IIS 5.1 gives random 12029 errors on ISAPI extension

Hi,

I have developed a high-performance ISAPI extension that uses worker threads
to service requests. It works great except for spurious 12029 errors
("Attempt to connect to the server failed.").

I have a test application that uses WinInet functions to connect to my ISAPI
extension (running on the same computer). The test application sends
requests synchronously so that it never starts a new request before the
previous one has completed. I am running only a single instance of this test
application.

The errors occur randomly, about 1 error per 1000-2000 requests.

By placing some OutputDebugString calls in my ISAPI extension I verified
that the error occurrs before my HttpExtensionProc() function is called. I
also ran Performance Monitor to check the "Current ISAPI Extension Requests"
counter. It never went past 2 during the time the errors were reported.

Any ideas how to debug this problem?

My test machine is a single-processor 2,4 GHz workstation-grade computer. I
am running Windows XP Pro with latest service packs and patches installed. I
have configured my ISAPI extension to run in an isolated process.

--

Mikko Noromaa (mikkon@excelsql.com)
- SQL in Excel, check out ExcelSQL! - see http://www.excelsql.com -

Mikko
Fri Jul 11 09:37:47 CDT 2003

Replying to myself...

I think I found the cause of this problem. During development, I tested my
ISAPI extension by killing the last dllhost.exe process and then copying my
ISAPI dll over the previous version. If I instead do NET START/STOP W3SVC,
the problem goes away! Looks like IIS is doing some extra maintenance if its
Dllhost process dies unexpectedly, and it cannot accept requests during that
maintenance...

By the way, after killing the Dllhost process, the 12029 errors occurred for
about 1 minute (about 5-10 errors in that time). After that they stopped
happening.

--

Mikko Noromaa (mikkon@excelsql.com)
- SQL in Excel, check out ExcelSQL! - see http://www.excelsql.com -



"Mikko Noromaa" <mikkon@excelsql.com> wrote in message
news:unA3qg6RDHA.3192@tk2msftngp13.phx.gbl...
> Hi,
>
> I have developed a high-performance ISAPI extension that uses worker
threads
> to service requests. It works great except for spurious 12029 errors
> ("Attempt to connect to the server failed.").
>
> I have a test application that uses WinInet functions to connect to my
ISAPI
> extension (running on the same computer). The test application sends
> requests synchronously so that it never starts a new request before the
> previous one has completed. I am running only a single instance of this
test
> application.
>
> The errors occur randomly, about 1 error per 1000-2000 requests.
>
> By placing some OutputDebugString calls in my ISAPI extension I verified
> that the error occurrs before my HttpExtensionProc() function is called. I
> also ran Performance Monitor to check the "Current ISAPI Extension
Requests"
> counter. It never went past 2 during the time the errors were reported.
>
> Any ideas how to debug this problem?
>
> My test machine is a single-processor 2,4 GHz workstation-grade computer.
I
> am running Windows XP Pro with latest service packs and patches installed.
I
> have configured my ISAPI extension to run in an isolated process.
>
> --
>
> Mikko Noromaa (mikkon@excelsql.com)
> - SQL in Excel, check out ExcelSQL! - see http://www.excelsql.com -
>
>