Learn about MySQL and PostgreSQL high availability and fault tolerance

Understand the high availability and fault tolerance of MySQL and PostgreSQL

Abstract: This article will introduce the high availability and fault tolerance of MySQL and PostgreSQL two relational database management systems, including master-slave replication, multi-master replication, Automatic failover and other functions, and provide relevant code examples.

1. MySQL high availability and fault tolerance implementation method

1. Master-Slave Replication
   Master-Slave Replication is a commonly used method in MySQL to achieve high availability and fault tolerance. Fault-tolerant approach. The master database (Master) receives write operations and transmits the written data to the slave database (Slave). The slave database regularly synchronizes the data updates of the master database to maintain data consistency. When the main database fails, you can manually promote the slave database to the main database to achieve failover.

The following is a simple MySQL master-slave replication example:

# 主库配置（my.cnf文件中）
server-id=1
log-bin=mysql-bin
binlog-format=ROW

# 从库配置（my.cnf文件中）
server-id=2
master-host=主库IP地址
master-user=用户名
master-password=密码

2. Multi-Master Replication (Multi-Master Replication)
   Multi-Master Replication is a high-level implementation in MySQL Another approach to availability and fault tolerance. Unlike master-slave replication, which has only one master database, multi-master replication allows multiple master databases to receive write operations and synchronize the written data to other master databases. This increases the system's concurrent processing capabilities and provides higher availability.

The following is a simple MySQL multi-master replication example:

# 主库1配置（my.cnf文件中）
server-id=1
log-bin=mysql-bin
binlog-format=ROW
auto_increment_increment=2
auto_increment_offset=1

# 主库2配置（my.cnf文件中）
server-id=2
log-bin=mysql-bin
binlog-format=ROW
auto_increment_increment=2
auto_increment_offset=2

3. Automatic Failover
   Automatic failover is an aspect of MySQL high availability An important function, it can automatically promote a slave database to the master database when the master database fails to maintain the continuity of the system.

The following is a simple MySQL automatic failover example:

# 使用MySQL自带的工具MHA进行自动故障转移配置
[server default]
priority=1
manager_workdir=/usr/local/mha
manager_log=/usr/local/mha/manager.log

[server1]
hostname=主库1IP地址
ssh_user=用户名
repl_user=复制用户名
repl_password=复制密码

[server2]
hostname=主库2IP地址
ssh_user=用户名
repl_user=复制用户名
repl_password=复制密码

2. PostgreSQL high availability and fault tolerance implementation method

1. Streaming replication ( Streaming Replication)
   Streaming replication is a commonly used method in PostgreSQL to achieve high availability and fault tolerance. Similar to MySQL's master-slave replication, streaming replication transfers write operations from the master database to one or more slave databases, and the slave databases regularly synchronize data from the master database to maintain consistency. When the main library fails, you can manually promote the slave library to the main library.

The following is a simple PostgreSQL streaming replication example:

# 主库配置（postgresql.conf文件中）
wal_level = hot_standby
max_wal_senders = 5
wal_keep_segments = 32
synchronous_commit = on

# 从库配置（recovery.conf文件中）
standby_mode = on
primary_conninfo = 'host=主库IP地址 port=5432 user=用户名 password=密码 application_name=从库名称'
trigger_file = '/tmp/failover'

2. High Availability Cluster (High Availability Cluster)
   High availability cluster is a high-availability and high-availability cluster in PostgreSQL. Another approach to fault tolerance. By forming multiple nodes into a cluster, when a node fails, other nodes can automatically take over the service, thereby achieving automatic failover.

The following is a simple PostgreSQL high availability cluster example (using Pgpool-II):

# 配置Pgpool-II的pgpool.conf文件
backend_hostname0=主库1IP地址
backend_port0=5432
backend_weight0=1
backend_data_directory0='/data'

backend_hostname1=主库2IP地址
backend_port1=5432
backend_weight1=1
backend_data_directory1='/data'

# 配置Pgpool-II的pcp.conf文件
pgpool_hostname0=主库1IP地址
pgpool_port0=9999
pgpool_username0=用户名
pgpool_password0=密码

pgpool_hostname1=主库2IP地址
pgpool_port1=9999
pgpool_username1=用户名
pgpool_password1=密码

Conclusion: Both MySQL and PostgreSQL provide a variety of high availability and fault tolerance features , you can choose the appropriate method according to actual needs to ensure the stability and continuity of the system. In actual applications, factors such as database performance, data consistency, and fault recovery time must also be considered to comprehensively select an appropriate solution.

References:

1. https://dev.mysql.com/doc/refman/8.0/en/replication.html
2. https://www .postgresql.org/docs/current/high-availability.html

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