Eureka源码简单解析

一.客户端

DiscoveryClient：客户端

核心接口：EurekaClient 

public interface EurekaClient extends LookupService {

    // ========================
    // getters for InstanceInfo
    // ========================

    /**
     * @param region the region that the Applications reside in
     * @return an {@link com.netflix.discovery.shared.Applications} for the matching region. a Null value
     *         is treated as the local region.
     */
    public Applications getApplicationsForARegion(@Nullable String region);

    /**
     * Get all applications registered with a specific eureka service.
     *
     * @param serviceUrl The string representation of the service url.
     * @return The registry information containing all applications.
     */
    public Applications getApplications(String serviceUrl);

    /**
     * Gets the list of instances matching the given VIP Address.
     *
     * @param vipAddress The VIP address to match the instances for.
     * @param secure true if it is a secure vip address, false otherwise
     * @return - The list of {@link InstanceInfo} objects matching the criteria
     */
    public List<InstanceInfo> getInstancesByVipAddress(String vipAddress, boolean secure);

    /**
     * Gets the list of instances matching the given VIP Address in the passed region.
     *
     * @param vipAddress The VIP address to match the instances for.
     * @param secure true if it is a secure vip address, false otherwise
     * @param region region from which the instances are to be fetched. If <code>null</code> then local region is
     *               assumed.
     *
     * @return - The list of {@link InstanceInfo} objects matching the criteria, empty list if not instances found.
     */
    public List<InstanceInfo> getInstancesByVipAddress(String vipAddress, boolean secure, @Nullable String region);

    /**
     * Gets the list of instances matching the given VIP Address and the given
     * application name if both of them are not null. If one of them is null,
     * then that criterion is completely ignored for matching instances.
     *
     * @param vipAddress The VIP address to match the instances for.
     * @param appName The applicationName to match the instances for.
     * @param secure true if it is a secure vip address, false otherwise.
     * @return - The list of {@link InstanceInfo} objects matching the criteria.
     */
    public List<InstanceInfo> getInstancesByVipAddressAndAppName(String vipAddress, String appName, boolean secure);

    // ==========================
    // getters for local metadata
    // ==========================

    /**
     * @return in String form all regions (local + remote) that can be accessed by this client
     */
    public Set<String> getAllKnownRegions();

    /**
     * @return the current self instance status as seen on the Eureka server.
     */
    public InstanceInfo.InstanceStatus getInstanceRemoteStatus();

    /**
     * @deprecated see {@link com.netflix.discovery.endpoint.EndpointUtils} for replacement
     *
     * Get the list of all eureka service urls for the eureka client to talk to.
     *
     * @param zone the zone in which the client resides
     * @return The list of all eureka service urls for the eureka client to talk to.
     */
    @Deprecated
    public List<String> getDiscoveryServiceUrls(String zone);

    /**
     * @deprecated see {@link com.netflix.discovery.endpoint.EndpointUtils} for replacement
     *
     * Get the list of all eureka service urls from properties file for the eureka client to talk to.
     *
     * @param instanceZone The zone in which the client resides
     * @param preferSameZone true if we have to prefer the same zone as the client, false otherwise
     * @return The list of all eureka service urls for the eureka client to talk to
     */
    @Deprecated
    public List<String> getServiceUrlsFromConfig(String instanceZone, boolean preferSameZone);

    /**
     * @deprecated see {@link com.netflix.discovery.endpoint.EndpointUtils} for replacement
     *
     * Get the list of all eureka service urls from DNS for the eureka client to
     * talk to. The client picks up the service url from its zone and then fails over to
     * other zones randomly. If there are multiple servers in the same zone, the client once
     * again picks one randomly. This way the traffic will be distributed in the case of failures.
     *
     * @param instanceZone The zone in which the client resides.
     * @param preferSameZone true if we have to prefer the same zone as the client, false otherwise.
     * @return The list of all eureka service urls for the eureka client to talk to.
     */
    @Deprecated
    public List<String> getServiceUrlsFromDNS(String instanceZone, boolean preferSameZone);

    // ===========================
    // healthcheck related methods
    // ===========================

    /**
     * @deprecated Use {@link #registerHealthCheck(com.netflix.appinfo.HealthCheckHandler)} instead.
     *
     * Register {@link HealthCheckCallback} with the eureka client.
     *
     * Once registered, the eureka client will invoke the
     * {@link HealthCheckCallback} in intervals specified by
     * {@link EurekaClientConfig#getInstanceInfoReplicationIntervalSeconds()}.
     *
     * @param callback app specific healthcheck.
     */
    @Deprecated
    public void registerHealthCheckCallback(HealthCheckCallback callback);

    /**
     * Register {@link HealthCheckHandler} with the eureka client.
     *
     * Once registered, the eureka client will first make an onDemand update of the
     * registering instanceInfo by calling the newly registered healthcheck handler,
     * and subsequently invoke the {@link HealthCheckHandler} in intervals specified
     * by {@link EurekaClientConfig#getInstanceInfoReplicationIntervalSeconds()}.
     *
     * @param healthCheckHandler app specific healthcheck handler.
     */
    public void registerHealthCheck(HealthCheckHandler healthCheckHandler);

    /**
     * Register {@link EurekaEventListener} with the eureka client.
     *
     * Once registered, the eureka client will invoke {@link EurekaEventListener#onEvent} 
     * whenever there is a change in eureka client's internal state.  Use this instead of 
     * polling the client for changes.  
     * 
     * {@link EurekaEventListener#onEvent} is called from the context of an internal thread 
     * and must therefore return as quickly as possible without blocking.
     * 
     * @param eventListener
     */
    public void registerEventListener(EurekaEventListener eventListener);
    
    /**
     * Unregister a {@link EurekaEventListener} previous registered with {@link EurekaClient#registerEventListener}
     * or injected into the constructor of {@link DiscoveryClient}
     * 
     * @param eventListener
     * @return True if removed otherwise false if the listener was never registered.
     */
    public boolean unregisterEventListener(EurekaEventListener eventListener);
    
    /**
     * @return the current registered healthcheck handler
     */
    public HealthCheckHandler getHealthCheckHandler();

    // =============
    // other methods
    // =============

    /**
     * Shuts down Eureka Client. Also sends a deregistration request to the eureka server.
     */
    public void shutdown();
    
    /**
     * @return the configuration of this eureka client
     */
    public EurekaClientConfig getEurekaClientConfig();
    
    /**
     * @return the application info manager of this eureka client
     */
    public ApplicationInfoManager getApplicationInfoManager();
}

二.服务端

EurekaBootStrap：服务端入口类

核心接口：InstanceRegistry

public interface InstanceRegistry extends LeaseManager<InstanceInfo>, LookupService<String> {

    void openForTraffic(ApplicationInfoManager applicationInfoManager, int count);

    void shutdown();

    @Deprecated
    void storeOverriddenStatusIfRequired(String id, InstanceStatus overriddenStatus);

    void storeOverriddenStatusIfRequired(String appName, String id, InstanceStatus overriddenStatus);

    boolean statusUpdate(String appName, String id, InstanceStatus newStatus,
                         String lastDirtyTimestamp, boolean isReplication);

    boolean deleteStatusOverride(String appName, String id, InstanceStatus newStatus,
                                 String lastDirtyTimestamp, boolean isReplication);

    Map<String, InstanceStatus> overriddenInstanceStatusesSnapshot();

    Applications getApplicationsFromLocalRegionOnly();

    List<Application> getSortedApplications();

    /**
     * Get application information.
     *
     * @param appName The name of the application
     * @param includeRemoteRegion true, if we need to include applications from remote regions
     *                            as indicated by the region {@link java.net.URL} by this property
     *                            {@link com.netflix.eureka.EurekaServerConfig#getRemoteRegionUrls()}, false otherwise
     * @return the application
     */
    Application getApplication(String appName, boolean includeRemoteRegion);

    /**
     * Gets the {@link InstanceInfo} information.
     *
     * @param appName the application name for which the information is requested.
     * @param id the unique identifier of the instance.
     * @return the information about the instance.
     */
    InstanceInfo getInstanceByAppAndId(String appName, String id);

    /**
     * Gets the {@link InstanceInfo} information.
     *
     * @param appName the application name for which the information is requested.
     * @param id the unique identifier of the instance.
     * @param includeRemoteRegions true, if we need to include applications from remote regions
     *                             as indicated by the region {@link java.net.URL} by this property
     *                             {@link com.netflix.eureka.EurekaServerConfig#getRemoteRegionUrls()}, false otherwise
     * @return the information about the instance.
     */
    InstanceInfo getInstanceByAppAndId(String appName, String id, boolean includeRemoteRegions);

    void clearRegistry();

    void initializedResponseCache();

    ResponseCache getResponseCache();

    long getNumOfRenewsInLastMin();

    int getNumOfRenewsPerMinThreshold();

    int isBelowRenewThresold();

    List<Pair<Long, String>> getLastNRegisteredInstances();

    List<Pair<Long, String>> getLastNCanceledInstances();

    /**
     * Checks whether lease expiration is enabled.
     * @return true if enabled
     */
    boolean isLeaseExpirationEnabled();

    boolean isSelfPreservationModeEnabled();

}

两者通过HTTP请求用InstanceInfo进行信息交互。

通信时涉及的动作有Heartbeat, Register, Cancel, StatusUpdate, DeleteStatusOverride。