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Today, I will talk to you about the matters needing attention of the event scheduler in MySQL failover, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following contents for you. I hope you can get something according to this article.

Event Scheduler (event) is a new task scheduler in MySQL5.1, which solves functions that can only be accomplished by relying on system-scheduled tasks in previous versions.

Here's a case study:

Enable event:

Mysql > set global event_scheduler=ON

Query OK, 0 rows affected (0.01 sec)

Mysql > show variables like 'event%'

+-+ +

| | Variable_name | Value |

+-+ +

| | event_scheduler | ON |

+-+ +

In the master-slave architecture, create an event on master:

Mysql > show create event testevent\ G

* * 1. Row *

Event: testevent

Sql_mode: STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION

Time_zone: SYSTEM

Create Event: CREATE DEFINER= `root` @ `% `EVENT `testevent` ON SCHEDULE EVERY 1 DAY STARTS '2017-09-11 23 EVENT 50V 00' ON COMPLETION NOT PRESERVE ENABLE DO create table test02 as select * from test01

Character_set_client: utf8

Collation_connection: utf8_general_ci

Database Collation: utf8_general_ci

1 row in set (0.00 sec)

Use slave to synchronize, and then check the event status of master and slave

Master

Mysql > show events\ G

* * 1. Row *

Db: test

Name: testevent

Definer: root@%

Time zone: SYSTEM

Type: RECURRING

Execute at: NULL

Interval value: 1

Interval field: DAY

Starts: 2017-09-11 23:50:00

Ends: NULL

Status: ENABLED

Originator: 2

Character_set_client: utf8

Collation_connection: utf8_general_ci

Database Collation: utf8_general_ci

Slave

Mysql > show events\ G

* * 1. Row *

Db: test

Name: testevent

Definer: root@%

Time zone: SYSTEM

Type: RECURRING

Execute at: NULL

Interval value: 1

Interval field: DAY

Starts: 2017-09-11 23:50:00

Ends: NULL

Status: SLAVESIDE_DISABLED

Originator: 2

Character_set_client: utf8

Collation_connection: utf8_general_ci

Database Collation: utf8_general_ci

In other words, event can only be triggered on master, but not on slave. If it is triggered on slave, synchronization will be broken. When master / slave failover occurs, slave becomes master, and event state needs to be enabled manually:

Alter event' testevent' enable

After reading the above, do you have any further understanding of the considerations of the event scheduler in MySQL failover? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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