Eureka重要對象簡介

在進行分析EurekaClient和EurekaServer之間通信的源碼之前，我們首先需要熟悉一下幾個實體類

InstanceInfo

這個類代表著EurekaClient實例，客戶端向服務端請求註冊時就會攜帶著這個實例，這個實例中包含了當前客戶端的一些基本信息：

    private volatile String instanceId;

    private volatile String appName;
    @Auto
    private volatile String appGroupName;

    private volatile String ipAddr;

    private static final String SID_DEFAULT = "na";
    @Deprecated
    private volatile String sid = SID_DEFAULT;

    private volatile int port = DEFAULT_PORT;
    private volatile int securePort = DEFAULT_SECURE_PORT;

    @Auto
    private volatile String homePageUrl;
    @Auto
    private volatile String statusPageUrl;
    @Auto
    private volatile String healthCheckUrl;
    @Auto
    private volatile String secureHealthCheckUrl;
    @Auto
    private volatile String vipAddress;
    @Auto
    private volatile String secureVipAddress;
    @XStreamOmitField
    private String statusPageRelativeUrl;
    @XStreamOmitField
    private String statusPageExplicitUrl;
    @XStreamOmitField
    private String healthCheckRelativeUrl;
    @XStreamOmitField
    private String healthCheckSecureExplicitUrl;
    @XStreamOmitField
    private String vipAddressUnresolved;
    @XStreamOmitField
    private String secureVipAddressUnresolved;
    @XStreamOmitField
    private String healthCheckExplicitUrl;
    @Deprecated
    private volatile int countryId = DEFAULT_COUNTRY_ID; // Defaults to US
    private volatile boolean isSecurePortEnabled = false;
    private volatile boolean isUnsecurePortEnabled = true;
    private volatile DataCenterInfo dataCenterInfo;
    private volatile String hostName;
    private volatile InstanceStatus status = InstanceStatus.UP;
    private volatile InstanceStatus overriddenStatus = InstanceStatus.UNKNOWN;
    @XStreamOmitField
    private volatile boolean isInstanceInfoDirty = false;
    private volatile LeaseInfo leaseInfo;
    @Auto
    private volatile Boolean isCoordinatingDiscoveryServer = Boolean.FALSE;
    @XStreamAlias("metadata")
    private volatile Map<String, String> metadata;
    @Auto
    private volatile Long lastUpdatedTimestamp;
    @Auto
    private volatile Long lastDirtyTimestamp;
    @Auto
    private volatile ActionType actionType;
    @Auto
    private volatile String asgName;
    private String version = VERSION_UNKNOWN;

InstanceStatus

這個枚舉中包含了客戶端可能存在的狀態

        UP, 
        DOWN, 
        STARTING, 
        OUT_OF_SERVICE, 
        UNKNOWN;

Lease

這個類是服務端用來保存客戶端的租約信息的，其中holder中持有的就是InstanceInfo對象

// 租約過期時間
 public static final int DEFAULT_DURATION_IN_SECS = 90;
//客戶端實例
private T holder;
//服務下線時間
private long evictionTimestamp;
//註冊起始時間
private long registrationTimestamp;
//取消註冊時間
private long serviceUpTimestamp;
// 最後更新時間
private volatile long lastUpdateTimestamp;
//租約持續時間
private long duration;

PeerEurekaNode

這個對象代表著集群節點信息

 /**
     * 服務地址
     */
    private final String serviceUrl;
    /**
     * Eureka-Server 配置
     */
    private final EurekaServerConfig config;
    /**
     * 批任務同步最大延遲
     */
    private final long maxProcessingDelayMs;
    /**
     * 應用實例註冊表
     */
    private final PeerAwareInstanceRegistry registry;
    /**
     * 目標 host
     */
    private final String targetHost;
    /**
     * 集群  EurekaHttpClient
     */
    private final HttpReplicationClient replicationClient;

    /**
     * 批量任務分發器
     */
    private final TaskDispatcher<String, ReplicationTask> batchingDispatcher;
    /**
     * 單任務分發器
     */
    private final TaskDispatcher<String, ReplicationTask> nonBatchingDispatcher;

EurekaHttpClient

這個是Eureka客戶端與服務端通信的介面

public interface EurekaHttpClient {

    EurekaHttpResponse<Void> register(InstanceInfo info);

    EurekaHttpResponse<Void> cancel(String appName, String id);

    EurekaHttpResponse<InstanceInfo> sendHeartBeat(String appName, String id, InstanceInfo info, InstanceStatus overriddenStatus);

    EurekaHttpResponse<Void> statusUpdate(String appName, String id, InstanceStatus newStatus, InstanceInfo info);

    EurekaHttpResponse<Void> deleteStatusOverride(String appName, String id, InstanceInfo info);

    EurekaHttpResponse<Applications> getApplications(String... regions);

    EurekaHttpResponse<Applications> getDelta(String... regions);

    EurekaHttpResponse<Applications> getVip(String vipAddress, String... regions);

    EurekaHttpResponse<Applications> getSecureVip(String secureVipAddress, String... regions);

    EurekaHttpResponse<Application> getApplication(String appName);

    EurekaHttpResponse<InstanceInfo> getInstance(String appName, String id);

    EurekaHttpResponse<InstanceInfo> getInstance(String id);

    void shutdown();
}

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