各位老鐵們，老張與大家又見面了。看到各位在博客裏面給我的留言和訪問量的情況，我很是欣慰，也謝謝大家對我的認可。我寫這些博客，就是想把自己對於MySQL數據庫的一些看法和自己平時的實戰經驗分享出來，我們可以一起探討，共同進步。也保證今後只要一有空就更新博文，推出更多的乾貨。
我的學生經常對我說：“張老師，每次我遇到報錯，有時還是會百度，但是最煩的是不知道百度哪篇帖子說的是正確的".其實這些呢，都是因爲自己還沒有對MySQL數據庫核心知識的不熟悉，和對技術掌握的不牢固。平時下得功夫還是不到位。我們做技術這個行業，還是需要自己給自己加發條，促使自己每天都要學習一些新的知識。理論配合實驗一起，先要學會多問自己幾個問題，一個實驗多做幾遍，可能會得到不同的實驗效果。學習知識要踏實下來，學會多做實驗總結。我想今後再遇到報錯，可能自己就會有一個清晰的解題思路，這個需要一定時間的磨練。
也有人經常問Oracle和MySQL到底有啥區別，其實MySQL數據庫上手很簡單，難的是後期架構的設計與維護。老張三部曲中第一部曲MHA希望對大家在線上部署方面有幫助。
今兒給大家介紹第二部曲，MM+keepalived的環境部署，我們會多種數據庫的架構就可以靈活應用到我們的公司。根據公司業務的不同，選擇合適的集羣架構。
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MM+keepalived
簡介：
雙主配合keepalived這種架構設計，也是基於主從複製的原理而搭建的。
使用MySQL主主複製技術+Keepalived是一種簡單、便捷的解決方案，在高可用集羣環境中，keepalived使用VIP，使用Keepalived自帶的服務監控功能和自定義腳本來實現MySQL故障時自動切換，非常靈活。
應用範圍：
一般中小型公司都使用這種架構，搭建比較方便簡單；
可以採用主從或者主主模式，在 master 節點發生故障後，利用 keepalived 高可用機制實現快速切換到 slave 節點。原來的從庫變成新的主庫。
個人建議：
一定要完善好切換腳本，keepalived 的切換機制要合理，避免切換不成功的現象發生。
從庫的配置儘快要與主庫一致，不能太次；避免主庫宕機發生切換，新的主庫（原來的從庫）影響線上業務進行。
對於延遲的問題，在這套架構中，也不能避免。可以使用 mysql 5.7 中增強半同步完成。也可以改變架構使用 PXC，完成時時同步功能，基本上沒有延遲；
keepalived 無法解決腦裂的問題，因此在進行服務異常判斷時，可以修改我們的判斷腳本，通過對第三方節點補充檢測來決定是否進行切換，可降低腦裂問題產生的風險。
採用 keepalived 這個架構，在設置兩節點狀態時，都要設置成不搶佔模式，都是 backup 狀態，通過優先級，來決定誰是主庫。避免腦裂，衝突現象發生。
安裝好 mysql 需要的一些依賴包；建議配置好 yum 源，用 yum 安裝 keepalived 即可。
搭建架構之前理清思路：
首先需要裝有兩臺mysql的數據庫服務器，兩者之間互爲主從模式，都可讀寫。其實就只有一臺服務器A負責數據的寫入工作，而另一臺服務器B作爲我們的備用數據庫；
安裝keepalived的軟件包，個人建議使用yum安裝就可以，很方便。當然我們要知道yum安裝之後的軟件路徑在什麼位置。
整理好keepalived的配置文件，理清keepalived的三種狀態信息。還要準備一個監控MySQL的腳本，便於檢測到宕機順利發生切換的過程。
所有提供服務的從服務器與備用服務器B進行主從同步。----雙主從庫模式
在兩臺服務器A和B，當配置keepalived的參數文件中，要注意兩臺機器都要採用backup這種狀態，就是nopreempt這種非搶佔模式，避免出現衝突，發生腦裂現象。
架構圖展示：
實驗部署環境介紹：
192.168.56.100 主 ---master1
192.168.56.101 備庫---master2
都是乾淨環境沒有任何數據
VIP：192.168.56.111
MySQL數據庫版本5.7.14，採用GTID模式搭建主從環境
注意事項：
兩臺機器的防火牆必須是關閉狀態。
兩臺MySQL數據庫配置文件中server-id絕對不能一樣，要不會報1593這個主從同步的錯誤，導致搭建不成功。
實戰開始：
首先先要搭建兩臺MySQL數據庫爲互爲主從的架構模式。
添加主從同步賬號：
在192.168.56.100：
grant replication slave on *.* to 'bak'@'192.168.56.%' identified by '123456';
flush privileges;
在192.168.56.101：
grant replication slave on *.* to 'bak'@'192.168.56.%' identified by '123456';
flush privileges;
配置同步信息：
先在192.168.56.101上：
CHANGE MASTER TO MASTER_HOST='192.168.56.100',MASTER_USER='bak',MASTER_PASSWORD='123456',master_auto_position=1;
打開主從同步開關：
start slave；
查看主從同步狀態：
root@db 10:49: [(none)]> show slave status\G; *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.56.100 Master_User: bak Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mybinlog.000005 Read_Master_Log_Pos: 234 Relay_Log_File: node2-relay-bin.000010 Relay_Log_Pos: 365 Relay_Master_Log_File: mybinlog.000005 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 234 Relay_Log_Space: 572 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 3306100 Master_UUID: 913cc1d6-771a-11e7-8fe1-080027f1fd08 Master_Info_File: mysql.slave_master_info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: Executed_Gtid_Set: 5a668126-771d-11e7-b14c-08002783b39d:1-2, 913cc1d6-771a-11e7-8fe1-080027f1fd08:1-13 Auto_Position: 1 Replicate_Rewrite_DB: Channel_Name: Master_TLS_Version: 1 row in set (0.00 sec)
從庫兩個工作的線程：IO，SQL都爲yes，代表同步搭建成功 Slave_IO_Running: Yes Slave_SQL_Running: Yes
再在192.168.56.100上：
配置主從同步信息：
CHANGE MASTER TO MASTER_HOST='192.168.56.101',MASTER_USER='bak',MASTER_PASSWORD='123456',master_auto_position=1;
開啓主從開關：
start slave；
查看主從同步狀態：
root@db 10:49: [(none)]> show slave status\G; *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.56.101 Master_User: bak Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mybinlog.000005 Read_Master_Log_Pos: 234 Relay_Log_File: node1-relay-bin.000008 Relay_Log_Pos: 365 Relay_Master_Log_File: mybinlog.000005 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 234 Relay_Log_Space: 572 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 3306101 Master_UUID: 5a668126-771d-11e7-b14c-08002783b39d Master_Info_File: mysql.slave_master_info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: Executed_Gtid_Set: 5a668126-771d-11e7-b14c-08002783b39d:1-2, 913cc1d6-771a-11e7-8fe1-080027f1fd08:1-13 Auto_Position: 1 Replicate_Rewrite_DB: Channel_Name: Master_TLS_Version: 1 row in set (0.00 sec)
同理 Slave_IO_Running: Yes Slave_SQL_Running: Yes 從庫兩個工作的線程：IO，SQL都爲yes，代表同步搭建成功。
分別兩臺機器上安裝keepalived的軟件包，可以使用yum安裝方式
yum -y install keepalived;
Loaded plugins: fastestmirror, refresh-packagekit, security Loading mirror speeds from cached hostfile * c6-media: file:///media/CentOS/repodata/repomd.xml: [Errno 14] Could not open/read file:///media/CentOS/repodata/repomd.xml Trying other mirror. file:///media/cdrecorder/repodata/repomd.xml: [Errno 14] Could not open/read file:///media/cdrecorder/repodata/repomd.xml Trying other mirror. c6-media | 4.0 kB 00:00 ... Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package keepalived.x86_64 0:1.2.7-3.el6 will be installed --> Finished Dependency Resolution Dependencies Resolved ====================================================================================================================================== Package Arch Version Repository Size ====================================================================================================================================== Installing: keepalived x86_64 1.2.7-3.el6 c6-media 174 k Transaction Summary ====================================================================================================================================== Install 1 Package(s) Total download size: 174 k Installed size: 526 k Downloading Packages: Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Installing : keepalived-1.2.7-3.el6.x86_64 1/1 Verifying : keepalived-1.2.7-3.el6.x86_64 1/1 Installed: keepalived.x86_64 0:1.2.7-3.el6 Complete!
證明keepalived軟件已經存在：
rpm -qa|grep keepalived keepalived-1.2.7-3.el6.x86_64
在兩臺機器上分別配置檢測MySQL數據庫的腳本：
首先進入到yum安裝後的軟件目錄下：
cd /etc/keepalived vim check_mysql.py
腳本通過查看MySQL進程的存在，和是否可以連接，來判斷MySQL的狀態
（這裏只展現了腳本中判斷的一部分）
def existMySQL(self): cmd="ps -ef | egrep -i \"mysqld\" | grep %s | egrep -iv \"mysqld_safe\" | grep -v grep | wc -l" % self.dbport mysqldNum = os.popen(cmd).read() cmd ="netstat -tunlp | grep \":%s\" | wc -l" % self.dbport mysqlPortNum= os.popen(cmd).read() #print mysqldNum, mysqlPortNum if ( int(mysqldNum) <= 0): print "error" return 1 if ( int(mysqldNum) > 0 and mysqlPortNum <= 0): return 1 return 0 def connect(self): # print "in db conn" # print "host : %s, port: %d, user: %s, password: %s" % (self.dbhost, self.dbport, self.dbuser, self.dbpassword) try: self.conn=MySQLdb.connect(host="%s"%self.dbhost, port=self.dbport,user="%s"%dbuser, passwd="%s"%self.dbpassword) except Exception, e: # print " Error" print e return 1 return 0 def disconnect(self): if (self.conn): self.conn.close() self.conn = None
在兩臺機器上修改keepalived的配置文件：
192.168.56.100上面
vim /etc/keepalived/keepalived.conf
vrrp_instance VI_100 {
state BACKUP
nopreempt
interface eth0
virtual_router_id 100
priority 100
advert_int 5
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
vs_mysql_100
}
virtual_ipaddress {
192.168.56.111
}
}192.168.56.101上面：
vrrp_instance VI_101 {
state BACKUP
nopreempt
interface eth0
virtual_router_id 100
priority 90
advert_int 5
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
vs_mysql_101
}
virtual_ipaddress {
192.168.56.111
}
}總結：可以看到兩臺機器的state都是backup並且都是非搶佔模式nopreempt，通過優先級的高低來決定誰是主庫。（這裏192.168.56.100是主）還有注意virtual_router_id(虛擬路由id）要保持一致。
接下來可以啓動兩臺機器的keepalived進程：
192.168.56.100：
[root@node1 keepalived]# /etc/init.d/keepalived start Starting keepalived: [ OK ]
觀察日誌中信息的變化：
cat /var/log/messages
Aug 3 10:52:17 node1 Keepalived_vrrp[6760]: Opening file '/etc/keepalived/keepalived.conf'. Aug 3 10:52:17 node1 Keepalived_vrrp[6760]: Configuration is using : 62711 Bytes Aug 3 10:52:17 node1 Keepalived_vrrp[6760]: Using LinkWatch kernel netlink reflector... Aug 3 10:52:17 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) Entering BACKUP STATE Aug 3 10:52:17 node1 Keepalived_vrrp[6760]: VRRP sockpool: [ifindex(2), proto(112), fd(11,12)] Aug 3 10:52:17 node1 Keepalived_healthcheckers[6759]: Opening file '/etc/keepalived/keepalived.conf'. Aug 3 10:52:17 node1 Keepalived_healthcheckers[6759]: Configuration is using : 4431 Bytes Aug 3 10:52:17 node1 Keepalived_healthcheckers[6759]: Using LinkWatch kernel netlink reflector... Aug 3 10:52:18 node1 Keepalived_vrrp[6760]: VRRP_Script(vs_mysql_100) succeeded Aug 3 10:52:33 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) Transition to MASTER STATE Aug 3 10:52:38 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) Entering MASTER STATE Aug 3 10:52:38 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) setting protocol VIPs. Aug 3 10:52:38 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) Sending gratuitous ARPs on eth0 for 192.168.56.111 Aug 3 10:52:38 node1 Keepalived_healthcheckers[6759]: Netlink reflector reports IP 192.168.56.111 added Aug 3 10:52:43 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) Sending gratuitous ARPs on eth0 for 192.168.56.111
可以看到它從backup狀態切換到master的狀態了，並且發送了一個廣播協議，證明192.168.56.111已經在本臺機器上面，其他機器不要再使用了。
[root@node1 keepalived]# ip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 08:00:27:f1:fd:08 brd ff:ff:ff:ff:ff:ff inet 192.168.56.100/24 brd 192.168.56.255 scope global eth0 inet 192.168.56.111/32 scope global eth0 inet6 fe80::a00:27ff:fef1:fd08/64 scope link valid_lft forever preferred_lft forever
192.168.56.101:
[root@node2 ~]# /etc/init.d/keepalived start Starting keepalived: [ OK ]
cat /var/log/messages
Aug 3 10:53:28 node2 Keepalived_healthcheckers[8111]: Interface queue is empty Aug 3 10:53:28 node2 Keepalived_healthcheckers[8111]: Netlink reflector reports IP 192.168.56.101 added Aug 3 10:53:28 node2 Keepalived_healthcheckers[8111]: Netlink reflector reports IP fe80::a00:27ff:fe83:b39d added Aug 3 10:53:28 node2 Keepalived_healthcheckers[8111]: Registering Kernel netlink reflector Aug 3 10:53:28 node2 Keepalived_healthcheckers[8111]: Registering Kernel netlink command channel Aug 3 10:53:28 node2 Keepalived_healthcheckers[8111]: Opening file '/etc/keepalived/keepalived.conf'. Aug 3 10:53:28 node2 Keepalived_healthcheckers[8111]: Configuration is using : 4561 Bytes Aug 3 10:53:28 node2 Keepalived_healthcheckers[8111]: Using LinkWatch kernel netlink reflector... Aug 3 10:53:28 node2 Keepalived_vrrp[8112]: Opening file '/etc/keepalived/keepalived.conf'. Aug 3 10:53:28 node2 Keepalived_vrrp[8112]: Configuration is using : 62577 Bytes Aug 3 10:53:28 node2 Keepalived_vrrp[8112]: Using LinkWatch kernel netlink reflector... Aug 3 10:53:28 node2 Keepalived_vrrp[8112]: VRRP_Instance(VI_101) Entering BACKUP STATE Aug 3 10:53:28 node2 Keepalived_vrrp[8112]: VRRP sockpool: [ifindex(2), proto(112), fd(12,13)] Aug 3 10:53:28 node2 Keepalived_vrrp[8112]: VRRP_Script(vs_mysql_101) succeeded
這臺服務器就是正常的backup狀態，時刻準備着接管主庫的服務。
模擬一下主庫宕機的故障切換：
主庫192.168.56.100上面執行關閉MySQL服務操作：
mysqladmin -uroot -proot123 shutdown
這時再查看一下keepalived日誌的情況：
cat /var/log/messages Aug 3 11:04:17 node1 Keepalived_vrrp[6760]: VRRP_Script(vs_mysql_100) failed Aug 3 11:04:18 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) Entering FAULT STATE Aug 3 11:04:18 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) removing protocol VIPs. Aug 3 11:04:18 node1 Keepalived_healthcheckers[6759]: Netlink reflector reports IP 192.168.56.111 removed Aug 3 11:04:18 node1 Keepalived_vrrp[6760]: VRRP_Instance(VI_100) Now in FAULT state
已經把vip removed了，並且keepalived的狀態變成了fault
在備庫192.168.56.101上面查看日誌：
cat /var/log/messages Aug 3 11:04:29 node2 Keepalived_vrrp[8112]: VRRP_Instance(VI_101) Transition to MASTER STATE Aug 3 11:04:34 node2 Keepalived_vrrp[8112]: VRRP_Instance(VI_101) Entering MASTER STATE Aug 3 11:04:34 node2 Keepalived_vrrp[8112]: VRRP_Instance(VI_101) setting protocol VIPs. Aug 3 11:04:34 node2 Keepalived_vrrp[8112]: VRRP_Instance(VI_101) Sending gratuitous ARPs on eth0 for 192.168.56.111 Aug 3 11:04:34 node2 Keepalived_healthcheckers[8111]: Netlink reflector reports IP 192.168.56.111 added Aug 3 11:04:39 node2 Keepalived_vrrp[8112]: VRRP_Instance(VI_101) Sending gratuitous ARPs on eth0 for 192.168.56.111
備庫已經從backup狀態切換成master狀態了。並且VIP（192.168.56.111）已經切換過來。
查看ip地址：
[root@node2 ~]# ip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 08:00:27:83:b3:9d brd ff:ff:ff:ff:ff:ff inet 192.168.56.101/24 brd 192.168.56.255 scope global eth0 inet 192.168.56.111/32 scope global eth0 inet6 fe80::a00:27ff:fe83:b39d/64 scope link valid_lft forever preferred_lft forever
主備庫切換成功。
實戰演練過程結束，希望對大家學習MySQL高可用集羣有幫助。
今後我們可能還會遇到其他的MySQL高可用架構，學習它的時候，先不要忙於搭建，要先弄清原理，整理好實驗過程的思路，遇到報錯，一步步地去排查。自己的水平也會在這個歷練的過程中，得到提升。
今後我們可以一起討論，在寫博的過程中難免可能會有一些筆誤，或是想不周全的地方，希望大家諒解。有不對的地方歡迎各位老鐵指定。（MySQL高可用集羣第二部曲完結）
第一步曲直通車>> 企業中MySQL主流高可用架構實戰三部曲之MHA