/* Copyright (c) 1997-2002 Microsoft Corporation Module Name: WorkerThread.c Abstract: IIS maintains a pool of threads to handle incoming HTTP requests. When all of these threads are in use, new requests will be rejected. If all the pool threads are in a wait state (for instance, running ISAPI dlls that are waiting for a query on a remote database to complete), IIS may reject incoming requests even if there is plenty of CPU power to handle them. One way of avoiding this situation is to offload processing of these types of requests to a worker thread, releasing the IIS thread back to the pool so that it can be used for another request. This basic sample demonstrates how to implement this in an ISAPI dll. */ #define WIN32_LEAN_AND_MEAN #include #include #include /* global variables */ DWORD g_dwThreadCount = 0; /* local functions prototypes */ DWORD WINAPI WorkerFunction(LPVOID); BOOL SendHttpHeaders(EXTENSION_CONTROL_BLOCK *, LPCSTR , LPCSTR, BOOL); /* Purpose: This is required ISAPI Extension DLL entry point. Arguments: pVer - poins to extension version info structure Returns: always returns TRUE */ BOOL WINAPI GetExtensionVersion(OUT HSE_VERSION_INFO *pVer) { /* tell the server our version number and extension description */ pVer->dwExtensionVersion = MAKELONG(HSE_VERSION_MINOR, HSE_VERSION_MAJOR); strncpy_s(pVer->lpszExtensionDesc, sizeof(pVer->lpszExtensionDesc), "ISAPI Worker Thread Extension Sample", HSE_MAX_EXT_DLL_NAME_LEN - 1); return TRUE; } /* Purpose: Create a thread to handle extended processing. It will be passed the address of a function ("WorkerFunction") to run, and the address of the ECB associated with this session. Arguments: pECB - pointer to the extenstion control block Returns: HSE_STATUS_PENDING to mark this request as pending */ DWORD WINAPI HttpExtensionProc(IN EXTENSION_CONTROL_BLOCK *pECB) { DWORD dwThreadID; /* NOTE: in production environment you'd probably want to limit the number of threads created */ CreateThread( NULL, // Pointer to thread security attributes 0, // Initial thread stack size, in bytes WorkerFunction, // Pointer to thread function pECB, // The ECB is the argument for the new thread 0, // Creation flags &dwThreadID); // Pointer to returned thread identifier /* update global thread count */ InterlockedIncrement(&g_dwThreadCount); /* Return HSE_STATUS_PENDING to release IIS pool thread without losing connection */ return HSE_STATUS_PENDING; } /* Purpose: Show how to perform extended processing in ISAPI DLL without tying IIS threads. Arguments: vECB - points to current extension control block Returns: returns 0 */ DWORD WINAPI WorkerFunction(IN LPVOID vECB) { char szHeader[] = "Content-type: text/html\r\n\r\n"; char szContent[] = "

Worker Thread Sample

" "
"; /* Initialize local ECB pointer to void pointer passed to thread */ EXTENSION_CONTROL_BLOCK *pECB = vECB; DWORD dwSize = strlen(szContent); /* Send outgoing header */ SendHttpHeaders(pECB, "200 OK", szHeader, FALSE); /* Simulate extended processing for 5 seconds */ Sleep(5000); /* Send content */ pECB->WriteClient(pECB->ConnID, szContent, &dwSize, 0); /* Inform server that the request has been satisfied, and the connection may now be dropped */ pECB->ServerSupportFunction(pECB->ConnID, HSE_REQ_DONE_WITH_SESSION, NULL, NULL, NULL); /* update global thread count */ InterlockedDecrement(&g_dwThreadCount); return 0; } /* Purpose: Send specified HTTP status string and any additional header strings using new ServerSupportFunction() request HSE_SEND_HEADER_EX_INFO Arguments: pECB - pointer to the extension control block pszStatus - HTTP status string (e.g. "200 OK") pszHeaders - any additional headers, separated by CRLFs and terminated by empty line Returns: TRUE if headers were successfully sent FALSE otherwise */ BOOL SendHttpHeaders(EXTENSION_CONTROL_BLOCK *pECB, LPCSTR pszStatus, LPCSTR pszHeaders, BOOL fKeepConnection) { HSE_SEND_HEADER_EX_INFO header_ex_info; BOOL success; header_ex_info.pszStatus = pszStatus; header_ex_info.pszHeader = pszHeaders; header_ex_info.cchStatus = strlen(pszStatus); header_ex_info.cchHeader = strlen(pszHeaders); header_ex_info.fKeepConn = fKeepConnection; success = pECB->ServerSupportFunction(pECB->ConnID, HSE_REQ_SEND_RESPONSE_HEADER_EX, &header_ex_info, NULL, NULL); return success; } /* Routine Description: This function is called when the WWW service is shutdown. Arguments: dwFlags - HSE_TERM_ADVISORY_UNLOAD or HSE_TERM_MUST_UNLOAD Return Value: TRUE when extension is ready to be unloaded, */ BOOL WINAPI TerminateExtension(IN DWORD dwFlags) { /* Our threads are deterministic and will complete not much later than 5 seconds from now */ /* wait for all threads to terminate, sleeping for 1 sec */ while (g_dwThreadCount > 0) SleepEx(1000, FALSE); /* make sure the last thread indeed exited */ SleepEx(1000, FALSE); return TRUE; }