Hello,

I am running an Apache/2.2.17 (Ubuntu) with mod_perl 2.0 and Perl version 5.10.1. I created a module CitySearcher.pm that has a handler method to handle the request from the browser. The module has roughly the following format (simplified):

package CitySearcher;

use strict;

...
use Tree::Trie;
use threads::shared;
use APR::OS;

my $TRIE :shared;
my $TRIE_LOCK :shared = {};

sub handler {
    my $r = shift;
    $r->content_type('text/html');
    
    ...
    
    my $request = new CGI;
    my $tid = APR::OS::current_thread_id();
    lock($TRIE_LOCK);
    if(!defined($TRIE)) {
        print stream "$$-$tid: creating trie\n";
        my $trie = new Tree::Trie;
        ...
        #populate $trie
        ...        
        $TRIE = shared_clone($trie);
    }
    
    print stream "$$-$tid: returning trie\n";
    
    ...
    #use trie
    ...

    return Apache2::Const::OK;
}

1;
[download]

Then I restart the server and pound the server with about 25 calls within milliseconds to the page. Here is the ouput from the stream:

10320-3056253808: creating trie
10320-3056253808: returning trie
10320-3064646512: returning trie
10320-3056253808: returning trie
10320-3064646512: returning trie
10320-3064646512: returning trie
10320-3056253808: returning trie
10320-3064646512: returning trie
10320-3056253808: returning trie
10320-3064646512: returning trie
10320-3064646512: returning trie
10320-3022682992: creating trie
10320-3022682992: returning trie
10320-3047861104: creating trie
10320-3047861104: returning trie
10320-3056253808: returning trie
10320-3056253808: returning trie
10320-3022682992: returning trie
10320-3064646512: returning trie
10320-3031075696: creating trie
10320-3031075696: returning trie
10320-3064646512: returning trie
10320-3022682992: returning trie
10320-3056253808: returning trie
10320-3056253808: returning trie
10320-3039468400: creating trie
10320-3039468400: returning trie
10320-3022682992: returning trie
10320-3064646512: returning trie
10320-3056253808: returning trie
[download]

As you can see, thread 3056253808 initially creates the trie and then thread 3064646512 uses it too (no creating trie output). A little bit later thread 3022682992 comes along and creates a trie again. Why was the trie not shared? All threads are clearly running in the same process.

Thank you very much for your help.

Sincerely,

Pawel

SOLVED (I think):

I removed PerlInitHandler Apache2::Reload from my Apache configuration. Looks like the shared variables are removed when the Apache2::Reload module does its thing. I hope this tip helps anyone with a similar problem in the future.