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From Dirk-Willem van Gulik <di...@webweaving.org>
Subject Re: general/5060: User track generates flawed records.
Date Mon, 27 Sep 1999 08:20:01 GMT
The following reply was made to PR mod_usertrack/5060; it has been noted by GNATS.

From: Dirk-Willem van Gulik <dirkx@webweaving.org>
To: Sefera Armond <sefer@hotmail.com>
Cc: apbugs@hyperreal.org
Subject: Re: general/5060: User track generates flawed records.
Date: Mon, 27 Sep 1999 10:14:49 +0200 (CEST)

 On 23 Sep 1999, Sefera Armond wrote:
 
 > We have enabled the user-track module using cookies. And since we have made this change,
the logs generated by the apache began showing invalid entries in roughly 8% of the log entries.
 > Instead of showing "210.80.20.55.374637468346" we get only "-" or sometimes "378463478463"
in around 8% of the entries. We couldn't figure out why this is happenning and assumed (since
we couldn't find anything explaining this) that this must be some k ind of a bug.
 > We get high amount of pageviews a day, so this may not be noticeable on a lower number
of pageviews.
 > If you can explain/solve/bug-fix this we'll be extermly glad.
 
 Well, the way the write to the log file is done, it is not entirely atomic
 or mutexed to make it serialized as far as I recall. We just do (or did)
 an fputs() followed by a fputc() or a newline and a fflush(). And I do not
 think that this was ever fixed, or is going to be fixed prior to 2.0.
 
 So this might be the culprit.
 
 What you could try is just make a log of _only_ the cookies. Using
 CustomLog and see if that gives the same corruption. By coincidence I have
 a customer with reasonably high volume site (mmaped_static/freebsd/PII/400
 and 25-40 hits/sec) where we are logging to a (shared) SQL database, which
 has atomic (well serialized) writes. From that I am fairly sure that
 mod_usertrack emits something sound. And that it is sound by the time
 it arrives at mod_custom_log.
 
 Another option could be that some custom module is zapping r->notes
 somehow. That has happened before. Anything special in the setup ?
 
 Dw
 

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