Further improvements for db pooling (#18)

* Convert pooling ENV to integer

* Add ENV to enable db pooling

---------

Co-authored-by: Sandro Mani <manisandro@gmail.com>

Author: danceb

README.md

@@ -24,6 +24,7 @@ Environment variables
 | `TENANT_HEADER`              | `<empty>`                   | The name of the HTTP header which contains the tenant name for multi-tenant setups. |
 | `TENANT_PATH_PREFIX`         | `@service_prefix@/@tenant@` | URL path prefix for all QWC services for multi-tenant setups.                       |
 | `TENANT_ACCESS_COOKIE_PATH`  | `<tenant_path_prefix>`      | Path for which the access cookie is valid for multi-tenant setups.                  |
+| `ENABLE_POOLING`             | `False`                     | Enable db connection pooling. Defaults are used, if the following ENV are not set.  |
 | `POOL_SIZE`                  | `5`                         | Maximum number of possible data base connections.                                   |
 | `MAX_OVERFLOW`               | `10`                        | Additional connections beyond pool_size during peak load.                           |
 | `POOL_TIMEOUT`               | `30`                        | Time (in seconds) to wait for a connection to become available.                     |

qwc_services_core/database.py

@@ -18,21 +18,26 @@ def db_engine(self, conn_str):
         see https://docs.sqlalchemy.org/en/latest/core/engines.html#postgresql
         """
 
-        db_pool_size = os.environ.get('POOL_SIZE', 5)
-        db_max_overflow = os.environ.get('MAX_OVERFLOW', 10)
-        db_pool_timeout = os.environ.get('POOL_TIMEOUT', 30)
-        db_pool_recycle = os.environ.get('POOL_RECYCLE', -1)
+        db_enable_pooling = os.environ.get('ENABLE_POOLING', 'False').lower() in ('t', 'true')
+        db_pool_size = int(os.environ.get('POOL_SIZE', 5))
+        db_max_overflow = int(os.environ.get('MAX_OVERFLOW', 10))
+        db_pool_timeout = int(os.environ.get('POOL_TIMEOUT', 30))
+        db_pool_recycle = int(os.environ.get('POOL_RECYCLE', -1))
 
         engine = self.engines.get(conn_str)
         if not engine:
-            engine = create_engine(
-                conn_str, 
-                poolclass=QueuePool,
-                pool_size=db_pool_size,
-                max_overflow=db_max_overflow, 
-                pool_timeout=db_pool_timeout,
-                pool_recycle=db_pool_recycle,
-                pool_pre_ping=True, echo=False)
+            if db_enable_pooling:
+                engine = create_engine(
+                    conn_str, 
+                    poolclass=QueuePool,
+                    pool_size=db_pool_size,
+                    max_overflow=db_max_overflow, 
+                    pool_timeout=db_pool_timeout,
+                    pool_recycle=db_pool_recycle,
+                    pool_pre_ping=True, echo=False)
+            else:
+                engine = create_engine(
+                    conn_str, pool_pre_ping=True, echo=False)
             self.engines[conn_str] = engine
         return engine