durusmail: quixote-users: mod_scgi on Apache2
mod_scgi on Apache2
2005-07-18
2005-07-18
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2005-07-21
2005-07-19
mod_scgi on Apache2
Bo Yang
2005-07-30
Our 4-month old Chinese book/movie/music-based  social-network site
douban.com is serving 150k pages (20k visits) daily. It's been
running on apache2/mod_scgi/quixote/mysql on one single server from
day one.

The scgi/quixote part of our site was fine, until we reached around
50k hits per day. Then I started to have freezes occasionally. Now it
freezes daily. When there're hundreds of users waiting, there's no
time for any diagnosis. I just quickly clear up the old (scgi)
processes and do a restart.

I've switched back and forth between scgi 1.4 and 1.2, and bumped up
max_children to 10, and these made no difference.

Now the reason I've not reported this sooner. We're using memcached,
to prepare for the (fingers crossed) arrival of the million page-view
day. Most data queries go to memcache-python client first, then to
mysql only if data is not found at the memcache. memcahed's python
client is pretty much broken. besides data consistency, there've been
reports of  crash/freeze.

I thought my problem was memcached related but changed my mind last
week. The scgi freezes are rather random, but I did find one tiny
pattern. It happened three times around the time mysql backup cron
jobs run around 3 a.m. each day. mysqldump was configured to lock up
each table in turn. so some of the unlucky write requests might have
to wait for few minutes to get through. The backups took about 15
minutes, but scgi froze right there, all the way to the morning when
I woke up in panic.

I've considered downgrading to apache1, but saw this discussion and
decided to be more constructive. Any hint will be appreciated.

A big thank-you to the quixote team, by the way.

- Bo

On Jul 19, 2005, at 2:40 AM, Neil Schemenauer wrote:

> On Mon, Jul 18, 2005 at 11:22:48AM -0700, mso@oz.net wrote:
>
>> What other kinds of problem reports have you gotten?  Things that
>> haven't been fixed?
>>
>
> The most recent report was of zombie Apache processes after the SCGI
> server had been down for a while.  I can't reproduce that one so I
> don't know what's going on there.  All the other problems that I
> know of have been fixed in the latest (unreleased) version.
>
> Obviously it would be nice to have someone like Jon Corbet of
> LWN.net say that mod_scgi for Apache 2 works for them.  Even without
> such feedback, I'm much more confident in module than I was when I
> first wrote that warning.
>
>   Neil
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