Java 微服务治理深化：熔断限流降级、灰度发布与全链路压测

// QPS 限流：直接限制访问速率
FlowRule rule = new FlowRule("inventory_service");
rule.setGrade(RuleConstant.FLOW_GRADE_QPS);
rule.setCount(1000);
rule.setControlBehavior(RuleConstant.CONTROL_BEHAVIOR_RATE_LIMITER); // 匀速排队
rule.setMaxQueueingTimeMs(500);                                       // 排队超时
FlowRuleManager.loadRules(Collections.singletonList(rule));

DegradeRule degradeRule = new DegradeRule("payment_service");
degradeRule.setGrade(RuleConstant.DEGRADE_GRADE_RT);        // 慢调用比例
degradeRule.setCount(200);                                   // RT 阈值 200ms
degradeRule.setTimeWindow(30);                               // 熔断窗口 30s
degradeRule.setSlowRatioThreshold(0.5);                      // 慢调用比例 50%

DegradeRule exceptionRule = new DegradeRule("payment_service");
exceptionRule.setGrade(RuleConstant.DEGRADE_GRADE_EXCEPTION_RATIO); // 异常比例
exceptionRule.setCount(0.2);                                 // 20% 异常触发
exceptionRule.setTimeWindow(30);

@RestController
public class OrderController {
    @SentinelResource(
        value = "createOrder",
        blockHandler = "createOrderBlock",     // 限流/熔断触发
        fallback = "createOrderFallback"       // 业务异常兜底
    )
    public Result createOrder(OrderRequest req) {
        // 核心逻辑
        return orderService.create(req);
    }

    // 限流兜底（签名必须与业务方法匹配，可加 BlockException 参数）
    public Result createOrderBlock(OrderRequest req, BlockException ex) {
        return Result.busy("系统繁忙，请稍后重试");
    }

    // 业务异常兜底
    public Result createOrderFallback(OrderRequest req, Throwable t) {
        log.error("createOrder failed", t);
        return Result.fallback("订单创建失败，已记录");
    }
}

// 白名单/黑名单：基于调用来源控制
AuthorityRule rule = new AuthorityRule();
rule.setResource("admin_api");
rule.setLimitApp("gateway-app");            // 来源应用
rule.setStrategy(RuleConstant.AUTHORITY_WHITE); // 白名单
AuthorityRuleManager.loadRules(Collections.singletonList(rule));

// 服务端：注册时带上版本标签
spring:
  cloud:
    nacos:
      discovery:
        metadata:
          version: v2          # 灰度版本
          gray: "true"

// 网关：按请求头路由到带 gray 标签的服务
@Bean
public RouteLocator grayRouteLocator(RouteLocatorBuilder builder) {
    return builder.routes()
        .route(r -> r
            .header("x-version", "gray")        // 灰度请求
            .uri("lb://order-service"))         // 交给 LoadBalancer 按 metadata 选择
        .build();
}

public class GrayServiceInstanceListSupplier extends AbstractServiceInstanceListSupplier {
    @Override
    public Flux<List<ServiceInstance>> get() {
        return delegate.get().map(instances -> {
            String version = RequestContextHolder.get().getVersion(); // 当前请求版本
            List<ServiceInstance> matched = instances.stream()
                .filter(i -> version.equals(i.getMetadata().get("version")))
                .collect(Collectors.toList());
            return matched.isEmpty() ? instances : matched; // 匹配不到回退稳定集群
        });
    }
}

// 自定义 RestTemplate/Feign 拦截器透传灰度标签
@Component
public class GrayTagInterceptor implements ClientHttpRequestInterceptor {
    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body,
                                        ClientHttpRequestExecution execution)
            throws IOException {
        GrayContext ctx = GrayContextHolder.get();
        if (ctx != null && ctx.isGray()) {
            request.getHeaders().set("x-version", "gray");
        }
        return execution.execute(request, body);
    }
}

// 线程池场景注意：标签要随任务传递
// 用包装 Runnabe 把 ThreadLocal 复制到执行线程

// 数据源层面：根据压测标记切换影子数据源
public class StressRoutingDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return StressContextHolder.isStress() ? "stressDS" : "masterDS";
    }
}

@Configuration
public class DataSourceConfig {
    @Bean
    @Primary
    public DataSource routingDataSource(@Qualifier("masterDS") DataSource master,
                                        @Qualifier("stressDS") DataSource stress) {
        Map<Object, Object> map = new HashMap<>();
        map.put("masterDS", master);
        map.put("stressDS", stress);
        StressRoutingDataSource ds = new StressRoutingDataSource();
        ds.setDefaultTargetDataSource(master);
        ds.setTargetDataSources(map);
        return ds;
    }
}

# Nacos 配置：governance/order-service 规则集
sentinel:
  rules:
    - resource: "createOrder"
      grade: FLOW_GRADE_QPS
      count: 1000
      controlBehavior: RATE_LIMITER
    - resource: "payment_service"
      grade: DEGRADE_GRADE_RT
      count: 200
      timeWindow: 30
      slowRatioThreshold: 0.5