IGlobalTraceEventProvider::GetCurrentHttpRequestContext Method

 

Retrieves the HTTP context for trace events that are request specific.

Syntax

virtual HRESULT GetCurrentHttpRequestContext(  
   IHttpContext** ppHttpContext  
) = 0;  

Parameters

ppHttpContext
A pointer to the address of an IHttpContext interface; otherwise, NULL.

Return Value

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

Value	Definition
S_OK	Indicates that the operation was successful.
ERROR_NOT_SUPPORTED	Indicates that the method is not supported.

Remarks

CGlobalModule derived classes that register for GL_TRACE_EVENT event types receive an IGlobalTraceEventProvider pointer as a parameter on the CGlobalModule::OnGlobalTraceEvent pure virtual method. You can then retrieve an IHttpContext pointer by calling the GetCurrentHttpRequestContext method on that IGlobalTraceEventProvider pointer.

One possible use for GetCurrentHttpRequestContext is to provide custom buffering of events.

GetCurrentHttpRequestContext behavior depends on implementation. You should use the following information as a guideline, but it may not be correct in all scenarios:

• Classes that provide HTTP trace events declare a private``IHttpContext pointer member variable. This variable is initialized during construction to a valid IHttpContext pointer. When you call GetCurrentHttpRequestContext, the dereferenced ppHttpContext parameter is set to this variable, and S_OK is returned.

• Classes that provide global trace events do not modify the ppHttpContext parameter and return ERROR_NOT_SUPPORTED immediately.

Notes for Implementers

IGlobalTraceEventProvider implementers are responsible for memory management with this data; therefore, IGlobalTraceEventProvider implementers that use dynamic memory allocation must release or call delete on the IHttpContext pointer when it is no longer needed.

Notes for Callers

IGlobalTraceEventProvider implementers are responsible for memory management with this data; therefore, IGlobalTraceEventProvider clients must not release or call delete on the returned IHttpContext pointer when this data is no longer needed.

Example

The following code example demonstrates how to create a global module that listens for GL_TRACE_EVENT events and declares and initializes an HTTP_TRACE_CONFIGURATION structure that filters for events. The module then retrieves the IHttpContext pointer by calling the GetCurrentHttpRequestContext method.

#pragma warning( disable : 4290 )
#pragma warning( disable : 4530 )

#define _WINSOCKAPI_
#include <windows.h>
#include <sal.h>
#include <tchar.h>
#include <initguid.h>
#include <httptrace.h>
#include <httpserv.h>
#include <httpcach.h>

// The CGlobalTraceModule class creates the CGlobalModule 
// class and registers for GL_TRACE_EVENT events.
class CGlobalContainerModule : public CGlobalModule
{
public:
    // Creates the destructor for the 
    // CGlobalTraceModule class.
    virtual ~CGlobalContainerModule()
    {

    }

    // The RegisterGlobalModule method creates and registers 
    // a new CGlobalTraceModule for GL_TRACE_EVENT events.
    // dwServerVersion: the current server version.
    // pModuleInfo: the current IHttpModuleRegistrationInfo pointer.
    // pGlobalInfo: the current IHttpServer pointer.
    // return: ERROR_NOT_ENOUGH_MEMORY if the heap is out of 
    // memory; otherwise, the value from the call to the 
    // SetGlobalNotifications method on the pModuleInfo pointer.
    static HRESULT RegisterGlobalModule
    (
        DWORD dwServerVersion,
        IHttpModuleRegistrationInfo* pModuleInfo,
        IHttpServer* pGlobalInfo
    )
    {        
        // The IHttpModuleRegistrationInfo 
        // pointermust not be NULL.
        if (NULL == pModuleInfo)
        {
            return E_INVALIDARG;
        }

        // Get the HTTP_MODULE_ID from the 
        // IHttpModuleRegistrationInfo pointer.
        HTTP_MODULE_ID moduleId = 
            pModuleInfo->GetId();

        // The HTTP_MODULE_ID pointer 
        // must not be NULL.
        if (NULL == moduleId)
        {
            return E_INVALIDARG;
        }

        // Create a new CGlobalContainerModule pointer
        // using the HTTP_MODULE_ID from the 
        // IHttpModuleRegistrationInfo pointer.
        CGlobalContainerModule* containerModule = 
            new CGlobalContainerModule(moduleId);

        // Return an out-of-memory error if the containerModule 
        // is NULL after the call to the new operator.
        if (NULL == containerModule)
        {            
            return HRESULT_FROM_WIN32(ERROR_NOT_ENOUGH_MEMORY);
        }                                          

        // Attempt to set global notification 
        // for an GL_TRACE_EVENT event by using 
        // the traceModule as a listener.
        HRESULT hr = pModuleInfo->SetGlobalNotifications
            (containerModule, GL_TRACE_EVENT);

        // Return the HRESULT from the call to 
        // the SetGlobalNotifications method.        
        return hr;
    }

    // The OnGlobalTraceEvent method is the callback
    // method for GL_TRACE_EVENT events in the pipeline.
    // pProvider: the IGlobalTraceEventProvider pointer.
    // return: GL_NOTIFICATION_CONTINUE.
    virtual 
    GLOBAL_NOTIFICATION_STATUS
    OnGlobalTraceEvent
    (
        IN IGlobalTraceEventProvider* pProvider
    )
    {
        // If the IGlobalTraceEventProvider pointer 
        // is NULL, return GL_NOTIFICATION_CONTINUE.
        if (NULL == pProvider)
        {
            return GL_NOTIFICATION_CONTINUE;
        }

        // Declare an IHttpContext pointer.
        IHttpContext* httpContext = NULL;

        // Declare an HRESULT and initialize
        // the HRESULT to E_FAIL.
        HRESULT hr = E_FAIL;

        // Call the GetCurrentHttpRequestContext
        // method on the IGlobalTraceEventProvider
        // pointer.
        hr = pProvider->GetCurrentHttpRequestContext(&httpContext);

        // Return GL_NOTIFICATION_CONTINUE.
        return GL_NOTIFICATION_CONTINUE;
    }

    // The Terminate method is required for
    // non-abstract CGlobalTraceModule classes.
    // This method calls delete on this.
    virtual VOID Terminate(VOID)
    {
        delete this;
    }
    // Creates the constructor for the CGlobalTraceModule 
    // class. This constructor initializes the CEventWriter
    // to write to the application event log.
    // moduleId: the current module identifier.
    CGlobalContainerModule(HTTP_MODULE_ID moduleId)        
    {
        m_moduleId = moduleId;
    }
private:
    // Specify the HTTP_MODULE_ID
    // for this module.
    HTTP_MODULE_ID m_moduleId;
};

// The RegisterModule method is the 
// main entry point for the DLL.
// dwServerVersion: the current server version.
// pModuleInfo: the current 
// IHttpModuleRegistrationInfo pointer.
// pGlobalInfo: the current IHttpServer pointer.
// return: the value returned by calling the
// CGlobalContainerModule::RegisterGlobalModule
// method.
HRESULT
__stdcall
RegisterModule(
    DWORD dwServerVersion,
    IHttpModuleRegistrationInfo* pModuleInfo,
    IHttpServer* pGlobalInfo
)
{        
    // Call the static method for initialization.
    return CGlobalContainerModule::RegisterGlobalModule            
        (dwServerVersion, 
         pModuleInfo, 
         pGlobalInfo);             
}

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 Technical Preview
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

See Also

IGlobalTraceEventProvider Interface