add sqlalchemy client pool configuration options via env vars (#5751)

Author: benedikt-bartscher

reflex/environment.py

@@ -556,6 +556,18 @@ class EnvironmentVariables:
     # Whether to check db connections before using them.
     SQLALCHEMY_POOL_PRE_PING: EnvVar[bool] = env_var(True)
 
+    # The size of the database connection pool.
+    SQLALCHEMY_POOL_SIZE: EnvVar[int] = env_var(5)
+
+    # The maximum overflow size of the database connection pool.
+    SQLALCHEMY_MAX_OVERFLOW: EnvVar[int] = env_var(10)
+
+    # Recycle connections after this many seconds.
+    SQLALCHEMY_POOL_RECYCLE: EnvVar[int] = env_var(-1)
+
+    # The timeout for acquiring a connection from the pool.
+    SQLALCHEMY_POOL_TIMEOUT: EnvVar[int] = env_var(30)
+
     # Whether to ignore the redis config error. Some redis servers only allow out-of-band configuration.
     REFLEX_IGNORE_REDIS_CONFIG_ERROR: EnvVar[bool] = env_var(False)
 

reflex/model.py

@@ -96,6 +96,10 @@ def get_engine_args(url: str | None = None) -> dict[str, Any]:
         "echo": environment.SQLALCHEMY_ECHO.get(),
         # Check connections before returning them.
         "pool_pre_ping": environment.SQLALCHEMY_POOL_PRE_PING.get(),
+        "pool_size": environment.SQLALCHEMY_POOL_SIZE.get(),
+        "max_overflow": environment.SQLALCHEMY_MAX_OVERFLOW.get(),
+        "pool_recycle": environment.SQLALCHEMY_POOL_RECYCLE.get(),
+        "pool_timeout": environment.SQLALCHEMY_POOL_TIMEOUT.get(),
     }
     conf = get_config()
     url = url or conf.db_url