Eureka caching mechanism

One, Eureka Server

Eureka Server existence of three variables :( Registry, readWriteCacheMap, readOnlyCacheMap ) Save the service registration information, by default scheduled task to synchronize every 30s will readWriteCacheMap readOnlyCacheMap, clean up every 60s over 90s not to renew node, Eureka Client updates every 30s from readOnlyCacheMap service registration information, and UI service registration information from the registry update

Three-level cache

Cache	Types of	Explanation
registry	ConcurrentHashMap	Real-time updates , AbstractInstanceRegistry class member variables, UI client requests service registration information is here
readWriteCacheMap	Guava Cache/LoadingCache	Real-time updates , ResponseCacheImpl class member variables, buffer time 180 seconds
readOnlyCacheMap	ConcurrentHashMap	Cycle update , ResponseCacheImpl class member variable, by default every 30s from readWriteCacheMap update, Eureka client update here from the default service registration information, can be configured to update directly from readWriteCacheMap

Cache configuration

Configuration	default	Explanation
eureka.server.useReadOnlyResponseCache	true	Client from readOnlyCacheMap update data, false is skipped readOnlyCacheMap updates directly from readWriteCacheMap
eureka.server.responsecCacheUpdateIntervalMs	30000	readWriteCacheMap update to readOnlyCacheMap cycle, default 30s
eureka.server.evictionIntervalTimerInMs	60000	清理未续约节点周期，默认60s
eureka.instance.leaseExpirationDurationInSeconds	90	清理未续约节点超时时间，默认90s

二、Eureka Client

Eureka Client存在两种角色：服务提供者和服务消费者，作为服务消费者一般配合Ribbon或Feign（Feign内部使用Ribbon）使用。Eureka Client启动后，作为服务提供者立即向Eureka Server注册，默认情况下每30s续约；作为服务消费者立即向Server全量更新服务注册信息，默认情况下每30s增量更新服务注册信息；Ribbon延时1s向Client获取使用的服务注册信息，默认每30s更新使用的服务注册信息，只保存状态为UP的服务。

二级缓存

缓存	类型	说明
localRegionApps	AtomicReference	周期更新，类DiscoveryClient成员变量，Eureka Client保存服务注册信息，启动后立即向Server全量更新，默认每30s增量更新
upServerListZoneMap	ConcurrentHashMap	周期更新，类LoadBalancerStats成员变量，Ribbon保存使用且状态为UP的服务注册信息，启动后延时1s向Client更新，默认每30s更新

缓存相关配置

配置	默认	说明
eureka.instance.leaseRenewalIntervalInSeconds	30	Eureka Client续约周期，默认30s
eureka.client.registryFetchIntervalSeconds	30	Eureka Client incremental update period, default 30s (normally incremental update, timeout, or the like is inconsistent with the Server side where the total amount Update)
ribbon.ServerListRefreshInterval	30000	Ribbon update cycle, default 30s