I've had expected results with a .pl script that had $|=1 in it running through mod_perl2, up until a recent fresh RedHat EL 5 installation where I had to reinstall my environment/software (via yum / rpms). Here is some environment-related info: Embedded Perl version v5.8.8 for Apache/2.2.3 (mod_perl v2.0.4) ... all x86_64.

/etc/httpd/conf.d/perl.conf:

LoadModule perl_module modules/mod_perl.so
PerlRequire "/etc/httpd/mod_perl-startup.pl"
Alias /perl/ "/var/www/cgi-bin/"
<Directory /var/www/cgi-bin>
    SetHandler perl-script
    PerlResponseHandler ModPerl::Registry
    PerlOptions +ParseHeaders
    Options +ExecCGI
</Directory>

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/etc/httpd/mod_perl-startup.pl: 

if ( ! $ENV{MOD_PERL}) { die "GATEWAY_INTERFACE not Perl!"; }
use lib qw(/usr/local/lib);
use ModPerl::Util (); #for CORE::GLOBAL::exit
use Apache2::RequestRec ();
use Apache2::RequestIO ();
use Apache2::RequestUtil ();
use Apache2::ServerRec ();
use Apache2::ServerUtil ();
use Apache2::Connection ();
use Apache2::Log ();
use APR::Table ();
use ModPerl::Registry ();
use Apache2::Const -compile => ':common';
use APR::Const -compile => ':common';
1;

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The test script being accessed via Firefox/IE (doesn't matter what browser): 

#!/usr/bin/perl -W
use strict;
print "Content-type: text/html\n\n";
$|=1;

for (my $x=1; $x<=10; $x++) {
    print($x);
    sleep 1;
}

exit(0);

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Apache starts normally... all other functions that I've used in the mod_perl environment work as expected... The $|=1 command doesn't do anything--printing still behaves in a buffered manner. I have a similar installation in RHEL 4 where unbuffered printing works as expected (via $|=1). I found a few interesting posts on Google... first, this one: http://www.nntp.perl.org/group/perl.beginners.cgi/2006/07/msg12693.html, which basically describes that perl's STDOUT is redirected to Socket. Looking at the mod_perl2 documentation (http://perl.apache.org/docs/2.0/api/Apache2/RequestIO.html#C_print_, it references setting $|=1 as one would expect to create the desired unbuffered behavior.

What am I missing... I feel like it's some configuration within mod_perl itself (mod_perl-startup.pl / perl.conf) or Apache's config (httpd.conf)? Any help is GREATLY appreciated! Thank you in advance, and please let me know if additional environment info is needed...

In reply to mod_perl2 unbuffered printing by cappaberra

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