Michal Čihař - Blog Archives for phpMyAdmin

Steve, I know that caching usually helps. But from all test I've made with MediaWiki installation on phpMyAdmin wiki, I can see that enabling any caching slows things down quite a lot.

With memcached based caching, each request takes about 15 seconds, if I add XCache backend for variables, it slows down things to 10 seconds and I receive same results with file based caching. So it doesn't seem to be problem with memcached, but rather MediaWiki issue. Unfortunately it's quite a lot of PHP code to investigate and I didn't find anything obvious in low level caching interface.

So say good bye to variable caching, opcode cache is enough for now and MySQL seems to handle the load quite well.

As I wrote in previous post, memcached didn't help as expected with wiki performace, so it was time to look for something else.

Since I'm using lighttpd, I still considered using of XCache, but the Debian package is not really up to date (now it even does not install with current php), so it was too much effort.

But today I decided it's time to try it. I built package from current version (you can get it on debian.cihar.com), installed and it seems to increase performance a lot. Most visible it is on wiki pages, which now take about quarter of time to process. I only hope it won't have any stability impacts, but it survived fine stress tests I did so far.

I've been using memcached for some time on phpMyAdmin wiki and it seemed to help. But recently the performance went down. I didn't have time to investigate it till today and it turns out to be caused by memcached. When I switch it off, page load time goes from 16 seconds to 0.25 seconds.

I tried to search for some similar problems on the net, but I didn't succeed. So for now wiki runs without memcached and I will look at other possibilities of caching later.

Update: If you're interested about versions, it is MediaWiki: 1.7.1, PHP: 5.2.3-1 (cgi-fcgi), MySQL: 5.0.41-Debian_2-log and I have enabled persistent connections to MySQL.

As phpMyAdmin themes for trunk are not compatible with 2.10.x releases, there was created 2.10 branch for themes compatible with those releases.

Today I added 2.10 themes to demo server and they are also available as subversion snapshots. I hope this will help fixing possible issues with them.

After returning from Easter vacation, I was afraid of my full mailbox. This was quite correct, but fortunately some people also were not working, so it is not that bad. Anyway I didn't read it all so far, so don't be afraid if reaction on your mail (especially about Gammu and Wammu) will take longer.

The worst thing which happened was, that somebody managed to fuck up MySQL server serving phpMyAdmin demo in some very unusual way, which was not detected by my scripts, which are checking whether demo server is still alive. This lead to almost day outage, because I had to restore MySQL manually this morning. Anyway this case should be now also caught and the script for checking is getting more and more complex. Maybe I should better use Monit (or other monitoring software) for this instead of home made shell script. But shell script seems to do good job in most cases :-).

Off topic PS: Thanks to everybody who helped to release Debian 4.0!

It's probably time to give up. I tried to tweak tailor to make it able to convert my repositories to Subversion for several times, but without any success. It also fails to convert it to Bazaar-NG or Git. Those are list of all VCS I consider to use in future.

I'd prefer to switch to subversion, because it is widely used and most people will be willing to use it, but I have not find any way to convert current VCS data to it. Maybe I will start with empty repository and forget the history.

After few days of outage, demo server is back running. To avoid possible problems, I now run it under separate vserver. This should limit any impacts of demo server to rest of services running on this host as it provides much better separation than chroot used before.

There still might be some issues with new setup, please tell me about them.

I was unable to complete demo server setup today, so you will have to wait longer for demo server availability. I hope I will manage this during weekend.

I'm sorry for todays server outage, but it seems to be caused by some DOS attack. As a result of this I decided to temporary disable demo server, because it was target of this attack.

Demo will be back during tommorow, when I make some stricter restrictions on access to it.

When I talked last November about 10,000 visitors, I really didn't expect that in four months, wiki will double this value. Looks like it is useful source of information for users. Only thing a bit frightens me - there are only few contributors and almost none except developers and few well known users. This is wiki, feel free to edit it!

PS: Server with twice more memory serves pages much better, hopefully you also noticed this. Anyway further donations are welcome ;-).