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winapiserverxmlhttp

How to prevent OnDemandConnRouteHelper.dll from being loaded and unloaded every http request?

Calling IServerXmlHttpRequest.Open:

var http = (IServerXMLHTTPRequest2) new CreateComObject(CLASS_ServerXMLHTTP60);
http.Open("GET", "https://thepiratebay.org/description.php?id=54783221", false, "mhalifa", "hunter2");

causes the library OnDemandConnRouteHelper.dll to be loaded and unloaded every time:

| Time               | Operation                 | Path                                            | Result                        |
|--------------------|---------------------------|-------------------------------------------------|-------------------------------|
| 3:08:29.0705523 PM | CreateFile                | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0705941 PM | QueryBasicInformationFile | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0706149 PM | CloseFile                 | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0708557 PM | CreateFile                | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0709287 PM | CreateFileMapping         | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | FILE LOCKED WITH ONLY READERS |
| 3:08:29.0712518 PM | CreateFileMapping         | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0714096 PM | Load Image                | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0714328 PM | QueryNameInformationFile  | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0717643 PM | CreateFile                | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0807774 PM | CloseFile                 | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |
| 3:08:29.0810143 PM | QueryNameInformationFile  | C:\WINDOWS\SysWOW64\OnDemandConnRouteHelper.dll | SUCCESS                       |

As you can see, this excursion adds 10.462 ms to my http request.

When the entire request is ~30 ms, this extra load and unload of a dll every time increases the operation times by 50%.

And cuts my throughput from 50 requests/sec → 33 requests/sec.

Enough of the motivation for the question, and on to the questions

  • what is OnDemandConnRouteHelper.dll
  • is there something i can do to my request to not require help?
  • can i ask the ServerXMLHTTPRequest object to not use the helper?
  • can i convince ServerXMLHTTPRequest to keep the dll loaded in my process forever?

In other words: i want my 50% back - how do i get it?

Conn Route Helper

I don't know what this dll does, but the only useful function is documented to:

The OnDemandGetRoutingHint function looks up a destination in the Route Request cache and, if a match is found, return the corresponding Interface ID.

Which sounds interesting and all. But if you immediately unload the dll, you throw away the cache with it - thus destroying any usefulness of the cache.

Solution

  • It's not an answer, but a workaround is to load the library once manually.

    There is no need in Windows to unload a DLL before program exit - the DLLs will be unloaded when the process is torn down by Windows.

    So there's no harm in calling:

    • LoadLibrary('OnDemandConnRouteHelper');

    In fact, there's no harm in calling it multiple times.

    Just don't call UnloadLibrary; because then it has to be loaded again.