[pmwiki-devel] Internal server error message

[Petko Yotov]

[Re-posting to the list.]

Is there anything in the Apache error_log?

Does it happen when you edit pages, or when you only read pages of your 
wiki? Does it happen to specific pages, or not? Does it always happen to 
the specific pages, or sometimes it happens, sometimes it doesn't for 
the same page?

Have you enabled some recipes? Does the problem still appear when the 
recipes are disabled?

Do you have some complex wiki markups like embedded pagelists? Pagelists 
are not really designed to be embedded in other pagelists (there is a 
global $Cursor variable which may get overwritten and lead to infinite 
loops and crashes). If that's the case, there is no easy solution.

Do you have complex page text variables (PTVs) containing other page 
text variables, or containing markup expressions, or conditionals? It is 
possible that at some point there is an infinite loop which consumes all 
the CPU/RAM resources of the server. Recent PmWiki versions try to 
detect the embedded PTVs and exit the infinite loops, but there might be 
something it fails to detect.

The automatic tasks that PmWiki does from time to time are:
- updating the wiki.d/.pageindex file for faster searches, this might 
rarely cause high CPU/RAM usage, if your files reside on a network hard 
drive attached to the server;
- retrieving the blocklists from the internet, this might rarely cause 
high CPU/RAM usage if your server doesn't have a stable/fast incoming 
internet connection
- processing the blocklists: look at the downloaded blocklist pages (in 
SiteAdmin/): if they look like HTML, try disabling those blocklists. In 
the past blocklist providers have dropped their websites so wikis were 
getting content from some cybersquatters which was not adapted for the 
blocklist engine.

There may be more cases, but as you can imagine, intermittent errors are 
hard to debug.

Petko


On 08.10.2014 19:26, Randy Brown wrote:
> For the past few weeks, all the wikis I've tested have developed an
> occasional problem: when pmwiki.php is running, the server runs out of
> virtual memory and is unable to create a child process. I get an
> "Internal Server Error" message. It seems to occur for anywhere from a
> few minutes at a time to a few hours, and during that time if I keep
> trying I'll get a certain percentage of successful response - it can
> range mostly successful to rarely successful.
> 
> My web host says that when they accessed one site my account suddenly
> went from 0 to 100% virtual memory usage.
> 
> The problem occurs even on websites that I haven't changed for months.
> When it's happening to one site, it's happening to the others too.
> 
> I've tried adjusting in php.ini the max_memory allowed, both up and
> down, with no effect.
> 
> I get the problem even when I block all IP addresses except for my
> own.
> 
> The only theory I can think of is that some cron job that PmWiki runs
> in background, such as blocklist, is starting to consume tons of
> memory for reasons unknown. But I would think that such an issue would
> affect lots of websites, not just mine, and I haven't seen this
> problem reported before, so it seems unlikely.
> 
> Any theories that might help me track down the cause of this?
> 
> Randy
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