Mini Spring Cloud

Jan 18, 2024 · peanut996

服务注册

代码分支: service-registry

为了演示，写一个非常简单的单机版的服务注册和发现中心，命名图图

@RestController
@SpringBootApplication
public class TutuServerApplication {
    private static Logger logger = LoggerFactory.getLogger(TutuServerApplication.class);

    private ConcurrentHashMap<String, Set<Server>> serverMap = new ConcurrentHashMap<>();

    public static void main(String[] args) {
        SpringApplication.run(TutuServerApplication.class, args);
    }

    /**
     * 服务注册
     *
     * @param serviceName
     * @param ip
     * @param port
     * @return
     */
    @PostMapping("register")
    public boolean register(@RequestParam("serviceName") String serviceName, @RequestParam("ip") String ip, @RequestParam("port") Integer port) {
        logger.info("register service, serviceName: {}, ip: {}, port: {}", serviceName, ip, port);
        serverMap.putIfAbsent(serviceName.toLowerCase(), Collections.synchronizedSet(new HashSet<>()));
        Server server = new Server(ip, port);
        serverMap.get(serviceName).add(server);
        return true;
    }

    /**
     * 服务注销
     *
     * @param serviceName
     * @param ip
     * @param port
     * @return
     */
    @PostMapping("deregister")
    public boolean deregister(@RequestParam("serviceName") String serviceName, @RequestParam("ip") String ip, @RequestParam("port") Integer port) {
        logger.info("deregister service, serviceName: {}, ip: {}, port: {}", serviceName, ip, port);
        Set<Server> serverSet = serverMap.get(serviceName.toLowerCase());
        if (serverSet != null) {
            Server server = new Server(ip, port);
            serverSet.remove(server);
        }
        return true;
    }

    /**
     * 根据服务名称查询服务列表
     *
     * @param serviceName
     * @return
     */
    @GetMapping("list")
    public Set<Server> list(@RequestParam("serviceName") String serviceName) {
        Set<Server> serverSet = serverMap.get(serviceName.toLowerCase());
        logger.info("list service, serviceName: {}, serverSet: {}", serviceName, JSON.toJSONString(serverSet));
        return serverSet != null ? serverSet : Collections.emptySet();
    }

    /**
     * 查询所有服务名称列表
     *
     * @return
     */
    @GetMapping("listServiceNames")
    public Enumeration<String> listServiceNames() {
        return serverMap.keys();
    }

    /**
     * 服务
     */
    public static class Server {
        private String ip;

        private Integer port;
        
        //Construct、Getters、equals、hashCode
    }
}

配置application.yml:

server:
  port: 6688

spring-cloud-commons服务注册相关API:

ServiceInstance和Registration，表示系统中服务的实例
ServiceRegistry，服务注册和注销接口
AbstractAutoServiceRegistration，自动注册和注销服务。监听WebServerInitializedEvent(Web服务启动完毕事件)，WebServerInitializedEvent触发时注册服务实例；@PreDestroy注解修饰的方法注销服务实例。

服务注册功能实现

TutuDiscoveryProperties，配置服务注册中心地址:

@ConfigurationProperties("spring.cloud.tutu.discovery")
public class TutuDiscoveryProperties {

    @Autowired
    private InetUtils inetUtils;

    private String serverAddr;

    private String service;

    private String ip;

    private int port = -1;

    private boolean secure = false;

    @PostConstruct
    public void init() throws Exception {
        if (!StringUtils.hasLength(ip)) {
            //获取服务IP地址
            ip = inetUtils.findFirstNonLoopbackHostInfo().getIpAddress();
        }
    }

    //getters and setters
}

TutuRegistration，图图服务注册实例:

public class TutuRegistration implements Registration {

    private TutuDiscoveryProperties tutuDiscoveryProperties;

    public TutuRegistration(TutuDiscoveryProperties tutuDiscoveryProperties) {
        this.tutuDiscoveryProperties = tutuDiscoveryProperties;
    }

    @Override
    public boolean isSecure() {
        return tutuDiscoveryProperties.isSecure();
    }

    @Override
    public URI getUri() {
        return DefaultServiceInstance.getUri(this);
    }
  
    //getters and setters
}

注册和注销TutuRegistration的接口TutuServiceRegistry:

public class TutuServiceRegistry implements ServiceRegistry<Registration> {
  private static final Logger logger = LoggerFactory.getLogger(TutuServiceRegistry.class);

  private TutuDiscoveryProperties tutuDiscoveryProperties;

  public TutuServiceRegistry(TutuDiscoveryProperties tutuDiscoveryProperties) {
    this.tutuDiscoveryProperties = tutuDiscoveryProperties;
  }

  /**
   * 注册服务实例
   *
   * @param registration
   */
  @Override
  public void register(Registration registration) {
    Map<String, Object> param = new HashMap<>();
    param.put("serviceName", tutuDiscoveryProperties.getService());
    param.put("ip", tutuDiscoveryProperties.getIp());
    param.put("port", tutuDiscoveryProperties.getPort());

    String result = HttpUtil.post(tutuDiscoveryProperties.getServerAddr() + "/register", param);
    if (Boolean.parseBoolean(result)) {
      logger.info("register service successfully, serviceName: {}, ip: {}, port: {}",
              tutuDiscoveryProperties.getService(), tutuDiscoveryProperties.getIp(), tutuDiscoveryProperties.getPort());
    } else {
      logger.error("register service failed, serviceName: {}, ip: {}, port: {}",
              tutuDiscoveryProperties.getService(), tutuDiscoveryProperties.getIp(), tutuDiscoveryProperties.getPort());
      throw new RuntimeException("register service failed, serviceName");
    }
  }

  /**
   * 注销服务实例
   *
   * @param registration
   */
  @Override
  public void deregister(Registration registration) {
    Map<String, Object> param = new HashMap<>();
    param.put("serviceName", tutuDiscoveryProperties.getService());
    param.put("ip", tutuDiscoveryProperties.getIp());
    param.put("port", tutuDiscoveryProperties.getPort());

    String result = HttpUtil.post(tutuDiscoveryProperties.getServerAddr() + "/deregister", param);
    if (Boolean.parseBoolean(result)) {
      logger.info("de-register service successfully, serviceName: {}, ip: {}, port: {}",
              tutuDiscoveryProperties.getService(), tutuDiscoveryProperties.getIp(), tutuDiscoveryProperties.getPort());
    } else {
      logger.warn("de-register service failed, serviceName: {}, ip: {}, port: {}",
              tutuDiscoveryProperties.getService(), tutuDiscoveryProperties.getIp(), tutuDiscoveryProperties.getPort());
    }
  }
}

AbstractAutoServiceRegistration实现类:

public class TutuAutoServiceRegistration extends AbstractAutoServiceRegistration<Registration> {

    private TutuRegistration tutuRegistration;

    protected TutuAutoServiceRegistration(ServiceRegistry<Registration> serviceRegistry, TutuRegistration tutuRegistration) {
        super(serviceRegistry, null);
        this.tutuRegistration = tutuRegistration;
    }

    @Override
    protected Registration getRegistration() {
        if (tutuRegistration.getPort() < 0) {
            //设置服务端口
            tutuRegistration.setPort(this.getPort().get());
        }
        return tutuRegistration;
    }
}

自动装配: TutuServiceRegistryAutoConfiguration:

/**
 * 自动配置服务注册相关类
 */
@Configuration
@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled", matchIfMissing = true)
public class TutuServiceRegistryAutoConfiguration {

    @Bean
    @ConditionalOnMissingBean
    public TutuDiscoveryProperties tutuProperties() {
        return new TutuDiscoveryProperties();
    }

    @Bean
    public TutuRegistration tutuRegistration(TutuDiscoveryProperties tutuDiscoveryProperties) {
        return new TutuRegistration(tutuDiscoveryProperties);
    }

    @Bean
    public TutuServiceRegistry tutuServiceRegistry(TutuDiscoveryProperties tutuDiscoveryProperties) {
        return new TutuServiceRegistry(tutuDiscoveryProperties);
    }

    @Bean
    public TutuAutoServiceRegistration tutuAutoServiceRegistration(ServiceRegistry<Registration> serviceRegistry, TutuRegistration tutuRegistration) {
        return new TutuAutoServiceRegistration(serviceRegistry, tutuRegistration);
    }
}

META-INF/spring.factories:

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
  com.github.cloud.tutu.registry.TutuServiceRegistryAutoConfiguration

测试:

1、maven install

2、启动服务注册和发现中心TutuServerApplication

3、启动服务提供者ProviderApplication，其代码如下:

@RestController
@SpringBootApplication
public class ProviderApplication {

    @Value("${server.port}")
    private Integer port;

    public static void main(String[] args) {
        SpringApplication.run(ProviderApplication.class, args);
    }

    @PostMapping("/echo")
    public String echo() {
        return "Port of the service provider: " + port;
    }
}

配置application.yml:

spring:
  application:
    name: provider-application
  cloud:
    tutu:
      discovery:
        server-addr: localhost:6688
        service: ${spring.application.name}

# 随机端口
server:
  port: ${random.int[10000,20000]}

4、浏览器中访问http://localhost:6688/list?serviceName=provider-application 或执行命令 curl -X GET 'http://localhost:6688/list?serviceName=provider-application' ，响应报文如下，说明服务已经注册到服务注册中心

[
  {
  "ip": "192.168.47.1",
  "port": 19588
  }
]

服务发现

代码分支: service-discovery

spring-cloud-commons定义的服务发现接口org.springframework.cloud.client.discovery.DiscoveryClient:

public interface DiscoveryClient extends Ordered {

	/**
	 * Gets all ServiceInstances associated with a particular serviceId.
	 * @param serviceId The serviceId to query.
	 * @return A List of ServiceInstance.
	 */
	List<ServiceInstance> getInstances(String serviceId);

	/**
	 * @return All known service IDs.
	 */
	List<String> getServices();
}

仅需实现DiscoveryClient接口即可，实现类:

/**
 * 服务发现实现类
 */
public class TutuDiscoveryClient implements DiscoveryClient {
    private static final Logger logger = LoggerFactory.getLogger(TutuDiscoveryClient.class);

    private TutuDiscoveryProperties tutuDiscoveryProperties;

    public TutuDiscoveryClient(TutuDiscoveryProperties tutuDiscoveryProperties) {
        this.tutuDiscoveryProperties = tutuDiscoveryProperties;
    }

    @Override
    public List<ServiceInstance> getInstances(String serviceId) {
        Map<String, Object> param = new HashMap<>();
        param.put("serviceName", serviceId);

        String response = HttpUtil.get(tutuDiscoveryProperties.getServerAddr() + "/list", param);
        logger.info("query service instance, serviceId: {}, response: {}", serviceId, response);
        return JSON.parseArray(response).stream().map(hostInfo -> {
            TutuServiceInstance serviceInstance = new TutuServiceInstance();
            serviceInstance.setServiceId(serviceId);
            String ip = ((JSONObject) hostInfo).getString("ip");
            Integer port = ((JSONObject) hostInfo).getInteger("port");
            serviceInstance.setHost(ip);
            serviceInstance.setPort(port);
            return serviceInstance;
        }).collect(Collectors.toList());
    }

    @Override
    public List<String> getServices() {
        String response = HttpUtil.post(tutuDiscoveryProperties.getServerAddr() + "/listServiceNames", new HashMap<>());
        logger.info("query service instance list, response: {}", response);
        return JSON.parseArray(response, String.class);
    }
}

自动装配TutuDiscoveryAutoConfiguration:

@Configuration
public class TutuDiscoveryAutoConfiguration {

    @Bean
    @ConditionalOnMissingBean
    public TutuDiscoveryProperties tutuDiscoveryProperties() {
        return new TutuDiscoveryProperties();
    }

    @Bean
    public DiscoveryClient tutuDiscoveryClient(TutuDiscoveryProperties tutuDiscoveryProperties) {
        return new TutuDiscoveryClient(tutuDiscoveryProperties);
    }
}

spring.factories:

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
  com.github.cloud.tutu.registry.TutuServiceRegistryAutoConfiguration,\
  com.github.cloud.tutu.discovery.TutuDiscoveryAutoConfiguration

测试:

1、maven install，启动服务注册和发现中心TutuServerApplication，启动服务提供者ProviderApplication，启动服务消费者ConsumerApplication(后续测试步骤均同此，不再提及)

服务消费者代码如下:

@SpringBootApplication
public class ConsumerApplication {

  public static void main(String[] args) {
    SpringApplication.run(ConsumerApplication.class, args);
  }

  @RestController
  static class HelloController {

    @Autowired
    private DiscoveryClient discoveryClient;

    private RestTemplate restTemplate = new RestTemplate();

    @GetMapping("/hello")
    public String hello() {
      List<ServiceInstance> serviceInstances = discoveryClient.getInstances("provider-application");
      if (serviceInstances.size() > 0) {
        ServiceInstance serviceInstance = serviceInstances.get(0);
        URI uri = serviceInstance.getUri();
        String response = restTemplate.postForObject(uri.toString() + "/echo", null, String.class);
        return response;
      }

      throw new RuntimeException("No service instance for provider-application found");
    }
  }
}

application.yml:

spring:
  application:
    name: consumer-application
  cloud:
    tutu:
      discovery:
        server-addr: localhost:6688
        service: ${spring.application.name}

2、访问http://localhost:8080/hello ,相应报文如下:

Port of the service provider: 19922

集成ribbon实现客户端负载均衡

代码分支: load-balancer

关于ribbon

(翻译自官方文档)ribbon是一个提供如下功能的依赖包:

负载均衡
容错机制
支持多种协议(HTTP, TCP, UDP)，支持异步和响应式的调用方式
缓存和批处理

ribbon核心API

一、IClientConfig接口

定义加载和读取ribbon客户端配置的方法，实现类DefaultClientConfigImpl

二、IPing接口

顾名思义，判断服务是否存活，实现类:

NoOpPing，不做检查，认为服务存活
DummyPing，不做检查，认为服务存活

三、ServerList接口

获取服务实例列表的接口，实现类:

ConfigurationBasedServerList，基于配置获取服务实例列表

四、IRule接口

负载均衡规则，实现类:

RoundRobinRule，轮询
RandomRule，随机
WeightedResponseTimeRule，根据响应时间分配权重，响应时间越短权重越大
BestAvailableRule，跳过被熔断器标记为"tripped"状态的、并且选择并发请求数最小的服务实例
ZoneAvoidanceRule，根据所属zone和可用性筛选服务实例，在没有多zone的情况下退化为轮询RoundRobinRule
AvailabilityFilteringRule，过滤掉一直连接失败或活跃连接数超过配置值的服务实例
RetryRule，对其他负载均衡规则的包装，在一段时间内失败重试

五、ServerListFilter接口

服务实例过滤器

六、ServerListUpdater接口

PollingServerListUpdater，起一个周期任务更新服务实例列表

七、ILoadBalancer接口

负载均衡接口，实现类：

BaseLoadBalancer，手动设置服务实例，根据负载均衡规则IRule筛选服务实例
DynamicServerListLoadBalancer，使用ServerListUpdater动态更新服务实例列表
ZoneAwareLoadBalancer，支持zone

集成ribbon实现客户端负载均衡(一)

spring-cloud-commons负载均衡相关API:

ServiceInstanceChooser接口，服务实例选择器，根据服务提供者的服务名称选择服务实例

/**
 * Implemented by classes which use a load balancer to choose a server to send a request to.
 */
public interface ServiceInstanceChooser {

	/**
	 * Chooses a ServiceInstance from the LoadBalancer for the specified service.
	 */
	ServiceInstance choose(String serviceId);

	/**
	 * Chooses a ServiceInstance from the LoadBalancer for the specified service and LoadBalancer request.
	 */
	<T> ServiceInstance choose(String serviceId, Request<T> request);
}

LoadBalancerClient接口

/**
 * Represents a client-side load balancer.
 */
public interface LoadBalancerClient extends ServiceInstanceChooser {

	/**
	 * Executes request using a ServiceInstance from the LoadBalancer for the specified service.
	 */
	<T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException;

	/**
	 * Executes request using a ServiceInstance from the LoadBalancer for the specified service.
	 */
	<T> T execute(String serviceId, ServiceInstance serviceInstance, LoadBalancerRequest<T> request) throws IOException;

	/**
	 * Creates a proper URI with a real host and port for systems to utilize. Some systems
	 * use a URI with the logical service name as the host, such as
	 * http://myservice/path/to/service. This will replace the service name with the
	 * host:port from the ServiceInstance.
	 */
	URI reconstructURI(ServiceInstance instance, URI original);
}

本节只关注ServiceInstanceChooser接口的choose方法，下一节讲解LoadBalancerClient接口的三个方法。

负载均衡功能实现:

RibbonClientConfiguration，配置ribbon核心API默认实现类:

/**
 * 配置ribbon默认组件
 */
@Configuration
public class RibbonClientConfiguration {

    @Value("${ribbon.client.name}")
    private String name;

    @Bean
    @ConditionalOnMissingBean
    public IClientConfig ribbonClientConfig() {
        DefaultClientConfigImpl config = new DefaultClientConfigImpl();
        config.loadProperties(name);
        return config;
    }

    @Bean
    @ConditionalOnMissingBean
    public IRule ribbonRule(IClientConfig config) {
        ZoneAvoidanceRule rule = new ZoneAvoidanceRule();
        rule.initWithNiwsConfig(config);
        return rule;
    }

    @Bean
    @ConditionalOnMissingBean
    public IPing ribbonPing(IClientConfig config) {
        return new DummyPing();
    }

    @Bean
    @ConditionalOnMissingBean
    public ServerList<Server> ribbonServerList(IClientConfig config) {
        ConfigurationBasedServerList serverList = new ConfigurationBasedServerList();
        serverList.initWithNiwsConfig(config);
        return serverList;
    }

    @Bean
    @ConditionalOnMissingBean
    public ServerListUpdater ribbonServerListUpdater(IClientConfig config) {
        return new PollingServerListUpdater(config);
    }

    @Bean
    @ConditionalOnMissingBean
    public ServerListFilter<Server> ribbonServerListFilter(IClientConfig config) {
        ServerListSubsetFilter filter = new ServerListSubsetFilter();
        filter.initWithNiwsConfig(config);
        return filter;
    }

    @Bean
    @ConditionalOnMissingBean
    public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
                                            ServerList<Server> serverList, ServerListFilter<Server> serverListFilter,
                                            IRule rule, IPing ping, ServerListUpdater serverListUpdater) {
        return new ZoneAwareLoadBalancer<>(config, rule, ping, serverList,
                serverListFilter, serverListUpdater);
    }
}

只需实现ribbon核心API中的获取服务实例列表接口ServerList，实现类TutuServerList:

/**
 * 查询图图服务实例列表
 */
public class TutuServerList extends AbstractServerList<TutuServer> {
    private static Logger logger = LoggerFactory.getLogger(TutuServerList.class);

    private TutuDiscoveryProperties discoveryProperties;

    private String serviceId;

    public TutuServerList(TutuDiscoveryProperties discoveryProperties) {
        this.discoveryProperties = discoveryProperties;
    }

    /**
     * 查询服务实例列表
     *
     * @return
     */
    @Override
    public List<TutuServer> getInitialListOfServers() {
        return getServer();
    }

    /**
     * 查询服务实例列表
     *
     * @return
     */
    @Override
    public List<TutuServer> getUpdatedListOfServers() {
        return getServer();
    }

    private List<TutuServer> getServer() {
        Map<String, Object> param = new HashMap<>();
        param.put("serviceName", serviceId);

        String response = HttpUtil.get(discoveryProperties.getServerAddr() + "/list", param);
        logger.info("query service instance, serviceId: {}, response: {}", serviceId, response);
        return JSON.parseArray(response).stream().map(hostInfo -> {
            String ip = ((JSONObject) hostInfo).getString("ip");
            Integer port = ((JSONObject) hostInfo).getInteger("port");
            return new TutuServer(ip, port);
        }).collect(Collectors.toList());
    }

    public String getServiceId() {
        return serviceId;
    }

    @Override
    public void initWithNiwsConfig(IClientConfig iClientConfig) {
        this.serviceId = iClientConfig.getClientName();
    }
}

配置TutuServerList，替换RibbonClientConfiguration中配置的默认实现:

@Configuration
@RibbonClients(defaultConfiguration = TutuRibbonClientConfiguration.class)
public class RibbonTutuAutoConfiguration {
}

/**
 * 自定义ribbon组件
 */
@Configuration
public class TutuRibbonClientConfiguration {

    @Bean
    @ConditionalOnMissingBean
    public ServerList<?> ribbonServerList(IClientConfig config,
                                          TutuDiscoveryProperties discoveryProperties) {
        TutuServerList serverList = new TutuServerList(discoveryProperties);
        serverList.initWithNiwsConfig(config);
        return serverList;
    }
}

每一个Provider服务集群（应用名称即spring.application.name相同的所有应用服务提供者）对应一套ribbon核心API。SpringClientFactory继承自NamedContextFactory，为每一套ribbon核心API创建一个子spring应用上下文（ApplicationContext），来隔离不同服务的ribbon核心API配置，可以定制化不同服务的负载均衡规则（扩展篇实现）。

SpringClientFactory的构造函数参数RibbonClientConfiguration配置ribbon默认的核心API。

修饰RibbonTutuAutoConfiguration配置类的注解RibbonClients引入了自动配置类RibbonClientConfigurationRegistrar，将RibbonClients注解指定的defaultConfiguration属性的值即TutuRibbonClientConfiguration配置类包装为RibbonClientSpecification。RibbonClientSpecification作为SpringClientFactory的属性，用来覆盖RibbonClientConfiguration配置类指定的默认的核心API，比如TutuRibbonClientConfiguration配置类使用TutuServerList替换RibbonClientConfiguration配置类中指定的ConfigurationBasedServerList。

可能表述得不清楚，为了充分理解子spring容器的创建逻辑，可以在下面的测试环节debug如下几个方法:

RibbonClientConfigurationRegistrar#registerBeanDefinitions
RibbonAutoConfiguration#springClientFactory
SpringClientFactory的构造函数和方法

LoadBalancerClient实现类RibbonLoadBalancerClient:

/**
 * ribbon负载均衡客户端
 */
public class RibbonLoadBalancerClient implements LoadBalancerClient {

    private SpringClientFactory clientFactory;

    public RibbonLoadBalancerClient(SpringClientFactory clientFactory) {
        this.clientFactory = clientFactory;
    }

    /**
     * 选择服务实例
     */
    @Override
    public ServiceInstance choose(String serviceId) {
        return choose(serviceId, null);
    }

    /**
     * 选择服务实例
     */
    @Override
    public <T> ServiceInstance choose(String serviceId, Request<T> request) {
        ILoadBalancer loadBalancer = clientFactory.getInstance(serviceId, ILoadBalancer.class);
        Server server = loadBalancer.chooseServer("default");
        if (server != null) {
            return new TutuServiceInstance(serviceId, server.getHost(), server.getPort());
        }

        return null;
    }
}

自动装配spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
  com.github.cloud.loadbalancer.ribbon.config.RibbonAutoConfiguration,\
  com.github.cloud.loadbalancer.ribbon.config.RibbonTutuAutoConfiguration

测试:

1、在mini-spring-cloud-provider-example文件夹下执行命令mvn spring-boot:run启动多个服务提供者

服务消费者代码:

@SpringBootApplication
public class ConsumerApplication {

    public static void main(String[] args) {
        SpringApplication.run(ConsumerApplication.class, args);
    }
    
    @RestController
    static class HelloController {

      private RestTemplate restTemplate = new RestTemplate();

        @GetMapping("/world")
        public String world() {
            ServiceInstance serviceInstance = loadBalancerClient.choose("provider-application");
            if (serviceInstance != null) {
                URI uri = serviceInstance.getUri();
                String response = restTemplate.postForObject(uri.toString() + "/echo", null, String.class);
                return response;
            }

            throw new RuntimeException("No service instance for provider-application found");
        }
    }
}

2、多次访问http://localhost:8080/world, 通过响应报文中的端口可知请求以轮询的方式分配给服务提供者(默认的负载均衡规则ZoneAvoidanceRule在没有多zone的情况下退化为轮询规则)

集成ribbon实现客户端负载均衡(二)

简化调用方式，达到如下的效果，使用服务提供者的名称替换IP和端口

restTemplate.postForObject("http://provider-application/echo", null, String.class);

实现LoadBalancerClient的execute方法和reconstructURI方法:

public class RibbonLoadBalancerClient implements LoadBalancerClient {

    /**
     * 重建请求URI，将服务名称替换为服务实例的IP:端口
     */
    @Override
    public URI reconstructURI(ServiceInstance server, URI original) {
        try {
            //将服务名称替换为服务实例的IP:端口，例如http://provider-application/echo被重建为http://192.168.100.1:8888/echo
            StringBuilder sb = new StringBuilder();
            sb.append(original.getScheme()).append("://");
            sb.append(server.getHost());
            sb.append(":").append(server.getPort());
            sb.append(original.getRawPath());
            if (StrUtil.isNotEmpty(original.getRawQuery())) {
                sb.append("?").append(original.getRawQuery());
            }
            URI newURI = new URI(sb.toString());
            return newURI;
        } catch (URISyntaxException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * 处理http请求
     */
    @Override
    public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
        ServiceInstance serviceInstance = choose(serviceId);
        return execute(serviceId, serviceInstance, request);
    }

    /**
     * 处理http请求
     *
     */
    @Override
    public <T> T execute(String serviceId, ServiceInstance serviceInstance, LoadBalancerRequest<T> request) throws IOException {
        try {
            return request.apply(serviceInstance);
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }
}

reconstructURI方法，重建请求URI，将服务名称替换为服务实例的IP:端口，例如http://provider-application/echo 被重建为http://192.168.100.1:8888/echo
execute方法，处理http请求

有了RibbonLoadBalancerClient的reconstructURI和execute方法，将所有http请求委托给RibbonLoadBalancerClient即可。其实spring-cloud-commons已经帮我们配置好拦截RestTemplate的http请求委托给RibbonLoadBalancerClient的拦截器LoadBalancerInterceptor，配置类（有删减）如下:

LoadBalancerAutoConfiguration配置类为每一个被LoadBalanced注解修饰的RestTemplate增加LoadBalancerInterceptor拦截器。

LoadBalancerInterceptor将http请求委托给LoadBalancerClient执行，其中requestFactory.createRequest使用ServiceRequestWrapper包装原始的http请求

ServiceRequestWrapper调用LoadBalancerClient#reconstructURI方法重建请求URI，将服务名称替换为服务实例的IP:端口

测试:

服务消费者代码如下:

@SpringBootApplication
public class ConsumerApplication {

    public static void main(String[] args) {
        SpringApplication.run(ConsumerApplication.class, args);
    }

    @Configuration
    static class RestTemplateConfiguration {

        /**
         * 赋予负载均衡的能力
         *
         * @return
         */
        @LoadBalanced
        @Bean
        public RestTemplate restTemplate() {
            return new RestTemplate();
        }
    }

    @RestController
    static class HelloController {

        @Autowired
        private RestTemplate loadBalancedRestTemplate;

        @GetMapping("/foo")
        public String foo() {
            return loadBalancedRestTemplate.postForObject("http://provider-application/echo", null, String.class);
        }
    }
}

访问http://localhost:8080/foo

集成Feign简化调用方式

代码分支: open-feign

关于feign

Open Feign 是一个简化http调用方式的Java客户端。使用示例:

interface HelloService {

  @RequestLine("GET /hello")
  String hello();
}

@Test
public void testOpenFeign() {
  HelloService helloService = Feign.builder()
          .target(HelloService.class, "http://localhost:8080");
  String response = helloService.hello();
}

Spring Cloud基于Open Feign开发了Spring Cloud OpenFeign ，得以支持Spring Mvc的注解（通过实现了feign的Contract接口的实现类SpringMvcContract），使用示例:

interface WorldService {

    @GetMapping("/world")
    String world();
}

@Test
public void testSpringCloudOpenFeign() {
    WorldService worldService = Feign.builder()
            .contract(new SpringMvcContract())
            .target(WorldService.class, "http://localhost:8080");
    String response = worldService.world();
}

可以dubug上面两个示例，代码放在测试类FeignTest中，重点关注Contract接口对注解的解析

Open Feign工作流程

Open Feign核心API

一、Contract接口

负责解析Feign客户端接口的类注解、方法注解和参数。

实现类feign.Contract.Default支持Open Feign的注解，比如上面第一个示例中的RequestLine注解。

Spring Cloud OpenFeign开发的实现类SpringMvcContract支持Spring MVC的注解，如GetMapping、PostMapping、RequestMapping。

二、Encoder接口

编码器，将请求对象编码为请求体

三、Decoder接口

解码器，将响应体解码为对象

四、RequestInterceptor拦截器接口

对请求进行拦截处理

五、Client接口

提交http请求的接口

功能实现

@EnableFeignClients注解开启集成Feign客户端，该注解Import配置类FeignClientsRegistrar:

/**
 * 启用Feign
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(FeignClientsRegistrar.class)
public @interface EnableFeignClients {
}

配置类FeignClientsRegistrar扫描每个被FeignClient注解修饰的接口，基于JDK动态代理生成对象，注册到bean容器:

/**
 * 往bean容器中注册Feign客户端
 */
public class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar {

    /**
     * 往bean容器中注册Feign客户端
     */
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        //为FeignClient注解修饰的接口生成代理bean即Feign客户端，并注册到bean容器
        String packageName = ClassUtils.getPackageName(importingClassMetadata.getClassName());
        //扫描所有被FeignClient注解修饰的接口
        Set<Class<?>> classes = ClassUtil.scanPackageByAnnotation(packageName, FeignClient.class);
        for (Class<?> clazz : classes) {
            GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
            //使用FeignClientFactoryBean生成Feign客户端
            beanDefinition.setBeanClass(FeignClientFactoryBean.class);
            String clientName = clazz.getAnnotation(FeignClient.class).value();
            beanDefinition.getPropertyValues().addPropertyValue("contextId", clientName);
            beanDefinition.getPropertyValues().addPropertyValue("type", clazz);

            //将Feign客户端注册进bean容器
            String beanName = clazz.getName();
            registry.registerBeanDefinition(beanName, beanDefinition);
        }
    }
}

注意BeanDefinition指定的beanClass为FeignClientFactoryBean，它是FactoryBean的实现类，bean容器取其getObject方法返回值作为bean:

/**
 * 生成Feign客户端的FactoryBean
 */
public class FeignClientFactoryBean implements FactoryBean<Object>, ApplicationContextAware {

    private String contextId;

    private Class<?> type;

    private ApplicationContext applicationContext;

    @Override
    public Object getObject() throws Exception {
        FeignContext feignContext = applicationContext.getBean(FeignContext.class);
        Encoder encoder = feignContext.getInstance(contextId, Encoder.class);
        Decoder decoder = feignContext.getInstance(contextId, Decoder.class);
        Contract contract = feignContext.getInstance(contextId, Contract.class);
        Client client = feignContext.getInstance(contextId, Client.class);

        return Feign.builder()
                .encoder(encoder)
                .decoder(decoder)
                .contract(contract)
                .client(client)
                .target(new HardCodedTarget<>(type, contextId, "http://" + contextId));
    }

    //other methods
}

跟ribbon一样，每一个Provider服务集群（应用名称即spring.application.name相同的所有应用服务提供者）对应一套feign核心API。FeignContext继承自NamedContextFactory，为每一套feign核心API创建一个子spring应用上下文（ApplicationContext），来隔离不同服务的feign核心API配置(扩展篇实现)。

FeignContext:

/**
 * 为每个feign客户端创建一个应用上下文(ApplicationContext)，隔离每个feign客户端的配置
 */
public class FeignContext extends NamedContextFactory<FeignClientSpecification> {

    public FeignContext() {
        super(FeignClientsConfiguration.class, "feign", "feign.client.name");
    }
}

FeignClientsConfiguration配置类配置feign的核心API

/**
 * 配置feign的核心API
 */
@Configuration
public class FeignClientsConfiguration {

    @Bean
    @ConditionalOnMissingBean
    public Encoder encoder() {
        return new Encoder.Default();
    }

    @Bean
    @ConditionalOnMissingBean
    public Decoder decoder() {
        return new Decoder.Default();
    }

    @Bean
    @ConditionalOnMissingBean
    public Contract contract() {
        return new SpringMvcContract();
    }

    @Bean
    @ConditionalOnMissingBean
    public Client client(LoadBalancerClient loadBalancerClient) {
        return new LoadBalancerFeignClient(loadBalancerClient, new Client.Default(null, null));
    }
}

SpringMvcContract简单实现支持Spring MVC的PostMapping注解:

/**
 * feign支持Spring MVC的注解
 */
public class SpringMvcContract extends Contract.BaseContract {

    @Override
    protected void processAnnotationOnClass(MethodMetadata data, Class<?> clz) {
        //TODO 解析接口注解
    }

    @Override
    protected void processAnnotationOnMethod(MethodMetadata data, Annotation annotation, Method method) {
        //解析方法注解
        //解析PostMapping注解
        if (annotation instanceof PostMapping) {
            PostMapping postMapping = (PostMapping) annotation;
            data.template().method(Request.HttpMethod.POST);
            String path = postMapping.value()[0];
            if (!path.startsWith("/") && !data.template().path().endsWith("/")) {
                path = "/" + path;
            }
            data.template().uri(path, true);
        }

        //TODO 解析其他注解
    }

    @Override
    protected boolean processAnnotationsOnParameter(MethodMetadata data, Annotation[] annotations, int paramIndex) {
        //TODO 解析参数
        return true;
    }
}

LoadBalancerFeignClient组合ribbon的客户端负载均衡能力选择服务示例，然后发送http请求:

/**
 * 具备负载均衡能力的feign client
 */
public class LoadBalancerFeignClient implements Client {

    private LoadBalancerClient loadBalancerClient;

    private Client delegate;

    public LoadBalancerFeignClient(LoadBalancerClient loadBalancerClient, Client delegate) {
        this.loadBalancerClient = loadBalancerClient;
        this.delegate = delegate;
    }

    @SuppressWarnings("deprecation")
    @Override
    public Response execute(Request request, Request.Options options) throws IOException {
        try {
            //客户端负载均衡
            URI original = URI.create(request.url());
            String serviceId = original.getHost();
            //选择服务实例
            ServiceInstance serviceInstance = loadBalancerClient.choose(serviceId);
            //重建请求URI
            URI uri = loadBalancerClient.reconstructURI(serviceInstance, original);

            Request newRequest = Request.create(request.httpMethod(), uri.toASCIIString(), new HashMap<>(),
                    request.body(), StandardCharsets.UTF_8);
            return delegate.execute(newRequest, options);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

自动装配:

@Configuration
public class FeignAutoConfiguration {

    @Bean
    public FeignContext feignContext() {
        return new FeignContext();
    }
}

spring.factories:

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
  com.github.cloud.openfeign.FeignAutoConfiguration

测试:

消费者代码，使用@EnableFeignClients注解启用Feign:

@EnableFeignClients
@SpringBootApplication
public class ConsumerApplication {

    public static void main(String[] args) {
        SpringApplication.run(ConsumerApplication.class, args);
    }

    @RestController
    static class HelloController {

        @Autowired
        private EchoService echoService;

        @GetMapping("/bar")
        public String bar() {
            return echoService.echo();
        }
    }
}

Feign客户端:

@FeignClient("provider-application")
public interface EchoService {

    @PostMapping("echo")
    String echo();
}

访问http://localhost:8080/bar

API网关

代码分支: api-gateway-netflix-zuul

关于Netflix Zuul

Netflix Zuul是一个提供动态路由、监控、弹性容量、安全等功能的基于第七层网络协议的应用程序网关。

Zuul核心框架和执行流程

ZuulServlet负责拦截http请求，然后将http请求交给由ZuulFilter组成的过滤器链处理，ZuulFilter加载模块负责加载ZuulFilter。

可见ZuulFilter过滤器是zuul框架中的核心，API网关的鉴权、限流、权限、熔断、协议转换、错误码统一、缓存、日志、监控、告警等等功能可以实现ZuulFilter过滤器来实现。

ZuulFilter过滤器类型及执行顺序

ZuulFilter过滤器分为四种类型：

pre类型：调用远程服务之前执行
route：路由、发起远程调用
post：向客户端输出响应报文
error：处理过滤器链执行过程中出现的错误

ZuulServlet.service方法:

从ZuulServlet.service方法中能看出四种类型的过滤器的执行顺序如下图所示：

功能实现

EnableZuulProxy注解启用API网关功能

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(ZuulServerAutoConfiguration.class)
public @interface EnableZuulProxy {
}

EnableZuulProxy注解引入配置类ZuulServerAutoConfiguration，该配置类配置了ZuulServlet、过滤器加载模块的FilterRegistry、实现的三个ZuulFilter以及PreDecorationFilter过滤器需要使用的路由定位器RouteLocator。


@Configuration
@EnableConfigurationProperties({ZuulProperties.class})
public class ZuulServerAutoConfiguration {

  @Autowired
  protected ZuulProperties zuulProperties;

  /**
   * 注册ZuulServlet，用于拦截处理http请求
   */
  @Bean
  public ServletRegistrationBean zuulServlet() {
    return new ServletRegistrationBean<>(new ZuulServlet(), zuulProperties.getServletPath());
  }

  /**
   * 路由定位器
   */
  @Bean
  public RouteLocator simpleRouteLocator() {
    return new SimpleRouteLocator(zuulProperties);
  }

  /**
   * pre类型过滤器，根据RouteLocator来进行路由规则的匹配
   */
  @Bean
  public ZuulFilter preDecorationFilter(RouteLocator routeLocator) {
    return new PreDecorationFilter(routeLocator);
  }

  /**
   * route类型过滤器，使用ribbon负载均衡器进行http请求
   */
  @Bean
  ZuulFilter ribbonRoutingFilter(LoadBalancerClient loadBalancerClient) {
    return new RibbonRoutingFilter(loadBalancerClient);
  }

  /**
   * post类型过滤器，向客户端输出响应报文
   */
  @Bean
  ZuulFilter sendResponseFilter() {
    return new SendResponseFilter();
  }

  /**
   * 注册过滤器
   */
  @Bean
  public FilterRegistry filterRegistry(Map<String, ZuulFilter> filterMap) {
    FilterRegistry filterRegistry = FilterRegistry.instance();
    filterMap.forEach((name, filter) -> {
      filterRegistry.put(name, filter);
    });
    return filterRegistry;
  }
}

只针对正常流程实现了以下三个过滤器，想了解更多过滤器可以参考这篇文章: Spring Cloud 源码分析（四）Zuul：核心过滤器

pre类型过滤器PreDecorationFilter，使用路由定位器RouteLocator根据请求路径匹配路由，将路由信息放进请求上下文RequestContext中

/**
 * pre类型过滤器，根据RouteLocator来进行路由规则的匹配
 */
public class PreDecorationFilter extends ZuulFilter {
  private static Logger logger = LoggerFactory.getLogger(PreDecorationFilter.class);

  private RouteLocator routeLocator;

  public PreDecorationFilter(RouteLocator routeLocator) {
    this.routeLocator = routeLocator;
  }

  @Override
  public String filterType() {
    return PRE_TYPE;
  }

  @Override
  public int filterOrder() {
    return 5;
  }

  @Override
  public boolean shouldFilter() {
    return true;
  }

  @Override
  public Object run() throws ZuulException {
    RequestContext requestContext = RequestContext.getCurrentContext();
    String requestURI = requestContext.getRequest().getRequestURI();
    //获取匹配的路由
    Route route = routeLocator.getMatchingRoute(requestURI);
    if (route != null) {
      requestContext.put(REQUEST_URI_KEY, route.getPath());
      requestContext.set(SERVICE_ID_KEY, route.getLocation());
    } else {
      logger.error("获取不到匹配的路由, requestURI: {}", requestContext);
    }

    return null;
  }
}

路由定位器:

/**
 * 路由定位器
 */
public interface RouteLocator {

  /**
   * 获取匹配的路由
   *
   * @param path
   * @return
   */
  Route getMatchingRoute(String path);
}

/**
 * 路由定位器实现类
 */
public class SimpleRouteLocator implements RouteLocator {

  private ZuulProperties zuulProperties;

  private PathMatcher pathMatcher = new AntPathMatcher();

  public SimpleRouteLocator(ZuulProperties zuulProperties) {
    this.zuulProperties = zuulProperties;
  }

  @Override
  public Route getMatchingRoute(String path) {
    for (Map.Entry<String, ZuulProperties.ZuulRoute> entry : zuulProperties.getRoutes().entrySet()) {
      ZuulProperties.ZuulRoute zuulRoute = entry.getValue();
      String pattern = zuulRoute.getPath();
      if (pathMatcher.match(pattern, path)) {
        String targetPath = path.substring(pattern.indexOf("*") - 1);
        return new Route(targetPath, zuulRoute.getServiceId());
      }
    }

    return null;
  }
}

route类型过滤器RibbonRoutingFilter，根据PreDecorationFilter过滤器匹配的路由信息发起远程调用，将调用结果放进请求上下文RequestContext

/**
 * route类型过滤器，使用ribbon负载均衡器进行http请求
 */
public class RibbonRoutingFilter extends ZuulFilter {
  private static Logger logger = LoggerFactory.getLogger(RibbonRoutingFilter.class);

  private LoadBalancerClient loadBalancerClient;

  public RibbonRoutingFilter(LoadBalancerClient loadBalancerClient) {
    this.loadBalancerClient = loadBalancerClient;
  }

  @Override
  public String filterType() {
    return ROUTE_TYPE;
  }

  @Override
  public int filterOrder() {
    return 10;
  }

  @Override
  public boolean shouldFilter() {
    RequestContext requestContext = RequestContext.getCurrentContext();
    return requestContext.get(SERVICE_ID_KEY) != null;
  }

  @Override
  public Object run() throws ZuulException {
    try {
      RequestContext requestContext = RequestContext.getCurrentContext();
      //使用ribbon的负载均衡能力发起远程调用
      //TODO 简单实现，熔断降级章节再完善
      String serviceId = (String) requestContext.get(SERVICE_ID_KEY);
      ServiceInstance serviceInstance = loadBalancerClient.choose(serviceId);
      if (serviceInstance == null) {
        logger.error("根据serviceId查询不到服务示例，serviceId: {}", serviceId);
        return null;
      }

      String requestURI = (String) requestContext.get(REQUEST_URI_KEY);
      String url = serviceInstance.getUri().toString() + requestURI;
      HttpRequest httpRequest = HttpUtil.createRequest(Method.POST, url);
      HttpResponse httpResponse = httpRequest.execute();

      //将响应报文的状态码和内容写进请求上下文中
      requestContext.setResponseStatusCode(httpResponse.getStatus());
      requestContext.setResponseDataStream(httpResponse.bodyStream());

      return httpResponse;
    } catch (Exception e) {
      rethrowRuntimeException(e);
    }
    return null;
  }
}

post类型过滤器SendResponseFilter，将RibbonRoutingFilter过滤器发起远程调用的结果作为响应报文输出给客户端

/**
 * post类型过滤器，向客户端输出响应报文
 */
public class SendResponseFilter extends ZuulFilter {
  private static Logger logger = LoggerFactory.getLogger(SendResponseFilter.class);

  @Override
  public String filterType() {
    return POST_TYPE;
  }

  @Override
  public int filterOrder() {
    return 1000;
  }

  @Override
  public boolean shouldFilter() {
    return RequestContext.getCurrentContext()
            .getResponseDataStream() != null;
  }

  @Override
  public Object run() throws ZuulException {
    //向客户端输出响应报文
    RequestContext requestContext = RequestContext.getCurrentContext();
    InputStream inputStream = requestContext.getResponseDataStream();
    try {
      HttpServletResponse servletResponse = requestContext.getResponse();
      servletResponse.setCharacterEncoding("UTF-8");

      OutputStream outStream = servletResponse.getOutputStream();
      StreamUtils.copy(inputStream, outStream);
    } catch (Exception e) {
      rethrowRuntimeException(e);
    } finally {
      //关闭输入输出流
      if (inputStream != null) {
        try {
          inputStream.close();
        } catch (Exception e) {
          logger.error("关闭输入流失败", e);
        }
      }

      //Servlet容器会自动关闭输出流
    }
    return null;
  }
}

测试:

启动API网关ApiGatewayApplication

API网关代码:


@EnableZuulProxy
@SpringBootApplication
public class ApiGatewayApplication {

  public static void main(String[] args) {
    SpringApplication.run(ApiGatewayApplication.class, args);
  }
}

配置application.yml:

spring:
  application:
    name: api-gateway-application
  cloud:
    tutu:
      discovery:
        server-addr: localhost:6688
        service: ${spring.application.name}

server:
  port: 8888

zuul:
  servlet-path: /*
  routes:
    route_provider_application:
      path: /provider-application/**
      service-id: provider-application

访问http://localhost:8888/provider-application/echo

流量控制和熔断降级

TODO 待研究完Sentinel再写本章节，估计得隔一段时间~~~

更新

Sentinel源码不难，感兴趣的小伙伴阅读sentinel-core模块即可，推荐几篇文章:

Sentinel入门查看官方文档《Sentinel官方文档》 ,如果想阅读源码需要重点理解《基本原理》和《Sentinel核心类解析》章节：
- 《Sentinel基本原理》
- 《Sentinel核心类解析》
下面四篇文章来自于github用户all4you的项目sentinel-tutorial ，作者写得非常用心和精彩，给作者点个star吧

Sentinel整合到Spring Cloud的原理也很简单，具体查看Spring Web拦截器SentinelWebInterceptor 和SentinelWebTotalInterceptor，还有支持SentinelResource注解的SentinelResourceAspect切面类，我就不整合到该项目了。

非常感谢阅读到此的小伙伴，希望小伙伴们在此issue 留言发表评论，也可以写下希望我写的下一个项目，Netty/RocketMQ等等。

撒花~~~