[mod_python] requests are blocking when using req.sendfile

Graham Dumpleton graham.dumpleton at gmail.com
Tue Sep 23 18:51:11 EDT 2008

2008/9/24 Matt Barnicle <mattb at wageslavery.org>:
> well, there are a couple reasons why i didn't try that straight
> away.  i'm not really the best at sysadmin type stuff.  if something
> were to go wrong this is our one and only live server at the moment
> so i avoid upgrading packages unless i know it's necessary.  i
> didn't realize before but we're actually using v3.2.8.  it's pretty
> recent, however if you think that the installing the latest version
> is essential towards figuring out the problem i will do it.

That is not pretty recent, it is 2 1/2 years old. There have one minor
and one more significant release since then.

You can see what has changed or been fixed in between version you are
using and latest version at:


It may indeed not be necessary to upgrade, but it would have been a good start.

When I get the chance I will look again at your post then and see if I
can work out what you are talking about. Be patient, I may not get to
it straight away.


> - m@
>> And what happens if you stop using an older version of mod_python
>> and use the latest version?
>> In other words, upgrade to mod_python 3.3.1 and then we may be
> able to
>> help. The older versions have various bugs in them and there is no
>> point us trying to debug an issue that may have already been fixed.
>> Graham
>> 2008/9/23 Matt Barnicle <mattb at wageslavery.org>:
>>> i'm having an issue with our site, which seems to be directly
>>> related to using req.sendfile.  on our site, we have secure music
>>> downloads.  the user has to go through a series of steps in order
>>> to
>>> gain access to the music (fyi, we run a legitimate service, not a
>>> pirate or warez site).  just some background info..  basically we
>>> can't offer a direct download link or the security can be
>>> bypassed.
>>> so downloading is done through the handler, which runs the checks,
>>> and if everything looks good, the file is sent to the browser
>>> using
>>> req.sendfile with the local path to the file on disk.
>>> it works..  but the problem is, requests start backing up whenever
>>> a
>>> download is being sent.  it looks like new requests are being sent
>>> to the apache process that is tied up sending the download file.
>>> i
>>> don't understand why this is happening though.  i would think that
>>> while it's sending the file, no new requests would be queued in
>>> that
>>> process.  i can verify this easily by downloading a file, and
>>> while
>>> it's downloading, clicking on a link on the site from the same
>>> window in which i downloaded in.  the request will stay in the
>>> WAIT
>>> state (according to mod_status) until the download is finished,
>>> then
>>> the page will load and the queue will clear up.  now if i change
>>> the
>>> download link to a static file, served directly by apache, this
>>> problem disappears.
>>> what can i do to fix this?  it's a major issue right now.  many
>>> times a day you can go to the site and it will hang for perhaps 1
>>> to
>>> 3 minutes, then it will load, due to the above described
>>> situation.
>>> version notes:
>>> CentOS release 5 (Final)
>>> apache 2.2.3
>>> mod_python 3.2
>>> using prefork compiled into apache.  misc apache configuration:
>>> KeepAlive Off
>>> <IfModule prefork.c>
>>>  StartServers       8
>>>  MinSpareServers    5
>>>  MaxSpareServers   20
>>>  ServerLimit      256
>>>  MaxClients       256
>>>  MaxRequestsPerChild  4000
>>> </IfModule>
>>> thank you for your time and consideration..
>>> - m@
>>> _______________________________________________
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>>> Mod_python at modpython.org
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