SpringCloudConsul源码分析（三）服务发现

程序猿阿越
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一、com.netflix.loadbalancer核心抽象及Consul的实现

1.1 Server

  • com.netflix.loadbalancer.Server代表Consul注册中心里的一个服务实例
  • ConsulServer继承了Server，扩展一些Consul特有的属性，比如Map<String, String> metadata、HealthService
public class ConsulServer extends Server {
	private final MetaInfo metaInfo;
	private final HealthService service;
	private final Map<String, String> metadata;

1.2 ServerList

  • ServerList定义了两个方法，用于获取List
    • getInitialListOfServers初始化获取
    • getUpdatedListOfServers会被频繁调用，用于定时更新List
public interface ServerList<T extends Server> {
	// 初始化获取List<Server>
    public List<T> getInitialListOfServers();
    // 定时获取List<Server>
    public List<T> getUpdatedListOfServers();   
}
  • ServerList.getUpdatedListOfServers的触发点是DynamicServerListLoadBalancer的构造方法，而构造方法的触发，依赖于对于某个服务的首次Feign或Ribbon调用，每个服务会对应一个Spring上哪下文，也就对应一个DynamicServerListLoadBalancer（服务拆分多，耦合紧密，开启的定时更新服务列表线程就多，consul的压力也就大）
  public DynamicServerListLoadBalancer(IClientConfig clientConfig, IRule rule, IPing ping, ServerList<T> serverList, ServerListFilter<T> filter, ServerListUpdater serverListUpdater) {
        super(clientConfig, rule, ping);
  		...
  		// 这里触发
        this.restOfInit(clientConfig);
    }
  • 无论是首次触发，还是定时任务触发，都是走DynamicServerListLoadBalancer.updateListOfServers
  public void updateListOfServers() {
        List<T> servers = new ArrayList<T>();
        if (serverListImpl != null) {
            // 1. ConsulServerList的获取服务列表
            servers = serverListImpl.getUpdatedListOfServers();
            if (filter != null) {
  				// 2. HealthServiceServerListFilter过滤不健康的服务
                servers = filter.getFilteredListOfServers(servers);
            }
        }
        // 3. copyOnWrite机制，更新内存里的服务列表
        updateAllServerList(servers);
    }
  • 最终都是走ConsulServerList#getServers
	/**
   * 根据serviceName查询service
   * http://localhost:8500/v1/health/service/testConsulApp?passing=false&token=
   * 查询参数包括
   * 1、tag 目标服务必须包含的tag 仅支持一个kv对
   * 2、queryPassing 是否过滤非健康状态的服务（默认是否，通过HealthServiceServerListFilter过滤非健康的服务）
   * 3、datacenter 数据中心（Consul支持跨数据中心的服务发现）
   * 4、token 客户端跟Consul交互的凭证
   * @return
   */
  private List<ConsulServer> getServers() {
  	if (this.client == null) {
  		return Collections.emptyList();
  	}
  	HealthServicesRequest request = HealthServicesRequest.newBuilder()
  			.setTag(getTag()).setPassing(this.properties.isQueryPassing())
  			.setQueryParams(createQueryParamsForClientRequest())
  			.setToken(this.properties.getAclToken()).build();
  	Response<List<HealthService>> response = this.client
  			.getHealthServices(this.serviceId, request);
  	if (response.getValue() == null || response.getValue().isEmpty()) {
  		return Collections.emptyList();
  	}
  	return transformResponse(response.getValue());
  }
  • 定时更新服务列表的时间间隔由ribbon.ServerListRefreshInterval控制，默认30s

1.3 ServerListFilter

  • ServerListFilter接口用于过滤服务实例列表
  public interface ServerListFilter<T extends Server> {
    public List<T> getFilteredListOfServers(List<T> servers);
	}
  • Consul的实现是HealthServiceServerListFilter
  public class HealthServiceServerListFilter implements ServerListFilter<Server> {
	@Override
	public List<Server> getFilteredListOfServers(List<Server> servers) {
		List<Server> filtered = new ArrayList<>();
		for (Server server : servers) {
		    // 如果是ConsulServer对象，取ConsulerServer的健康状态过滤
			if (server instanceof ConsulServer) {
				ConsulServer consulServer = (ConsulServer) server;
				if (consulServer.isPassingChecks()) {
					filtered.add(server);
				}
			} else { // 如果非ConsulServer对象，不过滤
				filtered.add(server);
			}
		}
		return filtered;
	}

}
  • 具体过滤逻辑，是取com.ecwid.consul.v1.health.model.HealthService#checks列表，如果列表里有一项检查没通过，则过滤
  public boolean isPassingChecks() {
		for (Check check : this.service.getChecks()) {
			if (check.getStatus() != Check.CheckStatus.PASSING) {
				return false;
			}
		}
		return true;
  }

1.4 IPing

  • IPing接口负责检测Server实例是否能Ping通
  public interface IPing {
    public boolean isAlive(Server server);
  }
  • Consul的实现是ConsulPing，不实际PingServer，只是看内存中的Server是否Check全是健康状态
  public class ConsulPing implements IPing {
	@Override
	public boolean isAlive(Server server) {
		boolean isAlive = true;
		if (server != null && server instanceof ConsulServer) {
			ConsulServer consulServer = (ConsulServer) server;
			return consulServer.isPassingChecks();
		}
		return isAlive;
	}
}

二、org.springframework.cloud.client.discovery核心抽象及Consul的实现

2.1 DiscoveryClient

  • org.springframework.cloud.client.discovery.DiscoveryClient接口主要是两个方法（部分不重要的省略了）
    • getInstances：根据serviceId查询所有服务实例
    • getServices：查询所有serviceId
public interface DiscoveryClient extends Ordered {
	List<ServiceInstance> getInstances(String serviceId);

	List<String> getServices();
}
  • Consul对于DiscoveryClient的实现是ConsulDiscoveryClient，这两个方法也只是调用consul接口 
    public List<ServiceInstance> getInstances(final String serviceId) {
  	return getInstances(serviceId,
  			new QueryParams(this.properties.getConsistencyMode()));
  }

    @Override
  public List<String> getServices() {
  	String aclToken = this.properties.getAclToken();
  	CatalogServicesRequest request = CatalogServicesRequest.newBuilder()
  			.setQueryParams(QueryParams.DEFAULT)
  			.setToken(this.properties.getAclToken()).build();
  	return new ArrayList<>(
  			this.client.getCatalogServices(request).getValue().keySet());
  }

三、org.springframework.cloud.netflix.ribbon核心抽象及Consul实现

3.1 ServerIntrospector

  • ServerIntrospector
    • isSecure：判断Server是否是安全的，DefaultServerIntrospector默认实现是取ribbon.securePorts，如果securePorts列表包含server的port则安全
    • getMetadata：获取Server的元数据，DefaultServerIntrospector默认实现是返回空Map
public interface ServerIntrospector {
    boolean isSecure(Server server);

    Map<String, String> getMetadata(Server server);
}
  • ConsulServerIntrospector继承DefaultServerIntrospector
    • getMetadata：取ConsulServer的metadata属性
    • isSecure：取ConsulServer的metadata属性。secure对应的value是否为true
public class ConsulServerIntrospector extends DefaultServerIntrospector {
	/**
	 * 1、优先ConsulServer的metadata的secure字段，判断是否安全
	 * 2、否则走父类，通过Server的端口判断，如果端口是443或8443则是安全的
	 */
	@Override
	public boolean isSecure(Server server) {
		Map<String, String> metadata = getMetadata(server);
		if (metadata != null && metadata.containsKey("secure")) {
			return metadata.getOrDefault("secure", "false").equalsIgnoreCase("true");
		}
		return super.isSecure(server);
	}

	/**
	 * MetaData的来源支持ConsulServer自己的MetaData
	 */
	@Override
	public Map<String, String> getMetadata(Server server) {
		if (server instanceof ConsulServer) {
			ConsulServer consulServer = (ConsulServer) server;
			return consulServer.getMetadata();
		}
		return super.getMetadata(server);
	}

}

四、spring-cloud-consul-discovery特有

4.1 ConsulCatalogWatch

  • ConsulCatalogWatch：启动一个定时任务，每秒更新consulIndex，并且发送HeartbeatEvent事件
  • 感觉没啥用，通过spring.cloud.consul.discovery.catalog-services-watch.enabled=false可以关闭
  • ConsulCatalogWatch#catalogServicesWatch执行定时任务的核心逻辑
public void catalogServicesWatch() {
		long index = -1;
		if (this.catalogServicesIndex.get() != null) {
			index = this.catalogServicesIndex.get().longValue();
		}
		// 1. 获取所有service信息，只包含了serviceName，http://127.0.0.1:8500/v1/catalog/services?wait=2s&index=812407&token=
		CatalogServicesRequest request = CatalogServicesRequest.newBuilder()
				.setQueryParams(new QueryParams(
						this.properties.getCatalogServicesWatchTimeout(), index))
				.setToken(this.properties.getAclToken()).build();
		Response<Map<String, List<String>>> response = this.consul
				.getCatalogServices(request);
		// 2. 更新consulIndex
		Long consulIndex = response.getConsulIndex();
		if (consulIndex != null) {
			this.catalogServicesIndex.set(BigInteger.valueOf(consulIndex));
		}
		// 3. 发送HeartbeatEvent事件
		this.publisher.publishEvent(new HeartbeatEvent(this, consulIndex));
	}

五、总结

  • 几个核心抽象及consul实现
  • 每个被调用的服务名对应一个SpringIOC容器，每个容器包含一个ILoadBalancer，会启动一个线程更新BaseLoadBalancer里的List upServerList，默认30s更新一次
  • ConsulCatalogWatch看起来没啥用，考虑关闭spring.cloud.consul.discovery.catalog-services-watch.enabled=false
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