Galera Cluster, while often overlooked, is a sophisticated and robust database solution whose full potential is frequently misunderstood. While many IT professionals are aware of its existence, they usually fail to grasp the depth of its capabilities. Understanding Galera's true strengths can unlock significant improvements in database operations, making it a hidden gem in the world of high-availability database solutions.
Galera Cluster is a synchronous multi-master database cluster technology that has revolutionized high-availability solutions for MariaDB/MySQL databases. Here's a brief introduction : Galera Cluster was developed by Codership Oy, a Finnish company founded in 2007. The technology was released with the goal of addressing limitations in traditional MariaDB/MySQL replication methods.
It's main keypoints are :
- True multi-master replication
- virtually synchronous replication
- Active-active high availability
It's main main benefits are :
- Almost no slave lag
- Automatic node provisioning (and restoration)
- Strong consistency across the cluster
Write-set replication is a key feature of Galera Cluster that ensures data consistency across all nodes in the cluster. In this approach, each transaction is captured as a write-set, which contains all the changes made to the database during that transaction. This write-set is then replicated to all nodes in the cluster simultaneously, ensuring that every node receives the same information. Once a write-set arrives at a node, it undergoes a certification process. This certification is a crucial step that determines whether the transaction can be applied without conflicts. The process checks if the write-set conflicts with any transactions that have been committed since the original transaction began. If no conflicts are detected, the transaction is committed on all nodes, maintaining consistency across the entire cluster. This combination of write-set replication and certification ensures that all nodes in the Galera Cluster remain synchronized and consistent, even in the face of concurrent writes to different nodes.
Galera Cluster excels in scenarios demanding:
- High Availability: It provides seamless failover with no data loss, ensuring continuous database operations even if a node fails.
- Strong Consistency: All nodes remain synchronized, eliminating issues like slave lag common in traditional replication setups.
Scalability: Easily add or remove nodes to handle varying workloads, making it ideal for cloud environments. - Multi-Master Writes: Allows writes to any node, improving performance and flexibility for distributed applications.
- Geographic Distribution: Supports efficient replication across multiple data centers, enhancing disaster recovery capabilities.
- Read-Heavy Workloads: Provides excellent read scalability by allowing reads from any node.
- Near Real-Time Replication: Synchronous replication ensures all nodes have up-to-date data almost instantly.
Yet, while powerful, Galera is not a one-size-fits-all solution and has several important limitations that make it unsuitable for certain scenarios :
- Large Transactions: requires special setup and intimitate knowledge of said transactions to handle large ones.
- Unstable Networks: Performance and availability may suffer in environments with unreliable network connections due to its synchronous replication model.
- Write-Heavy Workloads: Not ideal for applications that rely heavily on write operations.
- Unsupported Storage Engines: Fully supports only the InnoDB storage engine, making it unsuitable for systems that could benefit from other engines.
- Very low Latency Requirements: Not recommended for applications needing close to real-time behavior, as synchronous replication does introduce some delays here and there.
- Unsupported SQL Operations: Issues may arise with unsupported SQL operations like explicit LOCK TABLES.
Galera Cluster represents a significant advancement in database replication technology, offering a robust solution for organizations seeking high availability, strong consistency, and scalability. Its multi-master architecture, coupled with synchronous replication, ensures data integrity across all nodes while providing the flexibility to read and write anywhere. Galera's ability to easily scale and its support for geographic distribution make it particularly well-suited for modern, distributed environments. While not a universal solution for all database needs, Galera Cluster excels in specific scenarios. As businesses continue to have need for reliable and scalable database solutions, Galera Cluster stands out as a powerful option that can meet the demanding requirements of today's data-driven applications.
As any tool, just dont use it to solve the wrong issue.
published in linkedin : https://www.linkedin.com/pulse/galera-often-overlooked-still-powerful-sylvain-arbaudie-aabce/
