Galera is a synchronous multi-master replication library developed by Codership Oy that implements the write set replication interface for distributed database clustering. Written primarily in C++, the library enables multiple database nodes to maintain synchronized copies of data in real-time, supporting multi-primary architectures where any node can accept write operations. The software is distributed under GPLv2 and serves as the core replication engine for MariaDB and MySQL-based clusters, providing fault tolerance and high availability through data consistency mechanisms across distributed systems.
The repository implements the wsrep API specification, which defines how database servers communicate replication events and maintain cluster state. This design allows Galera to work as a pluggable replication solution for MySQL-compatible databases, enabling organizations to convert single-master database deployments into multi-master clusters without requiring application-level changes. The library handles the complex coordination required to ensure that all nodes in a cluster apply transactions in the same order and maintain identical data states, even when network partitions or node failures occur.
Building Galera requires CMake, the Check unit test library, Boost development packages, and OpenSSL development packages, with optional support for the Asio C++ library. The repository includes platform-specific build instructions for Ubuntu 20.04 and later as well as RHEL 8 and later systems. The build process supports creating a MySQL/Galera demo distribution by integrating with the mysql-wsrep repository, allowing developers to test the replication library with a complete MySQL installation.
The repository's classification spans multiple related domains including galera cluster management, multi-master clustering, synchronous replication, real-time synchronization, and distributed database systems. Its integration with MySQL and MariaDB ecosystems positions it as a critical component for organizations requiring high-availability database infrastructure.
Galera addresses the challenge of maintaining data consistency across geographically distributed or logically separated database nodes while allowing applications to read and write to any node in the cluster. This capability eliminates single points of failure inherent in traditional master-slave replication architectures and enables load balancing of both read and write operations across multiple database instances.
