Configuration and conflict resolution of Galera Cluster multi-master cluster

Galera Cluster is a database cluster architecture based on multi-master replication, with the advantage that all nodes can receive write requests at the same time. When building a Galera cluster, you need to pay attention to: 1. Ensure that the node resources are sufficient and the network is stable; 2. Carefully configure the my.cnf file, especially the wsrep_provider_options and gcache.size parameters; 3. Correctly initialize the cluster and monitor the logs. Even if the configuration is correct, conflicts may occur. They need to be resolved through log analysis and application layer policies, and performance can be improved through network optimization, parameter tuning and application layer optimization. Continuous monitoring and log analysis are key to maintaining Galera clusters.

Galera Cluster: The charm and challenges of multi-main architecture

Many developers are discouraged by multi-main database clusters, thinking that they are complex and difficult to manage, and even think that they are inherently prone to problems. In fact, this is not the case. Galera Cluster, an architecture based on multi-main replication, has advantages that are incomparable to a single-main architecture in some scenarios. This article will talk about the configuration of Galera Cluster, potential conflicts, and how to resolve these issues gracefully. After reading it, you will have a deeper understanding of the operating mechanism of Galera Cluster and master some practical troubleshooting techniques.

Basic knowledge lays the foundation: Galera's kernel

The core of Galera Cluster is its Write-Set-based replication mechanism. This is not a simple database master-slave replication, but all nodes can receive write requests at the same time and ensure data consistency through a clever algorithm. The core of this algorithm is Write-Set, which tracks the rows of data modified by each transaction. By comparing Write-Set, Galera is able to detect conflicts and adopt corresponding strategies to resolve them. This is essentially different from the traditional log replication-based architecture. Understanding the Write-Set mechanism is the key to understanding Galera.

Configuring Galera: Take a step by step

Building a Galera Cluster is not easy, you need to carefully consider several key factors:

• Node selection: Ensure that all nodes have sufficient CPU, memory and storage resources, and that the network connection is stable and low latency. Network jitter is a nightmare for Galera clusters, which directly leads to conflicts and data inconsistencies.
• Configuration file: Galera's configuration file (usually my.cnf ) needs to be carefully configured, such as wsrep_provider_options . This parameter determines which storage engine Galera uses, as well as some important replication parameters. There are many mysteries here, and if you are not careful, it will lead to cluster instability. For example, setting the gcache.size parameter too small will lead to frequent synchronization and affect performance; setting it too large will waste memory. You need to adjust based on the actual data volume and load.
• Cluster Initialization: The cluster initialization process is crucial. You need to make sure that all nodes are joined to the cluster correctly and that data is synchronized. This process requires patience and close attention to the log.

Code example: A simple three-node cluster configuration fragment

 <code class="language-mysql">[mysqld]<br> wsrep_on = ON<br> wsrep_cluster_name = my_galera_cluster<br> wsrep_provider = /usr/lib/galera/libgalera_smm.so<br> wsrep_cluster_address = gcomm://node1,node2,node3<br> wsrep_node_name = node1 # 每个节点需修改此参数<br>wsrep_node_address = 192.168.1.101 # 每个节点需修改此参数<br>innodb_autoinc_lock_mode = 2</code> 

Remember, the above is just an example, you need to modify the corresponding parameters according to your actual environment.

Conflict handling: the key to resolving conflicts

Even if the configuration is correct, conflicts may still occur in the Galera cluster. This is usually because multiple nodes modify the same data row at the same time. Galera will try to resolve these conflicts automatically, but sometimes requires manual intervention.

• Conflict detection: Galera will detect conflicts by comparing Write-Set. If a conflict is detected, it tries to resolve it using a different strategy, for example, selecting a modification of a node as the end result, or rolling back the transaction.
• Conflict Log: Pay close attention to Galera's logs, which will log all conflict events. Analyzing these logs can help you understand the causes of the conflict and take corresponding measures.
• Application layer policy: Sometimes, you need to take measures at the application layer to avoid conflicts. For example, use optimistic locks or pessimistic locks to control concurrent access.

Performance Optimization and Best Practices

The performance of Galera Cluster is affected by many factors, such as network latency, node resources, and code quality at the application layer.

• Network optimization: Ensure stable network connections and low latency. High-speed network connections can be used and network congestion can be avoided.
• Parameter tuning: Adjust Galera's configuration parameters according to the actual load, such as gcache.size and wsrep_incoming_addresses .
• Application layer optimization: Avoid unnecessary database operations, use appropriate indexes, and optimize SQL statements.

Galera Cluster is a powerful tool, but it also requires careful configuration and management. Only by understanding its underlying mechanism and mastering some troubleshooting techniques can we give full play to its advantages and avoid falling into various pitfalls. Remember, monitoring and log analysis are key to maintaining Galera clusters. Only by continuing to learn and practice can you become an expert in Galera Cluster.

The above is the detailed content of Configuration and conflict resolution of Galera Cluster multi-master cluster. For more information, please follow other related articles on the PHP Chinese website!