Corosync is an open-source cluster messaging and membership library used for implementing high availability (HA) and fault-tolerant systems. It provides the underlying communication infrastructure for many clustering solutions, including the Linux-HA project and Pacemaker. Let’s explore its history and features:

History of Corosync:
– Corosync originated as the Next Generation OpenAIS (Application Interface Specification) project in 2005. It was initially developed to replace the aging OpenAIS project, which aimed to provide a standard interface for cluster communication.
– In 2008, the project was renamed to Corosync to reflect its focus on reliable cluster messaging. It became a standalone project and gained popularity in the open-source HA clustering community.
– Corosync has since evolved through collaborative development efforts, with contributions from various organizations and individuals.

Features of Corosync:
1. Cluster Communication: Corosync provides a reliable and efficient messaging layer for interprocess communication among cluster nodes. It allows nodes to exchange cluster-related information and synchronize their activities.
2. Membership and Quorum: Corosync manages the membership of cluster nodes, detecting node failures or additions to the cluster. It ensures that only healthy and active nodes participate in cluster operations. Additionally, Corosync supports quorum configurations to ensure consistent decision-making in case of network partitions or node failures.
3. Fault Detection and Recovery: Corosync monitors the health of cluster nodes and detects failures. Upon detecting a failure, it triggers appropriate recovery actions, such as initiating failover or restarting failed resources.
4. Scalability: Corosync is designed to scale from small clusters with a few nodes to large-scale deployments with hundreds or even thousands of nodes. It efficiently handles the communication and coordination required in distributed environments.
5. High Performance: Corosync is optimized for performance, offering low-latency and high-throughput cluster messaging. It leverages advanced network protocols and techniques to minimize overhead and deliver efficient communication.
6. Flexible Configuration: Corosync allows flexible configuration to adapt to different cluster environments. Administrators can define parameters such as network interfaces, communication protocols, messaging reliability settings, and encryption options.
7. Integration with Cluster Resource Managers: Corosync seamlessly integrates with cluster resource managers like Pacemaker, enabling comprehensive high availability and resource management solutions. It forms the communication backbone for the cluster stack, enabling cluster-wide coordination and decision-making.
8. Reliability and Robustness: Corosync is designed to provide high reliability and fault tolerance. It utilizes mechanisms like heartbeat messages, quorum calculations, and fault detection algorithms to ensure the stability and availability of cluster services.
9. Active Development and Community Support: Corosync benefits from an active development community and ongoing improvements. It is backed by a community of users and developers who contribute to its development, support, and maintenance.
10. Open-Source and Platform Agnostic: Corosync is open-source and can run on various operating systems, including Linux distributions. Its open nature encourages community involvement, customization, and integration with other open-source projects.

Corosync plays a crucial role in enabling reliable cluster communication and coordination in high availability environments. Its robust feature set, scalability, and community support make it a popular choice for implementing fault-tolerant systems and building resilient clusters.