Eureka vs Zookeeper: What are the differences?

Introduction:

Eureka and Zookeeper are both popular open-source tools used for service discovery and coordination in distributed systems. While they serve similar purposes, there are key differences between the two.

1. Architecture: Eureka is based on a client-server architecture, where there is a centralized server that keeps track of service instances, while the clients register with the server. On the other hand, Zookeeper follows a distributed architecture where multiple servers form a clustered ensemble, providing high availability.

2. Data Consistency: Eureka prioritizes availability over consistency. It uses an eventual consistency model, where there might be some delay in propagating updates across all instances. In contrast, Zookeeper emphasizes consistency and uses a strong consistency model, ensuring that all clients see the same view of the data at any given time.

3. Service Monitoring: Eureka provides built-in health monitoring of services, regularly checking if they are up or down. It automatically handles instances that are not responsive or healthy. In Zookeeper, monitoring of services needs to be implemented separately using custom solutions.

4. Service Discovery Mechanism: Eureka uses a peer-to-peer replication mechanism for service discovery. Clients periodically fetch the registry information from the Eureka server and cache it locally. Zookeeper, on the other hand, maintains a hierarchical namespace called Znodes, which clients can access to discover and coordinate services.

5. Availability and Scalability: Eureka is designed to be highly available and scales horizontally. It provides self-preservation mechanisms that prevent cascading failures and allow the system to continue working even if some instances fail. Zookeeper ensures high availability by replicating data across the ensemble, and it can handle a large number of concurrent clients.

6. Integration with Other Technologies: Eureka is particularly well-suited for integration with Spring Cloud ecosystem, providing seamless integration with Spring Boot applications. Zookeeper, being a general-purpose coordination service, can be integrated with various platforms and frameworks, making it more versatile for different use cases.

In summary, Eureka and Zookeeper differ in their architecture, data consistency models, service monitoring approaches, service discovery mechanisms, availability and scalability features, as well as integration capabilities with other technologies.