refactoring

image_prediction/flask.py

@@ -14,6 +14,29 @@ def run_prediction_server(app, host, port):
     serve(app, host=host, port=port, _quiet=False)
 
 
+def run_in_process(func):
+    p = multiprocessing.Process(target=func)
+    p.start()
+    p.join()
+
+
+def wrap_in_process(func_to_wrap):
+    def build_function_and_run_in_process(*args, **kwargs):
+        def func():
+            try:
+                result = func_to_wrap(*args, **kwargs)
+                return_dict["result"] = result
+            except:
+                logger.error(traceback.format_exc())
+
+        manager = multiprocessing.Manager()
+        return_dict = manager.dict()
+        run_in_process(func)
+        return return_dict.get("result", None)
+
+    return build_function_and_run_in_process
+
+
 def make_prediction_server(predict_fn: Callable):
     app = Flask(__name__)
 
@@ -29,32 +52,27 @@ def make_prediction_server(predict_fn: Callable):
         resp.status_code = 200
         return resp
 
-    @app.route("/predict", methods=["POST"])
+    def __failure():
-    def predict():
-        def predict_fn_wrapper(pdf, return_dict):
-            return_dict["result"] = predict_fn(pdf)
-
-        def process():
-            # Tensorflow does not free RAM. Workaround is running service_estimator in process.
-            # https://stackoverflow.com/questions/39758094/clearing-tensorflow-gpu-memory-after-model-execution
-            pdf = request.data
-            manager = multiprocessing.Manager()
-            return_dict = manager.dict()
-            p = multiprocessing.Process(target=predict_fn_wrapper, args=(pdf, return_dict))
-            p.start()
-            p.join()
-            return return_dict["result"]
-
-        logger.info("Analysing document...")
-        try:
-            predictions = process()
-            response = jsonify(predictions)
-            logger.debug("Analysis completed.")
-            return response
-        except Exception:
-            logger.exception(f"Analysis failed\n{traceback.format_exc()}")
         response = jsonify("Analysis failed")
         response.status_code = 500
         return response
 
+    @app.route("/predict", methods=["POST"])
+    def predict():
+
+        # Tensorflow does not free RAM. Workaround: Run prediction function (which instantiates a model) in sub-process.
+        # See: https://stackoverflow.com/questions/39758094/clearing-tensorflow-gpu-memory-after-model-execution
+        predict_fn_wrapped = wrap_in_process(predict_fn)
+
+        logger.info("Analysing...")
+        predictions = predict_fn_wrapped(request.data)
+
+        if predictions:
+            response = jsonify(predictions)
+            logger.info("Analysis completed.")
+            return response
+        else:
+            logger.error("Analysis failed.")
+            return __failure()
+
     return app

test/unit_tests/mocked_server_test.py

@@ -12,11 +12,10 @@ logger.setLevel(logging.CRITICAL + 1)
 
 def predict_fn(x: bytes):
     x = int(x.decode())
-    match x:
+    if x == 42:
-        case 42:
         return True
-        case _:
+    else:
-            raise Exception
+        raise Exception("intentional test exception")
 
 
 @pytest.fixture