Service Discovery: Eureka Clients
Eureka Client篇
1. 引入Client？
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Camden.SR5</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
2. 注册Client？
当客户端向服务器注册的时候，客户端会提供元数据，such as host and port, health indicator URL, home page etc。
Euraka从每一个客户端接收心跳包。如果指定的时间内没有收到心跳包，那么将会删除注册。
两种方式：
- @EnableEurekaClient。Eureka专用
- @EnableDiscoveryClient。通用
3. EnableEurekaClient ？
EnableEurekaClient 注释可以是应用拥有两种角色：
- instance。it registers itself
- client。 it can query the registry to locate other services
4. ServiceInstance接口？
DiscoveryClient：
public interface DiscoveryClient {
String description();
ServiceInstance getLocalServiceInstance();
List<ServiceInstance> getInstances(String var1);
List<String> getServices();
}
public interface ServiceInstance {
String getServiceId();
String getHost();
int getPort();
boolean isSecure();
URI getUri();
Map<String, String> getMetadata();
}
可以看出：
- 主要是获取url，元数据。
5. @EurekaClient？
可以查询Application，Instance，InstanceStatus
6. EurekaClientConfigBean & eureka.client.*
@ConfigurationProperties("eureka.client")
public class EurekaClientConfigBean implements EurekaClientConfig, EurekaConstants {
public static final String PREFIX = "eureka.client";
@Autowired(
required = false
)
PropertyResolver propertyResolver;
public static final String DEFAULT_URL = "http://localhost:8761/eureka/";
public static final String DEFAULT_ZONE = "defaultZone";
private static final int MINUTES = 60;
private boolean enabled = true;
private EurekaTransportConfig transport = new CloudEurekaTransportConfig();
/**
* Indicates how often(in seconds) to fetch the registry information from the eureka
* server.
*/
private int registryFetchIntervalSeconds = 30;
/**
* Indicates how often(in seconds) to replicate instance changes to be replicated to
* the eureka server.
*/
private int instanceInfoReplicationIntervalSeconds = 30;
/**
* Indicates how long initially (in seconds) to replicate instance info to the eureka
* server
*/
private int initialInstanceInfoReplicationIntervalSeconds = 40;
/**
* Indicates how often(in seconds) to poll for changes to eureka server information.
* Eureka servers could be added or removed and this setting controls how soon the
* eureka clients should know about it.
*/
private int eurekaServiceUrlPollIntervalSeconds = 300;
private String proxyPort;
private String proxyHost;
private String proxyUserName;
private String proxyPassword;
/**
* Indicates how long to wait (in seconds) before a read from eureka server needs to
* timeout.
*/
private int eurekaServerReadTimeoutSeconds = 8;
/**
* Indicates how long to wait (in seconds) before a connection to eureka server needs
* to timeout. Note that the connections in the client are pooled by
* org.apache.http.client.HttpClient and this setting affects the actual connection
* creation and also the wait time to get the connection from the pool.
*/
private int eurekaServerConnectTimeoutSeconds = 5;
private String backupRegistryImpl;
private int eurekaServerTotalConnections = 200;
private int eurekaServerTotalConnectionsPerHost = 50;
private String eurekaServerURLContext;
private String eurekaServerPort;
private String eurekaServerDNSName;
private String region = "us-east-1";
private int eurekaConnectionIdleTimeoutSeconds = 30;
private String registryRefreshSingleVipAddress;
private int heartbeatExecutorThreadPoolSize = 2;
private int heartbeatExecutorExponentialBackOffBound = 10;
private int cacheRefreshExecutorThreadPoolSize = 2;
private int cacheRefreshExecutorExponentialBackOffBound = 10;
private Map<String, String> serviceUrl = new HashMap();
private boolean gZipContent;
private boolean useDnsForFetchingServiceUrls;
private boolean registerWithEureka;
private boolean preferSameZoneEureka;
private boolean logDeltaDiff;
private boolean disableDelta;
private String fetchRemoteRegionsRegistry;
...
7. EurekaInstanceConfigBean？
@ConfigurationProperties("eureka.instance")
public class EurekaInstanceConfigBean implements CloudEurekaInstanceConfig, EnvironmentAware {
private static final String UNKNOWN = "unknown";
private HostInfo hostInfo;
private InetUtils inetUtils;
private String appname = "unknown";
private String appGroupName;
private boolean instanceEnabledOnit;
private int nonSecurePort = 80;
private int securePort = 443;
private boolean nonSecurePortEnabled = true;
private boolean securePortEnabled;
/**
* Indicates how often (in seconds) the eureka client needs to send heartbeats to
* eureka server to indicate that it is still alive. If the heartbeats are not
* received for the period specified in leaseExpirationDurationInSeconds, eureka
* server will remove the instance from its view, there by disallowing traffic to this
* instance.
*
* Note that the instance could still not take traffic if it implements
* HealthCheckCallback and then decides to make itself unavailable.
*/
private int leaseRenewalIntervalInSeconds = 30;
/**
* Indicates the time in seconds that the eureka server waits since it received the
* last heartbeat before it can remove this instance from its view and there by
* disallowing traffic to this instance.
*
* Setting this value too long could mean that the traffic could be routed to the
* instance even though the instance is not alive. Setting this value too small could
* mean, the instance may be taken out of traffic because of temporary network
* glitches.This value to be set to atleast higher than the value specified in
* leaseRenewalIntervalInSeconds.
*/
private int leaseExpirationDurationInSeconds = 90;
private String virtualHostName = "unknown";
private String instanceId;
private String secureVirtualHostName = "unknown";
private String aSGName;
private Map<String, String> metadataMap = new HashMap();
private DataCenterInfo dataCenterInfo;
private String ipAddress;
private String statusPageUrlPath;
private String statusPageUrl;
private String homePageUrlPath;
/**
* Gets the absolute home page URL for this instance. The users can provide the
* homePageUrlPath if the home page resides in the same instance talking to eureka,
* else in the cases where the instance is a proxy for some other server, users can
* provide the full URL. If the full URL is provided it takes precedence.
*
* It is normally used for informational purposes for other services to use it as a
* landing page. The full URL should follow the format http://${eureka.hostname}:7001/
* where the value ${eureka.hostname} is replaced at runtime.
*/
private String homePageUrl;
private String healthCheckUrlPath;
private String healthCheckUrl;
private String secureHealthCheckUrl;
private String namespace;
private String hostname;
private boolean preferIpAddress;
private InstanceStatus initialStatus;
private String[] defaultAddressResolutionOrder;
private Environment environment;
public String getHostname() {
return this.getHostName(false);
}
private EurekaInstanceConfigBean() {
this.dataCenterInfo = new MyDataCenterInfo(Name.MyOwn);
this.statusPageUrlPath = "/info";
this.homePageUrlPath = "/";
this.healthCheckUrlPath = "/health";
this.namespace = "eureka";
this.preferIpAddress = false;
this.initialStatus = InstanceStatus.UP;
this.defaultAddressResolutionOrder = new String[0];
}
public EurekaInstanceConfigBean(InetUtils inetUtils) {
this.dataCenterInfo = new MyDataCenterInfo(Name.MyOwn);
this.statusPageUrlPath = "/info";
this.homePageUrlPath = "/";
this.healthCheckUrlPath = "/health";
this.namespace = "eureka";
this.preferIpAddress = false;
this.initialStatus = InstanceStatus.UP;
this.defaultAddressResolutionOrder = new String[0];
this.inetUtils = inetUtils;
this.hostInfo = this.inetUtils.findFirstNonLoopbackHostInfo();
this.ipAddress = this.hostInfo.getIpAddress();
this.hostname = this.hostInfo.getHostname();
}
}
7.1 状态页和健康检查
eureka:
instance:
statusPageUrlPath: ${management.context-path}/info
healthCheckUrlPath: ${management.context-path}/health
7.2 启用health
eureka:
client:
healthcheck:
enabled: true
8. 认证？
eureka.client.serviceUrl.defaultZone http://user:password@localhost:8761/eureka
9. 元数据？
基础：hostname, IP address, port numbers, status page and health check. 其他：eureka.instance.metadataMap