mysql out of sync

MySQL is a widely used open source relational database management system that is widely used in many enterprise application systems. However, when performing master-slave replication in a MySQL database, out-of-synchronization may sometimes occur. This situation may lead to data inconsistency, affect data integrity and reliability, and bring potential risks and losses to the enterprise.

This article will discuss the reasons and solutions for MySQL database out of synchronization from the following aspects, helping enterprise administrators to better maintain the MySQL database system and ensure data consistency and security.

1. MySQL database master-slave replication mechanism

MySQL database master-slave replication is an important function of the MySQL database system and can be used for data backup and failure recovery. The master-slave replication mechanism is to copy the data on the master database (Master) to the backup database (Slave) to achieve data synchronization and backup purposes.

In MySQL database master-slave replication, communication is achieved through asynchronous replication. The Master server will write DML (Data Manipulation Language) operations into the binary log (Binlog). Binlog records all data operation records, including Insert, Update, Delete and other operations. The Slave server will copy the operation records in the main server Binlog to its own Relay log, and perform these operations locally to achieve the purpose of synchronizing data.

2. Reasons for MySQL database out of sync

MySQL database out of sync is a common problem, which may lead to data loss, data inconsistency and other problems. When analyzing the reasons why the MySQL database is out of sync, you need to consider the following aspects:

1. Network problems

Network problems are one of the common reasons for the MySQL database being out of sync, such as network interruption and packet loss. etc. will cause the data transmission of master-slave replication to be affected. If the Slave server cannot receive the Binlog log from the Master server in time, it may cause the Slave server data to lag behind the Master server and the data to be out of sync.

2. Abnormal operation of the master server

During the master-slave replication process, if the master server performs an abnormal operation, such as DROP DATABASE or TRUNCATE TABLE on the master server, then It is easy to cause synchronization interruption and replication cannot continue.

3. The load on the Slave server is too high

If the load on the Slave server is too high, for example, there are a large number of query requests, the Slave server may not be able to process the replication stream in time, resulting in replication delays.

4. Hardware failure

Hardware failure is another common problem in MySQL database synchronization. If the hardware on the Master server fails, such as hard disk failure, power outage, etc., the Binlog log may be lost, thus affecting the master-slave synchronization.

5. Database versions are inconsistent

If the Master and Slave database versions are inconsistent, for example, the Master uses MySQL version 5.7 and the Slave uses MySQL version 8.0, it may cause data to be out of sync.

3. Methods to solve the MySQL database out of synchronization

When the database is out of sync, measures need to be taken in time to solve the problem as soon as possible to avoid affecting the normal operation of the database. Here are several ways to solve the MySQL database out of sync problem:

1. Check the network and hardware

When checking the MySQL database out of sync problem, you first need to rule out network problems or hardware problems. You can use the ping command to test whether the network between the master and slave servers is smooth and check the status of the hardware devices to ensure that they are running normally.

2. Restart the replication service

If the MySQL database master-slave replication is interrupted, you can try to restart the replication service to retry the replication process and restore the synchronization state. After the replication service is started, you can use the show slave status command to obtain the current replication status, and restart replication with the following command:

MySQL> STOP SLAVE;
MySQL> START SLAVE;

3. Synchronize the master and slave database versions

If the Master and Slave database versions are inconsistent, you can try to synchronize their versions, such as upgrading the MySQL version on the Slave server to match the Master server to further ensure data synchronization.

4. Adjust database parameters

When solving the MySQL database out-of-synchronization problem, you can try to adjust the database parameters to optimize database load balancing, replication delay and other issues. For example, you can increase the processing power of the Slave server, increase network bandwidth, optimize the replication process, etc.

5. Use data synchronization tools

When building the MySQL database master-slave replication architecture, you can use some excellent data synchronization tools, such as MaxScale, SymmetricDS and TiDB, etc., to improve the efficiency of data synchronization. Reliability and stability.

To sum up, MySQL database out-of-synchronization is a common problem in enterprise applications. It is usually caused by network problems, abnormal operation of the master-slave server, excessive load on the slave server, hardware failure, inconsistent database versions, etc. Administrators can solve the MySQL database out-of-synchronization problem, improve the reliability and stability of the database, and ensure data security by checking the network and hardware, restarting the replication service, synchronizing master-slave database versions, adjusting database parameters, and using data synchronization tools. Consistency and completeness.

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