十一. SpringCloud Alibaba (13)

主启动

@EnableDiscoveryClient @SpringBootApplication @EnableFeignClients public class OrderNacosMain84 { public static void main(String[] args) { SpringApplication.run(OrderNacosMain84.class, args); } }

配置类

@Configuration public class ApplicationContextConfig { @Bean @LoadBalanced public RestTemplate getRestTemplate() { return new RestTemplate(); } }

service

@Component public class PaymentFallbackService implements PaymentService { @Override public CommonResult<Payment> paymentSQL(Long id) { return new CommonResult<>(44444, "服务降级返回,=> PaymentFallbackService", new Payment(id, "errorSerial")); } }

controller

fallback管运行异常

blockHandler管配置违规

若 blockHandler 和 fallback 都进行了配置，则被限流降级而抛出 BlockException 只会进入 blockHandler处理逻辑

@RestController @Slf4j public class CircleBreakerController { public static final String SERVICE_URL = "http://nacos-payment-provider"; @Resource private RestTemplate restTemplate; //① 没有配置 // @SentinelResource(value = "fallback") //② fallback只负责业务异常 // @SentinelResource(value = "fallback",fallback = "handlerFallback") //③ blockHandler只负责sentinel控制台配置违规 // @SentinelResource(value = "fallback",blockHandler = "blockHandler") @RequestMapping("/consumer/fallback/{id}") @SentinelResource(value = "fallback", fallback = "handlerFallback", blockHandler = "blockHandler", exceptionsToIgnore = {IllegalArgumentException.class}) public CommonResult<Payment> fallback(@PathVariable Long id) { CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/" + id, CommonResult.class, id); if (id == 4) { throw new IllegalArgumentException( "IllegalArgumentException,非法参数异常！"); } else if (result.getData() == null) { throw new NullPointerException( "NullPointerException,该ID没有对应记录,空指针异常"); } return result; } //本例是fallback public CommonResult handlerFallback(@PathVariable Long id, Throwable e) { Payment payment = new Payment(id, "null"); return new CommonResult<>(444, "兜底异常handlerFallback,exception内容 " + e.getMessage(), payment); } //本例是blockHandler public CommonResult blockHandler(@PathVariable Long id, BlockException blockException) { Payment payment = new Payment(id, "null"); return new CommonResult<>(445, "blockHandler-sentinel限流,无此流水: blockException " + blockException.getMessage(), payment); } //==> OpenFeign @Resource private PaymentService paymentService; @GetMapping(value = "/consumer/paymentSQL/{id}") public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id) { return paymentService.paymentSQL(id); } }

测试

测试轮询：:84/consumer/fallback/1

测试@SentinelResource

没有任何配置：给客户error页面，不友好

添加fallback，blockHandler，exceptionsToIgnore：① 忽略了非法参数异常，出现非法参数异常仍是系统错误页面，② 其他情况都有了兜底方案

5.10 规则持久化

是什么

一旦我们重启应用，Sentinel规则消失，生产环境需要将配置规则进行持久化

怎么做

将限流规则持久进Nacos保存，只要刷新8401某个rest地址，Sentinel控制台的流控规则就能看的到，只要Nacos里面的配置不删除，针对8401上的流控规则持续有效。

步骤演示

现象：我们先在Sentinel配置一条流控规则，当重启8401后，该流控规则就会失效消失了！

修改8401

pom

<!--SpringCloud ailibaba sentinel-datasource-nacos 做持久化用 --> <dependency> <groupId>com.alibaba.csp</groupId> <artifactId>sentinel-datasource-nacos</artifactId> </dependency>

yml （添加Nacos数据源配置）

添加Nacos业务规则配置（规则即可以保存在Sentinel中，也可以保存在Nacos中等，只要是一个持久化媒介就行）

[ { "resource":"/rateLimit/byUrl", //资源名称 "limitApp":"default", //来源应用 "grade":1, //阈值类型，0表示线程数，1表示QPS "count":1, //单机阈值 "strategy":0, //流控模式，0表示直接，1表示关联，2表示链路 "controlBehavior":0, //流控效果，0表示快速失败，1表示Warm Up，2表示排队等候 "clusterMode":false //是否集群 } ]

启动8401 刷新Sentinel发现业务规则有了

停止8401，再看sentinel，发现停机后流控规则消失了！

重启8401，再看sentinel，多次调用接口，多次刷新sentinel后，发现流控规则重新出现了，持久化验证成功！

6. Seata处理分布式事务 6.1 分布式事务问题

分布式之前

单机库存没有这个问题