1. 负载均衡核心概念

1.1 什么是负载均衡？

负载均衡是将网络流量或工作负载分配到多个计算资源（如服务器、服务实例）的技术，旨在优化资源使用、最大化吞吐量、最小化响应时间，并避免任何单个资源的过载。

// 负载均衡的现实比喻
public class LoadBalancerAnalogy {
    
    /**
     * 餐厅服务 vs 负载均衡
     */
    public class RestaurantComparison {
        // 餐厅领班 → 负载均衡器
        // 多个服务员 → 服务实例
        // 顾客请求 → 服务调用
        // 服务员状态 → 健康检查
        // 特殊需求 → 路由策略
    }
    
    /**
     * 没有负载均衡的问题
     */
    public class WithoutLoadBalancer {
        // 1. 单点故障：单个服务实例宕机导致服务不可用
        // 2. 性能瓶颈：所有流量集中到单个实例
        // 3. 资源浪费：部分实例空闲，部分实例过载
        // 4. 扩展困难：无法动态调整实例数量
    }
}

1.2 负载均衡的核心价值

2. 负载均衡架构与模式

2.1 负载均衡架构类型

2.2 主流负载均衡技术对比

特性	Spring Cloud LoadBalancer	Ribbon	Nginx	HAProxy
部署位置	客户端	客户端	服务端	服务端
服务发现	集成	集成	需要插件	需要配置
配置方式	代码/配置	代码/配置	配置文件	配置文件
健康检查	支持	支持	强大	强大
动态更新	支持	支持	重载配置	重载配置
性能	中等	中等	高	非常高
功能丰富度	中等	中等	丰富	丰富

3. Spring Cloud LoadBalancer 实战

3.1 环境准备与依赖配置

<!-- pom.xml 负载均衡依赖 -->
<dependencies>
    <!-- Spring Cloud LoadBalancer -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-loadbalancer</artifactId>
    </dependency>
    
    <!-- Spring Cloud Commons -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-commons</artifactId>
    </dependency>
    
    <!-- Nacos Discovery -->
    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
    </dependency>
    
    <!-- Web -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    
    <!-- Actuator -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
    
    <!-- Reactor for Reactive Programming -->
    <dependency>
        <groupId>io.projectreactor</groupId>
        <artifactId>reactor-core</artifactId>
    </dependency>
</dependencies>

3.2 基础配置与自动装配

# application.yml 负载均衡配置
spring:
  application:
    name: order-service
  cloud:
    nacos:
      discovery:
        server-addr: 192.168.1.100:8848
        namespace: dev
        group: DEFAULT_GROUP
    loadbalancer:
      enabled: true
      # 缓存配置
      cache:
        enabled: true
        capacity: 256
        ttl: 30s
      # 健康检查配置
      health-check:
        enabled: true
        interval: 30s
        initial-delay: 0s
      # 重试配置
      retry:
        enabled: true
        max-attempts: 3
        backoff:
          initial-interval: 1000ms
          max-interval: 2000ms
          multiplier: 2.0
# 负载均衡日志
logging:
  level:
    org.springframework.cloud.loadbalancer: DEBUG
    reactor.netty: INFO
# 监控端点
management:
  endpoints:
    web:
      exposure:
        include: loadbalancer,health,metrics
  endpoint:
    loadbalancer:
      enabled: true

3.3 基础负载均衡使用

// 订单服务 - 负载均衡客户端
@RestController
@RequestMapping("/orders")
@Slf4j
public class OrderController {
    
    /**
     * 使用LoadBalanced RestTemplate
     */
    @Autowired
    @Qualifier("loadBalancedRestTemplate")
    private RestTemplate restTemplate;
    
    /**
     * 使用WebClient进行响应式负载均衡
     */
    @Autowired
    private WebClient.Builder webClientBuilder;
    
    /**
     * 使用LoadBalancerClient进行细粒度控制
     */
    @Autowired
    private LoadBalancerClient loadBalancerClient;
    
    /**
     * 创建订单 - 自动负载均衡调用用户服务
     */
    @PostMapping
    public ResponseEntity<Order> createOrder(@RequestBody OrderRequest request) {
        log.info("创建订单请求: {}", request);
        
        try {
            // 1. 验证用户信息 - 使用RestTemplate
            User user = validateUser(request.getUserId());
            
            // 2. 验证商品信息 - 使用WebClient
            Product product = validateProduct(request.getProductId());
            
            // 3. 创建订单
            Order order = orderService.createOrder(request, user, product);
            
            return ResponseEntity.ok(order);
            
        } catch (Exception e) {
            log.error("创建订单失败", e);
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
        }
    }
    
    /**
     * 使用RestTemplate进行服务调用（自动负载均衡）
     */
    private User validateUser(String userId) {
        String url = "http://user-service/users/" + userId;
        
        ResponseEntity<User> response = restTemplate.getForEntity(url, User.class);
        
        if (!response.getStatusCode().is2xxSuccessful()) {
            throw new RuntimeException("用户验证失败: " + response.getStatusCode());
        }
        
        return response.getBody();
    }
    
    /**
     * 使用WebClient进行响应式服务调用
     */
    private Product validateProduct(String productId) {
        return webClientBuilder.build()
            .get()
            .uri("http://product-service/products/" + productId)
            .retrieve()
            .bodyToMono(Product.class)
            .block(); // 生产环境建议使用响应式编程
    }
    
    /**
     * 手动负载均衡示例
     */
    @GetMapping("/manual-lb/{userId}")
    public ResponseEntity<String> manualLoadBalancing(@PathVariable String userId) {
        ServiceInstance instance = loadBalancerClient.choose("user-service");
        
        if (instance == null) {
            return ResponseEntity.status(HttpStatus.SERVICE_UNAVAILABLE)
                .body("没有可用的用户服务实例");
        }
        
        String url = String.format("http://%s:%s/users/%s",
            instance.getHost(), instance.getPort(), userId);
        
        log.info("手动选择服务实例: {}:{}", instance.getHost(), instance.getPort());
        
        try {
            ResponseEntity<String> response = new RestTemplate().getForEntity(url, String.class);
            return ResponseEntity.ok("通过实例 " + instance.getInstanceId() + " 调用成功: " + response.getBody());
        } catch (Exception e) {
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
                .body("服务调用失败: " + e.getMessage());
        }
    }
}
// 负载均衡配置类
@Configuration
public class LoadBalancerConfiguration {
    
    /**
     * 配置负载均衡的RestTemplate
     */
    @Bean
    @LoadBalanced
    public RestTemplate loadBalancedRestTemplate() {
        return new RestTemplateBuilder()
            .setConnectTimeout(Duration.ofSeconds(5))
            .setReadTimeout(Duration.ofSeconds(10))
            .additionalInterceptors(new LoadBalancerLoggingInterceptor())
            .build();
    }
    
    /**
     * 配置负载均衡的WebClient
     */
    @Bean
    @LoadBalanced
    public WebClient.Builder loadBalancedWebClientBuilder() {
        return WebClient.builder()
            .filter(new LoadBalancerClientFilter())
            .filter(new LoggingFilter());
    }
}
// 负载均衡日志拦截器
@Slf4j
class LoadBalancerLoggingInterceptor implements ClientHttpRequestInterceptor {
    
    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, 
                                      ClientHttpRequestExecution execution) throws IOException {
        long startTime = System.currentTimeMillis();
        
        try {
            ClientHttpResponse response = execution.execute(request, body);
            
            long duration = System.currentTimeMillis() - startTime;
            log.debug("服务调用: {} {}, 状态: {}, 耗时: {}ms",
                request.getMethod(), request.getURI(), 
                response.getStatusCode(), duration);
                
            return response;
        } catch (IOException e) {
            long duration = System.currentTimeMillis() - startTime;
            log.error("服务调用失败: {} {}, 耗时: {}ms, 错误: {}",
                request.getMethod(), request.getURI(), duration, e.getMessage());
            throw e;
        }
    }
}

4. 负载均衡算法实战

4.1 内置负载均衡算法

// 负载均衡算法配置
@Configuration
public class LoadBalancerAlgorithmConfig {
    
    /**
     * 轮询负载均衡器
     */
    @Bean
    public ReactorLoadBalancer<ServiceInstance> roundRobinLoadBalancer(
            Environment environment,
            LoadBalancerClientFactory loadBalancerClientFactory) {
        
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
        return new RoundRobinLoadBalancer(
            loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class),
            name
        );
    }
    
    /**
     * 随机负载均衡器
     */
    @Bean
    @Primary
    public ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(
            Environment environment,
            LoadBalancerClientFactory loadBalancerClientFactory) {
        
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
        return new RandomLoadBalancer(
            loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class),
            name
        );
    }
}
// 自定义负载均衡算法 - 权重轮询
@Component
public class WeightedRoundRobinLoadBalancer implements ReactorServiceInstanceLoadBalancer {
    
    private final String serviceId;
    private final ServiceInstanceListSupplier serviceInstanceListSupplier;
    
    // 权重计数器
    private final AtomicInteger position = new AtomicInteger(0);
    private volatile List<ServiceInstance> lastInstances = Collections.emptyList();
    
    public WeightedRoundRobinLoadBalancer(ServiceInstanceListSupplier serviceInstanceListSupplier, 
                                         String serviceId) {
        this.serviceId = serviceId;
        this.serviceInstanceListSupplier = serviceInstanceListSupplier;
    }
    
    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        return serviceInstanceListSupplier.get(request).next()
            .map(instances -> processInstanceResponse(instances, request));
    }
    
    private Response<ServiceInstance> processInstanceResponse(List<ServiceInstance> instances, 
                                                             Request request) {
        if (instances.isEmpty()) {
            log.warn("没有可用的服务实例: {}", serviceId);
            return new EmptyResponse();
        }
        
        // 更新实例列表
        if (!instances.equals(lastInstances)) {
            lastInstances = instances;
            position.set(0);
        }
        
        // 基于权重的选择逻辑
        ServiceInstance instance = selectWeightedInstance(instances);
        
        if (instance != null) {
            log.debug("权重轮询选择实例: {}:{}", instance.getHost(), instance.getPort());
            return new DefaultResponse(instance);
        }
        
        return new EmptyResponse();
    }
    
    private ServiceInstance selectWeightedInstance(List<ServiceInstance> instances) {
        // 计算总权重
        int totalWeight = instances.stream()
            .mapToInt(instance -> getWeight(instance))
            .sum();
        
        if (totalWeight <= 0) {
            return instances.get(position.getAndIncrement() % instances.size());
        }
        
        // 权重轮询算法
        int currentPos = position.getAndUpdate(pos -> (pos + 1) % totalWeight);
        int currentWeight = 0;
        
        for (ServiceInstance instance : instances) {
            currentWeight += getWeight(instance);
            if (currentPos < currentWeight) {
                return instance;
            }
        }
        
        return instances.get(0);
    }
    
    private int getWeight(ServiceInstance instance) {
        String weightStr = instance.getMetadata().get("weight");
        if (weightStr != null) {
            try {
                return Integer.parseInt(weightStr);
            } catch (NumberFormatException e) {
                log.warn("无效的权重配置: {}", weightStr);
            }
        }
        return 1; // 默认权重
    }
}
// 自定义负载均衡算法 - 最少连接数
@Component
public class LeastConnectionLoadBalancer implements ReactorServiceInstanceLoadBalancer {
    
    private final String serviceId;
    private final ServiceInstanceListSupplier serviceInstanceListSupplier;
    
    // 连接数统计
    private final ConcurrentHashMap<String, AtomicInteger> connectionCounts = new ConcurrentHashMap<>();
    private final ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
    
    public LeastConnectionLoadBalancer(ServiceInstanceListSupplier serviceInstanceListSupplier, 
                                      String serviceId) {
        this.serviceId = serviceId;
        this.serviceInstanceListSupplier = serviceInstanceListSupplier;
        
        // 定期清理过期的连接统计
        scheduler.scheduleAtFixedRate(this::cleanupConnectionCounts, 1, 1, TimeUnit.MINUTES);
    }
    
    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        return serviceInstanceListSupplier.get(request).next()
            .map(instances -> processInstanceResponse(instances, request));
    }
    
    private Response<ServiceInstance> processInstanceResponse(List<ServiceInstance> instances, 
                                                             Request request) {
        if (instances.isEmpty()) {
            return new EmptyResponse();
        }
        
        // 选择连接数最少的实例
        ServiceInstance selectedInstance = instances.stream()
            .min(Comparator.comparingInt(this::getConnectionCount))
            .orElse(instances.get(0));
        
        if (selectedInstance != null) {
            // 增加连接计数
            incrementConnectionCount(selectedInstance);
            
            log.debug("最少连接选择实例: {}:{} (连接数: {})", 
                selectedInstance.getHost(), selectedInstance.getPort(),
                getConnectionCount(selectedInstance));
                
            return new DefaultResponse(selectedInstance);
        }
        
        return new EmptyResponse();
    }
    
    private int getConnectionCount(ServiceInstance instance) {
        String instanceId = getInstanceId(instance);
        AtomicInteger count = connectionCounts.get(instanceId);
        return count != null ? count.get() : 0;
    }
    
    private void incrementConnectionCount(ServiceInstance instance) {
        String instanceId = getInstanceId(instance);
        connectionCounts.computeIfAbsent(instanceId, k -> new AtomicInteger(0))
            .incrementAndGet();
    }
    
    public void decrementConnectionCount(ServiceInstance instance) {
        String instanceId = getInstanceId(instance);
        AtomicInteger count = connectionCounts.get(instanceId);
        if (count != null) {
            count.decrementAndGet();
        }
    }
    
    private String getInstanceId(ServiceInstance instance) {
        return instance.getHost() + ":" + instance.getPort();
    }
    
    private void cleanupConnectionCounts() {
        // 清理长时间没有活动的连接统计
        connectionCounts.entrySet().removeIf(entry -> 
            entry.getValue().get() <= 0);
    }
    
    @PreDestroy
    public void destroy() {
        scheduler.shutdown();
    }
}

4.2 基于响应时间的负载均衡

// 响应时间感知的负载均衡器
@Component
@Slf4j
public class ResponseTimeAwareLoadBalancer implements ReactorServiceInstanceLoadBalancer {
    
    private final String serviceId;
    private final ServiceInstanceListSupplier serviceInstanceListSupplier;
    
    // 响应时间统计
    private final ConcurrentHashMap<String, ResponseTimeStats> responseTimeStats = new ConcurrentHashMap<>();
    private final ScheduledExecutorService statsCleaner = Executors.newSingleThreadScheduledExecutor();
    
    public ResponseTimeAwareLoadBalancer(ServiceInstanceListSupplier serviceInstanceListSupplier, 
                                        String serviceId) {
        this.serviceId = serviceId;
        this.serviceInstanceListSupplier = serviceInstanceListSupplier;
        
        // 定期清理统计信息
        statsCleaner.scheduleAtFixedRate(this::cleanupStats, 5, 5, TimeUnit.MINUTES);
    }
    
    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        return serviceInstanceListSupplier.get(request).next()
            .map(instances -> processInstanceResponse(instances, request));
    }
    
    private Response<ServiceInstance> processInstanceResponse(List<ServiceInstance> instances, 
                                                             Request request) {
        if (instances.isEmpty()) {
            return new EmptyResponse();
        }
        
        // 基于响应时间的选择逻辑
        ServiceInstance selectedInstance = selectByResponseTime(instances);
        
        if (selectedInstance != null) {
            log.debug("响应时间感知选择实例: {}:{} (平均响应时间: {}ms)", 
                selectedInstance.getHost(), selectedInstance.getPort(),
                getAverageResponseTime(selectedInstance));
                
            return new DefaultResponse(selectedInstance);
        }
        
        return new EmptyResponse();
    }
    
    private ServiceInstance selectByResponseTime(List<ServiceInstance> instances) {
        // 过滤掉响应时间过长的实例
        List<ServiceInstance> healthyInstances = instances.stream()
            .filter(instance -> {
                double avgResponseTime = getAverageResponseTime(instance);
                return avgResponseTime < 5000; // 5秒阈值
            })
            .collect(Collectors.toList());
        
        if (healthyInstances.isEmpty()) {
            return instances.get(0); // 没有健康实例时返回第一个
        }
        
        // 选择响应时间最短的实例
        return healthyInstances.stream()
            .min(Comparator.comparingDouble(this::getAverageResponseTime))
            .orElse(healthyInstances.get(0));
    }
    
    /**
     * 记录响应时间
     */
    public void recordResponseTime(ServiceInstance instance, long responseTime) {
        String instanceId = getInstanceId(instance);
        ResponseTimeStats stats = responseTimeStats.computeIfAbsent(
            instanceId, k -> new ResponseTimeStats());
        stats.record(responseTime);
    }
    
    private double getAverageResponseTime(ServiceInstance instance) {
        String instanceId = getInstanceId(instance);
        ResponseTimeStats stats = responseTimeStats.get(instanceId);
        return stats != null ? stats.getAverage() : 100.0; // 默认100ms
    }
    
    private String getInstanceId(ServiceInstance instance) {
        return instance.getHost() + ":" + instance.getPort();
    }
    
    private void cleanupStats() {
        long now = System.currentTimeMillis();
        responseTimeStats.entrySet().removeIf(entry -> 
            now - entry.getValue().getLastUpdateTime() > 300000); // 5分钟过期
    }
    
    @PreDestroy
    public void destroy() {
        statsCleaner.shutdown();
    }
    
    /**
     * 响应时间统计类
     */
    @Data
    private static class ResponseTimeStats {
        private long totalResponseTime = 0;
        private int requestCount = 0;
        private long lastUpdateTime = System.currentTimeMillis();
        
        public void record(long responseTime) {
            this.totalResponseTime += responseTime;
            this.requestCount++;
            this.lastUpdateTime = System.currentTimeMillis();
        }
        
        public double getAverage() {
            return requestCount > 0 ? (double) totalResponseTime / requestCount : 0.0;
        }
    }
}
// 响应时间监控拦截器
@Component
@Slf4j
public class ResponseTimeMonitoringInterceptor implements ClientHttpRequestInterceptor {
    
    @Autowired
    private ResponseTimeAwareLoadBalancer responseTimeLoadBalancer;
    
    @Autowired
    private ServiceInstanceChooser serviceInstanceChooser;
    
    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, 
                                      ClientHttpRequestExecution execution) throws IOException {
        long startTime = System.currentTimeMillis();
        ServiceInstance selectedInstance = null;
        
        try {
            // 获取选择的实例（需要扩展框架以获取此信息）
            // 这里简化实现，实际需要修改框架
            
            ClientHttpResponse response = execution.execute(request, body);
            long responseTime = System.currentTimeMillis() - startTime;
            
            // 记录响应时间
            if (selectedInstance != null) {
                responseTimeLoadBalancer.recordResponseTime(selectedInstance, responseTime);
            }
            
            log.debug("请求 {} 响应时间: {}ms", request.getURI(), responseTime);
            return response;
            
        } catch (IOException e) {
            long responseTime = System.currentTimeMillis() - startTime;
            log.error("请求失败: {}, 耗时: {}ms", request.getURI(), responseTime, e);
            throw e;
        }
    }
}

5. 高级负载均衡特性

5.1 区域感知负载均衡

// 区域感知负载均衡器
@Component
@Slf4j
public class ZoneAwareLoadBalancer implements ReactorServiceInstanceLoadBalancer {
    
    private final String serviceId;
    private final ServiceInstanceListSupplier serviceInstanceListSupplier;
    
    // 区域配置
    private final String localZone = System.getenv().getOrDefault("ZONE", "default");
    private final double crossZoneTrafficRatio = 0.2; // 跨区域流量比例
    
    public ZoneAwareLoadBalancer(ServiceInstanceListSupplier serviceInstanceListSupplier, 
                                String serviceId) {
        this.serviceId = serviceId;
        this.serviceInstanceListSupplier = serviceInstanceListSupplier;
    }
    
    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        return serviceInstanceListSupplier.get(request).next()
            .map(instances -> processInstanceResponse(instances, request));
    }
    
    private Response<ServiceInstance> processInstanceResponse(List<ServiceInstance> instances, 
                                                             Request request) {
        if (instances.isEmpty()) {
            return new EmptyResponse();
        }
        
        // 按区域分组
        Map<String, List<ServiceInstance>> instancesByZone = instances.stream()
            .collect(Collectors.groupingBy(this::getInstanceZone));
        
        // 优先选择同区域实例
        List<ServiceInstance> localZoneInstances = instancesByZone.getOrDefault(localZone, 
            Collections.emptyList());
        
        ServiceInstance selectedInstance;
        
        if (!localZoneInstances.isEmpty() && shouldChooseLocal()) {
            // 选择同区域实例
            selectedInstance = chooseFromInstances(localZoneInstances);
            log.debug("区域感知选择同区域实例: {}:{} (区域: {})", 
                selectedInstance.getHost(), selectedInstance.getPort(), localZone);
        } else {
            // 选择跨区域实例
            List<ServiceInstance> crossZoneInstances = instancesByZone.entrySet().stream()
                .filter(entry -> !entry.getKey().equals(localZone))
                .flatMap(entry -> entry.getValue().stream())
                .collect(Collectors.toList());
                
            if (!crossZoneInstances.isEmpty()) {
                selectedInstance = chooseFromInstances(crossZoneInstances);
                log.debug("区域感知选择跨区域实例: {}:{} (区域: {})", 
                    selectedInstance.getHost(), selectedInstance.getPort(), 
                    getInstanceZone(selectedInstance));
            } else {
                selectedInstance = chooseFromInstances(instances);
            }
        }
        
        return new DefaultResponse(selectedInstance);
    }
    
    private boolean shouldChooseLocal() {
        // 控制跨区域流量比例
        return Math.random() > crossZoneTrafficRatio;
    }
    
    private ServiceInstance chooseFromInstances(List<ServiceInstance> instances) {
        // 简单的随机选择，可替换为其他算法
        int index = ThreadLocalRandom.current().nextInt(instances.size());
        return instances.get(index);
    }
    
    private String getInstanceZone(ServiceInstance instance) {
        return instance.getMetadata().getOrDefault("zone", "default");
    }
}
// 多区域配置
@Configuration
public class MultiZoneConfiguration {
    
    /**
     * 区域感知负载均衡配置
     */
    @Bean
    @Primary
    public ReactorLoadBalancer<ServiceInstance> zoneAwareLoadBalancer(
            Environment environment,
            LoadBalancerClientFactory loadBalancerClientFactory) {
        
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
        return new ZoneAwareLoadBalancer(
            loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class),
            name
        );
    }
    
    /**
     * 区域过滤器 - 只返回健康且同区域优先的实例
     */
    @Bean
    public ServiceInstanceListSupplier zonePreferenceServiceInstanceListSupplier(
            ConfigurableApplicationContext context) {
        
        return ServiceInstanceListSupplier.builder()
            .withBlockingDiscoveryClient()
            .withBlockingHealthChecks()
            .withZonePreference()
            .withCaching()
            .build(context);
    }
}

5.2 基于标签的负载均衡

// 标签路由负载均衡器
@Component
@Slf4j
public class TagBasedLoadBalancer implements ReactorServiceInstanceLoadBalancer {
    
    private final String serviceId;
    private final ServiceInstanceListSupplier serviceInstanceListSupplier;
    
    public TagBasedLoadBalancer(ServiceInstanceListSupplier serviceInstanceListSupplier, 
                               String serviceId) {
        this.serviceId = serviceId;
        this.serviceInstanceListSupplier = serviceInstanceListSupplier;
    }
    
    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        return serviceInstanceListSupplier.get(request).next()
            .map(instances -> processInstanceResponse(instances, request));
    }
    
    private Response<ServiceInstance> processInstanceResponse(List<ServiceInstance> instances, 
                                                             Request request) {
        if (instances.isEmpty()) {
            return new EmptyResponse();
        }
        
        // 获取请求的标签信息
        Map<String, String> requestTags = extractRequestTags(request);
        
        // 基于标签选择实例
        ServiceInstance selectedInstance = selectInstanceByTags(instances, requestTags);
        
        if (selectedInstance != null) {
            log.debug("标签路由选择实例: {}:{} (标签: {})", 
                selectedInstance.getHost(), selectedInstance.getPort(),
                selectedInstance.getMetadata());
                
            return new DefaultResponse(selectedInstance);
        }
        
        // 没有匹配标签时使用默认算法
        return new RandomLoadBalancer(serviceInstanceListSupplier, serviceId)
            .choose(request).block();
    }
    
    private Map<String, String> extractRequestTags(Request request) {
        Map<String, String> tags = new HashMap<>();
        
        // 从请求上下文获取标签信息
        if (request.getContext() instanceof HttpRequest) {
            HttpRequest httpRequest = (HttpRequest) request.getContext();
            
            // 从Header获取标签
            String userType = httpRequest.getHeaders().getFirst("X-User-Type");
            if (userType != null) {
                tags.put("userType", userType);
            }
            
            String trafficType = httpRequest.getHeaders().getFirst("X-Traffic-Type");
            if (trafficType != null) {
                tags.put("trafficType", trafficType);
            }
        }
        
        return tags;
    }
    
    private ServiceInstance selectInstanceByTags(List<ServiceInstance> instances, 
                                                Map<String, String> requestTags) {
        if (requestTags.isEmpty()) {
            return null; // 没有标签信息，使用默认算法
        }
        
        // 查找匹配标签的实例
        List<ServiceInstance> matchedInstances = instances.stream()
            .filter(instance -> matchesTags(instance, requestTags))
            .collect(Collectors.toList());
        
        if (!matchedInstances.isEmpty()) {
            // 随机选择一个匹配的实例
            int index = ThreadLocalRandom.current().nextInt(matchedInstances.size());
            return matchedInstances.get(index);
        }
        
        // 没有完全匹配时，尝试部分匹配
        List<ServiceInstance> partialMatchedInstances = instances.stream()
            .filter(instance -> partialMatchesTags(instance, requestTags))
            .collect(Collectors.toList());
            
        if (!partialMatchedInstances.isEmpty()) {
            int index = ThreadLocalRandom.current().nextInt(partialMatchedInstances.size());
            return partialMatchedInstances.get(index);
        }
        
        return null;
    }
    
    private boolean matchesTags(ServiceInstance instance, Map<String, String> requestTags) {
        Map<String, String> instanceTags = instance.getMetadata();
        
        return requestTags.entrySet().stream()
            .allMatch(entry -> entry.getValue().equals(instanceTags.get(entry.getKey())));
    }
    
    private boolean partialMatchesTags(ServiceInstance instance, Map<String, String> requestTags) {
        Map<String, String> instanceTags = instance.getMetadata();
        
        long matchCount = requestTags.entrySet().stream()
            .filter(entry -> entry.getValue().equals(instanceTags.get(entry.getKey())))
            .count();
            
        return matchCount > 0; // 至少匹配一个标签
    }
}
// 标签路由配置
@Configuration
public class TagBasedRoutingConfiguration {
    
    /**
     * 自定义请求上下文，用于传递标签信息
     */
    @Bean
    public LoadBalancerRequestFactory loadBalancerRequestFactory(
            LoadBalancerClient loadBalancerClient) {
        
        return new LoadBalancerRequestFactory(loadBalancerClient) {
            @Override
            public HttpRequest createHttpRequest(RequestData requestData) {
                // 创建自定义HttpRequest，携带标签信息
                HttpRequest httpRequest = super.createHttpRequest(requestData);
                
                // 添加标签Header
                if (requestData.getHeaders() != null) {
                    // 传递用户类型标签
                    String userType = requestData.getHeaders().getFirst("X-User-Type");
                    if (userType != null) {
                        httpRequest.getHeaders().set("X-User-Type", userType);
                    }
                    
                    // 传递流量类型标签
                    String trafficType = requestData.getHeaders().getFirst("X-Traffic-Type");
                    if (trafficType != null) {
                        httpRequest.getHeaders().set("X-Traffic-Type", trafficType);
                    }
                }
                
                return httpRequest;
            }
        };
    }
}

6. 负载均衡监控与运维

6.1 负载均衡监控

// 负载均衡监控服务
@Component
@Slf4j
public class LoadBalancerMonitor {
    
    @Autowired
    private MeterRegistry meterRegistry;
    
    private final Map<String, LoadBalancerStats> serviceStats = new ConcurrentHashMap<>();
    
    /**
     * 监控负载均衡指标
     */
    @Scheduled(fixedRate = 30000) // 每30秒执行一次
    public void monitorLoadBalancerMetrics() {
        try {
            // 监控服务实例分布
            monitorInstanceDistribution();
            
            // 监控负载均衡效果
            monitorLoadDistribution();
            
            // 检查健康状态
            checkInstanceHealth();
            
            // 生成监控报告
            generateMonitoringReport();
            
        } catch (Exception e) {
            log.error("负载均衡监控异常", e);
        }
    }
    
    private void monitorInstanceDistribution() {
        // 监控每个服务的实例数量和分布
        // 实现具体的监控逻辑
    }
    
    private void monitorLoadDistribution() {
        // 监控负载分布情况
        // 检查是否有实例过载或空闲
    }
    
    private void checkInstanceHealth() {
        // 检查实例健康状态
        // 标记不健康的实例
    }
    
    private void generateMonitoringReport() {
        // 生成监控报告
        LoadBalancerReport report = new LoadBalancerReport();
        report.setTimestamp(Instant.now());
        report.setServiceStats(new HashMap<>(serviceStats));
        report.setOverallHealth(calculateOverallHealth());
        
        log.info("负载均衡监控报告: {}", report);
        
        // 发送到监控系统
        sendToMonitoringSystem(report);
    }
    
    /**
     * 记录负载均衡决策
     */
    public void recordLoadBalancerDecision(String serviceId, ServiceInstance selectedInstance, 
                                         List<ServiceInstance> availableInstances) {
        LoadBalancerStats stats = serviceStats.computeIfAbsent(
            serviceId, k -> new LoadBalancerStats());
            
        stats.recordDecision(selectedInstance, availableInstances.size());
        
        // 记录指标
        Counter.builder("loadbalancer.requests")
            .tag("service", serviceId)
            .tag("instance", getInstanceId(selectedInstance))
            .register(meterRegistry)
            .increment();
    }
    
    /**
     * 记录实例响应时间
     */
    public void recordInstanceResponseTime(String serviceId, ServiceInstance instance, 
                                         long responseTime, boolean success) {
        LoadBalancerStats stats = serviceStats.computeIfAbsent(
            serviceId, k -> new LoadBalancerStats());
            
        stats.recordResponseTime(instance, responseTime, success);
        
        // 记录指标
        Timer.builder("loadbalancer.response.time")
            .tag("service", serviceId)
            .tag("instance", getInstanceId(instance))
            .tag("success", String.valueOf(success))
            .register(meterRegistry)
            .record(responseTime, TimeUnit.MILLISECONDS);
    }
    
    private String getInstanceId(ServiceInstance instance) {
        return instance.getHost() + ":" + instance.getPort();
    }
    
    private double calculateOverallHealth() {
        if (serviceStats.isEmpty()) {
            return 1.0;
        }
        
        double totalHealth = serviceStats.values().stream()
            .mapToDouble(LoadBalancerStats::getHealthScore)
            .sum();
            
        return totalHealth / serviceStats.size();
    }
    
    private void sendToMonitoringSystem(LoadBalancerReport report) {
        // 发送到监控系统（如Prometheus、ELK等）
        log.debug("发送负载均衡监控报告");
    }
    
    /**
     * 获取负载均衡统计信息
     */
    public Map<String, LoadBalancerStats> getServiceStats() {
        return new HashMap<>(serviceStats);
    }
    
    /**
     * 负载均衡统计类
     */
    @Data
    public static class LoadBalancerStats {
        private final Map<String, InstanceStats> instanceStats = new ConcurrentHashMap<>();
        private long totalRequests = 0;
        private long errorRequests = 0;
        private Instant lastUpdateTime = Instant.now();
        
        public void recordDecision(ServiceInstance instance, int totalInstances) {
            String instanceId = getInstanceId(instance);
            InstanceStats stats = instanceStats.computeIfAbsent(
                instanceId, k -> new InstanceStats());
                
            stats.incrementRequestCount();
            totalRequests++;
            lastUpdateTime = Instant.now();
        }
        
        public void recordResponseTime(ServiceInstance instance, long responseTime, boolean success) {
            String instanceId = getInstanceId(instance);
            InstanceStats stats = instanceStats.computeIfAbsent(
                instanceId, k -> new InstanceStats());
                
            stats.recordResponseTime(responseTime, success);
            
            if (!success) {
                errorRequests++;
            }
            lastUpdateTime = Instant.now();
        }
        
        public double getHealthScore() {
            if (totalRequests == 0) {
                return 1.0;
            }
            
            double errorRate = (double) errorRequests / totalRequests;
            return 1.0 - errorRate;
        }
        
        private String getInstanceId(ServiceInstance instance) {
            return instance.getHost() + ":" + instance.getPort();
        }
        
        @Data
        public static class InstanceStats {
            private long requestCount = 0;
            private long totalResponseTime = 0;
            private long errorCount = 0;
            private long lastResponseTime = 0;
            private Instant lastUpdateTime = Instant.now();
            
            public void incrementRequestCount() {
                requestCount++;
                lastUpdateTime = Instant.now();
            }
            
            public void recordResponseTime(long responseTime, boolean success) {
                totalResponseTime += responseTime;
                lastResponseTime = responseTime;
                
                if (!success) {
                    errorCount++;
                }
                lastUpdateTime = Instant.now();
            }
            
            public double getAverageResponseTime() {
                return requestCount > 0 ? (double) totalResponseTime / requestCount : 0.0;
            }
            
            public double getErrorRate() {
                return requestCount > 0 ? (double) errorCount / requestCount : 0.0;
            }
        }
    }
    
    @Data
    public static class LoadBalancerReport {
        private Instant timestamp;
        private Map<String, LoadBalancerStats> serviceStats;
        private double overallHealth;
        private String recommendation;
    }
}
// 负载均衡监控控制器
@RestController
@RequestMapping("/loadbalancer")
@Slf4j
public class LoadBalancerMonitorController {
    
    @Autowired
    private LoadBalancerMonitor loadBalancerMonitor;
    
    /**
     * 获取负载均衡统计信息
     */
    @GetMapping("/stats")
    public ResponseEntity<Map<String, Object>> getLoadBalancerStats() {
        Map<String, Object> result = new HashMap<>();
        result.put("timestamp", Instant.now());
        result.put("serviceStats", loadBalancerMonitor.getServiceStats());
        result.put("overallHealth", loadBalancerMonitor.getServiceStats().values().stream()
            .mapToDouble(LoadBalancerMonitor.LoadBalancerStats::getHealthScore)
            .average()
            .orElse(1.0));
        
        return ResponseEntity.ok(result);
    }
    
    /**
     * 获取服务实例详情
     */
    @GetMapping("/services/{serviceName}/instances")
    public ResponseEntity<List<Map<String, Object>>> getServiceInstances(
            @PathVariable String serviceName) {
        
        // 这里需要实现获取服务实例详情的逻辑
        // 可以通过DiscoveryClient获取
        
        List<Map<String, Object>> instances = new ArrayList<>();
        
        // 模拟数据
        Map<String, Object> instance1 = new HashMap<>();
        instance1.put("instanceId", "192.168.1.101:8080");
        instance1.put("host", "192.168.1.101");
        instance1.put("port", 8080);
        instance1.put("zone", "zone-a");
        instance1.put("weight", 1);
        instance1.put("healthy", true);
        instances.add(instance1);
        
        Map<String, Object> instance2 = new HashMap<>();
        instance2.put("instanceId", "192.168.1.102:8080");
        instance2.put("host", "192.168.1.102");
        instance2.put("port", 8080);
        instance2.put("zone", "zone-b");
        instance2.put("weight", 2);
        instance2.put("healthy", true);
        instances.add(instance2);
        
        return ResponseEntity.ok(instances);
    }
    
    /**
     * 手动触发实例健康检查
     */
    @PostMapping("/services/{serviceName}/health-check")
    public ResponseEntity<Map<String, Object>> triggerHealthCheck(
            @PathVariable String serviceName) {
        
        Map<String, Object> result = new HashMap<>();
        result.put("serviceName", serviceName);
        result.put("timestamp", Instant.now());
        result.put("status", "Health check triggered");
        
        log.info("手动触发健康检查: {}", serviceName);
        
        return ResponseEntity.ok(result);
    }
}

总结

负载均衡是微服务架构中确保高可用和高性能的关键技术。通过本文的实战指南，我们掌握了：

核心负载均衡模式：

客户端负载均衡：在服务消费者端实现，减少网络跳转
服务端负载均衡：通过专用负载均衡器分发流量
算法多样性：轮询、随机、权重、最少连接等策略

高级特性：

区域感知路由：优先选择同区域实例降低延迟
标签路由：基于业务标签进行精细化路由
响应时间感知：根据实例性能动态调整权重
健康检查：自动剔除不健康实例

生产最佳实践：

实施多级负载均衡策略
建立完善的监控告警体系
定期进行负载测试和容量规划
实现优雅的故障转移和恢复机制

负载均衡不是简单的流量分发，而是需要根据业务特点、网络拓扑和性能要求进行精细化调优的系统工程。正确的负载均衡实践能够为微服务架构提供坚实的性能和可用性基础。

《服务治理》负载均衡：微服务架构的"智能调度器"

1. 负载均衡核心概念

1.1 什么是负载均衡？

1.2 负载均衡的核心价值

2. 负载均衡架构与模式

2.1 负载均衡架构类型

2.2 主流负载均衡技术对比

3. Spring Cloud LoadBalancer 实战

3.1 环境准备与依赖配置

3.2 基础配置与自动装配

3.3 基础负载均衡使用

4. 负载均衡算法实战

4.1 内置负载均衡算法

4.2 基于响应时间的负载均衡

5. 高级负载均衡特性

5.1 区域感知负载均衡

5.2 基于标签的负载均衡

6. 负载均衡监控与运维

6.1 负载均衡监控

总结

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《服务治理》负载均衡：微服务架构的"智能调度器"

1. 负载均衡核心概念

1.1 什么是负载均衡？

1.2 负载均衡的核心价值

2. 负载均衡架构与模式

2.1 负载均衡架构类型

2.2 主流负载均衡技术对比

3. Spring Cloud LoadBalancer 实战

3.1 环境准备与依赖配置

3.2 基础配置与自动装配

3.3 基础负载均衡使用

4. 负载均衡算法实战

4.1 内置负载均衡算法

4.2 基于响应时间的负载均衡

5. 高级负载均衡特性

5.1 区域感知负载均衡

5.2 基于标签的负载均衡

6. 负载均衡监控与运维

6.1 负载均衡监控

总结

热门文章

最新文章

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