[geeklog-devel] No articles on geeklog.net when not logged in?

[Dan Stoner]

Here is what I found... hope it helps someone.


1.
The PHP function filemtime() returns a unix timestamp that is precise to
the second.

This is a rather large window of time for two requests to interact (two
cache writes triggered within a second).



2.
> Who's familiar enough with that code to add some debug statements?


I poked at template.class.php.  It already has some debug bits ready to be
enabled:



 /**
  * Determines how much debugging output Template will produce.
  * This is a bitwise mask of available debug levels:
  * 0 = no debugging
  * 1 = debug variable assignments
  * 2 = debug calls to get variable
  * 4 = debug internals (outputs all function calls with parameters).
  * 8 = debug caching (incomplete)
  *
  * Note: setting $this->debug = true will enable debugging of variable
  * assignments only which is the same behaviour as versions up to release
7.2d.
  *
  * @var       int
  * @access    public
  */
  var $debug    = 0;





The "touch" command is used to create an empty file.  I suspect this is the
command that is actually creating the empty file. This code is a possible
area to investigate:



        if ($TEMPLATE_OPTIONS['cache_by_language']) {
            $extra_path = $_CONF['language'] . '/' . $extra_path;
            if (!is_dir($TEMPLATE_OPTIONS['path_cache'] .
$_CONF['language'])) {
                @mkdir($TEMPLATE_OPTIONS['path_cache'] .
$_CONF['language']);
                @touch($TEMPLATE_OPTIONS['path_cache'] . $_CONF['language']
. '/index.html');
            }
        }




And there are already some debug statements in there just waiting for debug
to be set to level 8.

        if ($this->debug & 8) {
            printf("<check_cache> Look for %s<br>", $filename);
        }



The actual write of the cache file begins at Line 1685. There are no debug
statements there. What does PHP do if the file write fails? I don't see any
error trapping / exception handling in there.

        $f = @fopen($filename,'w');
        if ($f !== false ) {
            if ($TEMPLATE_OPTIONS['incl_phpself_header']) {
                fwrite($f,
"<?php if (!defined('VERSION')) {
    die ('This file can not be used on its own.');
} ?>\n");
            }
            fwrite($f, $tmplt);
            fclose($f);




3. After writing up everything above, I was thinking back to some
experience with Wordpress caching in a previous life and some of the
hiccups we ran into.

If PHP is using one of its caching systems such as Alternative PHP Cache
(APC), and depending on the server configuration (FastCGI), you can get
unexpected results trying to use functions such as filemtime since one PHP
process may cache the previous stat result even though another PHP process
has "changed something on the filesystem".


4. A server configuration difference in either PHP process mode (modphp vs.
fastcgi vs. php-fpm), PHP cache layer, etc. could explain why Tom is not
able to reproduce the issue.

Or, the actual traffic hitting geeklog.net is just particular or peculiar.



- Dan Stoner




On Tue, Sep 1, 2015 at 2:34 AM, Dirk Haun <dirk at haun-online.de> wrote:

> Tom wrote:
>
> > Yes clearing the articles fixes the problem (which I just did).  Not sure
> > why but it only seems to happen on Geeklog.net one in a blue moon (the
> cache
> > files exist but have no text).
>
> We seem to have a few more blue moons these days. I noticed the problem
> again a few days ago and deleted the cache and now it has happened again.
>
> Who's familiar enough with that code to add some debug statements?
>
> Dirk
>
>
> --
> https://www.themobilepresenter.com/
>
> _______________________________________________
> geeklog-devel mailing list
> geeklog-devel at lists.geeklog.net
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>
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