Django on Dreamhost: incomplete headers

I’ve recently bought a hosting in Dreamhost. There were two reasons:

1. It’s possible to run Django on it
2. It’s cheap

It’s a shared hosting, where many sites are served from a single physical machine. Each machine probably serves as much sites as possible, where the hardware capacity is the limit. The Dreamhost servers are pretty busy. My server for instance:

[shasta]$ uptime
16:03:42 up 31 days, 13:59, 6 users, load average: 10.48, 9.74, 9.24

It’s not the processing power that is the bottleneck here, at least on “my” server. There’s usually about 40% of idle processor time. However, when I ran tail command, it would get killed every now and then. Strange. Perhaps there’s a “garbage process collector” running on the site, terminating non essential jobs here and there.

Well, I bought the hosting and moved my main site to Dreamhost. PHP software ― PhpBB and MediaWiki ― is working great. I decided to try running Django, so I developed a small application and installed it. I followed the instructions, voila, it worked. I was happy.

At least until the Django app would eventually stop responding. I clicked a link and the browser just waited for data. The data never came. I looked into the logs.

[Thu Nov 30 14:56:16 2006] [error] [client 83.xx.xxx.xx] FastCGI: comm with (dynamic) server “/home/automatthias/atopowe.pl/django.fcgi” aborted: (first read) idle timeout (120 sec)
[Thu Nov 30 14:56:16 2006] [error] [client 83.xx.xxx.xxx] FastCGI: incomplete headers (0 bytes) received from server “/home/automatthias/atopowe.pl/django.fcgi”

Something was wrong. Django isn’t officially supported on Dreamhost, so I couldn’t submit a complaint to the support. I searched the Web and found out that some guys had similar problems. Some other guys hadn’t. Dreamhost has many servers, and I figure it’s got something do to with the load of each server and… perhaps killing “non-essential” processes.

After some more research, I have found out that it’s not only Django users who’ve been experiencing that. There were also Rails users! You need to know, that Rails are officially supported on Dreamhost. I got interested and read on. Dreamhost support responded to the affected Rails user:

Check with our support team and ask if our process monitor has been killing your processes. If you have a lot of processes hanging around that may be the case. We recently updated our process monitor to specifically handle dispatch.fcgi processes specially so that is probably not the problem but it’s worth asking.

“specifically handle dispatch.fcgi processes”? Aha!

Inspecting my processes with “ps -ef” revealed that there were several “django.fcgi” processes running. Some of them were zombie (defunct). If the “dispatch.fcgi” processes are specifically handled, why don’t I pretend to run them? So I’ve changed my setup a little bit: I renamed my “django.fcgi” file to “dispatch.fcgi” and altered two lines in the “.htaccess” file, so they would refer to the new name:

RewriteRule ^(dispatch\.fcgi/.*)$ - [L]
RewriteRule ^(.*)$ dispatch.fcgi/$1 [L]

Guess what?

No timeouts, no 500s, no incomplete headers. It works like a charm.

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