MySQL Proxy

 mysql-proxy的配置选项大致可分为帮助选项、管理选项、代理选项及应用程序选项几类，下面一起去介绍它们。

           --help

           --help-admin

           --help-proxy

           --help-all ———— 以上四个选项均用于获取帮助信息；

           --proxy-address=host:port ———— 代理服务监听的地址和端口；

           --admin-address=host:port ———— 管理模块监听的地址和端口；

           --proxy-backend-addresses=host:port ———— 后端mysql服务器的地址和端口；

           --proxy-read-only-backend-addresses=host:port ———— 后端只读mysql服务器的地址和端口；

           --proxy-lua-script=file_name ———— 完成mysql代理功能的Lua脚本；

           --daemon ———— 以守护进程模式启动mysql-proxy；

           --keepalive ———— 在mysql-proxy崩溃时尝试重启之；

           --log-file=/path/to/log_file_name ———— 日志文件名称；

           --log-level=level ———— 日志级别；

           --log-use-syslog ———— 基于syslog记录日志；

           --plugins=plugin,.. ———— 在mysql-proxy启动时加载的插件；

           --user=user_name ———— 运行mysql-proxy进程的用户；

           --defaults-file=/path/to/conf_file_name ———— 默认使用的配置文件路径；其配置段使用[mysql-proxy]标识；

           --proxy-skip-profiling ———— 禁用profile；

           --pid-file=/path/to/pid_file_name ———— 进程文件名；

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function set_error(errmsg)
        proxy.response = {
                type = proxy.MYSQLD_PACKET_ERR,
                errmsg = errmsg or "error"
        }
end

function read_query(packet)
        if packet:byte() ~= proxy.COM_QUERY then
                set_error("[admin] we only handle text-based queries (COM_QUERY)")
                return proxy.PROXY_SEND_RESULT
        end

        local query = packet:sub(2)

        local rows = { }
        local fields = { }

        if query:lower() == "select * from backends" then
                fields = {
                        { name = "backend_ndx",
                          type = proxy.MYSQL_TYPE_LONG },

                        { name = "address",
                          type = proxy.MYSQL_TYPE_STRING },
                        { name = "state",
                          type = proxy.MYSQL_TYPE_STRING },
                        { name = "type",
                          type = proxy.MYSQL_TYPE_STRING },
                        { name = "uuid",
                          type = proxy.MYSQL_TYPE_STRING },
                        { name = "connected_clients",
                          type = proxy.MYSQL_TYPE_LONG },
                }

                for i = 1, #proxy.global.backends do
                        local states = {
                                "unknown",
                                "up",
                                "down"
                        }
                        local types = {
                                "unknown",
                                "rw",
                                "ro"
                        }
                        local b = proxy.global.backends[i]

                        rows[#rows + 1] = {
                                i,
                                b.dst.name,          -- configured backend address
                                states[b.state + 1], -- the C-id is pushed down starting at 0
                                types[b.type + 1],   -- the C-id is pushed down starting at 0
                                b.uuid,              -- the MySQL Server‘s UUID if it is managed
                                b.connected_clients  -- currently connected clients
                        }
                end
        elseif query:lower() == "select * from help" then
                fields = {
                        { name = "command",
                          type = proxy.MYSQL_TYPE_STRING },
                        { name = "description",
                          type = proxy.MYSQL_TYPE_STRING },
                }
                rows[#rows + 1] = { "SELECT * FROM help", "shows this help" }
                rows[#rows + 1] = { "SELECT * FROM backends", "lists the backends and their state" }
        else
                set_error("use ‘SELECT * FROM help‘ to see the supported commands")
                return proxy.PROXY_SEND_RESULT
        end

        proxy.response = {
                type = proxy.MYSQLD_PACKET_OK,
                resultset = {
                        fields = fields,
                        rows = rows
                }
        }
        return proxy.PROXY_SEND_RESULT
end
                                               

 service mysql-proxy start

[root@httpweb ~]# mysql -ufirefox -pfirefox -h192.168.1.201 --port=4041
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.0.99-agent-admin
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective

owners.
mysql> select * from backends;
+-------------+--------------------+---------+------+------+-------------------+
| backend_ndx | address            | state   | type | uuid | connected_clients |
+-------------+--------------------+---------+------+------+-------------------+
|           1 | 192.168.1.200:3306 | up      | rw   | NULL |                 0 |
|           2 | 192.168.1.202:3306 | up      | ro   | NULL |                 0 |
+-------------+--------------------+---------+------+------+-------------------+