Thanks!

The problem as far as I can tell is a simple mixup of http requests so user identities don't play into this. It might look like it since user A is getting the results of user B but as far as session management goes it is unaffected by this.

The URLs are very short.
This happens at random. This only starts to happen after the server has been running for a while - it's as if some resource is being consumed and once it's done this problem starts emerging.
When it starts happening it happens to all users.

What leads me to believe this is unrelated to my application code is that restarting apache makes the problem go away. User data is managed on the session object and I am not interfering with it in any way (no direct cookie code). This is also the reason I believe tomcat only will work. Also we have been running for sometime in a tomcat only mode and never had this problem (which is not definite evidence, i know).

The reason I am not jumping to proxy_http is that the application is currently using IP geo location which I suspect will not be available once we are behind a http proxy. We will be shutting off this functionality just so we can switch to proxy_http but it takes a few day to test.

Yuval


On Feb 11, 2009, at 4:38 AM, Christopher Schultz wrote:

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Yuval,

On 2/10/2009 3:44 PM, Yuval Perlov wrote:
We started restarting apache on a regular basis but if a user is in mid request (consider a user that just filled a big form and is upload a file).

So it appears that Apache is, over time, losing track of user
identities? That seems odd since neither mod_jk nor Apache httpd
actually do anything but forward the identity information from the
browser to Tomcat. Either an HTTP cookie or a URL parameter is used to
identify sessions, and both are provided with every request.

Do you have unusually long URLs? Unusually long request bodies? I'm just
trying to think of why any data would be mixed-up.

Does this happen seemingly randomly, or only for certain pages on your
site? Certain source IP addresses? We had some users that were getting
all messed up before we recognized that they were doing through google's
cache which was seriously confusing just about everything. Fortunately,
we could see from our server logs that some requests came from the
/real/ remote user and others came from google's domain.

Otherwise, all I can think of is that you have some bug in your
application <shrug>. How are you doing authentication? How about user
identification - aside from relying on session data in Tomcat.

We are contemplating two approaches:
1) moving to proxy_http. My only concern is that this won't help - maybe the problem is unrelated to AJP? Upgrading has helped some users but not
all and the problem exists in both mod_jk and proxy_ajp.

Trying mod_proxy_http will certainly give you more information. Can you
reproduce this problem in a safe environment?

2) getting rid of apache and moving tomcat to the front (much harder to
configure but ensures we are rid of this problem).

Are you /sure/ that a Tomcat-only setup doesn't exhibit this problem?

- -chris
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