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Posted to modperl@perl.apache.org by Dorian Taylor <do...@foobarsystems.com> on 2005/05/09 20:22:56 UTC

[mp2] [PATCH] implement ap_save_brigade

no tests currently, but there's a module on cpan that uses it.

http://search.cpan.org/~DORIAN/Apache-TrapSubRequest-0.01/

Re: Decaying Performance under newer apache/mp versions

Posted by Ricardo Ramos Massaro <ri...@gmail.com>.

On 5/9/05, J.e. Turcotte <je...@emagery.com> wrote:
> Has anyone encountered similar problems?  Does anyone have a deeper
> understanding of the whole apache/mp/perl setup to just ~know~ what these
> symptoms are indicitive of?

I'm sorry if this is completely unrelated, I am somewhat of a mp newbie.

I've been recently bitten by some very similar problems on some
scripts (not mp handlers) where CGI parameters and cookies were
not being read correctly -- sometimes my script was seeing GET
and POST parameters completely unrelated to what the browser sent.
My scripts all looked like:

use strict;
use CGI;
my $cgi = new CGI();
sub process {
  my $x = $cgi->param('x');
  # ...
}
process();

Because the problem only appears when an apache process
is executing a script for the second time, it is very hard to track
(reducing the number of apache children to 1 is very helpful
for debugging). This problem and many possible solutions
are described in great detail in

http://perl.apache.org/docs/general/perl_reference/perl_reference.html#my___Scoped_Variable_in_Nested_Subroutines

To understand why it is related to scripting in mp, see

http://perl.apache.org/docs/general/perl_reference/perl_reference.html#When_You_Cannot_Get_Rid_of_The_Inner_Subroutine

I changed "my $cgi = ..." to "local our $cgi = ..." and everything
started to work magically.

Ricardo

Re: Decaying Performance under newer apache/mp versions

Posted by "J.e. Turcotte" <je...@emagery.com>.

here's our connect:
$n is defined earlier, a central module that contains secure informations

Apache::DBI->connect_on_init (
            $n->database, $n->DBI_username, $n->DBI_password,
            { AutoCommit => 1, 'RaiseError' => 1
            }
         );

and we connect to MySQL (4.1.7)... though there is a separate database (set 
of tables) for the in-dev content, it is served by the same machine that 
successfully works without incident on the public machine (which conntects 
the same way, as well, connect_on_init).


----- Original Message ----- 
From: "Gedanken" <ge...@io.com>
To: "J.e. Turcotte" <je...@emagery.com>
Cc: <mo...@perl.apache.org>
Sent: Monday, May 09, 2005 3:33 PM
Subject: Re: Decaying Performance under newer apache/mp versions


>
> What database are you connecting to, and how are you connecting to it?
>
> -- 
> gedanken

Re: Decaying Performance under newer apache/mp versions

Posted by Gedanken <ge...@io.com>.

What database are you connecting to, and how are you connecting to it?

-- 
gedanken

Re: Decaying Performance under newer apache/mp versions

Posted by Perrin Harkins <pe...@elem.com>.

On Mon, 2005-05-09 at 15:22 -0400, J.e. Turcotte wrote:
> Our OS guys feel like it's gotta be a code 
> problem, while I feel that perhaps our apache and/or modperl installs on 
> these machines are not ideal, or that in the move from mp1 to mp2, some new 
> capacities in modperl2 are allowing a breakdown of otherwise good structures 
> under mp1.

If possible, I'd suggest you try to run your code on these machines with
mp1 as well, to determine if that is the source of your problems.
However, if you're doing lots of work with the Apache API and had to
change it to make things work under mp2, that won't be much help.

Problems of this nature usually result from one of these:

- A database handle that is opened prior to forking, or inadvertently
stashed in a closure so that when the database connection times out the
reconnection doesn't work.

- Some kind of socket or file access that is opened before forking and
then used simultaneously from multiple processes.

- An XS module with C code that gets flaky when used in a forking
scenario or in certain error conditions.

To track it down, I would suggest you add significant logging and/or
assertions to your application.  This would allow you to check for
various things (a valid database handle that responds to ping(), a valid
$r object, expected input, etc.) along the way, and see where things
fall apart when they do.  This will lead you to the problem.

You could also see what happens when you set a really short timeout on
connections in the database, to check if the problem involved
reconnecting.

- Perrin