misc: Use single SQLAlchemy engine and session maker

As recommended by SQLAlchemy [1], this change makes a single
instantiation of the database engine and session maker, instead of one
entity per handler.

It also uses the provided `URL` constructor to better define the
database URL structure.

[1] https://docs.sqlalchemy.org/en/20/core/connections.html#basic-usage

backend/config/config_manager.py

@@ -2,7 +2,6 @@
 import sys
 from pathlib import Path
 from typing import Final
-from urllib.parse import quote_plus
 
 import pydash
 import yaml
@@ -21,6 +20,7 @@
     ConfigNotWritableException,
 )
 from logger.logger import log
+from sqlalchemy import URL
 from yaml.loader import SafeLoader
 
 ROMM_USER_CONFIG_PATH: Final = f"{ROMM_BASE_PATH}/config"
@@ -76,7 +76,7 @@ def __init__(self, config_file: str = ROMM_USER_CONFIG_FILE):
             sys.exit(5)
 
     @staticmethod
-    def get_db_engine() -> str:
+    def get_db_engine() -> URL:
         """Builds the database connection string depending on the defined database in the config.yml file
 
         Returns:
@@ -90,9 +90,13 @@ def get_db_engine() -> str:
                 )
                 sys.exit(3)
 
-            return (
-                f"mariadb+mariadbconnector://{DB_USER}:%s@{DB_HOST}:{DB_PORT}/{DB_NAME}"
-                % quote_plus(DB_PASSWD)
+            return URL.create(
+                drivername="mariadb+mariadbconnector",
+                username=DB_USER,
+                password=DB_PASSWD,
+                host=DB_HOST,
+                port=DB_PORT,
+                database=DB_NAME,
             )
 
         # DEPRECATED

backend/decorators/database.py

@@ -1,6 +1,7 @@
 import functools
 
 from fastapi import HTTPException, status
+from handler.database.base_handler import sync_session
 from logger.logger import log
 from sqlalchemy.exc import ProgrammingError
 
@@ -12,7 +13,7 @@ def wrapper(*args, **kwargs):
             return func(*args, **kwargs)
 
         try:
-            with args[0].session.begin() as s:
+            with sync_session.begin() as s:
                 kwargs["session"] = s
                 return func(*args, **kwargs)
         except ProgrammingError as exc:

backend/handler/database/base_handler.py

@@ -2,8 +2,8 @@
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
 
+sync_engine = create_engine(ConfigManager.get_db_engine(), pool_pre_ping=True)
+sync_session = sessionmaker(bind=sync_engine, expire_on_commit=False)
 
-class DBBaseHandler:
-    def __init__(self) -> None:
-        self.engine = create_engine(ConfigManager.get_db_engine(), pool_pre_ping=True)
-        self.session = sessionmaker(bind=self.engine, expire_on_commit=False)
+
+class DBBaseHandler: ...