Mod_Proxy: File does not exist

We have been getting some strange errors in our error_log.


In the Mod_proxy mappings we have a reverse proxy for an
application,
which has been in production for a very long time.   
Yesterday I
noticed some errors that look like Apache tried to publish
the
documents locally instead of from the backend server.


The log file shows:


[Tue Feb 07 09:15:03 2006] [error] [client x.x.x.x] File
does not
exist: /usr/local/apache/htdocs/application


The lines in the config show:


ProxyPass            /application/
http://ba
ckend.application.com/application/
ProxyPassReverse     /application/
http://ba
ckend.application.com/application/


Normally all clients get the content from the backend server
without an
issue.


The Backend.application.com server is load balanced and we
saw a huge
amount of requests getting reverse proxied at the time of
these errors.



My question.


Is Apache trying to service the request from the local
filesystem
because of the backend not answering the request?


I am used to the usual "Upstream errors" if the
backend starts to
answer and times out. 


Thanks!

We do have several virtual servers.  These are each bound to
different
ip addresses.

We really don't publish any HTML from the local file system
on the
apache box.

This is what makes our issue seem like a breakdown in
mod_proxy.

I was able to get "File does not exist" messages
in the logs by
creating a new reverse mapping to a backend machine that is
not
available and then I hit this reverse mapping many times.

I got the following errors:

[Tue Feb 07 13:21:04 2006] [error] [client 10.x.x.x] File
does not
exist: /usr/local/apache/htdocs/junk
[Tue Feb 07 13:28:51 2006] [error] (110)Connection timed
out: proxy:
HTTP: attempt to connect to 192.168.1.100
(junk.anydomain.com) failed

I would be much happier if I only got the attempt to connect
errors.

I did not see these Connection Timeouts in production.