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Friday, February 9, 2018

Eureka (Netflix Registry)

Eureka is a Registry offered by Netflix that is based on a REST API. Eureka consists of two components: 
  • Eureka Server: a running instance of Eureka;
  • Eureka Client: a framework part of an application.

Eureka Client 

Eureka Client registers to an Eureka Server and sends an heartbeat every 30 seconds in order to inform Eureka server that the client instance is still alive.

Eureka Server 

The Eureka Client registers with Eureka Server and after fetching registry information, it stores locally and every 30 seconds, it refreshes those information.

  • If Eureka Server does not receive heartbeat over a configurable time, the Eureka Client instance is removed from the registry.
  • If the Eureka Server receives less heartbeat than forecasting, it goes into self-preservation: it stops expiring already registered instances.

Eureka is a registry that comes with different modes:
  1. Standalone
  2. Peer Aware

  • Eureka achieves high availability by a synchronization among Eureka peers. 
  • Eureka Server are aware of other instances, in fact every Eureka Server acts as Eureka Client and registers to its peer. 
  • Eureka Servers replicate registry information with peers. 

Eureka Client and Availability Zone

  • Eureka Client uses the same Availability Zone by default (a concept that matches the Availability Zone and Region of AWS cloud platform).  
  • Eureka Client manages failover by using service url from other zones.

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