Support configurable eventlog application names on Windows

This allows different instances to use the eventlog with different
identifiers, by setting the event_source GUC, similar to how
syslog_ident works.

Original patch by MauMau, heavily modified by Magnus Hagander

src/backend/utils/error/elog.c

@@ -123,6 +123,7 @@ static void write_syslog(int level, const char *line);
 static void write_console(const char *line, int len);
 
 #ifdef WIN32
+extern char *event_source;
 static void write_eventlog(int level, const char *line, int len);
 #endif
 
@@ -1673,7 +1674,7 @@ write_eventlog(int level, const char *line, int len)
 
 	if (evtHandle == INVALID_HANDLE_VALUE)
 	{
-		evtHandle = RegisterEventSource(NULL, "PostgreSQL");
+		evtHandle = RegisterEventSource(NULL, event_source ? event_source : "PostgreSQL");
 		if (evtHandle == NULL)
 		{
 			evtHandle = INVALID_HANDLE_VALUE;

src/backend/utils/misc/guc.c

@@ -412,6 +412,7 @@ bool		log_executor_stats = false;
 bool		log_statement_stats = false;		/* this is sort of all three
 												 * above together */
 bool		log_btree_build_stats = false;
+char	   *event_source;
 
 bool		check_function_bodies = true;
 bool		default_with_oids = false;
@@ -2819,6 +2820,19 @@ static struct config_string ConfigureNamesString[] =
 		NULL, assign_syslog_ident, NULL
 	},
 
+#ifdef WIN32
+	{
+		{"event_source", PGC_POSTMASTER, LOGGING_WHERE,
+			gettext_noop("Sets the application name used to identify"
+						 "PostgreSQL messages in the event log."),
+			NULL
+		},
+		&event_source,
+		"PostgreSQL",
+		NULL, NULL, NULL
+	},
+#endif
+
 	{
 		{"TimeZone", PGC_USERSET, CLIENT_CONN_LOCALE,
 			gettext_noop("Sets the time zone for displaying and interpreting time stamps."),

src/backend/utils/misc/postgresql.conf.sample

@@ -322,6 +322,8 @@
 #syslog_facility = 'LOCAL0'
 #syslog_ident = 'postgres'
 
+# This is only relevant when logging to eventlog (win32):
+#event_source = 'PostgreSQL'
 
 # - When to Log -
 

src/bin/pgevent/pgevent.c

@@ -15,16 +15,55 @@
 #include <windows.h>
 #include <olectl.h>
 #include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
 
 /* Global variables */
 HANDLE		g_module = NULL;	/* hModule of DLL */
 
+/*
+ * The event source is stored as a registry key.
+ * The maximum length of a registry key is 255 characters.
+ * http://msdn.microsoft.com/en-us/library/ms724872(v=vs.85).aspx
+ */
+char		event_source[256] = "PostgreSQL";
+
 /* Prototypes */
-STDAPI
-DllRegisterServer(void);
+HRESULT		DllInstall(BOOL bInstall, __in_opt LPCWSTR pszCmdLine);
+STDAPI		DllRegisterServer(void);
 STDAPI		DllUnregisterServer(void);
 BOOL WINAPI DllMain(HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved);
 
+/*
+ * DllInstall --- Passes the command line argument to DLL
+ */
+
+HRESULT
+DllInstall(BOOL bInstall,
+		   __in_opt LPCWSTR pszCmdLine)
+{
+	size_t		ret;
+
+	if (pszCmdLine && *pszCmdLine != '\0')
+		wcstombs_s(&ret, event_source, sizeof(event_source),
+				   pszCmdLine, sizeof(event_source));
+
+	/*
+	 * This is an ugly hack due to the strange behavior of "regsvr32 /i".
+	 *
+	 * When installing, regsvr32 calls DllRegisterServer before DllInstall.
+	 * When uninstalling (i.e. "regsvr32 /u /i"), on the other hand, regsvr32
+	 * calls DllInstall and then DllUnregisterServer as expected.
+	 *
+	 * This strange behavior forces us to specify -n (i.e. "regsvr32 /n /i").
+	 * Without -n, DllRegisterServer called before DllInstall would mistakenly
+	 * overwrite the default "PostgreSQL" event source registration.
+	 */
+	if (bInstall)
+		DllRegisterServer();
+	return S_OK;
+}
+
 /*
  * DllRegisterServer --- Instructs DLL to create its registry entries
  */
@@ -35,6 +74,7 @@ DllRegisterServer(void)
 	HKEY		key;
 	DWORD		data;
 	char		buffer[_MAX_PATH];
+	char		key_name[400];
 
 	/* Set the name of DLL full path name. */
 	if (!GetModuleFileName((HMODULE) g_module, buffer, sizeof(buffer)))
@@ -47,7 +87,10 @@ DllRegisterServer(void)
 	 * Add PostgreSQL source name as a subkey under the Application key in the
 	 * EventLog registry key.
 	 */
-	if (RegCreateKey(HKEY_LOCAL_MACHINE, "SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\PostgreSQL", &key))
+	_snprintf(key_name, sizeof(key_name),
+			"SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\%s",
+			  event_source);
+	if (RegCreateKey(HKEY_LOCAL_MACHINE, key_name, &key))
 	{
 		MessageBox(NULL, "Could not create the registry key.", "PostgreSQL error", MB_OK | MB_ICONSTOP);
 		return SELFREG_E_TYPELIB;
@@ -72,7 +115,7 @@ DllRegisterServer(void)
 					  "TypesSupported",
 					  0,
 					  REG_DWORD,
-					  (LPBYTE) &data,
+					  (LPBYTE) & data,
 					  sizeof(DWORD)))
 	{
 		MessageBox(NULL, "Could not set the supported types.", "PostgreSQL error", MB_OK | MB_ICONSTOP);
@@ -90,12 +133,17 @@ DllRegisterServer(void)
 STDAPI
 DllUnregisterServer(void)
 {
+	char		key_name[400];
+
 	/*
 	 * Remove PostgreSQL source name as a subkey under the Application key in
 	 * the EventLog registry key.
 	 */
 
-	if (RegDeleteKey(HKEY_LOCAL_MACHINE, "SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\PostgreSQL"))
+	_snprintf(key_name, sizeof(key_name),
+			"SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\%s",
+			  event_source);
+	if (RegDeleteKey(HKEY_LOCAL_MACHINE, key_name))
 	{
 		MessageBox(NULL, "Could not delete the registry key.", "PostgreSQL error", MB_OK | MB_ICONSTOP);
 		return SELFREG_E_TYPELIB;

src/bin/pgevent/pgevent.def

@@ -2,3 +2,4 @@
 EXPORTS
 	DllUnregisterServer ;
 	DllRegisterServer ;
+	DllInstall ;