HOWTO: Implement Thread-Pooled, Apartment Model COM Server in ATL

ID: Q244495

The information in this article applies to:

The Microsoft Active Template Library (ATL) 3.0, included with:
- Microsoft Visual C++, 32-bit Editions, version 6.0

SUMMARY

The Microsoft Active Template Library (ATL) allows you to define a pool of STA threads in an ATL out of process server with each object created running on its own thread. The steps in the "More Information" section of this article shows how to do this.

MORE INFORMATION

The following steps are needed to create objects out of a thread pool:

Derive your CExeModule or CServiceModule class from:


CComAutoThreadModule<>


CExeModule : public CComAutoThreadModule<>

Declare DECLARE_CLASSFACTORY_AUTO_THREAD() in each ATL class that can be run on an STA pool thread

Declare DECLARE_NOT_AGGREGATABLE() in each ATL class that can be run on an STA pool thread


DECLARE_NOT_AGGREGATABLE(CMyPooledObject)

Change the module CExeModule::Unlock() or CServiceModule::Unlock() method to call:


CComAutoThreadModule<>::Unlock()


LONG CExeModule::Unlock()
{
   LONG l = CComAutoThreadModule<>::Unlock();
   if (l == 0)
   {
     bActivity = true;
     SetEvent(hEventShutdown); // tell monitor that we transitioned to zero
   }
   return l;
}

If this is being done for a service, you will need to do one more step. Change the following code from:


inline void CServiceModule::Init(_ATL_OBJMAP_ENTRY* p, HINSTANCE h, UINT nServiceNameID, const GUID* plibid)
{
   CComModule::Init(p, h, plibid);

to:


inline void CServiceModule::Init(_ATL_OBJMAP_ENTRY* p, HINSTANCE h, UINT nServiceNameID, const GUID* plibid)
{
   CComAutoThreadModule<>::Init(p, h, plibid);

By default, ATL creates a pool of four threads per processor. You can change this in the _Module.Init() call in the tWinMain() function call by specifying the number of threads in the optional forth parameter. By default, CComAutoThreadModule uses CComSimpleThreadAllocator as the thread allocator. CComSimpleThreadAllocator uses a simple round robin scheme to creating objects in the thread pool.

REFERENCES

For more information lookup DECLARE_CLASS_FACTORY_AUTO_THREAD() and CComAutoThreadModule and the Microsoft Developer's Network (MSDN).

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

Q202128 BUG: ATL EXE Server Based on CComAutoThreadModule May Hang on Registration

Additional query words:

Keywords : kbActiveX kbCOMt kbLocalSvr kbService kbThread kbVC600 kbATL300 kbDSupport kbGrpMFCATL kbArchitecture
Version : WINDOWS:3.0
Platform : WINDOWS
Issue type : kbhowto