From cb00aed62ca697ee1ca8f979391f2d8a939f5bc2 Mon Sep 17 00:00:00 2001
From: Matthias Bisping <matthias.bisping@iqser.com>
Date: Sat, 2 Apr 2022 01:23:57 +0200
Subject: [PATCH] refactoring

---
 image_prediction/flask.py             | 60 +++++++++++++++++----------
 test/unit_tests/mocked_server_test.py |  9 ++--
 2 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/image_prediction/flask.py b/image_prediction/flask.py
index 7bc6eb1..0e9c448 100644
--- a/image_prediction/flask.py
+++ b/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
 
+    def __failure():
+        response = jsonify("Analysis failed")
+        response.status_code = 500
+        return response
+
     @app.route("/predict", methods=["POST"])
     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"]
+        # 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 document...")
-        try:
-            predictions = process()
+        logger.info("Analysing...")
+        predictions = predict_fn_wrapped(request.data)
+
+        if predictions:
             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
+            logger.info("Analysis completed.")
             return response
+        else:
+            logger.error("Analysis failed.")
+            return __failure()
 
     return app
diff --git a/test/unit_tests/mocked_server_test.py b/test/unit_tests/mocked_server_test.py
index ab82a33..4ddeaeb 100644
--- a/test/unit_tests/mocked_server_test.py
+++ b/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:
-        case 42:
-            return True
-        case _:
-            raise Exception
+    if x == 42:
+        return True
+    else:
+        raise Exception("intentional test exception")
 
 
 @pytest.fixture