mysql 高可用工具_MySQL Utilities 高可用工具体验
MySQL Utilities 高可用工具體驗
MySQL Utilities是MySQL官方的工具集，其中包括高可用相關的幾個工具。 以下是對當前最新版本1.6的使用體驗。
前提條件
MySQL Server 5.6+
基于GTID的復制
Python 2.6+
Connector/Python 2.0+
環境準備
在1臺機器準備3個不同端口的MySQL實例用于測試
192.168.107.211:9001(master)
192.168.107.211:9002(slave1)
192.168.107.211:9003(slave2)
軟件
OS: CentOS 7.1
MySQL: Percona Server 5.7.19
Python： 2.7.5
Connector/Python：2.1.7
mysql-utilities：1.6.5
創建MySQL實例1
生成實例1的配置文件my1.cnf
su - mysql
vi my1.cnf
[mysqld]
port=9001
datadir=/var/lib/mysql/data1
socket=/var/lib/mysql/data1/mysql.sock
basedir=/usr/
innodb_buffer_pool_size=128M
explicit_defaults_for_timestamp
skip-name-resolve
lower-case-table-names
expire-logs-days=7
plugin-load="rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so"
rpl_semi_sync_master_wait_point=AFTER_SYNC
rpl_semi_sync_master_wait_no_slave=ON
rpl_semi_sync_master_enabled=ON
rpl_semi_sync_slave_enabled=ON
rpl_semi_sync_master_timeout=5000
server-id=9001
log_bin=binlog
gtid-mode=ON
enforce-gtid-consistency=ON
log-slave-updates=ON
master-info-repository=TABLE
relay-log-info-repository=TABLE
report-host=192.168.107.211
log-error=/var/lib/mysql/data1/mysqld.log
pid-file=/var/lib/mysql/data1/mysqld.pid
general-log=ON
general-log-file=/var/lib/mysql/data1/node1.log
[mysqld_safe]
pid-file=/var/lib/mysql/data1/mysqld.pid
socket=/var/lib/mysql/data1/mysql.sock
nice = 0
創建MySQL實例
mysqld --defaults-file=my1.cnf --initialize-insecure
mysqld --defaults-file=my1.cnf &
mysql -S data1/mysql.sock -uroot -e "set sql_log_bin=OFF;GRANT ALL PRIVILEGES ON *.* TO 'admin'@'%' IDENTIFIED BY '12345' WITH GRANT OPTION"
創建MySQL實例2
sed s/9001/9002/g my1.cnf | sed s/data1/data2/g >my2.cnf
mysqld --defaults-file=my2.cnf --initialize-insecure
mysqld --defaults-file=my2.cnf &
mysql -S data2/mysql.sock -uroot -e "set sql_log_bin=OFF;GRANT ALL PRIVILEGES ON *.* TO 'admin'@'%' IDENTIFIED BY '12345' WITH GRANT OPTION"
創建MySQL實例3
sed s/9001/9003/g my1.cnf | sed s/data1/data3/g >my3.cnf
mysqld --defaults-file=my3.cnf --initialize-insecure
mysqld --defaults-file=my3.cnf &
mysql -S data3/mysql.sock -uroot -e "set sql_log_bin=OFF;GRANT ALL PRIVILEGES ON *.* TO 'admin'@'%' IDENTIFIED BY '12345' WITH GRANT OPTION"
利用mysqlreplicate建立復制
-bash-4.2$ mysqlreplicate --master=admin:12345@192.168.107.211:9001 --slave=admin:12345@192.168.107.211:9002 --rpl-user=repl:repl -v
WARNING: Using a password on the command line interface can be insecure.
# master on 192.168.107.211: ... connected.
# slave on 192.168.107.211: ... connected.
# master id = 9001
# slave id = 9002
# master uuid = b8ca6259-ab80-11e7-91fc-000c296dd240
# slave uuid = d842240c-ab80-11e7-960f-000c296dd240
# Checking InnoDB statistics for type and version conflicts.
# Checking storage engines...
# Checking for binary logging on master...
# Setting up replication...
# Granting replication access to replication user...
# Connecting slave to master...
# CHANGE MASTER TO MASTER_HOST = '192.168.107.211', MASTER_USER = 'repl', MASTER_PASSWORD = 'repl', MASTER_PORT = 9001, MASTER_AUTO_POSITION=1
# Starting slave from master's last position...
# IO status: Waiting for master to send event
# IO thread running: Yes
# IO error: None
# SQL thread running: Yes
# SQL error: None
# ...done.
除去各種檢查，mysqlreplicate真正做的事很簡單。如下
先在master上創建復制賬號
CREATE USER 'repl'@'192.168.107.211' IDENTIFIED WITH 'repl'
GRANT REPLICATION SLAVE ON *.* TO 'repl'@'192.168.107.211' IDENTIFIED WITH 'repl'
mysqlreplicate會為每個Slave創建一個復制賬號，除非通過以下SQL發現該賬號已經存在。
SELECT * FROM mysql.user WHERE user = 'repl' and host = '192.168.107.211'
然后在slave上設置復制
CHANGE MASTER TO MASTER_HOST = '192.168.107.211', MASTER_USER = 'repl', MASTER_PASSWORD = 'repl', MASTER_PORT = 9001, MASTER_AUTO_POSITION=1
在啟用GTID的情況的下，從哪兒開始復制完全由GTID決定，所以mysqlreplicate中的那些和復制起始位點相關的參數，比如-b，統統被無視,其效果相當于-b。
注意:mysqlreplicate不會理會當前的復制拓撲，所以如果把master和slave對調再執行一次，就變成主主復制了。
slave1的復制配置好后，用同樣的方法配置slave2的復制
mysqlreplicate --master=admin:12345@192.168.107.211:9001 --slave=admin:12345@192.168.107.211:9003 --rpl-user=repl:repl -v
通過mysqlrplshow查看復制拓撲
-bash-4.2$ mysqlrplshow --master=admin:12345@192.168.107.211:9001 --discover-slaves-login=admin:12345 -v
WARNING: Using a password on the command line interface can be insecure.
# master on 192.168.107.211: ... connected.
# Finding slaves for master: 192.168.107.211:9001
# Replication Topology Graph
192.168.107.211:9001 (MASTER)
|
+--- 192.168.107.211:9002 [IO: Yes, SQL: Yes] - (SLAVE)
|
+--- 192.168.107.211:9003 [IO: Yes, SQL: Yes] - (SLAVE)
mysqlrplshow通過在master上執行SHOW SLAVE HOSTS發現初步的復制拓撲。 由于Slave停止復制或改變復制源時不能立刻反應到master的SHOW SLAVE HOSTS上，所以初步獲取的復制拓撲可能存在冗余， 因此，mysqlrplshow還會再連到slave上執行SHOW SLAVE STATUS進行確認。
通過mysqlrpladmin檢查集群健康狀態
-bash-4.2$ mysqlrpladmin --master=admin:12345@192.168.107.211:9001 --slaves=admin:12345@192.168.107.211:9002,admin:12345@192.168.107.211:9003 health
WARNING: Using a password on the command line interface can be insecure.
# Checking privileges.
#
# Replication Topology Health:
+------------------+-------+---------+--------+------------+---------+
| host | port | role | state | gtid_mode | health |
+------------------+-------+---------+--------+------------+---------+
| 192.168.107.211 | 9001 | MASTER | UP | ON | OK |
| 192.168.107.211 | 9002 | SLAVE | UP | ON | OK |
| 192.168.107.211 | 9003 | SLAVE | UP | ON | OK |
+------------------+-------+---------+--------+------------+---------+
# ...done.
通過mysqlrpladmin elect挑選合適的新主
-bash-4.2$ mysqlrpladmin --master=admin:12345@192.168.107.211:9001 --slaves=admin:12345@192.168.107.211:9002,admin:12345@192.168.107.211:9003 elect
WARNING: Using a password on the command line interface can be insecure.
# Checking privileges.
# Electing candidate slave from known slaves.
# Best slave found is located on 192.168.107.211:9002.
# ...done.
然而，elect只是從slaves中選出第一個合格的slave，并不考慮復制是否已停止，以及哪個節點的日志更全。
下面把slave1的復制停掉
mysql -S data2/mysql.sock -uroot -e "stop slave"
再在master執行一條SQL
mysql -S data1/mysql.sock -uroot -e "create database test"
現在slave1上少了一個事務
-bash-4.2$ mysqlrpladmin --master=admin:12345@192.168.107.211:9001 --slaves=admin:12345@192.168.107.211:9002,admin:12345@192.168.107.211:9003 gtid
WARNING: Using a password on the command line interface can be insecure.
# Checking privileges.
#
# UUIDS for all servers:
+------------------+-------+---------+---------------------------------------+
| host | port | role | uuid |
+------------------+-------+---------+---------------------------------------+
| 192.168.107.211 | 9001 | MASTER | 5daf1e10-ac41-11e7-bcc4-000c296dd240 |
| 192.168.107.211 | 9002 | SLAVE | fe084f45-ac43-11e7-a343-000c296dd240 |
| 192.168.107.211 | 9003 | SLAVE | d0af3a6a-ac41-11e7-85e0-000c296dd240 |
+------------------+-------+---------+---------------------------------------+
#
# Transactions executed on the server:
+------------------+-------+---------+-------------------------------------------+
| host | port | role | gtid |
+------------------+-------+---------+-------------------------------------------+
| 192.168.107.211 | 9001 | MASTER | 5daf1e10-ac41-11e7-bcc4-000c296dd240:1-3 |
| 192.168.107.211 | 9002 | SLAVE | 5daf1e10-ac41-11e7-bcc4-000c296dd240:1-2 |
| 192.168.107.211 | 9003 | SLAVE | 5daf1e10-ac41-11e7-bcc4-000c296dd240:1-3 |
+------------------+-------+---------+-------------------------------------------+
# ...done.
但elect仍然會選slave1
-bash-4.2$ mysqlrpladmin --master=admin:12345@192.168.107.211:9001 --slaves=admin:12345@192.168.107.211:9002,admin:12345@192.168.107.211:9003 elect
WARNING: Using a password on the command line interface can be insecure.
# Checking privileges.
# Electing candidate slave from known slaves.
# Best slave found is located on 192.168.107.211:9002.
# ...done.
通過mysqlrpladmin switchover在線切換主備
-bash-4.2$ mysqlrpladmin --master=admin:12345@192.168.107.211:9001 --slaves=admin:12345@192.168.107.211:9002,admin:12345@192.168.107.211:9003 --new-master=admin:12345@192.168.107.211:9002 switchover
WARNING: Using a password on the command line interface can be insecure.
# Checking privileges.
# Performing switchover from master at 192.168.107.211:9001 to slave at 192.168.107.211:9002.
# Checking candidate slave prerequisites.
# Checking slaves configuration to master.
# Waiting for slaves to catch up to old master.
Slave 192.168.107.211:9002 did not catch up to the master.
ERROR: Slave 192.168.107.211:9002 did not catch up to the master.
switchover會連接到每一個節點并等待所有slave回放完日志才執行切換，因此有任何一個節點故障或任何一個slave復制故障都不會執行switchover。
啟動剛才停掉的slave1的復制
mysql -S data2/mysql.sock -uroot -e "start slave"
再次執行switchover，成功
-bash-4.2$ mysqlrpladmin --master=admin:12345@192.168.107.211:9001 --slaves=admin:12345@192.168.107.211:9002,admin:12345@192.168.107.211:9003 --new-master=admin:12345@192.168.107.211:9002 --demote-master switchover
WARNING: Using a password on the command line interface can be insecure.
# Checking privileges.
# Performing switchover from master at 192.168.107.211:9001 to slave at 192.168.107.211:9002.
# Checking candidate slave prerequisites.
# Checking slaves configuration to master.
# Waiting for slaves to catch up to old master.
# Stopping slaves.
# Performing STOP on all slaves.
# Demoting old master to be a slave to the new master.
# Switching slaves to new master.
# Starting all slaves.
# Performing START on all slaves.
# Checking slaves for errors.
# Switchover complete.
#
# Replication Topology Health:
+------------------+-------+---------+--------+------------+---------+
| host | port | role | state | gtid_mode | health |
+------------------+-------+---------+--------+------------+---------+
| 192.168.107.211 | 9002 | MASTER | UP | ON | OK |
| 192.168.107.211 | 9001 | SLAVE | UP | ON | OK |
| 192.168.107.211 | 9003 | SLAVE | UP | ON | OK |
+------------------+-------+---------+--------+------------+---------+
# ...done.
執行switchover時，有一段Waiting for slaves to catch up to old master.，如果任何一個slave有故障無法同步到和master相同的狀態，switchover會失敗。即switchover的前提條件是所有節點(包括master和所有salve)都是OK的。
通過mysqlrpladmin failover故障切換主備
-bash-4.2$ mysqlrpladmin --slaves=admin:12345@192.168.107.211:9001,admin:12345@192.168.107.211:9003 failover
WARNING: Using a password on the command line interface can be insecure.
# Checking privileges.
# Performing failover.
# Candidate slave 192.168.107.211:9001 will become the new master.
# Checking slaves status (before failover).
# Preparing candidate for failover.
# Creating replication user if it does not exist.
# Stopping slaves.
# Performing STOP on all slaves.
# Switching slaves to new master.
# Disconnecting new master as slave.
# Starting slaves.
# Performing START on all slaves.
# Checking slaves for errors.
# Failover complete.
#
# Replication Topology Health:
+------------------+-------+---------+--------+------------+---------+
| host | port | role | state | gtid_mode | health |
+------------------+-------+---------+--------+------------+---------+
| 192.168.107.211 | 9001 | MASTER | UP | ON | OK |
| 192.168.107.211 | 9003 | SLAVE | UP | ON | OK |
+------------------+-------+---------+--------+------------+---------+
# ...done.
failover時要求所有slave的SQL線程都是正常的，IO線程可以停止或異常。 如果未指定--candidates，一般會以slaves中第1個slave作為新主。 如果新主的binlog不是最新的，會先向擁有最新日志的slave復制，并等到binlog追平了再切換。
小結
從上面操作過程來看，借助MySQL Utilities管理MySQL集群還比較簡便，但結合代碼考慮到各種場景，這套工具和MHA比起來還不夠嚴謹。
沒有把從庫的READ_ONLY設置集成到腳本里
switchover時沒有終止運行中的事務，實際也沒有有效的手段阻止新的寫事務在舊master上執行。
failover不檢查master死活，需要DBA在調用failover前自己檢查，否則會引起腦裂。
總結
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