Comparison of cross-data center replication capabilities between TiDB and MySQL

Comparison of cross-data center replication capabilities between TiDB and MySQL

Introduction:
TiDB is a distributed relational database that can achieve high availability and disaster recovery through cross-data center replication. MySQL also provides some ways to achieve cross-data center replication. This article will compare the similarities and differences between TiDB and MySQL in cross-data center replication capabilities, and give corresponding code examples.

1. TiDB’s cross-data center replication capability
TiDB’s cross-data center replication capability is achieved by using the CDC (Change Data Capture) function in TiDB. CDC will record all data changes and send these records to subscribers. Subscribers can deploy a TiDB instance in other data centers to receive these changes and implement cross-data center replication.

The following is a code example for TiDB center replication:

// 创建CDC订阅任务
CREATE CDC TASK 'task_demo' 
    with start_ts = 0, 
    to = 'xxxxxx',
    filter_event = 'update';

// 启动CDC订阅任务
START CDC TASK 'task_demo';

2. MySQL’s cross-data center replication capabilities
MySQL provides several cross-data center replication solutions, such as based on Binary Log (Binary Log) replication, GTID (Global Transaction Identifiers)-based replication, etc.

The following is a code example for MySQL cross-data center replication:

-- 创建复制用户
CREATE USER 'repl'@'datasync.example.com' IDENTIFIED BY 'password';
GRANT REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'repl'@'datasync.example.com';

-- 主库上启动二进制日志复制
CHANGE MASTER TO
    MASTER_HOST='master.example.com',
    MASTER_PORT=3306,
    MASTER_USER='repl',
    MASTER_PASSWORD='password',
    MASTER_LOG_FILE='master-bin.000001',
    MASTER_LOG_POS=107;
START SLAVE;

-- 从库上启动复制
CHANGE MASTER TO
    MASTER_HOST='master.example.com',
    MASTER_PORT=3306,
    MASTER_USER='repl',
    MASTER_PASSWORD='password',
    MASTER_AUTO_POSITION=1;
START SLAVE;

3. Comparison of TiDB and MySQL cross-data center replication capabilities

1. Replication mechanism: TiDB usage CDC records and propagates data changes, while MySQL uses binary logs or GTIDs to achieve cross-data center replication.
2. Network delay: TiDB implements data synchronization through the Raft protocol and can tolerate a certain network delay, while MySQL replication mainly relies on network delay. Once the delay is too high, data synchronization may be slow or even fail.
3. Disaster tolerance: TiDB ensures disaster tolerance through distributed architecture and automatic data sharding. Even if one of the data centers fails, the data is still available. MySQL's disaster recovery capability is relatively weak and relies on a master-slave relationship. Once the master database fails, the entire database will be unavailable.

Conclusion:
TiDB and MySQL both provide cross-data center replication capabilities, but they differ in implementation methods and disaster recovery capabilities. TiDB implements a more flexible and reliable replication mechanism through CDC, which can tolerate certain network delays and failures and ensure high data availability and disaster recovery capabilities. The replication mechanism of MySQL is relatively simple and relies more on network delay and master-slave relationship. It is prone to data synchronization failure and the entire database becoming unavailable.

References:

• [TiDB official document](https://pingcap.com/docs-cn/stable/ticdc-overview/)
• [ MySQL official document](https://dev.mysql.com/doc/refman/8.0/en/replication-howto.html)

The code examples in the article are for reference only. In actual use, Please adjust according to the specific situation.

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