Spring Cloud series 5 Eureka cluster synchronization, self-protection mode and instance registration, heartbeat, offline

Cluster related important class com.net flix. Eureka. Registry. PeerAwareInstanceRegistryImpl: To ensure that the status of all Eureka Server nodes in the cluster is synchronized, all the following operations are synchronized to all services in the cluster: Registers, Renewals, Cancels, Expirations and Status Changes of services. Here are some partial methods:

• SyncUp: When the Eureka Server is restarted or a new Eureka Server node is added, initialization is performed to obtain all instance registration information from other nodes in the cluster, so that the service can be provided normally. When Eureka Server starts, it gets all registration information from other nodes, and if it fails to get synchronization, it denies service for a period of time (this value is determined).
• ReplicateToPeers: Registers, Renewals, Cancels, Expirations and Status Changes will be synchronized to all cluster nodes.
• Register: Registers the instance and copies the instance information to all eureka server nodes. If other Eureka servers call this node, the instance information is updated only on this node, avoiding notifying other nodes to perform the update
• Renew: Heartbeat, synchronize cluster
• cancel
• other

The states of Eureka Server clusters are asynchronously synchronized. Therefore, it is not guaranteed that the states of Eureka Server clusters are consistent, but the final state is basically guaranteed.

The Service Provider provides services externally and registers itself with the Eureka Server. If the configuration parameters of eureka. Client. RegisterWithEureka = true (default true), to the eureka Server registration for registration, eureka Server will save the registration information into memory.

Service Consumer in order to avoid each call to the Service request need to Eureka Server for a Service instance registration information, right now you need to set up Eureka. Client. FetchRegistry = true, it will be in the local cache all instances registration information. To ensure the validity of cached data, it periodically updates instances to the registry (the value is defined by eureka.client.registrie-fetch -interval-seconds, default is 30s).

There are two cases of a service being taken offline:

• When the Service Provider Service is shutdown, it notifies the Eureka Server to remove it, preventing clients from invoking the offline Service.
• Eureka Server will be timed (eureka.server.eviction-interval-timer-in-ms, default is 0, instances will not be deleted by default) for checking. If the instance does not receive heartbeat within a certain period (defined by eureka.instance.lease-expiration-duration-in-seconds, 90s by default), the instance is deregister.

In this case, The maximum value of the Eureka Client is [eureka.instance.lease-renewal- interval-seconds +] Eureka.client. registry-fetch-interval-seconds] indicates that the service is offline. Similarly, after a new service is online, the service consumers of Eureka Client need at most the same amount of time to discover that the service is online

When the service goes offline, it will be updated to the cache of other nodes of Eureka Server and Eureka Client. The process is similar to the register process above

The demo configuration is as follows:

server: port: 10761 spring: application: name: Cloud-registration-center ## Eureka: primary configuration property in EurekaInstanceConfigBean and EurekaClientConfigBean PreferIpAddress: true; lease-renewal- interval-seconds: Lease -expiration-duration-in-seconds: 7 Client: # Disable eureka client # enabled: False # registerWithEureka: true # fetchRegistry: False # How often does the client update the Eureka Server information from the Eureka Server cluster eureka-service-url-poll-interval-seconds Registrie-fetch -interval-seconds: 5 registrie-fetch -interval-seconds: http://127.0.0.1:10761/eureka/ # set in eureka server address, can simultaneously to multiple service registration # defaultZone: http://192.168.21.3:10761/eureka/, http://192.168.21.4:10761/eureka/ server: # renewal - percent - threshold: 0.1 # disable self-preservation mode enable-self-preservation mode If enable-self-preservation=true, set this parameter to true. # renewal-percent-threshold: Eviction -interval-timer-in-ms, iction is designed to be used at any time. The default is 0 eviction-interval-timer-in-ms. If the Eureka Server fails to obtain the registration information from the neighboring Eureka Server, how long does it wait to provide the registration service? 6000000 # Time frequency for updating node information between clusters peer-eureka-nodes-update-interval-ms: 60000Copy the code