IIS Log / Custom Error database discrepancies

[Mark Metzner]

We currently have custom error logging setup on all of our websites. We
have IIS setup to redirect to our custom 500-100.asp page which logs the
error to a database and then redirects to a friendly error message page.

Last week we were working on a pretty troublesome error on our intranet site
and noticed huge discrepencies between the IIS Log and our error log
database. On this particular day for this particular site, the IIS Log has
literally thousands more errors logged than our database does.

I am very familiar with ASP error logging and completely understand how our
current system is working. I've been given the task of figuring out why
there are more errors in the IIS Logs than in our "dbSiteErrorLog" database,
the destination db of our custom 500-100 page.

The log will show all thousands of " |-|ASP_0147|500_Server_Error" messages
that don't have any matching records in our site error log database.

Any ideas why this discrepancy exists?

Would IIS log an error and not redirect to our custom 500-100.asp page?

How would I resolve this problem?

Thanks so much for any help anyone can provide!!

 

[Aaron [SQL Server MVP]]

The log will show all thousands of " |-|ASP_0147|500_Server_Error"
messages

that don't have any matching records in our site error log database.

Some errors halt the IIS engine's processing, so it has no ability to go to
the 500 custom error handler. You will have to experiment with the
different errors in your log (that weren't caught by the error handler) and
try to reproduce them. Pre-processor items might do this (e.g. missing
#include file or missing %> delimiter).

There could also be problems in the 500 error handler, e.g. certain errors
are not handled correctly, but the error only shows up in certain cases.
For example, let's say your ASP page gets a 500 error because someone passed
in the literal string "response" and then you use eval against it:

<%
x = "response"
response.write eval(x)
%>

Response object error 'ASP 0185 : 80020003'
Missing Default Property
/500.asp, line 0
A default property was not found for the object.

Do you have any leads on the actual pages that are causing the errors that
aren't being recorded correctly?

 

[Mark Metzner]

Yes. It was occurring on the /default.asp page between the hours of
midnight and two in the morning everyday. Another programmer in my
department actually fixed the problem but is not around today to ask what he
had to do. I did notice that NONE of the ASP_0147 errors are logged, all
other errors I can seem to find a corresponding record for. These must be
"fatal" errors that stop the IIS engine's processing.

This pretty much means we will have to keep an eye on these kinds of errors
in the IIS logs and cannot assume that if there are no errors in the
dbSiteErrorLog database that none are occurring.

Out of curiosity, is there any more detailed information on this "ASP_0147"
error that I could read?

 

[Aaron [SQL Server MVP]]

http://support.microsoft.com/?kbid=311766

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