tailieunhanh - MySQL High Availability- P2

MySQL High Availability- P2: A lot of research has been done on replication, but most of the resulting concepts are never put into production. In contrast, MySQL replication is widely deployed but has never been adequately explained. This book changes that. Things are explained here that were previously limited to people willing to read a lot of source code and spend a lot of time debugging it in production, including a few late-night sessions. | ssh_user A combination of user and password that can be used for connecting to the machine that is running the server. Use this to execute administrative commands such as starting and stopping the server and reading and writing the configuration file. sql_user A combination of user and password for connecting to the server as a MySQL user account to execute SQL commands. machine An object that holds operating system-specific primitives. We chose the name to avoid a name conflict with the standard library os module. This parameter lets you use different techniques for starting and stopping the server as well as other tasks and operating system-specific parameters. The parameters will be covered later. server_id An optional parameter to hold the server s ID as defined in each server s configuration file. If this option is omitted the server ID will be read from the configuration file of the server. If there is no server ID in the configuration file either the server is a vagabond and does not participate in replication as master or slave. config_manager An optional parameter to hold a reference to a configuration manager that can be queried for information about the configuration for the server. and Use the connect and disconnect methods to establish a connection to the server before executing commands in a session and disconnect from the server after finishing the session respectively. These methods are useful because in some situations it is critical to keep the connection to the server open even after an SQL command has been executed. Otherwise for example when doing a FLUSH TABLES WITH READ LOCK the lock will automatically be released when the connection is dropped. command and command args Use these to execute a shell command or an SQL command on the server. The ssh and sql methods both return an iterable. ssh returns a list of the lines of output from the executed command whereas sql returns a list of .