Hey all, I'm hoping to get some help on this problem in which I suspect apache is the cause. I have trac installed and running, and whenever I click rapidly on links in Trac, I would get an error page "Unable to connect" shown. During this time, I cannot ssh into my linode from my machine (returns "connection refused"). After 20 or so seconds, everything goes back to normal until I click too many times in Trac and the problem repeats again. The problem is so frequent that it's unusable.

The logs errors.log, ssl_access.log, access.log don't shed any light as to why this is happening. In fact, I can't see where it fails in the logs.

I thought perhaps that I could decrease MaxClients to 25 for prefork, but this doesn't seem to have any effect.

Does anyone have an idea what's going on?

It seems unlikely that this would be a client limit issue with Apache since clicking in the same client browser should either reuse an existing connection or have torn an old one down if it is making a new one. Are you the only client to the box during the tests? If so, the default listen backlog of Apache should make it even less likely that it's a client limit issue, unless each thing you're clicking on is taking a very long time to respond.

I assume you're having Apache proxy the request to trac? When you get a connection refused by the client, is there any related log at all in the Apache logs or the trac log? If not, then the blockage would seem to be likely upstream of them and outside of their control.

Just for the heck of it - any chance you have any rate limiting going on in a firewall configuration? Maybe your rapid clicking is exceeding the rate limit and the delay then lets the average rate fall beneath the threshold. Though if so it sounds like you may have some pretty low limits.

If unsure, one test is just to temporarily disable any firewall you may have and see if the behavior changes. I might also test from different client locations in case what you're seeing is client side (some bad or limiting behavior in a local nat box or something).

-- David

Thank you! You were right. It wasn't apache after all. It was my firewall and its rate limiting was the culprit.