windows - multi-Instance support

.gitignore

@@ -23,6 +23,7 @@ __pycache__
 /backend/windows-runner/dist/
 logs.txt
 dcef.exe
+/backend/windows-runner/dcef.spec
 
 # nginx
 /backend/nginx/logs

backend/windows-runner/requirements.txt

@@ -1 +1,2 @@
-pywebview==4.0.1
+pywebview==4.0.1
+pywin32==305

backend/windows-runner/windows-runner.py

@@ -8,25 +8,39 @@
 import atexit
 import threading
 
+# https://stackoverflow.com/a/65501621
+from win32event import CreateMutex
+from win32api import CloseHandle, GetLastError
+from winerror import ERROR_ALREADY_EXISTS
+class SingleInstance:
+	""" Limits application to single instance """
+
+	def __init__(self):
+		self.mutexname = "dcef-qwertyuiopasdfghjklzxcvbnm1234567890"
+		self.mutex = CreateMutex(None, False, self.mutexname)
+		self.lasterror = GetLastError()
+
+	def is_secondary_instance(self):
+		return (self.lasterror == ERROR_ALREADY_EXISTS)
+
+	def is_primary_instance(self):
+		return not self.is_secondary_instance()
+
+	def __del__(self):
+		if self.mutex:
+			CloseHandle(self.mutex)
+
+
+
 
 def is_compiled():
-    if os.path.exists(__file__):
-        return False
-    else:
-        return True
+	if os.path.exists(__file__):
+		return False
+	else:
+		return True
 
-is_compiled = is_compiled()
-processes = []
-terminating_now = False
 
-if is_compiled:
-	BASE_DIR = os.path.realpath(os.path.dirname(sys.executable))
-else:
-	BASE_DIR = os.path.realpath(os.path.dirname(__file__) + '/../../release')
 
-LOG_FILE = BASE_DIR + '/dcef/logs.txt'
-if os.path.exists(LOG_FILE):
-	os.remove(LOG_FILE)
 
 def custom_print(source, *args, **kwargs):
 
@@ -46,6 +60,12 @@ def cleanup():
 	global terminating_now
 	if not terminating_now:  # Prevents cleanup from being called twice
 		terminating_now = True
+
+		# kill other instances of dcef.exe except this one
+		if is_compiled() and myapp.is_primary_instance():
+			custom_print("windows-runner:", "killing other instances of dcef.exe except primary with PID " +  str(os.getpid()))
+			os.system('taskkill /f /im dcef.exe /fi "PID ne ' + str(os.getpid()) + '"')
+
 		custom_print("windows-runner:", "cleaning up")
 		for process in processes:
 			custom_print("windows-runner:", "killing process", process.pid)
@@ -55,9 +75,13 @@ def cleanup():
 				custom_print("windows-runner:", "error killing process", process.pid, e)
 
 
+
 def create_window():
 	custom_print("windows-runner:", "creating window")
-	window = webview.create_window('DiscordChatExported-frontend','http://127.0.0.1:21011/',
+	title = 'DiscordChatExported-frontend'
+	if myapp.is_secondary_instance():
+		title += ' (secondary instance)'
+	window = webview.create_window(title, 'http://127.0.0.1:21011/',
 		width=1280,
 		height=720,
 		background_color='#36393F',
@@ -128,13 +152,13 @@ def start_nginx():
 
 def hide_console():
 	# https://github.com/pyinstaller/pyinstaller/issues/1339#issuecomment-122909830
-	if is_compiled:
+	if is_compiled():
 		whnd = ctypes.windll.kernel32.GetConsoleWindow()
 		if whnd != 0:
 			ctypes.windll.user32.ShowWindow(whnd, 0)
 
 def show_console():
-	if is_compiled:
+	if is_compiled():
 		whnd = ctypes.windll.kernel32.GetConsoleWindow()
 		if whnd != 0:
 			ctypes.windll.user32.ShowWindow(whnd, 1)
@@ -143,23 +167,49 @@ def show_console():
 
 
 def main():
-	custom_print("windows-runner:", "started")
-	atexit.register(cleanup)
-	th_nginx = start_nginx()
-	time.sleep(1)
-	th_mongodb = start_mongodb()
-	th_http_server = start_http_server()
-	th_fastapi = start_fastapi()
-	th_preprocess = start_preprocess()
-
-
-	th_preprocess.join()  # Wait for preprocess to finish
-	hide_console()
-	create_window()
-	show_console()
-	custom_print("windows-runner:", "finished")
-	cleanup()
+	if myapp.is_secondary_instance():
+		# second instance just needs to open another window, the backend services are already running
+		custom_print("windows-runner:", "started secondary instance")
+		hide_console()
+		create_window()
+		show_console()
+		custom_print("windows-runner:", "finished secondary instance")
 
+	else:
+		if os.path.exists(LOG_FILE):
+			os.remove(LOG_FILE)
+
+		custom_print("windows-runner:", "started primary instance")
+		atexit.register(cleanup)
+		th_nginx = start_nginx()
+		time.sleep(1)
+		th_mongodb = start_mongodb()
+		th_http_server = start_http_server()
+		th_fastapi = start_fastapi()
+		th_preprocess = start_preprocess()
+
+
+		th_preprocess.join()  # Wait for preprocess to finish
+
+		hide_console()
+		create_window()
+		show_console()
+
+		custom_print("windows-runner:", "finished primary instance")
+		cleanup()
+
+
+
+myapp = SingleInstance()
+processes = []
+terminating_now = False
+
+if is_compiled():
+	BASE_DIR = os.path.realpath(os.path.dirname(sys.executable))
+else:
+	BASE_DIR = os.path.realpath(os.path.dirname(__file__) + '/../../release')
+
+LOG_FILE = BASE_DIR + '/dcef/logs.txt'
 
 if __name__ == '__main__':
 	main()