问题
I want to change my python program from a normal connection to a Connection Pool so that the database connection doesn't get lost when no queries are sent for some hours, as well as the database not being overwhelmed with a bunch of queries at once at peak usage.
I'm using Python 3.7.4, mysql-connector-python 8.0.17, and MariaDB 10.4.7.
It works fine when I use a normal connection, but MariaDB apparently doesn't support the pool_reset_session setting of mysql.connector.pooling.MySQLConnectionPool
At the start of my code, it tries to create the database if it doesn't yet exist, and that is causing the errors I get.
import mysql.connector as mariadb
from mysql.connector import errorcode
from mysql.connector import pooling
cnx = mariadb.pooling.MySQLConnectionPool(user='root', password='password', host='localhost',
pool_name='connectionpool', pool_size=10, pool_reset_session=True)
try:
db = cnx.get_connection()
cursor = db.cursor()
cursor.execute("CREATE DATABASE IF NOT EXISTS tests")
print("Created database")
except mariadb.Error as err:
print(f"Failed creating database: {err}")
finally:
print("Finally (create)")
db.close()
I expected that this snippet would just create the database tests but instead I got the following two errors:
mysql.connector.errors.NotSupportedError: MySQL version 5.7.2 and earlier does not support COM_RESET_CONNECTION.
as well as
mysql.connector.errors.OperationalError: 1047 (08S01): Unknown command
From the traceback logs, it looks like this gets caused by trying to execute db.close() in line 17.
Full output with traceback: https://pastebin.com/H3SAvA9N
I am asking what I can do to fix this and if it's possible at all to use this sort of connection pooling with MariaDB 10.4.7 (I get confused because it says that MySQL <= 5.7.2 doesn't support this reset of connections after use even though I use MariaDB 10.4.7)
I also found out that MariaDB Connector/J does provide such an option, called useResetConnection but I don't want to learn Java just for this feature.
回答1:
I was facing the same issue with mysql-connector-python for mariaDB, and I downgraded mysql-connector-python version to 8.0.12 and it worked for me
回答2:
As @Georg Richter indicate, MariaDB for historical reason return a version like "5.5.5-10.4.10-MariaDB-1:10.4.10+maria~bionic-log"
MySQL python connector check explicitly version (https://github.com/mysql/mysql-connector-python/blob/b034f25ec8037f5d60015bf2ed4ee278ec12fd17/lib/mysql/connector/connection.py#L1157) and since MariaDB server appears as version 5.5.5, an error is thrown.
Since MariaDB 10.2.6, you can explicitly add version to cnf file.
With configuration like:
version=5.7.99-10.4.10-MariaDB
Connector will see version 5.7.99, and behave accordingly.
回答3:
When bumping the server version to 10.0, MariaDB had to add a prefix to the server version to avoid breaking replication (replication protocol expects a one digit major version number, for more information check this answer).
No matter if you use MariaDB 10.0 or 10.4, MySQL Connector/Python will always return version number 5.5.5:
>>> conn= mysql.connector.connect(user="foo")
>>> print(conn.get_server_version())
(5, 5, 5)
>>> cursor=conn.cursor()
>>> cursor.execute("select version()")
>>> row=cursor.fetchone()
>>> print(row)
('10.4.7-MariaDB-log',)
COM_RESET_CONNECTION which resets the connection on server side was introduced in MariaDB 10.2, so to make it work you have to change the code of MySQL Connector/Python, e.g. in _check_server_version (abstracts.py):
+ if server_version.startswith("5.5.5-")
+ server_version= server_version[6:]
This is of course not a generic solution, since it will not work for MariaDB versions prior 10.2. It might have also bad side effects when checking for certain features like X-Protocol, which isn't supported by MariaDB.
来源：https://stackoverflow.com/questions/58044497/is-there-a-way-to-use-pool-reset-connection-from-mysql-connector-python-with-m