Remove Singleton pattern from Database

Backend/app/__main__.py

@@ -15,7 +15,7 @@
 
 from app.common.config_constants import APP, HOST, PORT
 from app.common.PropertiesManager import PropertiesManager
-from app.database.Database import Database
+from app.database.DatabaseConnection import DatabaseConnection
 from app.logging.logging_constants import LOGGING_MAIN
 from app.logging.logging_schema import SpotifyElectronLogger
 from app.middleware.cors_middleware_config import (
@@ -49,7 +49,7 @@ async def lifespan_handler(app: FastAPI):
     """
     main_logger.info("Spotify Electron Backend Started")
 
-    Database()
+    DatabaseConnection()
 
     app.include_router(playlist_controller.router)
     app.include_router(song_controller.router)

Backend/app/database/Database.py → Backend/app/database/DatabaseConnection.py

@@ -5,6 +5,7 @@
 
 import sys
 from enum import StrEnum
+from functools import wraps
 from typing import Any
 
 from gridfs import GridFS
@@ -18,7 +19,6 @@
 from app.exceptions.base_exceptions_schema import SpotifyElectronException
 from app.logging.logging_constants import LOGGING_DATABASE
 from app.logging.logging_schema import SpotifyElectronLogger
-from app.patterns.Singleton import Singleton
 
 database_logger = SpotifyElectronLogger(LOGGING_DATABASE).getLogger()
 
@@ -34,31 +34,44 @@ class DatabaseCollection(StrEnum):
     SONG_BLOB_DATA = "songs"
 
 
-class Database(metaclass=Singleton):
-    """Singleton instance of the MongoDb connection"""
+def __is_connection__init__(func):
+    @wraps(func)
+    def wrapper(*args, **kwargs):
+        if DatabaseConnection.connection is not None:
+            return func(*args, **kwargs)
+
+    return wrapper
+
+
+class DatabaseConnection:
+    """MongoDB connection Instance"""
 
     TESTING_COLLECTION_NAME_PREFIX = "test."
     DATABASE_NAME = "SpotifyElectron"
+    connection = None
+    collection_name_prefix = None
 
     def __init__(self):
-        if not hasattr(self, "connection"):
-            try:
-                uri = getattr(PropertiesManager, MONGO_URI_ENV_NAME)
-                self.collection_name_prefix = self._get_collection_name_prefix()
-                client = self._get_mongo_client_class()
-                self.connection = client(uri, server_api=ServerApi("1"))[self.DATABASE_NAME]
-                self._ping_database_connection()
-            except (
-                DatabasePingFailed,
-                UnexpectedDatabasePingFailed,
-                Exception,
-            ) as exception:
-                self._handle_database_connection_error(exception)
-
+        try:
+            uri = getattr(PropertiesManager, MONGO_URI_ENV_NAME)
+            DatabaseConnection.collection_name_prefix = self._get_collection_name_prefix()
+            client = self._get_mongo_client_class()
+            DatabaseConnection.connection = client(uri, server_api=ServerApi("1"))[
+                self.DATABASE_NAME
+            ]
+            self._ping_database_connection()
+        except (
+            DatabasePingFailed,
+            UnexpectedDatabasePingFailed,
+            Exception,
+        ) as exception:
+            self._handle_database_connection_error(exception)
+
+    @__is_connection__init__
     def _ping_database_connection(self):
         """Pings database connection"""
         try:
-            ping_result = self.connection.command("ping")
+            ping_result = DatabaseConnection.connection.command("ping")  # type: ignore
             self._check_ping_result(ping_result)
         except ConnectionFailure as exception:
             raise DatabasePingFailed from exception
@@ -112,12 +125,9 @@ def _get_collection_name_prefix(self) -> str:
             else ""
         )
 
+    @__is_connection__init__
     @staticmethod
-    def get_instance():
-        """Method to retrieve the singleton instance"""
-        return Database()
-
-    def get_collection_connection(self, collection_name: DatabaseCollection) -> Collection:
+    def get_collection_connection(collection_name: DatabaseCollection) -> Collection:
         """Returns the connection with a collection
 
         Args:
@@ -126,9 +136,13 @@ def get_collection_connection(self, collection_name: DatabaseCollection) -> Coll
         Returns:
             Any: the connection to the collection
         """
-        return Database().connection[self.collection_name_prefix + collection_name]  # type: ignore
+        return DatabaseConnection.connection[  # type: ignore
+            DatabaseConnection.collection_name_prefix + collection_name  # type: ignore
+        ]
 
-    def get_gridfs_collection_connection(self, collection_name: DatabaseCollection) -> Any:
+    @__is_connection__init__
+    @staticmethod
+    def get_gridfs_collection_connection(collection_name: DatabaseCollection) -> Any:
         """Returns the connection with gridfs collection
 
         Args:
@@ -138,8 +152,8 @@ def get_gridfs_collection_connection(self, collection_name: DatabaseCollection)
             Any: the gridfs collection connection
         """
         return GridFS(
-            Database.get_instance().connection,  # type: ignore
-            collection=self.collection_name_prefix + collection_name,
+            DatabaseConnection.connection,  # type: ignore
+            collection=DatabaseConnection.collection_name_prefix + collection_name,  # type: ignore
         )
 
 

Backend/app/spotify_electron/playlist/providers/playlist_collection_provider.py

@@ -4,7 +4,7 @@
 
 from pymongo.collection import Collection
 
-from app.database.Database import Database, DatabaseCollection
+from app.database.DatabaseConnection import DatabaseCollection, DatabaseConnection
 
 
 def get_playlist_collection() -> Collection:
@@ -13,4 +13,4 @@ def get_playlist_collection() -> Collection:
     Returns:
         Collection: the playlist collection
     """
-    return Database().get_collection_connection(DatabaseCollection.PLAYLIST)
+    return DatabaseConnection.get_collection_connection(DatabaseCollection.PLAYLIST)

Backend/app/spotify_electron/song/providers/song_collection_provider.py

@@ -12,7 +12,7 @@
     ARCH_STREAMING_SERVERLESS_FUNCTION,
     ARCHITECTURE_ENV_NAME,
 )
-from app.database.Database import Database, DatabaseCollection
+from app.database.DatabaseConnection import DatabaseCollection, DatabaseConnection
 
 
 def get_song_collection() -> Collection:
@@ -22,8 +22,10 @@ def get_song_collection() -> Collection:
         Collection: the song collection depending on architecture
     """
     repository_map = {
-        ARCH_BLOB: Database().get_collection_connection(DatabaseCollection.SONG_BLOB_FILE),
-        ARCH_STREAMING_SERVERLESS_FUNCTION: Database().get_collection_connection(
+        ARCH_BLOB: DatabaseConnection.get_collection_connection(
+            DatabaseCollection.SONG_BLOB_FILE
+        ),
+        ARCH_STREAMING_SERVERLESS_FUNCTION: DatabaseConnection.get_collection_connection(
             DatabaseCollection.SONG_STREAMING
         ),
     }
@@ -35,4 +37,6 @@ def get_gridfs_song_collection() -> GridFS:
 
     :return GridFS: the gridfs song collection
     """
-    return Database().get_gridfs_collection_connection(DatabaseCollection.SONG_BLOB_DATA)
+    return DatabaseConnection.get_gridfs_collection_connection(
+        DatabaseCollection.SONG_BLOB_DATA
+    )

Backend/app/spotify_electron/user/providers/user_collection_provider.py

@@ -6,7 +6,7 @@
 from pymongo.collection import Collection
 
 import app.spotify_electron.user.base_user_service as base_user_service
-from app.database.Database import Database, DatabaseCollection
+from app.database.DatabaseConnection import DatabaseCollection, DatabaseConnection
 from app.logging.logging_constants import LOGGING_USER_COLLECTION_PROVIDER
 from app.logging.logging_schema import SpotifyElectronLogger
 from app.spotify_electron.user.user.user_schema import UserType
@@ -23,8 +23,10 @@ def get_user_associated_collection(user_name: str) -> Collection:
         Collection: the user collection
     """
     collection_map = {
-        UserType.USER: Database().get_collection_connection(DatabaseCollection.USER),
-        UserType.ARTIST: Database().get_collection_connection(DatabaseCollection.ARTIST),
+        UserType.USER: DatabaseConnection.get_collection_connection(DatabaseCollection.USER),
+        UserType.ARTIST: DatabaseConnection.get_collection_connection(
+            DatabaseCollection.ARTIST
+        ),
     }
 
     user_type = base_user_service.get_user_type(user_name)
@@ -43,7 +45,7 @@ def get_artist_collection() -> Collection:
     Returns:
         Collection: the artist collection
     """
-    return Database().get_collection_connection(DatabaseCollection.ARTIST)
+    return DatabaseConnection.get_collection_connection(DatabaseCollection.ARTIST)
 
 
 def get_user_collection() -> Collection:
@@ -52,7 +54,7 @@ def get_user_collection() -> Collection:
     Returns:
         Collection: the artist collection
     """
-    return Database().get_collection_connection(DatabaseCollection.USER)
+    return DatabaseConnection.get_collection_connection(DatabaseCollection.USER)
 
 
 def get_all_collections() -> list[Collection]:
@@ -62,7 +64,9 @@ def get_all_collections() -> list[Collection]:
         list[Collection]: all the users collections
     """
     collection_map = {
-        UserType.USER: Database().get_collection_connection(DatabaseCollection.USER),
-        UserType.ARTIST: Database().get_collection_connection(DatabaseCollection.ARTIST),
+        UserType.USER: DatabaseConnection.get_collection_connection(DatabaseCollection.USER),
+        UserType.ARTIST: DatabaseConnection.get_collection_connection(
+            DatabaseCollection.ARTIST
+        ),
     }
     return list(collection_map.values())

Backend/tests/test__database.py

@@ -5,16 +5,15 @@
 from pytest import raises
 
 from app.common.set_up_constants import MONGO_URI_ENV_NAME
-from app.database.Database import (
-    Database,
+from app.database.DatabaseConnection import (
+    DatabaseConnection,
     DatabasePingFailed,
-    Singleton,
     UnexpectedDatabasePingFailed,
 )
 
 
 @patch("sys.exit")
-@patch("app.database.Database.Database._get_mongo_client_class")
+@patch("app.database.DatabaseConnection.DatabaseConnection._get_mongo_client_class")
 def test_raise_exception_connection_failure(
     get_mongo_client_class_mock, sys_exit_mock, clean_modified_environments
 ):
@@ -24,20 +23,20 @@ def raise_exception_connection_failure(*arg):
     client_mock = Mock()
     database_connection_mock = Mock()
     database_connection_mock.command.side_effect = raise_exception_connection_failure
-    client_mock.return_value = {Database.DATABASE_NAME: database_connection_mock}
+    client_mock.return_value = {DatabaseConnection.DATABASE_NAME: database_connection_mock}
     get_mongo_client_class_mock.return_value = client_mock
 
     os.environ[MONGO_URI_ENV_NAME] = "mongo_uri"
-    Singleton._instances.clear()
+    DatabaseConnection.connection = None
     with raises(DatabasePingFailed):
-        Database()._ping_database_connection()
+        DatabaseConnection()._ping_database_connection()
 
     assert sys_exit_mock.call_count == 1
-    Singleton._instances.clear()
+    DatabaseConnection.connection = None
 
 
 @patch("sys.exit")
-@patch("app.database.Database.Database._get_mongo_client_class")
+@patch("app.database.DatabaseConnection.DatabaseConnection._get_mongo_client_class")
 def test_raise_exception_unexpected_connection_failure(
     get_mongo_client_class_mock, sys_exit_mock, clean_modified_environments
 ):
@@ -47,13 +46,13 @@ def raise_exception_connection_failure(*arg):
     client_mock = Mock()
     database_connection_mock = Mock()
     database_connection_mock.command.side_effect = raise_exception_connection_failure
-    client_mock.return_value = {Database.DATABASE_NAME: database_connection_mock}
+    client_mock.return_value = {DatabaseConnection.DATABASE_NAME: database_connection_mock}
     get_mongo_client_class_mock.return_value = client_mock
 
     os.environ[MONGO_URI_ENV_NAME] = "mongo_uri"
-    Singleton._instances.clear()
+    DatabaseConnection.connection = None
     with raises(UnexpectedDatabasePingFailed):
-        Database()._ping_database_connection()
+        DatabaseConnection()._ping_database_connection()
 
     assert sys_exit_mock.call_count == 1
-    Singleton._instances.clear()
+    DatabaseConnection.connection = None