Invalid Response From an Upstream Server

I have put together a Rails form-mailing application using Action
Mailer and deployed it in a variety of instances without any problem.
In my latest attempted deployment, however, I find that submitting the
form results in the following error:

The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request POST /formtool/

Reason: Error reading from remote server

I am running Apache 2.2.3 with a Mongrel cluster. It seems that the
submission spawns an additional mongrel instance.

Strangely, the problem just disappeared on its own for a while and now
it has returned.

Has anyone else encountered this; and, more importantly does anyone
know what I can do about it?


      ... doug

I think that it may be due to your current isp not adding a PTR record
for your deployment server in its name resolution servers. The mail
server will have trouble with reverse proxy lookup if this record is
either not entered or is incorrect. I do not know the exact details
of how it should be entered. You may want to work with the server
admin for your site.

Thanks for the response.

I really don't understand why there isn't more info available on this
particular problem. Perhaps it is because (for whatever reason) it
occurs so infrequently. As I said, I have quite a few deployments
that are working just fine. It's just this one that has a problem;
and, for the life of me, I don't know what really causes it.

However, I was finally able to Google what appears to be the
solution. The commentator acknowledged the problem and said that it
was an Apache issue that was fixed in version 2.2.4. Upgrading my
version of Apache from 2.2.3 to 2.2.8 on the particular deployment
that was experiencing the problem seems to have resolved the issue.
Based on that, I conclude that this particular commentator knew what
he was talking about. Accordingly, I would suggest that if anyone
else experiences this problem and they are using a version of Apache
earlier than 2.2.4, they should upgrade to at least 2.2.4.

Thanks for the input.

          ... doug