MySQL 讀寫分離方案－MySQL Proxy環境部署記錄

 

Mysql的讀寫分離可以使用MySQL Proxy和Amoeba實現，其實也可以使用MySQL-MMM實現讀寫分離的自動切換。MySQL Proxy有一項強大功能是實現"讀寫分離"，基本原理是讓主數據庫處理寫方面事務，讓從庫處理SELECT查詢；Amoeba for MySQL是一款優秀的中間件軟件，同樣可以實現讀寫分離，負載均衡等功能。下面重點說下Mysql Proxy:

MySQL Proxy處於客戶端應用程序和MySQL服務器之間，通過截斷、改變並轉發客戶端和后端數據庫之間的通信來實現其功能。代理服務器是和TCP/IP協議打交道，
而要理解MySQL Proxy的工作機制，同樣要清楚MySQL客戶端和服務器之間的通信協議，MySQL Protocol 包括認證和查詢兩個基本過程：
.................................
認證過程包括：
1）客戶端向服務器發起連接請求
2）服務器向客戶端發送握手信息
3）客戶端向服務器發送認證請求
4）服務器向客戶端發送認證結果
................................
如果認證通過，則進入查詢過程：
1）客戶端向服務器發起查詢請求
2）服務器向客戶端返回查詢結果
當然，這只是一個粗略的描述，每個過程中發送的包都是有固定格式的。MySQL Proxy要做的，就是介入協議的各個過程。首先MySQL Proxy以服務器的身份接受客戶端請求，
根據配置對這些請求進行分析處理，然后以客戶端的身份轉發給相應的后端數據庫服務器，再接受服務器的信息，返回給客戶端。所以MySQL Proxy需要同時實現客戶端和服務
器的協議。由於要對客戶端發送過來的SQL語句進行分析，還需要包含一個SQL解析器。可以說MySQL Proxy相當於一個輕量級的MySQL了，實際上，MySQL Proxy的admin server
是可以接受SQL來查詢狀態信息的。

MySQL Proxy通過lua 腳本來控制連接轉發的機制。主要的函數都是配合MySQL Protocol各個過程的，這一點從函數名上就能看出來：
connect_server()
read_handshake()
read_auth()
read_auth_result()
read_query()
read_query_result()

至於為什么采用lua 腳本語言，大概是因為MySQL Proxy中采用了wormhole 存儲引擎 的關系吧，這個蟲洞存儲引擎很有意思，數據的存儲格式就是一段lua腳本。

Mysql Proxy的原理圖

順便貼下Mysql Proxy的工作拓撲圖

部署MySQL Proxy實現讀寫分離並提高並發負載的操作記錄

0）機器環境

ip地址              角色         主機名
182.48.115.237     master      master-node
182.48.115.236     slave1      slave-node1
182.48.115.238     slave2      slave-node2
182.48.115.233     proxy       proxy-node

四台機器都關閉防火牆和selinux

綁定hosts設置（四台機器都要操作）
[root@master-node ~]# vim /etc/hosts
......
182.48.115.237   master-node
182.48.115.236   slave-node1
182.48.115.238   slave-node2
182.48.115.233   proxy-node

1）Mysql主從復制部署（在三台mysql節點機上部署，本案例是一主兩從架構）

mysql安裝參考：http://www.cnblogs.com/kevingrace/p/6109679.html
mysql主從部署參考：http://www.cnblogs.com/kevingrace/p/6256603.html

2）在proxy機器上安裝mysql-proxy

1）安裝mysql-proxy
mysql proxy實現讀寫分離是有lua腳本實現的
下載地址1：https://downloads.mysql.com/archives/proxy/#downloads
下載地址2: http://ftp.ntu.edu.tw/pub/MySQL/Downloads/MySQL-Proxy/

[root@proxy-node ~]# wget http://ftp.ntu.edu.tw/pub/MySQL/Downloads/MySQL-Proxy/mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz  
[root@proxy-node ~]# tar -zvxf mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz 
[root@proxy-node ~]# mv mysql-proxy-0.8.5-linux-el6-x86-64bit /usr/local/mysql-proxy
[root@proxy-node ~]# useradd -r mysql-proxy

2）提供服務腳本
[root@proxy-node ~]# vim /etc/init.d/mysql-proxy
#!/bin/bash
#
# mysql-proxy This script starts and stops the mysql-proxy daemon
#
# chkconfig: - 78 30
# processname: mysql-proxy
# description: mysql-proxy is a proxy daemon for mysql

# Source function library.
. /etc/rc.d/init.d/functions

prog="/usr/local/mysql-proxy/bin/mysql-proxy"

# Source networking configuration.
if [ -f /etc/sysconfig/network ]; then
    . /etc/sysconfig/network
fi

# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0

# Set default mysql-proxy configuration.
ADMIN_USER="admin"
ADMIN_PASSWD="admin"
ADMIN_LUA_SCRIPT="/usr/local/mysql-proxy/share/doc/mysql-proxy/admin.lua"
PROXY_OPTIONS="--daemon"
PROXY_PID=/var/run/mysql-proxy.pid
PROXY_USER="mysql-proxy"

# Source mysql-proxy configuration.
if [ -f /etc/sysconfig/mysql-proxy ]; then
    . /etc/sysconfig/mysql-proxy
fi

RETVAL=0

start() {
    echo -n $"Starting $prog: "
    daemon $prog $PROXY_OPTIONS --pid-file=$PROXY_PID --proxy-address="$PROXY_ADDRESS" --user=$PROXY_USER --admin-username="$ADMIN_USER" --admin-lua-script="$ADMIN_LUA_SCRIPT" --admin-password="$ADMIN_PASSWORD"
    RETVAL=$?
    echo
    if [ $RETVAL -eq 0 ]; then
        touch /var/lock/subsys/mysql-proxy
    fi
}

stop() {
    echo -n $"Stopping $prog: "
    killproc -p $PROXY_PID -d 3 $prog
    RETVAL=$?
    echo
    if [ $RETVAL -eq 0 ]; then
        rm -f /var/lock/subsys/mysql-proxy
        rm -f $PROXY_PID
    fi
}
# See how we were called.
case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        start
        ;;
    condrestart|try-restart)
        if status -p $PROXY_PIDFILE $prog >&/dev/null; then
            stop
            start
        fi
        ;;
    status)
        status -p $PROXY_PID $prog
        ;;
    *)
        echo "Usage: $0 {start|stop|restart|reload|status|condrestart|try-restart}"
        RETVAL=1
        ;;
esac

exit $RETVAL

[root@proxy-node ~]# chmod 755 /etc/init.d/mysql-proxy
[root@proxy-node ~]# chkconfig --add mysql-proxy

3）為服務腳本提供配置文件
[root@proxy-node ~]# vim /etc/sysconfig/mysql-proxy
# Options for mysql-proxy
ADMIN_USER="admin"
ADMIN_PASSWORD="admin"
ADMIN_ADDRESS=""
ADMIN_LUA_SCRIPT="/usr/local/mysql-proxy/share/doc/mysql-proxy/admin.lua"
PROXY_ADDRESS=""
PROXY_USER="mysql-proxy"
PROXY_OPTIONS="--daemon --log-level=info --log-use-syslog --plugins=proxy --plugins=admin --proxy-backend-addresses=182.48.115.237:3306 --proxy-read-only-backend-addresses=182.48.115.236:3306
 --proxy-read-only-backend-addresses=182.48.115.238:3306 --proxy-lua-script=/usr/local/mysql-proxy/share/doc/mysql-proxy/rw-splitting.lua"

配置參數解釋：
--daemon：以守護進程模式啟動mysql-proxy
--proxy-backend-addresses：后端可讀寫的mysql服務器的地址和端口
--proxy-read-only-backend-addresses：后端只讀mysql服務器的地址和端口
--proxy-lua-script：完成mysql代理功能的Lua腳本

4）提供admin.lua文件
[root@proxy-node ~]# vim /usr/local/mysql-proxy/share/doc/mysql-proxy/admin.lua
--[[ $%BEGINLICENSE%$
 Copyright (c) 2007, 2012, Oracle and/or its affiliates. All rights reserved.

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License as
 published by the Free Software Foundation; version 2 of the
 License.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 02110-1301  USA

 $%ENDLICENSE%$ --]]

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

5）為了測試更明顯，編輯rw-splitting.lua文件中的其中2個數值：
[root@proxy-node ~]# vim /usr/local/mysql-proxy/share/doc/mysql-proxy/rw-splitting.lua
.........
if not proxy.global.config.rwsplit then
        proxy.global.config.rwsplit = {
                min_idle_connections = 1,        //修改這個值，默認為4
                max_idle_connections = 1,        //修改這個值，默認為8

                is_debug = false
        }
end
........

注意：
mysql-proxy會檢測客戶端連接，當連接沒有超過min_idle_connections預設值時, 不會進行讀寫分離, 即查詢操作會發生到Master上。

6）啟動mysql-proxy
[root@proxy-node ~]# service mysql-proxy start
Starting /usr/local/mysql-proxy/bin/mysql-proxy:           [  OK  ]

[root@proxy-node ~]# service mysql-proxy status
mysql-proxy (pid  4655) is running...

[root@proxy-node ~]# netstat -tunlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name   
tcp        0      0 0.0.0.0:4041                0.0.0.0:*                   LISTEN      4655/mysql-proxy    
tcp        0      0 0.0.0.0:3306                0.0.0.0:*                   LISTEN      4655/mysql-proxy 


7）連接測試（在任意一台遠程客戶機上測試連接）
[root@slave-node2 ~]# mysql -uadmin -padmin -h182.48.115.233 --port=4041
Warning: Using a password on the command line interface can be insecure.
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, 2016, 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.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> SELECT * FROM backends;
+-------------+---------------------+---------+------+------+-------------------+
| backend_ndx | address             | state   | type | uuid | connected_clients |
+-------------+---------------------+---------+------+------+-------------------+
|           1 | 182.48.115.237:3306 | unknown | rw   | NULL |                 0 |
|           2 | 182.48.115.236:3306 | unknown | ro   | NULL |                 0 |
|           3 | 182.48.115.238:3306 | unknown | ro   | NULL |                 0 |
+-------------+---------------------+---------+------+------+-------------------+
3 rows in set (0.00 sec)

3）讀寫分離測試

1）在master-node數據庫上創建proxy用戶，從服務器也會同步這個操作。
mysql> GRANT ALL ON *.* TO 'wang'@'182.48.115.%' IDENTIFIED BY '123456';
Query OK, 0 rows affected (0.00 sec)
 
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
 
2）proxy-node機器上使用創建的proxy用戶登陸數據庫，進行數據操作
[root@proxy-node ~]# mysql -uwang -h182.48.115.233 -p123456
.......
mysql> create database huanqiutest;
Query OK, 1 row affected (0.00 sec)

mysql> use huanqiutest;
Database changed
mysql> create table haha( id int(5), name varchar(10));
Query OK, 0 rows affected (0.19 sec)

mysql> insert into haha values(1,"zhangbao");
Query OK, 1 row affected (0.00 sec)

mysql> insert into haha values(11,"shibo");
Query OK, 1 row affected (0.00 sec)

mysql> select * from haha;
+------+----------+
| id   | name     |
+------+----------+
|    1 | zhangbao |
|   11 | shibo    |
+------+----------+
2 rows in set (0.01 sec)
 
注意下面兩點：
-> 發現使用proxy用戶登陸數據庫寫入的數據只寫入master主庫，然后再同步到slave從庫。如果將從庫的slave同步功能關閉，則從庫就無法更新數據。
-> 登陸從庫服務器關閉slave同步功能（stop slave），這時再登陸proxy-noed機器肯定會查詢不出數據（能看到表，但是查詢不出數據）
-> 以上兩點真正實現了讀寫分離的效果！
 
3）查看狀態，在proxy-node機器上操作，可以看到狀態全部為up：
[root@proxy-node bin]# mysql -uadmin -padmin -h182.48.115.233 --port=4041
.......
 
mysql> SELECT * FROM backends;
+-------------+---------------------+---------+------+------+-------------------+
| backend_ndx | address             | state   | type | uuid | connected_clients |
+-------------+---------------------+---------+------+------+-------------------+
|           1 | 182.48.115.237:3306 | up      | rw   | NULL |                 0 |
|           2 | 182.48.115.236:3306 | up      | ro   | NULL |                 0 |
|           3 | 182.48.115.238:3306 | up      | ro   | NULL |                 0 |
+-------------+---------------------+---------+------+------+-------------------+
3 rows in set (0.00 sec)

讀寫分離，延遲是個大問題，要確保主從同步這一環節不要有延遲。
---------------mysql主從同步延遲原理----------------
－> mysql主從同步原理
主庫針對讀寫操作，順序寫 binlog，從庫單線程去主庫讀"寫操作的binlog",從庫取到 binlog在本地原樣執行(隨機寫),來保證主從數據邏輯上一致.
mysql的主從復制都是單線程的操作，主庫對所有DDL和DML產生 binlog，binlog是順序寫，所以效率很高，slave的Slave_IO_Running線程到主庫取日志，效率比較高，下一步問題來了，slave的 slave_sql_running線程將主庫的 DDL和DML操作在 slave實施。DML，DDL的IO操作是隨即的，不能順序的，成本高很多，還有可能slave上的其他查詢產生 lock，由於 slave_sql_running也是單線程的，所以 一個 DDL卡住了，需求需求執行一段時間，那么所有之后的DDL會等待這個 DDL執行完才會繼續執行，這就導致了延遲.由於master可以並發，Slave_sql_running線程卻不可以，所以主庫執行 DDL需求一段時間，在slave執行相同的DDL時，就產生了延遲.

-> 主從同步延遲產生原因
當主庫的TPS並發較高時，產生的DDL數量超過Slave一個 sql線程所能承受的范圍，那么延遲就產生了，當然還有就是可能與 slave的大型 query語句產生了鎖等待
首要原因：數據庫在業務上讀寫壓力太大，CPU計算負荷大，網卡負荷大，硬盤隨機IO太高
次要原因：讀寫 binlog帶來的性能影響，網絡傳輸延遲

->  mysql主從同步加速
1）sync_binlog在slave端設置為0
2）–logs-slave-updates 從服務器從主服務器接收到的更新不記入它的二進制日志。
3）直接禁用slave端的binlog
4）slave端，如果使用的存儲引擎是innodb，innodb_flush_log_at_trx_commit =2

再有就是進行分庫分表處理，這樣減少數據量的復制同步操作