Eureka as a component of service registration and discovery, Eureka2.0 already closed source, but this tutorial is to Eureka as the core expansion.
1, three modules
Spring Cloud Eureka is one of a suite of services Netflix micro Spring Cloud, based Netflix Eureka made a second package, is responsible for completion of the service management function micro-service architecture.
three important modules eueka's, Eureka-Server, Service-Provider, Service-Consumer
Eureka-Server: server, service registration and discovery;
Eureka-Client-Service-Provider: server, service provider, via http rest informed server registration, update, cancel the service;
Eureka-client-service-consumer: client, service consumers, need to get the address of a list of services from the server via http rest, and then with some of the load balancing policy (ribbon) to invoke server service.
2、eureka-server
Eureka Server service registration data storage layer is double ConcurrentHashMap (thread-safe and efficient Map collection).
The first layer key = spring.application.name application name is registered client instance; value is nested ConcurrentHashMap.
Unique instance ID key of the second layer = instanceId i.e. services, value of the object Lease, Lease object store registration information of all of this example, including IP, port, and other properties.
Declare statement is as follows:
Private of ConcurrentHashMap Final <String, the Map <String, Lease <InstanceInfo >>> Registry of ConcurrentHashMap new new = <String, the Map <String, Lease <InstanceInfo >>> ();
Service Registry is not persisted to the database, I think it is right for performance reasons. After all, the registry information is need to regularly get updated.
3. Create a service registry --demo
3.1, dependent on the introduction pom.xml
<dependencies> <!--www.1b23.com--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies>
3.2, eureka server startup code
//www.1b23.com
@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication { public static void main(String[] args) { SpringApplication.run(EurekaServerApplication.class, args);
}
}
@EnableEurekaServer main role is to initiate EurekaServer operating environment and context.
3.3, application configuration files
application configuration file can be xml or yml structure, I prefer xml structure, yml is indented format, I think the easier wrong.
server.port=8080
spring.application.name: eureka-server
Hostname # service registry instance
eureka.instance.hostname: localhost
# Indicates whether to register themselves on EurekaServer, the default is true. Due to the current application is EurekaServer, it is set to false
eureka.client.register-with-Eureka: false
#表示表示是否从EurekaServer获取注册信息，默认为true。单节点不需要同步其他的EurekaServer节点的数据
eureka.client.fetch-registry: false
#设置Eureka的地址
eureka.client.service-url.defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
3.4、查看eureka server
访问http://localhost:8080/地址。如图上部分
Environment: 环境，默认为test，生产环境建议改下，看着顺眼
Data center： 数据中心，生产环境建议改下
Current time：当前的系统时间
Uptime：已经运行了多少时间
Lease expiration enabled：是否启用租约过期 ，自我保护机制关闭时，该值默认是true， 自我保护机制开启之后为false。
Renews threshold： 每分钟最少续约数，Eureka Server 期望每分钟收到客户端实例续约的总数。
Renews (last min)： 最后一分钟的续约数量（不含当前，1分钟更新一次），Eureka Server 最后 1 分钟收到客户端实例续约的总数。
页面下部分：
total-avail-memory : 总共可用的内存
environment : 环境名称，默认test
num-of-cpus : CPU的个数
current-memory-usage : 当前已经使用内存的百分比
server-uptime : 服务启动时间
registered-replicas : 相邻集群复制节点
unavailable-replicas ：不可用的集群复制节点，
available-replicas ：可用的相邻集群复制节点
ipAddr：eureka服务端IP
status：eureka服务端状态