Django数据库连接池（mysql）

待我称王封你为后i 2022-07-28 09:58 303阅读 0赞

都知道django每次请求都会连接数据库和释放数据库连接。Django为每个请求使用新的数据库连接。一开始这个方法行得通。然而随着服务器上的负载的增加,创建/销毁连接数据库开始花大量的时间。要避免这个，你可以使用数据库连接池。

本文使用 DBUtils的连接池， 使Django持久化数据库连接。

## DBUtils实现django连接池 ##

[github代码][github]

#### DBUtils 是一套用于管理数据库连接池的Python包，为高频度高并发的数据库访问提供更好的性能，可以自动管理连接对象的创建和释放。并允许对非线程安全的数据库接口进行线程安全包装。 ####

#### django结合DBUtils使用，数据库连接管理完全交给DBUtils处理，平滑切换db backends。 ####

### django使用连接的过程： ###

*  请求开始： 新建连接（从DBUtils管理的连接池中获取连接）
 *  请求结束： 关闭连接（实际由DBUtils将连接返还连接池）

### DBUtils ###

DBUtils提供两种外部接口：

*  PersistentDB ：提供线程专用的数据库连接，并自动管理连接。
 *  PooledDB ：提供线程间可共享的数据库连接，并自动管理连接。

实测证明 PersistentDB 的速度是最高的，但是在某些特殊情况下，数据库的连接过程可能异常缓慢，而此时的PooledDB则可以提供相对来说平均连接时间比较短的管理方式。

### django settings ###

DATABASES = {
        "default": {
            "ENGINE": "db_pool.db.backends.mysql",
            "NAME": "xxx",
            "USER": "xxx",
            "PASSWORD": "xxx",
            "HOST": "mysql",
            "PORT": "3306",
            "ATOMIC_REQUESTS": True,
            "CHARSET": "utf8",
            "COLLATION": "utf8_bin",
            "POOL": {
                "mincached": 5,
                "maxcached ": 500,
            }
        }
    }

##### 其中连接池（POOL）配置参见 DBUtils的 PooledDB参数： #####

mincached: initial number of idle connections in the pool
        (0 means no connections are made at startup)
    maxcached: maximum number of idle connections in the pool
        (0 or None means unlimited pool size)
    maxshared: maximum number of shared connections
        (0 or None means all connections are dedicated)
        When this maximum number is reached, connections are
        shared if they have been requested as shareable.
    maxconnections: maximum number of connections generally allowed
        (0 or None means an arbitrary number of connections)
    blocking: determines behavior when exceeding the maximum
        (if this is set to true, block and wait until the number of
        connections decreases, otherwise an error will be reported)
    maxusage: maximum number of reuses of a single connection
        (0 or None means unlimited reuse)
        When this maximum usage number of the connection is reached,
        the connection is automatically reset (closed and reopened).
    setsession: optional list of SQL commands that may serve to prepare
        the session, e.g. ["set datestyle to ...", "set time zone ..."]
    reset: how connections should be reset when returned to the pool
        (False or None to rollback transcations started with begin(),
        True to always issue a rollback for safety's sake)
    failures: an optional exception class or a tuple of exception classes
        for which the connection failover mechanism shall be applied,
        if the default (OperationalError, InternalError) is not adequate
    ping: determines when the connection should be checked with ping()
        (0 = None = never, 1 = default = whenever fetched from the pool,
        2 = when a cursor is created, 4 = when a query is executed,
        7 = always, and all other bit combinations of these values)

[github]: https://github.com/pushiqiang/django_db_pool