Druid连接池的keepAlive

Druid连接池的keepAlive是指连接池中的minIdle数量以内的连接，空闲时间超过minEvictableIdleTimeMillis，则会执行keepAlive操作。keepAlive操作会向数据库发送一个测试SQL语句，以确保连接仍然有效。如果连接无效，则会将其从连接池中删除。如果连接有效，则会将其放回连接池中以供后续使用。

以下是一个使用Druid连接池的Python代码示例，其中包括了keepAlive的配置：

import pymysql
from sqlalchemy import create_engine
from sqlalchemy.pool import QueuePool
from DBUtils import PooledDB
import time

# 创建连接池
pool = PooledDB(
    creator=pymysql,
    maxconnections=6,
    mincached=2,
    maxcached=5,
    blocking=True,
    maxusage=None,
    setsession=[],
    ping=0,
    host='localhost',
    port=3306,
    user='root',
    password='123456',
    database='test',
    charset='utf8mb4',
    cursorclass=pymysql.cursors.DictCursor,
    connect_timeout=10,
    read_timeout=10,
    write_timeout=10,
    keepalive=600 # keepAlive的配置，单位为秒
)

# 从连接池中获取连接
conn = pool.connection()

# 使用连接进行数据库操作
engine = create_engine('mysql+pymysql://', creator=pool.getconn, poolclass=QueuePool, pool_size=6)
with engine.connect() as conn:
    result = conn.execute('SELECT * FROM test_table')
    for row in result:
        print(row)

# 将连接放回连接池中
pool.putconn(conn)