1.主从状态查看

mysql> SHOW SLAVE STATUS\G

*************************** 1. row ***************************

Slave_IO_State: Waiting for master to send event

Master_Host: localhost

Master_User: repl

Master_Port: 13000

Connect_Retry: 60

Master_Log_File: master-bin.000002

Read_Master_Log_Pos: 1307

Relay_Log_File: slave-relay-bin.000003

Relay_Log_Pos: 1508

Relay_Master_Log_File: master-bin.000002

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: 1307

Relay_Log_Space: 1858

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_UUID: 3e11fa47-71ca-11e1-9e33-c80aa9429562

Master_Info_File: /var/mysqld.2/data/master.info

SQL_Delay: 0

SQL_Remaining_Delay: NULL

Slave_SQL_Running_State: Reading event from the relay log

Master_Retry_Count: 10

Master_Bind:

Last_IO_Error_Timestamp:

Last_SQL_Error_Timestamp:

Master_SSL_Crl:

Master_SSL_Crlpath:

Retrieved_Gtid_Set: 3e11fa47-71ca-11e1-9e33-c80aa9429562:1-5

Executed_Gtid_Set: 3e11fa47-71ca-11e1-9e33-c80aa9429562:1-5

Auto_Position: 1

Replicate_Rewrite_DB:

Channel_name:

Master_TLS_Version: TLSv1.2

2.主从复制相关的表

Performance Schema 中有些关于主从同步的表，这些表里的数据 和 通过 SHOW SLAVE STATUS 查看的数据部分相同。

类别

表名

表数据描述

connection

replication_connection_configuration

Configuration parameters for connecting to the master.

replication_connection_status

Current status of the connection to the master.

transaction applier

replication_applier_configuration

Configuration parameters for the transaction applier on the slave.

replication_applier_status

Current status of the transaction applier on the slave.

replication_applier_status_by_coordinator

Status of the coordinator thread (empty unless the slave is multithreaded).

replication_applier_status_by_worker

Status of the applier thread or worker threads if the slave is multithreaded.

group members

replication_group_members

Provides network and status information for group members.

replication_group_member_stats

Provides statistical information about group members and transaction in which they participate.

3.SHOW SLAVE STATUS Information  In the Other Tables

下面这两种表在数据库MySQL中。

3.1 slave_relay_log_info 表

Line

Table Column

约等于SHOW SLAVE STATUS Column

Description

1

Number_of_lines

[None]

Number of lines in the file or columns in the table

2

Relay_log_name

Relay_Log_File

The name of the current relay log file

3

Relay_log_pos

Relay_Log_Pos

The current position within the relay log file; events up to this position have been executed on the slave database

4

Master_log_name

Relay_Master_Log_File

The name of the master binary log file from which the events in the relay log file were read

5

Master_log_pos

Exec_Master_Log_Pos

The equivalent position within the master's binary log file of events that have already been executed

6

Sql_delay

SQL_Delay

The number of seconds that the slave must lag the master

7

Number_of_workers

[None]

The number of slave worker threads for executing replication events (transactions) in parallel

8

Id

[None]

ID used for internal purposes; currently this is always 1

9

Channel_name

Channel_name

The name of the replication channel

注意：

(1)slave_relay_log_info 表存储的是持久化的状态，而 show slave status 输出的是内存中的状态，所以二者之间的一些指标数据可能不一致；

(2)stop slave 或者正常关闭 mysqld，都会将内存中的状态持久化到磁盘上(slave_relay_log_info表中)；启动 mysqld 时会读取磁盘状态，初始化给内存状态；start slave 时也会初始化内存状态。

(3)在从库启动的时候时，读取 slave_relay_log_info 表中存储的位置，并把值传给 “show slave status” 中的 Relay_Log_File、Relay_Log_Pos，下次 “start slave” 是从这个位置开始继续回放 relay log；

(4)slave sql thread 按照 Relay_Log_Name、Relay_Log_Pos 位置进行 realy log 的回放.

3.2  slave_master_info 表

Line

Table Column

约等于SHOW SLAVE STATUS Column

Description

1

Number_of_lines

[None]

Number of lines in the file, or columns in the table

2

Master_log_name

Master_Log_File

The name of the master binary log currently being read from the master

3

Master_log_pos

Read_Master_Log_Pos

The current position within the master binary log that have been read from the master

4

Host

Master_Host

The host name of the master

5

User_name

Master_User

The user name used to connect to the master

6

User_password

Password (not shown by SHOW SLAVE STATUS)

The password used to connect to the master

7

Port

Master_Port

The network port used to connect to the master

8

Connect_retry

Connect_Retry

The period (in seconds) that the slave will wait before trying to reconnect to the master

9

Enabled_ssl

Master_SSL_Allowed

Indicates whether the server supports SSL connections

10

Ssl_ca

Master_SSL_CA_File

The file used for the Certificate Authority (CA) certificate

11

Ssl_capath

Master_SSL_CA_Path

The path to the Certificate Authority (CA) certificates

12

Ssl_cert

Master_SSL_Cert

The name of the SSL certificate file

13

Ssl_cipher

Master_SSL_Cipher

The list of possible ciphers used in the handshake for the SSL connection

14

Ssl_key

Master_SSL_Key

The name of the SSL key file

15

Ssl_verify_server_cert

Master_SSL_Verify_Server_Cert

Whether to verify the server certificate

16

Heartbeat

[None]

Interval between replication heartbeats, in seconds

17

Bind

Master_Bind

Which of the slave's network interfaces should be used for connecting to the master

18

Ignored_server_ids

Replicate_Ignore_Server_Ids

The list of server IDs to be ignored. Note that forIgnored_server_idsthe list of server IDs is preceded by the total number of server IDs to ignore.

19

Uuid

Master_UUID

The master's unique ID

20

Retry_count

Master_Retry_Count

Maximum number of reconnection attempts permitted

21

Ssl_crl

[None]

Path to an SSL certificate revocation-list file

22

Ssl_crlpath

[None]

Path to a directory containing SSL certificate revocation-list files

23

Enabled_auto_position

Auto_position

If autopositioning is in use or not

24

Channel_name

Channel_name

The name of the replication channel

25

Tls_version

Master_TLS_Version

TLS version on master

注意：

slave io thread 按照 Master_Log_File、Read_Master_Log_Pos 位置读取主库的 binlog，并写入到本地 relay log。

4.slave_parallel_workers 对 复制延迟的影响

MySQL 5.7版本已经支持“真正”的并行复制功能，官方称为为enhanced multi-threaded slave(简称MTS)，因此复制延迟问题已经得到了极大的改进。

在MySQL 5.7中，设置参数slave_parallel_workers>0并且global.slave_parallel_type＝‘LOGICAL_CLOCK’，即可支持一个schema下，slave_parallel_workers个的worker线程并发执行relay log中主库提交的事务。其核心思想：一个组提交的事务都是可以并行回放(配合binary log group commit)。slave机器的relay log中last_committed相同的事务(sequence_num不同)可以并发执行。

注意：

(1)开启MTS功能后，推荐将参数master_info_repostitory设置为TABLE，这样性能可以有50%~80%的提升。这是因为并行复制开启后对于元master.info这个文件的更新将会大幅提升，资源的竞争也会变大。推荐将master_info_repository设置为TABLE，来减小这部分的开销。

(2)Coordinator thread on slave dispatches work across several worker threads。Each worker thread commits trx in isolation。

(3)推荐开启参数 slave_preserve_commit_order 。这是因为仅仅设置LOGICAL_CLOCK会存在问题--此时在slave上应用事务的顺序是无序的，和relay log中记录的事务顺序不一样，这样数据一致性是无法保证的，为了保证事务是按照relay log中记录的顺序来回放，就需要开启参数slave_preserve_commit_order。(The transactions that the slave applies in parallel may commit out of order, unless slave_preserve_commit_order=1.)

(4)设置 slave_parallel_workers 后，需要重启slave 进程

Setting slave_parallel_workers has no immediate effect. The state of the variable applies on all subsequent START SLAVE statements.

(5)实践中遇到的一个例子，我们将 slave_parallel_workers 由值4调整为16，延迟的速率得到了明显的改善。(具体值要操作硬件配置和从库的应用。注意此图是Delay的速率，值越大说明延迟趋势越严重)

5.XtraBackup 恢复过程，对/mysql/data数据文件赋权的时机

应该在 XXX/innobackupex --copy-back /XXX 过程之后再进行数据文件所有者变更，变更主要命令如下：

chown -R mysql:mysql /XXXX/mysql/data/

否则mysql 服务无法正常启动，报错信息如下：

.. ERROR! The server quit without updating PID file (/XXX/mysql/data/tcvm255.pid).

ERROR! MySQL is not running, but lock file (/var/lock/subsys/mysql) exists

查看mysql log 主要信息如下:

2017-06-19T10:48:18.112683+08:00 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for moredetails).2017-06-19T10:48:18.763038+08:00 0 [ERROR] InnoDB: The innodb_system data file 'ibdata1'must be writable2017-06-19T10:48:18.763074+08:00 0 [ERROR] InnoDB: The innodb_system data file 'ibdata1'must be writable2017-06-19T10:48:18.763080+08:00 0[ERROR] InnoDB: Plugin initialization aborted with error Generic error2017-06-19T10:48:19.364031+08:00 0 [ERROR] Plugin 'InnoDB' init functionreturned error.2017-06-19T10:48:19.364063+08:00 0 [ERROR] Plugin 'InnoDB'registration as a STORAGE ENGINE failed.2017-06-19T10:48:19.364075+08:00 0[ERROR] Failed to initialize builtin plugins.2017-06-19T10:48:19.364080+08:00 0 [ERROR] Aborting

6.主从复制如何设置指定的数据库

编辑从服务器上/etc/my.cnf的配置参数,通过参数(replicate-do-db)指定那个数据库可以进行复制；通过参数(replicate-ignore-db)，指定那个数据库可以进行复制。

replicate-do-db: Tells the slave SQL thread to restrict replication to the specified database.

replicate-ignore-db: Tells the slave SQL thread not to replicate to the specified database.

7.备份还原，启动实例报错

我们会遇到一种情况，原实例上有多个数据库，但是我们只需要备份还原一个库或部分库的情况。通过innobackupex工具备份指定库，例如 --databases="mysql XXXdb performance_schema"，然后再还原，可能报错。

2019-09-24T19:47:09.084293+08:00 0 [Note] /qqweixin/mysql/bin/mysqld (mysqld 5.7.21-log) starting as process 51778...2019-09-24T19:47:09.091489+08:00 0[Note] InnoDB: PUNCH HOLE support available2019-09-24T19:47:09.091559+08:00 0[Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins2019-09-24T19:47:09.091572+08:00 0[Note] InnoDB: Uses event mutexes2019-09-24T19:47:09.091582+08:00 0 [Note] InnoDB: GCC builtin __sync_synchronize() is used formemory barrier2019-09-24T19:47:09.091592+08:00 0 [Note] InnoDB: Compressed tables use zlib 1.2.3

2019-09-24T19:47:09.091601+08:00 0[Note] InnoDB: Using Linux native AIO2019-09-24T19:47:09.096199+08:00 0 [Note] InnoDB: Number of pools: 1

2019-09-24T19:47:09.096473+08:00 0[Note] InnoDB: Using CPU crc32 instructions2019-09-24T19:47:09.101033+08:00 0 [Note] InnoDB: Initializing buffer pool, total size = 220G, instances = 48, chunk size =512M2019-09-24T19:47:10.422726+08:00 0[Note] InnoDB: Completed initialization of buffer pool2019-09-24T19:47:10.650079+08:00 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the manpage of setpriority().2019-09-24T19:47:10.660276+08:00 0 [ERROR] InnoDB: The Auto-extending innodb_system data file './ibdata1' is of a different size 21248 pages (rounded down to MB) than specified in the .cnf file: initial 65536 pages, max 0 (relevant if non-zero) pages!

2019-09-24T19:47:10.660303+08:00 0[ERROR] InnoDB: Plugin initialization aborted with error Generic error2019-09-24T19:47:11.260892+08:00 0 [ERROR] Plugin 'InnoDB' init functionreturned error.2019-09-24T19:47:11.260934+08:00 0 [ERROR] Plugin 'InnoDB'registration as a STORAGE ENGINE failed.2019-09-24T19:47:11.260948+08:00 0[ERROR] Failed to initialize builtin plugins.2019-09-24T19:47:11.260963+08:00 0[ERROR] Aborting2019-09-24T19:47:11.260982+08:00 0[Note] Binlog end2019-09-24T19:47:11.262087+08:00 0 [Note] /qqweixin/mysql/bin/mysqld: Shutdown complete

解决方案

在数据目录下，删除ibdata1、ib_buffer_pool、ib_logfile0、ib_logfile1、ib_logfile2、ibtmp1文件。

执行的命令如下：

rm -rf ib*

此时，实例可以启动，但是搭建主从时，会报错：

2019-09-25T09:50:26.973154+08:00 0 [Warning] Info table is not ready to be used. Table 'mysql.slave_master_info'cannot be opened.2019-09-25T09:50:26.973165+08:00 0 [ERROR] Error in checking mysql.slave_master_info repository infotype of TABLE.2019-09-25T09:50:26.973171+08:00 0 [ERROR] Error creating master info: Error checking repositories.2019-09-25T09:50:26.973175+08:00 0 [ERROR] Slave: Failed to initialize the master info structure for channel ''; its record may still be present in 'mysql.slave_master_info'table, consider deleting it.2019-09-25T09:50:26.973182+08:00 0 [ERROR] Failed to create or recover replication inforepositories.2019-09-25T09:50:26.973186+08:00 0 [Note] Some of the channels are not created/initialized properly. Check for additional messages above. You will not be able to start replication on those channels until the issue is resolved and the server restarted.

如果数据库不是很大的话，建议考虑使用mysqldump 。

指定库备份

/weixinqq/mysql/bin/mysqldump --master-data=2 -uUID -pPWD --databases XXXdb --single-transaction -R --triggers > /backdbs/XXXdb.sql

导入还原

mysql -uUID -pPWD < /data/QQbackupDB/XXXdb.sql

-------------------------------------

上面这种情况的出现，常见错误原因是：主从mysql实例的配置文件(my.cnf)关于参数 innodb_data_file_path 的值设置的不相同，请留意。

8.通过XtraBackup 搭建主从

1.在GITD 模式下，通过XtraBackup恢复从实例，搭建主从，

change master to

master_host='XXX.XXX.XXX.XXX',

master_port=3306,

master_user='user_test',

master_password='pwd',

master_auto_position=1;

此时，主从搭建失败，一般会提示主键冲突，进一步分析原因是主从开始的【位点】 不对，例如，正确的同步关系应该是从330000位点开始同步，可以它科能从310000位点开始了同步。

解决方案：

如果备份是从主节点开始的，则

step 1:

reset master;

step 2:

set global gtid_purged=’开始真正需要同步的GTID′;

step 3

change master to

master_host='XXX.XXX.XXX.XXX',

master_port=3306,

master_user='user_test',

master_password='pwd',

master_auto_position=1;

step 4

start salve;

9.dump导入导出报错

再GTID模式下，导入时报错，信息如下

mysql: [Warning] Using a password on the command line interface can be insecure.

ERROR1840 (HY000) at line 24: @@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_EXECUTED is empty.

在dump导出时，添加--set-gtid-purged=off参数，避免将gtid信息导出。

10.通过xtrabackup备份，找不到xtrabackup_binlog_info文件

通过xtrabackup备份，而在搭建主从时却找不到xtrabackup_binlog_info文件。异常原因是，没有开启 log-bin 参数

解决方案: 开启MySQL的binlog日志

在配置文件中my.cnf 添加以下参数

log-bin = mysql-bin

资料学习：