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Feign + Sentinel 整合

feign:
  sentinel:
    enabled: true                   # 开启 Feign 的 Sentinel 支持

Feign Fallback 降级

@FeignClient(
    name = "user-service",
    path = "/api/users",
    fallback = UserFeignClientFallback.class     // 降级处理
)
public interface UserFeignClient {

    @GetMapping("/{id}")
    Result<User> getUser(@PathVariable("id") Long id);
}

@Component
public class UserFeignClientFallback implements UserFeignClient {

    @Override
    public Result<User> getUser(Long id) {
        log.warn("user-service 不可用，返回降级数据");
        return Result.error("用户服务暂时不可用");
    }
}

Feign FallbackFactory（获取异常原因）

@FeignClient(
    name = "product-service",
    path = "/api/products",
    fallbackFactory = ProductFeignClientFallbackFactory.class
)
public interface ProductFeignClient {

    @GetMapping("/{id}")
    Result<Product> getProduct(@PathVariable("id") Long id);

    @PutMapping("/{id}/stock")
    Result<Void> deductStock(@PathVariable("id") Long id,
                             @RequestParam("quantity") Integer quantity);
}

@Component
public class ProductFeignClientFallbackFactory
        implements FallbackFactory<ProductFeignClient> {

    @Override
    public ProductFeignClient create(Throwable cause) {
        return new ProductFeignClient() {
            @Override
            public Result<Product> getProduct(Long id) {
                log.error("商品服务调用失败: {}", cause.getMessage());
                return Result.error("商品服务暂时不可用");
            }

            @Override
            public Result<Void> deductStock(Long id, Integer quantity) {
                log.error("扣减库存失败: {}", cause.getMessage());
                return Result.error("库存服务暂时不可用");
            }
        };
    }
}

Sentinel 规则持久化到 Nacos

Sentinel 控制台配置的规则存储在内存中，重启丢失。通过 Nacos 持久化规则。

spring:
  cloud:
    sentinel:
      datasource:
        # 流控规则数据源
        flow:
          nacos:
            server-addr: localhost:8848
            data-id: ${spring.application.name}-sentinel-flow
            group-id: DEFAULT_GROUP
            data-type: json
            rule-type: flow

        # 降级规则数据源
        degrade:
          nacos:
            server-addr: localhost:8848
            data-id: ${spring.application.name}-sentinel-degrade
            group-id: DEFAULT_GROUP
            data-type: json
            rule-type: degrade

        # 热点参数规则
        param-flow:
          nacos:
            server-addr: localhost:8848
            data-id: ${spring.application.name}-sentinel-param-flow
            group-id: DEFAULT_GROUP
            data-type: json
            rule-type: param-flow

# Nacos → user-service-sentinel-flow
[
    {
        "resource": "getUser",
        "grade": 1,
        "count": 10,
        "limitApp": "default",
        "strategy": 0,
        "controlBehavior": 0
    },
    {
        "resource": "createOrder",
        "grade": 1,
        "count": 5,
        "limitApp": "default",
        "strategy": 0,
        "controlBehavior": 0
    }
]

# Nacos → user-service-sentinel-degrade
[
    {
        "resource": "getUser",
        "grade": 0,
        "count": 200,
        "timeWindow": 10,
        "minRequestAmount": 5,
        "slowRatioThreshold": 0.5
    },
    {
        "resource": "createOrder",
        "grade": 1,
        "count": 0.1,
        "timeWindow": 10
    }
]

完整配置总览

spring:
  cloud:
    sentinel:
      transport:
        dashboard: localhost:8858
      eager: true
      datasource:
        flow:
          nacos:
            server-addr: ${spring.cloud.nacos.config.server-addr}
            data-id: ${spring.application.name}-sentinel-flow
            group-id: SENTINEL_GROUP
            data-type: json
            rule-type: flow
        degrade:
          nacos:
            server-addr: ${spring.cloud.nacos.config.server-addr}
            data-id: ${spring.application.name}-sentinel-degrade
            group-id: SENTINEL_GROUP
            data-type: json
            rule-type: degrade

feign:
  sentinel:
    enabled: true

小结

• feign.sentinel.enabled=true 开启 Feign + Sentinel 整合。
• fallback 提供降级处理，fallbackFactory 获取降级原因。
• Sentinel 规则持久化到 Nacos：配置 datasource.flow/datasource.degrade 指定 Nacos Data ID。
• 规则 JSON 数组格式，重启不丢失。
• 推荐将流控、降级、热点参数三种规则都持久化到 Nacos。

上一节：Sentinel 流控与降级 下一节：Micrometer Tracing 与 Zipkin

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