Mariadb/Mysql 主從複製（1） mysql主從同步(4)-Slave延遲狀態監控

1、原理

　　mysql的主從數據同步是一個異步複製過程，須要master開啓bin-log日誌功能，bin-log記錄了master庫中的增、刪、修改、更新操做的sql語句，整個過程須要開啓3個線程，分別是master開啓I/O線程，slave開啓I/O線程和SQL線程

　　一、在slave服務器上執行start slave命令開啓主從複製開關，主從複製開始進行，slave I/O線程會經過master建立的受權用戶鏈接上master，並請求master從指定文件和位置以後發送bin-log日誌內容

　　二、master接收請求後，master I/O線程更加slave發送的指定bin-log日誌position點以後的內容，而後返回給slave的I/O線程；返回的信息中除了bin-log日誌外，還有在master服務器記錄的新的bin-log文件名及新的bin-log中的下一個指定更新位置（position）

　　三、slave I/O線程接收信息後，將接收的日誌內容一次添加到slave端的relay-log（中繼日誌）文件（mysql-relay-bin.xxxxxx）的最末端，並將讀取到的master端的bin-log文件名和position點記錄到master.info文件中，以便下次讀取時可以告知master從相應的bin-log文件名及最後一個position點開始發起請求

　　四、slave SQL 線程檢測到relay-log中I/O線程新增長的內容有更新，會當即分析relay-log日誌中的內容，將解析的sql語句按順序在slave裏執行，並記錄應用中繼日誌的文件名及位置點在relay-log.info中，執行成功後slave庫與master庫數據保持一致

　　總結

　　　　主從複製是異步的邏輯的SQL語句級的複製

　　　　複製時，主庫有一個I/O線程，從庫有兩個線程，I/O和SQL線程

　　　　做爲複製的全部mysql節點server-id都不能相同

　　　　bin-log文件只記錄對數據庫有更改的sql語句（數據庫內容的變動），不記錄任何查詢（select，slow）語句

　　原理流程圖以下：

 

　　主從複製條件

　　　　開啓binlog功能

　　　　主庫要創建帳號

　　　　從庫要配置master.info

　　　　start slave 開啓複製功能

 

 

2、環境

　　master：192.168.216.52

　　slave:192.168.216.53

mariadb版本10.2.24

[root@web2 ~]# rpm -qa Maria*
MariaDB-server-10.2.24-1.el7.centos.x86_64
MariaDB-compat-10.2.24-1.el7.centos.x86_64
MariaDB-common-10.2.24-1.el7.centos.x86_64
MariaDB-client-10.2.24-1.el7.centos.x86_64
[root@web2 ~]# 

 

3、安裝配置

　　一、添加mariadb，yum源

　　　　

[root@web2 ~]# cat /etc/yum.repos.d/mariadb.repo 
[mariadb]
name = MariaDB
baseurl = https://mirrors.ustc.edu.cn/mariadb/yum/10.2/centos7-amd64/
gpgkey=https://mirrors.ustc.edu.cn/mariadb/yum/RPM-GPG-KEY-MariaDB
gpgcheck=1

　　二、這裏yum安裝

　　　兩臺機器都安裝

　　　　yum install  mariadb-server

　　三、初始化mariadb，能夠忽略

　　　　參考：http://www.javashuo.com/article/p-xiiiwqiz-k.html 

　　四、配置master

 

-------------------修改配置文件（紅色部分關鍵，其餘爲優化）

[root@web2 my.cnf.d]# cat server.cnf
#
# These groups are read by MariaDB server.
# Use it for options that only the server (but not clients) should see
#
# See the examples of server my.cnf files in /usr/share/mysql/
#

# this is read by the standalone daemon and embedded servers
[server]

# this is only for the mysqld standalone daemon
[mysqld]
server-id=1 log-bin=mysql-bin #binlog-do-db=liting #binlog-ignore-db=mysql sync_binlog=1 binlog_checksum = none binlog_format = mixed port = 3306 socket = /var/lib/mysql/mysql.sock skip-external-locking
key_buffer_size = 256MB
max_allowed_packet      = 1MB
table_open_cache        = 256
sort_buffer_size        = 1MB
read_buffer_size        = 1MB
read_rnd_buffer_size    = 4MB
myisam_sort_buffer_size = 64MB
thread_cache_size       = 8
query_cache_size        = 16MB
thread_concurrency      = 8

[mysqldump]
quick
max_allowed_packet      = 16MB

[mysql]

no-auto-rehash

[myisamchk]

key_buffer_size         = 128MB
sort_buffer_size        = 128MB
read_buffer             = 2MB
write_buffer            = 2MB
[mysqlhotcopy]
interactive-timeout

#
# * Galera-related settings
#
[galera]
# Mandatory settings
#wsrep_on=ON
#wsrep_provider=
#wsrep_cluster_address=
#binlog_format=row
#default_storage_engine=InnoDB
#innodb_autoinc_lock_mode=2
#
# Allow server to accept connections on all interfaces.
#
#bind-address=0.0.0.0
#
# Optional setting
#wsrep_slave_threads=1
#innodb_flush_log_at_trx_commit=0

# this is only for embedded server
[embedded]

# This group is only read by MariaDB servers, not by MySQL.
# If you use the same .cnf file for MySQL and MariaDB,
# you can put MariaDB-only options here
[mariadb]

# This group is only read by MariaDB-10.2 servers.
# If you use the same .cnf file for MariaDB of different versions,
# use this group for options that older servers don't understand
[mariadb-10.2]

[root@web2 my.cnf.d]# 　　

 

----------------------受權 

 grant replication slave,replication client on *.* to 'tongbu'@'%' identified by '123456';

----------------------查看bin-log及position點

MariaDB [test3]> show master status;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000003 |      320|              |                  |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)

 

　　五、配置slave

 

--------------------修改配置

[root@web3 my.cnf.d]# cat server.cnf 
#
# These groups are read by MariaDB server.
# Use it for options that only the server (but not clients) should see
#
# See the examples of server my.cnf files in /usr/share/mysql/
#

# this is read by the standalone daemon and embedded servers
[server]

# this is only for the mysqld standalone daemon
[mysqld] socket = /var/lib/mysql/mysql.sock port = 3306 skip-external-locking
key_buffer_size =256MB
max_allowed_packet      = 1MB
table_open_cache        = 256
sort_buffer_size        = 1MB
read_buffer_size        = 1MB
read_rnd_buffer_size    = 4MB
myisam_sort_buffer_size = 64MB
thread_cache_size       = 8
query_cache_size        = 16MB
thread_concurrency      = 8 server-id = 2
#
# * Galera-related settings
#
[galera]
# Mandatory settings
#wsrep_on=ON
#wsrep_provider=
#wsrep_cluster_address=
#binlog_format=row
#default_storage_engine=InnoDB
#innodb_autoinc_lock_mode=2
#
# Allow server to accept connections on all interfaces.
#
#bind-address=0.0.0.0
#
# Optional setting
#wsrep_slave_threads=1
#innodb_flush_log_at_trx_commit=0

# this is only for embedded server
[embedded]

# This group is only read by MariaDB servers, not by MySQL.
# If you use the same .cnf file for MySQL and MariaDB,
# you can put MariaDB-only options here
[mariadb]

# This group is only read by MariaDB-10.2 servers.
# If you use the same .cnf file for MariaDB of different versions,
# use this group for options that older servers don't understand
[mariadb-10.2]

[root@web3 my.cnf.d]# 

[root@web3 my.cnf.d]# cat mysql-clients.cnf      #[mysql][mysqlcheck][mysqldump]也能夠寫在這個文件裏，master我是都卸載server.cnf裏面了 #
# These groups are read by MariaDB command-line tools
# Use it for options that affect only one utility
#

[mysql]
no-auto-rehash

[mysql_upgrade]

[mysqladmin]

[mysqlbinlog]

[mysqlcheck]
key_buffer_size         = 128MB
sort_buffer_size        = 128MB
read_buffer             = 2MB
write_buffer            = 2MB

[mysqldump]
quick
max_allowed_packet      = 16MB

[mysqlimport]

[mysqlshow]

[mysqlslap]
[mysqlhotcopy]
interactive-timeout
[root@web3 my.cnf.d]# 

---------------------slave進入mysql設置

　　slave指定master ip、用戶名、密碼、bin-log文件名、position（下面標記紅色部分）

[root@web3 my.cnf.d]#  mysql
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 12
Server version: 10.2.24-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

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

MariaDB [(none)]> change master to master_host='192.168.216.52',master_user='tongbu',master_password='123456',master_log_file='mysql-bin.000003',master_log_pos=320;MariaDB [(none)]> master_host='192.168.216.52',master_user='tongbu',master_password='123456',master_log_file='mysql-bin.000003',master_log_pos=320;

　MariaDB [(none)]> slave start;

 

 

　　

---------------查看狀態正常狀態以下：（正常狀態關注標記紫色部分)

MariaDB [(none)]> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.216.52
Master_User: tongbu
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000004
Read_Master_Log_Pos: 593
Relay_Log_File: web3-relay-bin.000006
Relay_Log_Pos: 828
Relay_Master_Log_File: mysql-bin.000004 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: 593
Relay_Log_Space: 1136
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: 1
Master_SSL_Crl: 
Master_SSL_Crlpath: 
Using_Gtid: No
Gtid_IO_Pos: 
Replicate_Do_Domain_Ids: 
Replicate_Ignore_Domain_Ids: 
Parallel_Mode: conservative
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
1 row in set (0.00 sec)


須要關注以下幾點
引用：http://www.javashuo.com/article/p-nlyvyhli-bg.html mysql主從同步(4)-Slave延遲狀態監控

#  1）Slave_IO_Running：該參數可做爲io_thread的監控項，Yes表示io_thread的和主庫鏈接正常並能實施複製工做，No則說明與主庫通信異常，多數狀況是由主從間網絡引發的問題；
   2）Slave_SQL_Running：該參數表明sql_thread是否正常，YES表示正常，NO表示執行失敗，具體就是語句是否執行經過，常會遇到主鍵重複或是某個表不存在。
   3）Seconds_Behind_Master：是經過比較sql_thread執行的event的timestamp和io_thread複製好的event的timestamp(簡寫爲ts)進行比較，而獲得的這麼一個差值；
        NULL—表示io_thread或是sql_thread有任何一個發生故障，也就是該線程的Running狀態是No，而非Yes。
        0 — 該值爲零，是咱們極爲渴望看到的狀況，表示主從複製良好，能夠認爲lag不存在。
        正值 — 表示主從已經出現延時，數字越大表示從庫落後主庫越多。
        負值 — 幾乎不多見，我只是聽一些資深的DBA說見過，其實，這是一個BUG值，該參數是不支持負值的，也就是不該該出現。 　　

 

　　六、測試，master建立一個test3的庫及t1的表

 

[root@web2 my.cnf.d]# mysql -uroot -p
Enter password: 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 11
Server version: 10.2.24-MariaDB-log MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

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

MariaDB [(none)]> 
MariaDB [(none)]> create database test3;
Query OK, 1 row affected (0.00 sec)

MariaDB [(none)]> use test3;
Database changed
MariaDB [test3]> create table t1(id varchar(20),name varchar(20));
Query OK, 0 rows affected (0.02 sec)

MariaDB [test3]> show tables; +-----------------+
| Tables_in_test3 |
+-----------------+
| t1              |
+-----------------+
1 row in set (0.00 sec)

MariaDB [test3]> 

　　

---------------slave查看已經同步過來了

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
| test3              |
+--------------------+
5 rows in set (0.00 sec)

MariaDB [(none)]> 

 

 

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