下面总结下和连接有关的timeout
slave-net-timeout
The number of seconds to wait for more data from the master before the slave considers the connection broken, aborts the read, and tries to reconnect. The first retry occurs immediately after the timeout. The interval between retries is controlled by the MASTER_CONNECT_RETRY option for the CHANGE MASTER TO statement, and the number of reconnection attempts is limited by the --master-retry-count option. The default is 3600 seconds (one hour).
当slave认为连接master的连接有问题时，就等待N秒，然后断开连接，重新连接master
net_read_timeout ：
The number of seconds to wait for more data from a connection before aborting the read. When the server is reading from the client, net_read_timeout is the timeout value controlling when to abort
在终止读之前，从一个连接获得数据而等待的时间秒数；当服务正在从客户端读取数据时，net_read_timeout控制何时超时。
net_write_timeout:
The number of seconds to wait for a block to be written to a connection before aborting the write.When the server is writing to the client, net_write_timeout is the timeout value controlling when to abort。
在终止写之前，等待多少秒把block写到连接；当服务正在写数据到客户端时，net_write_timeout控制何时超时
wait_timeout
The number of seconds the server waits for activity on a noninteractive connection before closing it.
与服务器端无交互状态的连接，直到被服务器端强制关闭而等待的时间
interactive_timeout ：
The number of seconds the server waits for activity on an interactive connection before closing it.
与服务器端无交互状态的连接，直到被服务器端强制关闭而等待的时间
connect_timeout
The number of seconds that the mysqld server waits for a connect packet before responding with Bad handshake. The default value is 10 seconds.
等待一个连接响应的时间
connect_timeout：在获取连接阶段（authenticate）起作用
interactive_timeout和wait_timeout：在连接空闲阶段（sleep）起作用
net_read_timeout和net_write_timeout：则是在连接繁忙阶段（query）起作用。
获取MySQL连接是多次握手的结果，除了用户名和密码的匹配校验外，还有IP->HOST->DNS->IP验证，任何一步都可能因为网络问题导致线程阻塞。为了防止线程浪费在不必要的校验等待上，超过connect_timeout的连接请求将会被拒绝。
即使没有网络问题，也不能允许客户端一直占用连接。对于保持sleep状态超过了wait_timeout（或interactive_timeout，取决于client_interactive标志）的客户端，MySQL会主动断开连接。
即使连接没有处于sleep状态，即客户端忙于计算或者存储数据，MySQL也选择了有条件的等待。在数据包的分发过程中，客户端可能来不及响应（发送、接收、或者处理数据包太慢）。为了保证连接不被浪费在无尽的等待中，MySQL也会选择有条件（net_read_timeout和net_write_timeout）地主动断开连接。
转自<http://blog.csdn.net/wyzxg/article/details/11022899>