MySQL dual master hot standby solution based on Keepalived

The MySQL dual master hot standby solution based on Keepalived ensures that the database service is not interrupted. 1. Keepalived monitors database instances and switches VIP to backup library when the main library fails; 2. MySQL replication function (such as GTID) ensures synchronization and consistency of data between the two main libraries; 3. Keepalived relies on the heartbeat package to detect the status of the main node through the VRRP protocol, and switches VIPs according to configuration parameters (priority, detection interval, etc.), and requires careful configuration to avoid split brain phenomenon; 4. Scripts need to be written to monitor MySQL status, and log problems are checked in combination; 5. High availability requires selecting appropriate hardware, regular backups, reasonable monitoring, and continuous maintenance and optimization.

MySQL dual-main hot standby solution based on Keepalived: In-depth analysis and practice

Many people want to understand that MySQL is highly available, but they always feel confused. In fact, the core sentence is just one sentence: ensure that the database service is not interrupted. The dual-main hot standby solution based on Keepalived is a powerful means to achieve this goal, but it cannot be solved by simple configuration, and there are many pitfalls in it. This article will give you an in-depth understanding and let you truly master this solution. After reading it, you can not only build it, but also deal with various emergencies.

Let’s talk about the basics first: What is Keepalived? It is a virtual IP (VIP) management tool that can monitor your database instance. Once the main library is hung, it can quickly switch VIP to the backup library to ensure that the service is not interrupted. It sounds simple, but the devil is hidden in the details. MySQL dual master hot standby means that both database servers can write data, and data synchronization is the key. This usually requires the use of MySQL replication functions, such as GTID replication, to ensure data consistency. Without data consistency, your hot backup becomes a joke.

The core lies in understanding the working mechanism of Keepalived. It mainly relies on the VRRP protocol (virtual routing redundant protocol) to realize VIP switching. Keepalived will send heartbeat packets to other Keepalived instances periodically. If the master node heartbeat is detected to be lost, it will take over the VIP and turn itself into a new master. This sounds beautiful, but in actual operation, you need to finely configure the various parameters of Keepalived, such as priority, detection interval, reservation time, etc. The wrong parameter configuration may cause the VIP switching to fail or the brain split phenomenon (both nodes think they are the master node).

Let's take a look at a simple example and feel the configuration of Keepalived:

 <code class="language-bash">vrrp_script check_mysql {</code><pre class='brush:php;toolbar:false;'> script "/usr/local/bin/check_mysql.sh"
interval 2
weight 100

}

vrrp_instance VI_1 {

 state MASTER
virtual_router_id 51
priority 100
interface eth0
virtual_ipaddress 192.168.1.100
virtual_ipaddress 192.168.1.101
track_script check_mysql

}

This configuration defines a VRRP instance named VI_1 , listening to the eth0 interface, with virtual IPs of 192.168.1.100 and 192.168.1.101 . The check_mysql.sh script is responsible for checking whether the MySQL service is running normally. The point is track_script , which allows Keepalived to monitor the state of MySQL. If MySQL is hung up, Keepalived will automatically switch VIPs according to the configuration. The check_mysql.sh script needs to be written by itself, and it usually checks whether the MySQL process is running and whether the database connection is normal.

Of course, this is just the most basic usage. Advanced usage includes: using different monitoring scripts to monitor more comprehensive metrics; configuring multiple VIPs to achieve load balancing; using other Keepalived functions, such as health checks, etc.

Let’s talk about common pitfalls. First of all, network jitter will affect Keepalived's heartbeat detection, resulting in misjudgment. Secondly, improper MySQL replication configuration may lead to inconsistent data. Again, the configuration of Keepalived itself also needs to be carefully considered. An incorrect configuration of one parameter may cause the entire system to be paralyzed. To debug these problems, you need to carefully analyze the Keepalived logs and troubleshoot them in combination with MySQL logs.

Lastly, on performance optimization and best practices. Choosing the right hardware, such as high-performance servers and network devices, can improve system stability and performance. Regular backup of databases can reduce the risk of data loss. A reasonable monitoring strategy can promptly detect potential problems. The most important thing is to have an in-depth understanding of the entire system so that you can quickly locate and solve problems when encountering them. Remember, high availability is not achieved overnight and requires continuous maintenance and optimization. Don't forget that the readability and maintainability of the code are also important. Writing clear and easy-to-understand code can save you a lot of time and energy in the future.

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