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Re: Application backtracking limit
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Re: Application backtracking limit


  • Subject: Re: Application backtracking limit
  • From: Jonathan Rochkind <email@hidden>
  • Date: Tue, 23 Mar 2004 10:51:41 -0600

Why is there a backtracking limit?

Because a WO component-based URL requires a component instance to process. WO keeps track of the last X component instances delivered, so that for any clicks on component actions in any of them (generating a URL that requires that component instance to handle)---the proper component instance can be pulled from WO's own server-side session-specific page cache, to handle the request. So you get that exception if you click on a link on a page that is no longer in that WO server-side cache. For instance by clicking the browser backtrack button more than 30 times.

At least that's the idea. I'm guessing it's unlikely you actually clicked the browser backtrack button more than 30 times. So there's probably something else going on that is confusingly triggering that error message.

One somewhat common situation that unfortunately triggers that message, due to a bug (or lack of feature) in WO----when your application takes too long to deliver the response, and you have multiple instances deployed. WO has various timeout values for receiving the response (which can be set in JavaMonitor). If the timeout is exceeded, WO gives up on the instance, and forwards the URL to another instance. The problem is, that as we said, a component-action URL requires a given component instance (in a given session) to handle the URL. So when WO forwards that URL to another instance, that doens't make any sense----that other instance is going to be unable to handle it. In some cases, for some reason you get a "session expired" error or even a "backtracked too far" error in this case.

There may be other cases that confusingly trigger the "backtracked too far" error too. Hopefully this gives you some background to try and figure out what's going on in your case.

--Jonathan

At 8:51 AM +0000 3/23/04, Sam Hart wrote:
Hi,

I have recently had a strange error from a WOProject, something along the lines of

"The application backtracking limit of 30 has been exceeded"

This continues until the session is culled.

Doing a search for this term returns "Missing page error" for probably most the WO based sites on the net.

I am going to investigate WOApplication's handlePageRestorationErrorInContext() but it does not seem like much of a solution.


Why is there a bactracking limit ?

how did I reach it ?

what other solutions are there ?


S a m

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