Build high-reliability database solutions using MySQL and PostgreSQL

Build high-reliability database solutions using MySQL and PostgreSQL

1. Introduction
In today's data-driven society, the reliability of the database has been given extremely high importance. In order to ensure the continued stable operation of the system and the security of the data, it is crucial to choose the appropriate database solution. MySQL and PostgreSQL, as currently the most commonly used open source relational database management systems (RDBMS), have powerful functions and good performance. This article will introduce how to use MySQL and PostgreSQL to build a highly reliable database solution, and provide relevant code examples for reference.

2. Database Replication (Replication)
   Database replication is a commonly used solution to increase reliability and performance. It achieves data backup and read-write load balancing by copying the change operations of the master database to one or more slave databases. Both MySQL and PostgreSQL support database replication.

2.1 MySQL database replication
MySQL database replication achieves data replication and synchronization through the master-slave mode. The following is a code example for MySQL database replication:

• In the main database, configure the following in the my.cnf file:

  [mysqld]
  server-id=1
  log-bin=mysql-bin
  binlog-do-db=my_database

• In the slave database, make the following configuration in the my.cnf file:

  [mysqld]
  server-id=2

• In the master database, create a user for replication and grant replication permissions:

  CREATE USER 'replication_user'@'%' IDENTIFIED BY 'password';
  GRANT REPLICATION SLAVE ON *.* TO 'replication_user'@'%';

• In the slave database, use the following command to start the replication process:

  CHANGE MASTER TO 
  MASTER_HOST='master_host',
  MASTER_USER='replication_user',
  MASTER_PASSWORD='password',
  MASTER_LOG_FILE='mysql-bin.000001',
  MASTER_LOG_POS=0;
  START SLAVE;

2.2 PostgreSQL database replication
PostgreSQL database replication performs data replication through streaming replication. Copy and sync. The following is a code example for PostgreSQL database replication:

• In the main database, open the postgresql.conf file and configure the following:

  listen_addresses = '*'
  wal_level = replica
  archive_mode = on
  archive_command = 'cp "%p" /path/to/archive/%f'
  max_wal_senders = 2
  wal_keep_segments = 10

• In the master database, open the pg_hba.conf file and add the connection settings of the slave database:

  host replication replication_user slave_ip/32 md5

• In the slave database, create the recovery.conf file and configure it as follows:

  standby_mode = on
  primary_conninfo = 'host=master_ip port=5432 user=replication_user password=password'
  restore_command = 'cp /path/to/archive/%f "%p"'

• In the slave database, run the following command to start the slave database:

  pg_ctl start -D /usr/local/pgsql/data

3. Database High Availability (High Availability)
   Database High Availability refers to the ability of a database system to remain operational despite failures. Both MySQL and PostgreSQL provide corresponding high availability solutions.

3.1 MySQL database high availability
MySQL database high availability can be achieved through master-slave mode and database clustering.

• Master-slave mode: Based on database replication, the master server is used for read and write operations, while the slave server is used for backup and read load balancing. When the master server fails, the slave server can automatically switch to the master server. The following is a code example for high availability of MySQL database based on master-slave mode:

• In the slave database, create a trigger and monitor the status of the master server:
  mysql> DELIMITER $$
  mysql> CREATE TRIGGER failover_trigger AFTER INSERT ON monitor
  -> FOR EACH ROW
  -> BEGIN
  -> DECLARE server_status INT;
  -> SET server_status = ( SELECT * FROM monitor ORDER BY timestamp DESC LIMIT 1);
  -> IF (server_status = 0) THEN
  -> -- switch to master
  -> END IF;
  -> ; END$$
  mysql> DELIMITER ;

• Database cluster: By forming multiple nodes into a cluster to share storage and computing resources, the high availability of the database is achieved. Common MySQL database cluster solutions include Percona XtraDB Cluster and Galera Cluster.

3.2 PostgreSQL database high availability
PostgreSQL database high availability can be achieved through master-slave mode and database clustering.

• Master-slave mode: The master-slave mode based on streaming replication can also achieve high availability of the PostgreSQL database. When the master server fails, the slave server can take over the work of the master server. The following is a code example for high availability of PostgreSQL database based on master-slave mode:

• In the standby server, monitor the status of the primary server by querying the pg_stat_replication view:
  SELECT * FROM pg_stat_replication ;

• Database cluster: PostgreSQL provides a solution called PostgreSQL's own cluster. It achieves high availability and load balancing of the database by forming multiple nodes into a cluster.

4. Conclusion
   By properly leveraging replication and high availability solutions for MySQL and PostgreSQL, we can build a highly reliable database solution. In actual applications, the appropriate solution must be selected based on specific business needs and actual conditions, and deployed and maintained according to the corresponding configuration. This article provides relevant code examples for readers' reference and practice.

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