mysql out of sync

MySQL is one of the most popular relational database management systems in the world. Its efficiency, reliability and scalability have been widely recognized. However, although MySQL itself is very stable, some users may encounter out-of-sync issues when using MySQL. This article will delve into the causes and solutions of MySQL out of sync.

1. Reasons for MySQL out of sync

1. Lack of synchronization of master-slave database data

The master-slave database is a common replication method for MySQL databases. The master database Responsible for writing data, while the slave database is responsible for synchronizing data from the master database. However, since data transmission between the master and slave databases takes time and the data is generated very quickly, the slave databases cannot update the data of the master database in time, resulting in data inconsistency between the master and slave databases, that is, out of synchronization.

2. Database read and write operation conflicts

When the MySQL database performs read and write operations, concurrent operations may occur. This will cause some data to be written to the master database, but due to the synchronization delay, the slave database is not updated in time, resulting in desynchronization. In addition, during read operations, if the data of some read operations conflicts with the data of simultaneous write operations, it will cause data inconsistency in the slave database.

3. Database configuration error

MySQL configuration is very flexible. During use, unreasonable configuration can also lead to out-of-synchronization problems. For example, if the bin-log, relay-log, master_log, sync_binlog, super_read_only and other parameters of MySQL master and slave data synchronization are configured incorrectly, it may lead to data inconsistency between the master and slave databases.

2. Solution to MySQL out of synchronization

1. Check the configuration parameters of the master-slave library

In the application scenario of using master-slave replication, check The problem of out-of-synchronization can be solved only if the replication mechanism of the database is normal. In MySQL, the master database updates data to the binary log binlog, and the slave database uses binlog to copy data. In distributed database applications, binary logs are very important. If binlog synchronization is abnormal, out-of-synchronization problems will occur.

2. Use MySQL tools to repair out-of-sync data

MySQL provides multiple tools to repair synchronization problems in the database. For example, the "mysqldump" command can back up or restore data and in some cases can solve the problem. There are other tools such as "myisamchk", "pt-table-checksum", etc. that can also be used to repair out-of-sync data.

3. Slow query optimization

If there are slow queries in the database, it will cause a delay in modifying some data. These modifications have a significant impact on data synchronization. Therefore, when using MySQL, you need to regularly optimize the slow queries of the database to improve the performance of the database.

4. Database Consistency Check

In order to ensure the data consistency of MySQL, regular consistency checks are required. This can be done by using MySQL tools. For example, the pt-table-checksum tool can detect whether the data in the slave database and the master database are consistent.

5. Database Mirroring

Database mirroring is a way to back up and replicate a database. Unlike master-slave replication, mirroring replication is asynchronous, that is, there are two copies. Copy each other and synchronize with each other after modification. After setting up the database as a mirror, data consistency and high availability can be guaranteed.

Summary:

MySQL is a very flexible database management system, but in order to ensure the reliability and consistency of data, managers need to carry out a series of maintenance and optimization work to solve the problem of master-slave Problems caused by library synchronization and lack of synchronization. From this point on, the normal operation of MySQL data can be ensured.

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