I haven't used the worker mpm, but it looks like you might want to
preload your handler in the httpd parent process. You can do with a
startup.pl file. It looks like each thread is initializing a copy of
@fruits, which is probably happening at thread creation.
However, your current setup will block according to the mod_perl docs,
so you may want to revisit your approach.
If all running interpreters are in use, mod_perl will clone new
interpreters to handle the request, up until this number of
interpreters is reached. when PerlInterpMax is reached, mod_perl will
block (via COND_WAIT()) until one becomes available (signaled via
COND_SIGNAL()).
On Tue, Aug 2, 2011 at 12:06 AM, Pawel Herman <busymeis...@gmail.com> wrote:
> Hello,
>
> I have read all the related documentation (at least those that I
> found) and I still cannot understand why the little program I wrote
> below does not share the variable as I would expect. The log file
> that I created clearly shows that we are running in a single process.
> Some threads see the shared variable and others do not. I even
> reduced the number of pooled interpreters to one and still no luck.
>
> You will need an Apache running in Ubuntu 11.04 with mod_perl 2.0.
> Then add this code:
>
> package U2D::TestSharing;
>
> use strict;
>
> use Apache2::Const -compile => qw(OK);
> use threads;
> use threads::shared;
> use APR::OS ();
> use Time::Format qw(%time);
> use Apache2::RequestRec;
>
> our @fruits :shared = ();
>
> sub handler {
> my $r = shift;
> $r->content_type('application/json');
>
> {
> logTestMessage('Waiting for lock.');
> lock(@fruits);
> logTestMessage('Acquired lock.');
> if(scalar(@fruits) == 0) {
> logTestMessage('Initializing fruits.');
> push(@fruits,'apple');
> push(@fruits,'banana');
> push(@fruits,'peach');
> }
> logTestMessage('Releasing lock.');
> }
>
> my $message = "I like to eat ".join(', ',@fruits).".";
>
> print $message;
> logTestMessage($message);
>
> return Apache2::Const::OK;
> }
>
> sub logTestMessage {
> my $message = shift;
> my $tid = APR::OS::current_thread_id();
> if(open(FILE,'>>/testSharing.log')) {
> print FILE $time{'dd-mm-yyyy hh:mm:ss:mmm'}.' '.$$.'-'.$tid.':
> + '.$message."\n";
> close(FILE);
> } else { print $!."\n"; }
> }
>
> 1;
>
> Add the following lines to apache2.conf (or uncomment the specified lines):
>
> <IfModule mpm_worker_module>
> StartServers 1
> MinSpareThreads 5
> ThreadsPerChild 20
> MaxRequestsPerChild 0
> ServerLimit 1
> PerlInterpMax 1
> </IfModule>
>
> To the site configuration also add:
>
> <Location /testSharing>
> SetHandler perl-script
> PerlResponseHandler U2D::TestSharing
> </Location>
>
> Then write a little JavaScript that loops 100 times and calls
> http://localhost/testSharing and check the log file. Here I am posting
> the beginning of the log on my machine:
>
> 02-08-2011 07:42:27:552 2669-3063479152: Waiting for lock.
> 02-08-2011 07:42:27:565 2669-3063479152: Acquired lock.
> 02-08-2011 07:42:27:566 2669-3063479152: Initializing fruits.
> 02-08-2011 07:42:27:566 2669-3063479152: Releasing lock.
> 02-08-2011 07:42:27:566 2669-3063479152: I like to eat apple, banana, peach.
> 02-08-2011 07:42:27:578 2669-3063479152: Waiting for lock.
> 02-08-2011 07:42:27:578 2669-3063479152: Acquired lock.
> 02-08-2011 07:42:27:578 2669-3063479152: Releasing lock.
> 02-08-2011 07:42:27:578 2669-3063479152: I like to eat apple, banana, peach.
> 02-08-2011 07:42:27:578 2669-3021515632: Waiting for lock.
> 02-08-2011 07:42:27:579 2669-3021515632: Acquired lock.
> 02-08-2011 07:42:27:579 2669-3021515632: Releasing lock.
> 02-08-2011 07:42:27:579 2669-3021515632: I like to eat apple, banana, peach.
> 02-08-2011 07:42:27:574 2669-3046693744: Waiting for lock.
> 02-08-2011 07:42:27:582 2669-3046693744: Acquired lock.
> 02-08-2011 07:42:27:582 2669-3046693744: Initializing fruits.
> 02-08-2011 07:42:27:582 2669-3046693744: Releasing lock.
> 02-08-2011 07:42:27:582 2669-3046693744: I like to eat apple, banana, peach.
> 02-08-2011 07:42:27:583 2669-3063479152: Waiting for lock.
> 02-08-2011 07:42:27:583 2669-3063479152: Acquired lock.
> 02-08-2011 07:42:27:583 2669-3063479152: Releasing lock.
> 02-08-2011 07:42:27:583 2669-3063479152: I like to eat apple, banana, peach.
> 02-08-2011 07:42:27:588 2669-3063479152: Waiting for lock.
> 02-08-2011 07:42:27:588 2669-3063479152: Acquired lock.
> 02-08-2011 07:42:27:588 2669-3063479152: Releasing lock.
> 02-08-2011 07:42:27:588 2669-3063479152: I like to eat apple, banana, peach.
> 02-08-2011 07:42:27:581 2669-3055086448: Waiting for lock.
> 02-08-2011 07:42:27:589 2669-3055086448: Acquired lock.
> 02-08-2011 07:42:27:589 2669-3055086448: Initializing fruits.
> 02-08-2011 07:42:27:589 2669-3055086448: Releasing lock.
> 02-08-2011 07:42:27:589 2669-3055086448: I like to eat apple, banana, peach.
> 02-08-2011 07:42:27:582 2669-3038301040: Waiting for lock.
> 02-08-2011 07:42:27:589 2669-3038301040: Acquired lock.
> 02-08-2011 07:42:27:589 2669-3038301040: Initializing fruits.
> 02-08-2011 07:42:27:589 2669-3038301040: Releasing lock.
> 02-08-2011 07:42:27:590 2669-3038301040: I like to eat apple, banana, peach.
> 02-08-2011 07:42:27:588 2669-3013122928: Waiting for lock.
> 02-08-2011 07:42:27:594 2669-3013122928: Acquired lock.
> 02-08-2011 07:42:27:594 2669-3013122928: Initializing fruits.
> 02-08-2011 07:42:27:594 2669-3013122928: Releasing lock.
> 02-08-2011 07:42:27:594 2669-3013122928: I like to eat apple, banana, peach.
>
> The fruits array is initialized multiple times. This is not expected
> since the fruits array is shared and we are always running in the same
> process. (Note: Thread 2669-3063479152 populates the array initially.
> Then thread 2669-3021515632 uses it but thread 2669-3046693744 creates
> the array again. Just as a side note: as I was testing this, I also
> ran into situations where multiple threads acquired the lock
> simultaneously. The expected behavior is that only one thread can
> lock at a time.) Can anyone tell me why this code does not work?
>
> Thank you for your help in advance. I hope someone can shed some light
> on this problem that I am having for weeks now.
>
> Sincerely,
>
> Pawel
>
