使用mysql-proxy 快速实现mysql 集群 读写分离

使用mysql-proxy 快速实现mysql 集群 读写分离

2011-12-29 17:03

目前较为常见的mysql读写分离分为两种： 1、 基于程序代码内部实现：在代码中对select操作分发到从库；其它操作由主库执行；这类方法也是目前生产环境应用最广泛，知名的如DISCUZ X2。优点是性能较好，因为在程序代码中实现，不需要增加额外的设备作为硬件开支。缺点是需要开发人员来实现，运维人员无从下手。 2、 基于中间代理层实现：我们都知道代理一般是位于客户端和服务器之间，代理服务器接到客户端请求后通过判断然后转发到后端数据库。在这有两个代表性程序 mysql-proxy：mysql-proxy为mysql开源项目，通过其自带的lua脚本进行sql判断，虽然是mysql官方产品，但是mysql官方并不建议将mysql-proxy用到生产环境。 amoeba：由陈思儒开发，作者曾就职于阿里巴巴，现就职于盛大。该程序由java语言进行开发，目前只听说阿里巴巴将其用于生产环境。另外，此项目严重缺少维护和推广（作者有个官方博客，很多用户反馈的问题发现作者不理睬） 经过上述简单的比较，通过程序代码实现mysql读写分离自然是一个不错的选择。但是并不是所有的应用都适合在程序代码中实现读写分离，像大型SNS、B2C这类应用可以在代码中实现，因为这样对程序代码本身改动较小；像一些大型复杂的java应用，这种类型的应用在代码中实现对代码改动就较大了。所以，像这种应用一般就会考虑使用代理层来实现。 下面我们看一下如何搭建mysql-proxy来实现mysql读写分离 环境拓扑如下： 关于mysql、mysql主从的搭建，在此不再演示，如下的操作均在mysql-proxy（192.168.1.200）服务器进行 一、安装mysql-proxy 1、安装lua (mysql-proxy需要使用lua脚本进行数据转发) #tar zxvf lua-5.1.4.tar.gz #cd lua-5.1.4 #vi Makefile，修改INSTALL_TOP= /usr/local/lua #make posix #make install 2、安装libevent #tar zxvf libevent-2.0.8-rc.tar.gz #cd libevent-2.0.8-rc #./configure --prefix=/usr/local/libevent #make && make install 3、安装check #tar zxvf check-0.9.8.tar.gz #cd check-0.9.8 #./configure && make && make install 4、安装mysql客户端 #tar zxvf mysql-5.0.92.tar.gz #cd mysql-5.0.92 #./configure --without-server && make && make install 5、设置环境变量 （安装mysql-proxy所需变量） #vi /etc/profile export LUA_CFLAGS="-I/usr/local/lua/include" LUA_LIBS="-L/usr/local/lua/lib -llua -ldl" LDFLAGS="-L/usr/local/libevent/lib -lm" export CPPFLAGS="-I/usr/local/libevent/include" export CFLAGS="-I/usr/local/libevent/include" # source /etc/profile 6、安装mysql-proxy #tar zxvf mysql-proxy-0.6.0.tar.gz #cd mysql-proxy-0.6.0 # ./configure --prefix=/usr/local/mysql-proxy --with-mysql --with-lua #make && make install 7、启动mysql-proxy 本次对两台数据库实现了读写分离；mysql-master为可读可写，mysql-slave为只读 #/usr/local/mysql-proxy/sbin/mysql-proxy --proxy-backend-addresses=192.168.1.201:3306 --proxy-read-only-backend-addresses=192.168.1.202:3306 --proxy-lua-script=/usr/local/mysql-proxy/share/mysql-proxy/rw-splitting.lua & 注：如果正常情况下启动后终端不会有任何提示信息，mysql-proxy启动后会启动两个端口4040和4041，4040用于SQL转发，4041用于管理mysql-proxy。如有多个mysql-slave可以依次在后面添加 二、测试 1、连接测试 因为默认情况下mysql数据库不允许用户在远程连接 mysql>grant all privileges on *.* to identified by '123456'; mysql>flush privileges; 客户端连接 #mysql -uroot -p123456 -h192.168.1.200 -P4040 2、读写分离测试 为了测试出mysql读写分离的真实性，在测试之前，需要开启两台mysql的log功能，然后在mysql-slave服务器停止复制 ① 、在两台mysql配置文件my.cnf中加入log=query.log，然后重启 ② 、在mysql-slave上执行SQL语句stop slave ③ 、在两台mysql上执行#tail -f /usr/local/mysql/var/query.log ④ 、在客户端上连接mysql（三个连接以上），然后执行create、select等SQL语句，观察两台mysql的日志有何变化 注：生产环境中除了进行程序调试外，其它不要开启mysql查询日志，因为查询日志记录了客户端的所有语句，频繁的IO操作将会导致mysql整体性能下降 总结：在上述环境中，mysql-proxy和mysql-master、mysql-slave三台服务器均存在单点故障。如果在可用性要求较高的场合，单点隐患是绝对不允许的。为了避免mysql-proxy单点隐患有两种方法，一种方法是mysql-proxy配合keepalived做双机，另一种方法是将mysql-proxy和应用服务安装到同一台服务器上；为了避免mysql-master单点故障可以使用DRBD+heartbear做双机；避免mysql-slave单点故障增加多台mysql-slave即可，因为mysql-proxy会自动屏蔽后端发生故障的mysql-slave。 附: mysql-proxy LUA 读写分离脚本代码: --[[ -- -- author : KDr2 -- version 0.01 -- SYNOPSIS: --- 1.维护了一个连接池 --- 2.读写分离，简单的将select开头的语句放到slave上执行 --- 3.事务支持，所有事务放到master上执行，事务中不更改连接 --- 4.简单日志 -- --]] --- config vars local min_idle_connections = 4 local max_idle_connections = 8 local log_level=1 local encoding="utf8" --- end of config -- 事务标识，在事务内不归还连接 local transaction_flags={} setmetatable(transaction_flags,{__index=function() return 0 end}) -- log system log={ level={debug=1,info=2,warn=3,error=4}, funcs={"debug","info","warn","error"}, } function log.log(level,m) if level >= log_level then local msg="[" .. os.date("%Y-%m-%d %X") .."] ".. log.funcs[level] .. ": " .. tostring(m) print(msg) -- TODO write msg into a log file. end end for i,v in ipairs(log.funcs) do log[v]=function(m) log.log(log.level[v],m) end end -- connect to server function connect_server() log.info(" starting connect_server ... ") local least_idle_conns_ndx = 0 local least_idle_conns = 0 for i = 1, #proxy.backends do local s = proxy.backends[i] local pool = s.pool local cur_idle = pool.users[""].cur_idle_connections log.debug("[".. s.address .."].connected_clients = " .. s.connected_clients) log.debug("[".. s.address .."].idling_connections = " .. cur_idle) log.debug("[".. s.address .."].type = " .. s.type) log.debug("[".. s.address .."].state = " .. s.state) if s.state ~= proxy.BACKEND_STATE_DOWN then -- try to connect to each backend once at least if cur_idle == 0 then proxy.connection.backend_ndx = i log.info("server [".. proxy.backends[i].address .."] open new connection") return end -- try to open at least min_idle_connections if least_idle_conns_ndx == 0 or ( cur_idle < min_idle_connections and cur_idle < least_idle_conns ) then least_idle_conns_ndx = i least_idle_conns = cur_idle end end end if least_idle_conns_ndx > 0 then proxy.connection.backend_ndx = least_idle_conns_ndx end if proxy.connection.backend_ndx > 0 then local s = proxy.backends[proxy.connection.backend_ndx] local pool = s.pool local cur_idle = pool.users[""].cur_idle_connections if cur_idle >= min_idle_connections then -- we have 4 idling connections in the pool, that's good enough log.debug("using pooled connection from: " .. proxy.connection.backend_ndx) return proxy.PROXY_IGNORE_RESULT end end -- open a new connection log.info("opening new connection on: " .. proxy.backends[proxy.connection.backend_ndx].address) end --- -- auth.packet is the packet function read_auth_result( auth ) if auth.packet:byte() == proxy.MYSQLD_PACKET_OK then -- 连接正常 proxy.connection.backend_ndx = 0 elseif auth.packet:byte() == proxy.MYSQLD_PACKET_EOF then -- we received either a -- * MYSQLD_PACKET_ERR and the auth failed or -- * MYSQLD_PACKET_EOF which means a OLD PASSWORD (4.0) was sent log.error("(read_auth_result) ... not ok yet"); elseif auth.packet:byte() == proxy.MYSQLD_PACKET_ERR then log.error("auth failed!") end end --- -- read/write splitting function read_query( packet ) log.debug("[read_query]") log.debug("authed backend = " .. proxy.connection.backend_ndx) log.debug("used db = " .. proxy.connection.client.default_db) if packet:byte() == proxy.COM_QUIT then proxy.response = { type = proxy.MYSQLD_PACKET_OK, } return proxy.PROXY_SEND_RESULT end if proxy.connection.backend_ndx == 0 then local is_read=(string.upper(packet:sub(2))):match("^SELECT") local target_type=proxy.BACKEND_TYPE_RW if is_read then target_type=proxy.BACKEND_TYPE_RO end for i = 1, #proxy.backends do local s = proxy.backends[i] local pool = s.pool local cur_idle = pool.users[proxy.connection.client.username].cur_idle_connections if cur_idle > 0 and s.state ~= proxy.BACKEND_STATE_DOWN and s.type == target_type then proxy.connection.backend_ndx = i break end end end -- sync the client-side default_db with the server-side default_db if proxy.connection.server and proxy.connection.client.default_db ~= proxy.connection.server.default_db then local server_db=proxy.connection.server.default_db local client_db=proxy.connection.client.default_db local default_db= (#client_db > 0) and client_db or server_db if #default_db > 0 then proxy.queries:append(2, string.char(proxy.COM_INIT_DB) .. default_db) proxy.queries:append(2, string.char(proxy.COM_QUERY) .. "set names '" .. encoding .."'") log.info("change database to " .. default_db); end end if proxy.connection.backend_ndx > 0 then log.debug("Query[" .. packet:sub(2) .. "] Target is [" .. proxy.backends[proxy.connection.backend_ndx].address .."]") end proxy.queries:append(1, packet) return proxy.PROXY_SEND_QUERY end --- -- as long as we are in a transaction keep the connection -- otherwise release it so another client can use it function read_query_result( inj ) local res = assert(inj.resultset) local flags = res.flags if inj.id ~= 1 then -- ignore the result of the USE <default_db> return proxy.PROXY_IGNORE_RESULT end is_in_transaction = flags.in_trans if flags.in_trans then transaction_flags[proxy.connection.server.thread_id] = transaction_flags[proxy.connection.server.thread_id] + 1 elseif inj.query:sub(2):lower():match("^%s*commit%s*$") or inj.query:sub(2):lower():match("^%s*rollback%s*$") then transaction_flags[proxy.connection.server.thread_id] = transaction_flags[proxy.connection.server.thread_id] - 1 if transaction_flags[proxy.connection.server.thread_id] < 0 then transaction_flags[proxy.connection.server.thread_id] = 0 end end log.debug("transaction res : " .. tostring(transaction_flags[proxy.connection.server.thread_id])); if transaction_flags[proxy.connection.server.thread_id]==0 or transaction_flags[proxy.connection.server.thread_id] == nil then -- isnot in a transaction, need to release the backend proxy.connection.backend_ndx = 0 end end --- -- close the connections if we have enough connections in the pool -- -- @return nil - close connection -- IGNORE_RESULT - store connection in the pool function disconnect_client() log.debug("[disconnect_client]") if proxy.connection.backend_ndx == 0 then for i = 1, #proxy.backends do local s = proxy.backends[i] local pool = s.pool local cur_idle = pool.users[proxy.connection.client.username].cur_idle_connections if s.state ~= proxy.BACKEND_STATE_DOWN and cur_idle > max_idle_connections then -- try to disconnect a backend proxy.connection.backend_ndx = i log.info("[".. proxy.backends[i].address .."] closing connection, idling: " .. cur_idle) return end end return proxy.PROXY_IGNORE_RESULT end end