When using SQL Alchemy in a Flask application, if the application
continuously sends queries to the database, it exceeds the maximum number
of connections in the connection pool. How can I solve this issue?
*sqlalchemy_engine.py*
import os
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.pool import QueuePool
class OrmEngine:
def __init__(self):
self.engine = create_engine(os.getenv('DATABASE_URL'),
poolclass=QueuePool,
pool_size=5,
max_overflow=3
)
self.session = sessionmaker(bind=self.engine)
*Example query*
with self.orm_engine.session() as session:
user_repository = UserRepository(session)
* user = user_repository.find_by_email(login_request.email)*
*My connection list*
MariaDB [(none)]> SHOW PROCESSLIST;
+-----+-------------+-----------------+------+---------+------+
--------------------------+------------------+----------+
| Id | User | Host | db | Command | Time | State
| Info | Progress |
+-----+-------------+-----------------+------+---------+------+
--------------------------+------------------+----------+
| 2 | system user | | NULL | Daemon | NULL | InnoDB
purge worker | NULL | 0.000 |
| 1 | system user | | NULL | Daemon | NULL | InnoDB
purge coordinator | NULL | 0.000 |
| 3 | system user | | NULL | Daemon | NULL | InnoDB
purge worker | NULL | 0.000 |
| 4 | system user | | NULL | Daemon | NULL | InnoDB
purge worker | NULL | 0.000 |
| 5 | system user | | NULL | Daemon | NULL | InnoDB
shutdown handler | NULL | 0.000 |
| 8 | root | localhost:56603 | NULL | Query | 0 | Init
| SHOW PROCESSLIST | 0.000 |
| 645 | root | localhost:64281 | tbot | Sleep | 74 |
| NULL | 0.000 |
| 662 | root | localhost:64334 | tbot | Sleep | 56 |
| NULL | 0.000 |
| 684 | root | localhost:64400 | tbot | Sleep | 33 |
| NULL | 0.000 |
| 705 | root | localhost:64476 | tbot | Sleep | 16 |
| NULL | 0.000 |
| 707 | root | localhost:64482 | tbot | Sleep | 14 |
| NULL | 0.000 |
| 709 | root | localhost:64488 | tbot | Sleep | 13 |
| NULL | 0.000 |
| 711 | root | localhost:64494 | tbot | Sleep | 12 |
| NULL | 0.000 |
| 713 | root | localhost:64500 | tbot | Sleep | 10 |
| NULL | 0.000 |
| 715 | root | localhost:64506 | tbot | Sleep | 9 |
| NULL | 0.000 |
| 717 | root | localhost:64512 | tbot | Sleep | 8 |
| NULL | 0.000 |
| 719 | root | localhost:64518 | tbot | Sleep | 7 |
| NULL | 0.000 |
| 720 | root | localhost:64521 | tbot | Sleep | 4 |
| NULL | 0.000 |
| 722 | root | localhost:64527 | tbot | Sleep | 3 |
| NULL | 0.000 |
| 724 | root | localhost:64533 | tbot | Sleep | 2 |
| NULL | 0.000 |
| 726 | root | localhost:64539 | tbot | Sleep | 1 |
| NULL | 0.000 |
+-----+-------------+-----------------+------+---------+------+
--------------------------+------------------+----------+
21 rows in set (0.000 sec)
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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