/PreforkAgent.pm
and give it a try.
Cheers,
Steffen
It is rather easy to integrate
cool! I'll take a look...
phil
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- References:
- Creating a 'load simulator' by calling Perl Programs - or Forking?
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