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From Terry Kennedy <>
Subject [users@httpd] LogFormat Combined - many logfile lines with no Referer or User-agent
Date Thu, 28 Jul 2011 07:20:40 GMT
  I'm using the default "LogFormat combined" directive in my httpd.conf
file. That should generate logfile lines using this pattern:

"%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\""

  There have always been occasional entries which don't contain the last
2 fields, for some reason.

  However, I have observed a HUGE increase in the number of logfile lines
missing these two fields, starting early in June, 2011. As an example,
one server (with a relatively constant number of requests over time) had
been logging 2,000 to 10,000 of these lines with missing data from August
2010 through May 2011. The number for June, 2011 was 496,700 lines.

  Even if the Referer and User-agent data was missing for some reason, I
would have expected httpd to log lines ending in "" "" or possibly "-" "-",
since there are escaped literal quotes on either side of both of those 
fields in the LogFormat config line. This makes me think that it is some-
thing going on inside Apache (perhaps triggered by some external change).

  There doesn't seem to be any pattern to client IP address, browser, etc.

  This is causing problems with Analog, since it discards any lines that
have a missing Referer field, and thus won't report those requests.

  My environment has a number of systems that are experiencing this issue.
However, other system seem mostly unaffected, with the number of these
lines below 10000 every month. The numbers above are from a system running
FreeBSD 6.4 and Apache 2.0.63 (I know, it's in the process of being up-
graded). That system has no virtual hosts and a relatively simple config. 

  I'm also seeing this on a newly-installed FreeBSD 8.2 system with Apache
2.2.19, though I don't have any historical data for this system as it is a
new install.

  I can't reproduce whatever events are causing this, either - a request
that was logged with a missing Referer and User-Agent shows up properly
when I try it again from the same client.

  Any ideas as to what I should do to troubleshoot this further?

        Terry Kennedy                New York, NY USA

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