Hello,

I am using Cache::FastMmap 1.34 with mod_perl 2.0.4 (Debian packaged) to help with configuration. I am using the PerlTransHandler hook to determine where on the filesystem a particular virtual host resides, by looking it up in a database then caching the results.

It mostly works, but every now and then it stops working. When it's not working Apache seems to hang on every page load, and I see this in the log:

[Thu Nov 12 23:30:56 2009] [notice] child pid 21117 exit signal Alarm 
+clock (14)
[Fri Nov 13 00:14:54 2009] [notice] child pid 21309 exit signal Alarm 
+clock (14)
[Fri Nov 13 00:49:55 2009] [error] [client 66.249.71.244] cache old sl
+ots mistmatch at /usr/local/lib/perl/5.10.0/Cache/FastMmap.pm line 65
+6.\n
[Fri Nov 13 01:46:04 2009] [error] [client 68.40.244.40] cache old slo
+ts mistmatch at /usr/local/lib/perl/5.10.0/Cache/FastMmap.pm line 656
+.\n
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Google doesn't turn up any obvious solutions for this.

My Apache configuration looks like this:

PerlModule My::VirtualHost
PerlTransHandler My::VirtualHost::TransHandler
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My code looks basically like this (in reality it is a bit more complicated):

package My::VirtualHost::TransHandler;
use strict;
use warnings;

use Apache2::Const -compile => qw(OK DECLINED);
use Apache2::RequestRec ();
use My::Config;
use DBI;
use Cache::FastMmap;

# This happens globally in the parent process
our $cache = Cache::FastMmap->new(
    read_cb => \&get_virthost,
    expire_time => '1m',
    init_file => 1,
    cache_not_found => 1,
    );

our($dbh,$sth);
sub get_sth {
    if (!$dbh) {
        $dbh = DBI->connect(My::Config::DB_DSN, My::Config::DB_USER, M
+y::Config::DB_PASS)
            or die "Couldn't connect to database\n";
        $sth = $dbh->prepare('SELECT virthost_id FROM virtual_hosts WH
+ERE url = lower(?)')
            or die "Couldn't prepare statement\n";
    }
    return $sth;
}

sub get_virthost {
    my($ctx,$hn)=@_;
    my $ret;
    eval {
        my $url = 'http://'.$hn;
        my $sth = get_sth();
        $sth->execute($url);
        my $row = $sth->fetchrow_arrayref();
        if ($row && defined($row->[0])) {
            $ret = $row->[0];
        } else {
            $ret = undef;
        }
        $sth->finish();
        return $ret;
    };
    if ($@) {
        # TODO: Some kind of error handling
        warn "Error getting virtual host: $@";
        $ret = undef;
    }
    $ret;
}

sub handler {
    my $r = shift;
    my $hn = $r->hostname();
    if (!$hn) {
        # TODO: Return some kind of error
        return Apache2::Const::DECLINED;
    }

    my $id = $cache->get($hn);
    if (defined($id)) {
        my $newfn = My::Config::BASE_PATH . "/virthosts/$id".$r->uri()
+;
        $r->filename($newfn);
        return Apache2::Const::OK;
    } else {
        return Apache2::Const::DECLINED;
    }
}
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My questions are:

• Does anybody see anything obviously wrong with what I'm doing?
• Has anybody done something similar before, successfully or unsuccessfully?

Thanks!