Enumerating the Replicas of a Service

This topic includes a code example that enumerates the installed instances of a replicated service on different host computers throughout an enterprise. To change the service account password for each instance of a replicated service, use this code example in conjunction with the code example in the Changing the Password on a Service's User Account topic.

The code example assumes that each service instance has its own service connection point (SCP) object in the directory. An SCP is an object of the serviceConnectionPoint class. This class has a keywords attribute, which is a multi-valued attribute replicated to each global catalog (GC) in the forest. The keywords attribute of each instance's SCP contains the service's product GUID. This enables finding all of the SCPs for the various service instances by searching a GC for objects with a keywords attribute that equals the product GUID.

The code example obtains an IDirectorySearch pointer to a GC, and uses the IDirectorySearch::ExecuteSearch method to search for the SCPs. Be aware that the GC contains a partial replica for each SCP. That is, it contains some of the SCP attributes, but not all. In this code example, focus on the serviceDNSName attribute, which contains the DNS name of the host server for that service instance. Because serviceDNSName is not one of the attributes replicated in a GC, the code example uses a two-step process to retrieve it. First, it uses the GC search to get the distinguished name (DN) of the SCP, then it uses that DN to bind directly to the SCP to retrieve the serviceDNSName property.

HRESULT EnumerateServiceInstances(
	 LPWSTR szQuery, 			// Search string filter.
	 LPWSTR *pszAttribs, 		// An array of attributes to retrieve.
	 DWORD dwAttribs, 		 // Number of attributes requested.
	 DWORD *pdwAttribs, 		 // Number of attributes retrieved.
	 ADS_ATTR_INFO **ppPropEntries  // Returns a pointer to the retrieved attributes.
		)
{
HRESULT hr;
IEnumVARIANT *pEnum = NULL;
IADsContainer *pCont = NULL;
VARIANT var;
IDispatch *pDisp = NULL;
BSTR  bstrPath = NULL;
ULONG lFetch;
IADs *pADs = NULL;
int iRows=0;
static IDirectorySearch *pSearch = NULL;
static ADS_SEARCH_HANDLE hSearch = NULL;

// Parameters for IDirectoryObject.
IDirectoryObject *pSCP = NULL;
 
// Structures and parameters for IDirectorySearch.
DWORD			 dwPref;
ADS_SEARCH_COLUMN   Col;
ADS_SEARCHPREF_INFO SearchPref[2];
 
// First time through; set up the search.
if (pSearch == NULL) 
{
	// Bind to the GC: namespace container object. The GC DN 
	// is a single immediate child of the GC: namespace, which must 
	// be obtained through enumeration.
	hr = ADsGetObject(L"GC:", 
		IID_IADsContainer, 
		(void**) &pCont );
	if (FAILED(hr)) {
		_tprintf(TEXT("ADsGetObject(GC) failed: 0x%x\n"), hr);
		goto Cleanup;
}
 
	// Obtain an enumeration interface for the GC container. 
	hr = ADsBuildEnumerator(pCont,&pEnum);
	if (FAILED(hr)) {
		_tprintf(TEXT("ADsBuildEnumerator failed: 0x%x\n"), hr);
		goto Cleanup;
}
 
	// Enumerate. There is only one child of the GC: object.
	hr = ADsEnumerateNext(pEnum,1,&var,&lFetch);
	if (( hr == S_OK ) && ( lFetch == 1 ) ) 
	{
		pDisp = V_DISPATCH(&var);
		hr = pDisp->QueryInterface( IID_IADs, (void**)&pADs);
		if (hr == S_OK) 
			hr = pADs->get_ADsPath(&bstrPath);
}
	if (FAILED(hr)) {
		_tprintf(TEXT("Enumeration failed: 0x%x\n"), hr);
		goto Cleanup;
}
 
	// Now bstrPath contains the ADsPath for the current GC.  
	// Bind the GC to get the search interface.
	hr = ADsGetObject(bstrPath, IID_IDirectorySearch, (void**)&pSearch);
	if (FAILED(hr)) {
		_tprintf(TEXT("Failed to bind search root: 0x%x\n"), hr);
		goto Cleanup;
} 
 
	// Set up a deep search.
	// Thousands of objects are not expected
	// in this example; request 1000 rows per page.
	dwPref=sizeof(SearchPref)/sizeof(ADS_SEARCHPREF_INFO);
	SearchPref[0].dwSearchPref =	ADS_SEARCHPREF_SEARCH_SCOPE;
	SearchPref[0].vValue.dwType =   ADSTYPE_INTEGER;
	SearchPref[0].vValue.Integer =  ADS_SCOPE_SUBTREE;
 
	SearchPref[1].dwSearchPref =	ADS_SEARCHPREF_PAGESIZE;
	SearchPref[1].vValue.dwType =   ADSTYPE_INTEGER;
	SearchPref[1].vValue.Integer =  1000;
 
	hr = pSearch->SetSearchPreference(SearchPref, dwPref);
	if (FAILED(hr))	{
		_tprintf(TEXT("Failed to set search prefs: 0x%x\n"), hr);
		goto Cleanup;
} 
 
	// Execute the search. From the GC, get the distinguished name 
	// of the SCP. Use the DN to bind to the SCP and get the other 
	// properties.
	hr = pSearch->ExecuteSearch(szQuery, pszAttribs, 1, &hSearch);
	if (FAILED(hr)) {
		_tprintf(TEXT("ExecuteSearch failed: 0x%x\n"), hr);
		goto Cleanup;
} 
}
 
// Get the next row.
hr = pSearch->GetNextRow(hSearch);
 
// Process the row.
if (SUCCEEDED(hr) && hr !=S_ADS_NOMORE_ROWS) 
{
	// Get the distinguished name of the object in this row.
	hr = pSearch->GetColumn(hSearch, L"distinguishedName", &Col);
	if FAILED(hr) { 
		_tprintf(TEXT("GetColumn failed: 0x%x\n"), hr);
		goto Cleanup;
}
	// Bind to the DN to get the properties.
	if (Col.dwADsType == ADSTYPE_CASE_IGNORE_STRING)
	{
		LPWSTR szSCPPath = new WCHAR[7 + lstrlenW(Col.pADsValues->CaseIgnoreString) + 1];
		wcscpy(szSCPPath, L"LDAP://");
		wcscat(szSCPPath, Col.pADsValues->CaseIgnoreString);
		hr = ADsGetObject(szSCPPath, IID_IDirectoryObject, (void**)&pSCP);
		delete szSCPPath;
		if (SUCCEEDED(hr)) 
		{
			hr = pSCP->GetObjectAttributes(pszAttribs, dwAttribs,
						ppPropEntries, pdwAttribs);
			if(FAILED(hr)) {
				_tprintf(TEXT("GetObjectAttributes Failed."), hr);
				goto Cleanup;
		}
	}
}
	pSearch->FreeColumn(&Col);}
 
Cleanup:
if (bstrPath)
	SysFreeString(bstrPath);
if (pSCP) 
	pSCP->Release();
if (pCont) 
	pCont->Release();
if (pEnum)
	ADsFreeEnumerator(pEnum);
if (pADs) 
	pADs->Release();
if (pDisp)
	pDisp->Release();
 
return hr;
 
}