IHttpServer::FlushKernelCache Method

Article
06/14/2022

Flushes the kernel cache for a specific Uniform Resource Identifier (URI).

Syntax

virtual HRESULT FlushKernelCache(  
   IN PCWSTR pszUrl  
) = 0;

Parameters

pszUrl
[IN] A pointer to a string that contains the URI to flush.

Return Value

An HRESULT. Possible values include, but are not limited to, those in the following table.

Value	Description
NO_ERROR	Indicates that the operation was successful.
ERROR_INVALID_PARAMETER	Indicates that an invalid value was passed in one of the parameters.
ERROR_NOT_SUPPORTED	Indicates that the operation is not supported within the current context.

Remarks

Developers can use the FlushKernelCache method to remove a specific URI from the kernel cache.

Note

The FlushKernelCache method differs from the IHttpResponse::DisableKernelCache method, which disables kernel caching for the URI that is processing the current response.

Example

The following code example demonstrates how to create an HTTP module that uses the FlushKernelCache method to flush the kernel cache for the /default.aspx URI.

#define _WINSOCKAPI_
#include <windows.h>
#include <sal.h>
#include <httpserv.h>

// Create a pointer for the global server interface.
IHttpServer * g_pHttpServer = NULL;

// Create the module class.
class MyHttpModule : public CHttpModule
{
public:
    REQUEST_NOTIFICATION_STATUS
    OnBeginRequest(
        IN IHttpContext * pHttpContext,
        IN IHttpEventProvider * pProvider
    )
    {
        UNREFERENCED_PARAMETER( pProvider );

        // Create an HRESULT to receive return values from methods.
        HRESULT hr;

        // Flush the kernel cache for the default.aspx page.
        hr = g_pHttpServer->FlushKernelCache(L"/default.aspx");

        // Test for an error.
        if (FAILED(hr))
        {
            // Set the error status for the request.
            pProvider->SetErrorStatus( hr );
            // End additional processing.
            return RQ_NOTIFICATION_FINISH_REQUEST;
        }

        // Return processing to the pipeline.
        return RQ_NOTIFICATION_CONTINUE;
    }

};

// Create the module's class factory.
class MyHttpModuleFactory : public IHttpModuleFactory
{
public:
    HRESULT
    GetHttpModule(
        OUT CHttpModule ** ppModule, 
        IN IModuleAllocator * pAllocator
    )
    {
        UNREFERENCED_PARAMETER( pAllocator );

        // Create a new instance.
        MyHttpModule * pModule = new MyHttpModule;

        // Test for an error.
        if (!pModule)
        {
            // Return an error if the factory cannot create the instance.
            return HRESULT_FROM_WIN32( ERROR_NOT_ENOUGH_MEMORY );
        }
        else
        {
            // Return a pointer to the module.
            *ppModule = pModule;
            pModule = NULL;
            // Return a success status.
            return S_OK;
        }            
    }

    void Terminate()
    {
        // Remove the class from memory.
        delete this;
    }
};

// Create the module's exported registration function.
HRESULT
__stdcall
RegisterModule(
    DWORD dwServerVersion,
    IHttpModuleRegistrationInfo * pModuleInfo,
    IHttpServer * pGlobalInfo
)
{
    UNREFERENCED_PARAMETER( dwServerVersion );

    // Store the pointer for the global server interface.
    g_pHttpServer = pGlobalInfo;

    // Set the request notifications and exit.
    return pModuleInfo->SetRequestNotifications(
        new MyHttpModuleFactory,
        RQ_BEGIN_REQUEST,
        0
    );
}

Your module must export the RegisterModule function. You can export this function by creating a module definition (.def) file for your project, or you can compile the module by using the /EXPORT:RegisterModule switch. For more information, see Walkthrough: Creating a Request-Level HTTP Module By Using Native Code.

You can optionally compile the code by using the __stdcall (/Gz) calling convention instead of explicitly declaring the calling convention for each function.

Requirements

Type	Description
Client	- IIS 7.0 on Windows Vista - IIS 7.5 on Windows 7 - IIS 8.0 on Windows 8 - IIS 10.0 on Windows 10
Server	- IIS 7.0 on Windows Server 2008 - IIS 7.5 on Windows Server 2008 R2 - IIS 8.0 on Windows Server 2012 - IIS 8.5 on Windows Server 2012 R2 - IIS 10.0 on Windows Server 2016
Product	- IIS 7.0, IIS 7.5, IIS 8.0, IIS 8.5, IIS 10.0 - IIS Express 7.5, IIS Express 8.0, IIS Express 10.0
Header	Httpserv.h

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