python redis链接建立实现分析
class ConnectionPool(object):...........
def __init__(self, connection_class=Connection, max_connections=None,
**connection_kwargs): #类初始化时调用构造函数
max_connections = max_connections or 2 ** 31
if not isinstance(max_connections, (int, long)) or max_connections < 0:#判断输入的max_connections是否合法
raise ValueError('"max_connections" must be a positive integer')
self.connection_class = connection_class#设置对应的参数
self.connection_kwargs = connection_kwargs
self.max_connections = max_connections
self.reset()#初始化ConnectionPool 时的reset操作
def reset(self):
self.pid = os.getpid()
self._created_connections = 0#已经创建的连接的计数器
self._available_connections = [] #声明一个空的数组，用来存放可用的连接
self._in_use_connections = set()#声明一个空的集合，用来存放已经在用的连接
self._check_lock = threading.Lock()
.......
def get_connection(self, command_name, *keys, **options):#在连接池中获取连接的方法
"Get a connection from the pool"
self._checkpid()
try:
connection = self._available_connections.pop()#获取并删除代表连接的元素，在第一次获取connectiong时，因为_available_connections是一个空的数组，
会直接调用make_connection方法
except IndexError:
connection = self.make_connection()
self._in_use_connections.add(connection) #向代表正在使用的连接的集合中添加元素
return connection
def make_connection(self): #在_available_connections数组为空时获取连接调用的方法
"Create a new connection"
if self._created_connections >= self.max_connections: #判断创建的连接是否已经达到最大限制，max_connections可以通过参数初始化
raise ConnectionError("Too many connections")
self._created_connections += 1 #把代表已经创建的连接的数值+1
return self.connection_class(**self.connection_kwargs) #返回有效的连接，默认为Connection(**self.connection_kwargs)
def release(self, connection):#释放连接，链接并没有断开，只是存在链接池中
"Releases the connection back to the pool"
self._checkpid()
if connection.pid != self.pid:
return
self._in_use_connections.remove(connection) #从集合中删除元素
self._available_connections.append(connection) #并添加到_available_connections 的数组中
def disconnect(self): #断开所有连接池中的链接
"Disconnects all connections in the pool"
all_conns = chain(self._available_connections,
self._in_use_connections)
for connection in all_conns:
connection.disconnect()
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