[jira] Commented: (MODPYTHON-76) input filter hangs in combination with mod_proxy

["Graham Dumpleton (JIRA)" <ji...@apache.org>]

    [ http://issues.apache.org/jira/browse/MODPYTHON-76?page=comments#action_12357955 ] 

Graham Dumpleton commented on MODPYTHON-76:
-------------------------------------------

For further details on this issue see developer mailing list posts.
  
  http://article.gmane.org/gmane.comp.apache.mod-python.devel/1341/match=martijn
  http://article.gmane.org/gmane.comp.apache.mod-python.devel/1350/match=martijn

The offending package that might be used as a test case is called Tramline, which is available from:

  http://faassen.n--tree.net/blog/view/weblog/2005/11/11/0
  http://codespeak.net/svn/rr/tramline/trunk/

If it really is a requirement that automatic flushing needs to be able to be turned off, suggest that add a new configuration directive called "PythonFlushFilter" be implemented. The default if not defined would be "On", with it being able to be specified as "Off".

But then, the mailing list posts suggest that the workaround of disabling the flush may not work for all Apache versions.


> input filter hangs in combination with mod_proxy
> ------------------------------------------------
>
>          Key: MODPYTHON-76
>          URL: http://issues.apache.org/jira/browse/MODPYTHON-76
>      Project: mod_python
>         Type: Bug
>   Components: core
>     Versions: 3.2, 3.1.4
>  Environment: Linux, Apache 2.024 and unreleased Apache 2.0.x svn version.
>     Reporter: Martijn Faassen

>
> Input filters hang when mod_proxy is in use. Other behavior seen is infinite calls of the input filter function even though the data has already
> been processed.
> In Apache 2.0.24, this problem seems to be fundamental; I have no way to get rid of the hang, except perhaps in the case of an input filter that
> does not change the size of the passed-through data.
> In svn Apache, the problem goes away as soon as I remove the filter.flush() in apache.py's FilterDispatch handler. svn Apache does according to its changelog contain a fix to mod_proxy's handling of input filters.
> For my application, use of mod_proxy is essential, as mod_python is essentially proxying another web server process.
> Output filters do not seem to be affected by the presence of filter.flush(), and in fact filter.flush() is important to make sure memory use remains small when handling large amounts of data being outputted by the server.
> All of this is rather hairy and I don't know quite what to blame; part of this seems indeed due to Apache itself, but perhaps not everything.

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