Multiple issues occurred while initially loading the model using lru_cache.

[dummyuser-123]

I have created an API for Real-ESRGAN using FastAPI, and it is working properly for multiple user requests. However, when I am initially loading the models (Real-ESRGAN and GFPGAN) using lru_cache (functools) to decrease the inference time, I am encountering following two errors during execution.

1. Sometimes I have getting faces of one user request mixed up with another user request.

2. In some requests, I have getting following error.

Traceback (most recent call last):
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/middleware/errors.py", line 164, in _call_
   await self.app(scope, receive, _send)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/middleware/exceptions.py", line 62, in _call_
   await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/_exception_handler.py", line 64, in wrapped_app
   raise exc
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
   await app(scope, receive, sender)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/routing.py", line 758, in _call_
   await self.middleware_stack(scope, receive, send)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/routing.py", line 778, in app
   await route.handle(scope, receive, send)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/routing.py", line 299, in handle
   await self.app(scope, receive, send)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/routing.py", line 79, in app
   await wrap_app_handling_exceptions(app, request)(scope, receive, send)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/_exception_handler.py", line 64, in wrapped_app
   raise exc
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
   await app(scope, receive, sender)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/routing.py", line 74, in app
   response = await func(request)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/fastapi/routing.py", line 299, in app
   raise e
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/fastapi/routing.py", line 294, in app
   raw_response = await run_endpoint_function(
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/fastapi/routing.py", line 193, in run_endpoint_function
   return await run_in_threadpool(dependant.call, **values)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/starlette/concurrency.py", line 42, in run_in_threadpool
   return await anyio.to_thread.run_sync(func, *args)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/anyio/to_thread.py", line 56, in run_sync
   return await get_async_backend().run_sync_in_worker_thread(
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/anyio/_backends/_asyncio.py", line 2134, in run_sync_in_worker_thread
   return await future
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/anyio/_backends/_asyncio.py", line 851, in run
   result = context.run(func, *args)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/api.py", line 102, in process_image
   intermediate_image = hd_process(img_array)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/api.py", line 58, in hd_process
   , , output = face_enhancer.enhance(img_array, has_aligned=False, only_center_face=False, paste_back=True)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/torch/utils/_contextlib.py", line 115, in decorate_context
   return func(*args, **kwargs)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/gfpgan/utils.py", line 144, in enhance
   restored_img = self.face_helper.paste_faces_to_input_image(upsample_img=bg_img)
 File "D:/Image Super Resolution/Models/Real-ESRGAN/env/lib/site-packages/facexlib/utils/face_restoration_helper.py", line 291, in paste_faces_to_input_image
   assert len(self.restored_faces) == len(self.inverse_affine_matrices), ('length of restored_faces and affine_matrices are different.')
 AssertionError: length of restored_faces and affine_matrices are different.

This is the small code snippet from my api:

@lru_cache()
def loading_model():
	real_esrgan_model_path = "D:/Image Super Resolution/Models/Real-ESRGAN/weights/RealESRGAN_x4plus.pth"
	gfpgan_model_path = "D:/Image Super Resolution/Models/Real-ESRGAN/env/Lib/site-packages/gfpgan/weights/GFPGANv1.3.pth"

	model = RRDBNet(num_in_ch=3, num_out_ch=3, num_feat=64, num_block=23, num_grow_ch=32, scale=4)
	netscale = 4

	upsampler = RealESRGANer(scale=netscale,model_path=real_esrgan_model_path,dni_weight=0.5,model=model,tile=0,tile_pad=10,pre_pad=0,half=False)
	face_enhancer = GFPGANer(model_path=gfpgan_model_path,upscale=4,arch='clean',channel_multiplier=2,bg_upsampler=upsampler)

	return face_enhancer


def hd_process(file):

	filename = file.filename.split('.')[0]
	save_path = os.path.join("temp_images", f"{filename}.jpg")

	content = file.file.read()
	with open(save_path, 'wb') as image_file:
	    image_file.write(content)

	img_array = cv2.imread(save_path, cv2.IMREAD_UNCHANGED)

	face_enhancer = loading_model()

	with torch.no_grad():
		_, _, output = face_enhancer.enhance(img_array, has_aligned=False, only_center_face=False, paste_back=True)

	output_rgb = cv2.cvtColor(output, cv2.COLOR_BGR2RGB)

	del face_enhancer
	torch.cuda.empty_cache()

	return output_rgb

What is the problem extracted during the initial model loading? I believe there is something common among multiple user requests, and this is causing the error.