Mysql 5.7 從節點配置多線程主從復制

本文轉載自查看原文 2018-10-21 19:55 1105 Mysql 5.7 從節點配置多線程主從復制/ mysql數據庫/ 阿里雲rds

Mysql 采用多線程進行復制是從 Mysql 5.6 開始支持的內容，但是 5.6 版本下有缺陷，雖然支持多線程，但是每個數據庫只能一個線程，也就是說如果我們只有一個數據庫，則主從復制時也只有一個線程在工作。相當於還是以前的單線程。從 Mysql 5.7 開始支持同一數據庫下並行主從復制。不過默認情況下，還是單數據庫單個線程，如果需要使用多線程，需要在從節點進行配置。

Mysql 5.7 對主從復制增加了一種類型，共有兩種類型，如下：

DATABASE 基於庫的並行復制，每個數據庫對應一個復制線程
LOGICAL_CLOCK 基於組提交的並行復制方式，同一個數據庫下可以有多個線程

下面的步驟，在從節點上進行配置。

查看當前配置

在開始配置之前，我們先看一下當前配置下的主從復制的進程數。

mysql> show processlist;
+----+-------------+-----------+------+---------+-------+--------------------------------------------------------+------------------+
| Id | User        | Host      | db   | Command | Time  | State                                                  | Info             |
+----+-------------+-----------+------+---------+-------+--------------------------------------------------------+------------------+
|  1 | system user |           | NULL | Connect | 91749 | Waiting for master to send event                       | NULL             |
|  2 | system user |           | NULL | Connect |   208 | Slave has read all relay log; waiting for more updates | NULL             |
| 37 | root        | localhost | NULL | Query   |     0 | starting                                               | show processlist |
+----+-------------+-----------+------+---------+-------+--------------------------------------------------------+------------------+
3 rows in set (0.00 sec)

從上面看出只有一個主進程在等待同步。

下面查看復制類型和並行數量配置

mysql> show variables like 'slave_parallel_type';
+---------------------+----------+
| Variable_name       | Value    |
+---------------------+----------+
| slave_parallel_type | DATABASE |
+---------------------+----------+
1 row in set (0.00 sec)

當前的復制類型是 DATABASE，也就是統一數據庫下只有一個線程進行復制，不能並行復制。

mysql> show variables like 'slave_parallel_workers';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| slave_parallel_workers | 0     |
+------------------------+-------+
1 row in set (0.01 sec)

當前並行工作的進程數是 0

配置多線程

1、停止從節點復制

1 2	mysql> stop slave; Query OK, 0 rows affected (0.01 sec)

2、設置復制類型為 LOGICAL_CLOCK

mysql> set global slave_parallel_type='logical_clock';
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'slave_parallel_type';
+---------------------+---------------+
| Variable_name       | Value         |
+---------------------+---------------+
| slave_parallel_type | LOGICAL_CLOCK |
+---------------------+---------------+
1 row in set (0.01 sec)

3、設置並行數量為 4

mysql> set global slave_parallel_workers=4;
Query OK, 0 rows affected (0.00 sec)


mysql> show variables like 'slave_parallel_workers';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| slave_parallel_workers | 4     |
+------------------------+-------+
1 row in set (0.00 sec)

4、啟動從節點復制

1 2	mysql> start slave; Query OK, 0 rows affected (0.02 sec)

5、查看一下當前工作的線程數

mysql> show processlist;
+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+
| Id | User        | Host      | db   | Command | Time | State                                                  | Info             |
+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+
| 37 | root        | localhost | NULL | Query   |    0 | starting                                               | show processlist |
| 38 | system user |           | NULL | Connect |    8 | Waiting for master to send event                       | NULL             |
| 39 | system user |           | NULL | Connect |    7 | Slave has read all relay log; waiting for more updates | NULL             |
| 40 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                  | NULL             |
| 41 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                  | NULL             |
| 42 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                  | NULL             |
| 43 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                  | NULL             |
+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+
7 rows in set (0.00 sec)

最后說一下為什么需要多線程復制？因為主從之間的同步會有延時，多線程的目的是為了盡量減少這個延時時間。雖然如何優化主從是一個系統的功能，不同的場景需要不同的解決方案，但是多線程至少從基礎上能減少延遲時間。另外根據數據庫的實際情況，能否真正減少延時，以及配置多少線程，則需要反復的測試得出適合自己的數據。

實例配置:

cat backup-my.cnf 
# This MySQL options file was generated by innobackupex.

# The MySQL server
[mysqld]
port = 3310
#innodb_checksum_algorithm=innodb
#innodb_log_checksum_algorithm=innodb
innodb_data_file_path=ibdata1:200M:autoextend
innodb_log_files_in_group=2
innodb_log_file_size=1572864000
#innodb_fast_checksum=false
#innodb_page_size=16384
#innodb_log_block_size=512
innodb_undo_directory=.
innodb_undo_tablespaces=0
server-id = 1234
binlog-format = ROW
gtid-mode = ON
enforce-gtid-consistency = true
relay_log_recovery = 1
sync-binlog = 0
skip_slave_start = 1

slave-parallel-type=LOGICAL_CLOCK
slave-parallel-workers=32
master_info_repository=TABLE
relay_log_info_repository=TABLE
relay_log_recovery=ON
#rds_encrypt_data=false
#innodb_encrypt_algorithm=aes_128_ecb

mysql> show processlist;
+----+-------------+-----------+------+---------+-------+----------------------------------------+------------------+
| Id | User        | Host      | db   | Command | Time  | State                                  | Info             |
+----+-------------+-----------+------+---------+-------+----------------------------------------+------------------+
|  2 | root        | localhost | NULL | Query   |     0 | starting                               | show processlist |
|  3 | system user |           | NULL | Connect |    13 | Queueing master event to the relay log | NULL             |
|  4 | system user |           | NULL | Connect |     0 | System lock                            | NULL             |
|  5 | system user |           | NULL | Connect | 49775 | Waiting for an event from Coordinator  | NULL             |
|  6 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
|  7 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
|  8 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
|  9 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 10 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 11 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 12 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 13 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 14 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 15 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 16 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 17 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 18 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 19 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 20 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 21 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 22 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 23 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 24 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 25 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 26 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 27 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 28 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 29 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 30 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 31 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 32 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 33 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 34 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 35 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
| 36 | system user |           | NULL | Connect |    13 | Waiting for an event from Coordinator  | NULL             |
+----+-------------+-----------+------+---------+-------+----------------------------------------+------------------+
35 rows in set (0.00 sec)

mysql> show global variables like 'slave_parallel_workers';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| slave_parallel_workers | 32    |
+------------------------+-------+
1 row in set (0.00 sec)

mysql> show global variables like '%slave_parallel_type%';
+---------------------+---------------+
| Variable_name       | Value         |
+---------------------+---------------+
| slave_parallel_type | LOGICAL_CLOCK |
+---------------------+---------------+
1 row in set (0.00 sec)

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