employeed Sqlalchemy - pool pre ping to help with db connect errors.

app/__init__.py

@@ -13,26 +13,13 @@ def create_app(config_class='config.Config'):
     app = Flask(__name__)
     app.config.from_object(config_class)
 
+    app.config['SQLALCHEMY_ENGINE_OPTIONS'] = config_class.SQLALCHEMY_ENGINE_OPTIONS
+
     db.init_app(app)
     migrate.init_app(app, db)
     login_manager.init_app(app)
     login_manager.login_view = 'auth.login'
 
-    with app.app_context():
-        # Enable connection ping only for PostgreSQL
-        if app.config['SQLALCHEMY_DATABASE_URI'].startswith("postgresql"):
-            from sqlalchemy import event, text
-            from sqlalchemy.exc import DisconnectionError
-
-            @event.listens_for(db.engine, "engine_connect")
-            def ping_connection(connection, branch):
-                if branch:
-                    return
-                try:
-                    connection.execution_options(isolation_level="AUTOCOMMIT").scalar(text("SELECT 1"))
-                except:
-                    raise DisconnectionError()
-
     from app.main import main
     from app.auth import auth
 

app/main.py

@@ -21,7 +21,8 @@ def index():
     background_url = None
 
     if image:
-        filename = image.filepath.replace('/images/', '')
+        path = image.thumb_path or image.filepath
+        filename = path.replace('/images/', '')
         background_url = url_for('main.serve_image', filename=filename)
 
     return render_template('index.html', background_url=background_url)

config.py

@@ -28,3 +28,6 @@ class Config:
 
     SQLALCHEMY_TRACK_MODIFICATIONS = False
 
+    SQLALCHEMY_ENGINE_OPTIONS = {
+        "pool_pre_ping": True
+    }