ZooKeeper
ZooKeeper is a distributed, open-source coordination service for distributed applications. It provides a high-performance and reliable coordination environment for distributed applications, allowing them to dynamically manage their configuration, discover services, and synchronize activities. ZooKeeper is designed to be easy to manage, reliable and secure, making it an ideal framework for managing distributed applications.
ZooKeeper can select a new leader in the cluster by electing a node to become the leader. This leader election process is based on the ZooKeeper Atomic Broadcast protocol. The leader is responsible for managing the state of the cluster, and ensuring that the cluster remains highly available and consistent. The leader also coordinates updates to the cluster state and ensures that any updates are propagated to all nodes in the cluster. To ensure fast leader election and cluster stability, ZooKeeper uses an algorithm called Fast Leader Election (FLE). FLE ensures that the leader election completes quickly and without interruption, even if some nodes in the cluster fail. This helps to ensure that the cluster is able to quickly recover from any disruptions or outages, allowing distributed applications to remain operational and consistent.
Eureka
Eureka is a cloud-native service registry for microservices. It provides an easy-to-use service registry, allowing services to register and discover other services in the network. Eureka makes it easy to manage service registrations, health checks, and metadata, helping to ensure that services remain available and perform optimally. It also provides built-in support for advanced features such as service routing, load balancing, and failover.
Eureka also provides a peer mode, which allows services to register and discover services in a distributed manner. In peer mode, the Eureka cluster is composed of multiple nodes, each of which stores a copy of the service registry and is responsible for maintaining the consistency of the registry. The nodes in the cluster communicate with each other to synchronize the state of the service registry, ensuring that all nodes in the cluster have the same view of the registry. This ensures that services can be discovered and accessed in a consistent way, regardless of which node is used to access the registry.