SpringCloud Alibaba_Sentinel实现熔断与限流

安装Sentinel

sentinel组件由两个部分组成：

• 核心库（Java客户端），不依赖任何框架和库，能够运行于Java运行时环境，同时对SpringCloud等框架也有较好的支持。
• 控制台（DashBoard）基于SpringBoot开发，打包后可以直接运行，不需要额外的Tomcat等应用容器

下载

https://github.com/alibaba/Sentinel/releases

运行命令

java -jar sentinel-dashboard-1.7.2.jar

注意：8080端口不能被占用

访问sentinel管理界面

http://localhost:8080
账号密码：sentinel

流控规则

基本介绍

• 资源名：唯一名称，默认请求路径
• 针对来源：Sentinel可以针对调用者进行限流，填写微服务名，默认default（不区分来源）
• 阈值类型/单机阈值
  • QPS（每秒请求数量）：当调用该api的QPS达到阈值的时候，进行限流
  • 线程数：当调用该api的线程数达到阈值的时候，进行限流
• 是否集群：不需要集群
• 流控模式：
  • 直接：api达到限流条件时，直接限流
    
  • 关联：当关联的资源达到阈值时，就限流自己
    
  • 链路：只记录指定链路上的流量（指定资源从入口资源进来的流量，如果达到阈值，就进行限流）
• 流控效果
  • 快速失败：直接失败。抛异常
  • Warm up：根据coldfactor（冷加载因子，默认3）的值，从阈值/coldfactor，经过预热时长，才达到设置的QPS阈值
    
    如：秒杀系统在开启瞬间，会有很多流量上来，很可能把系统打死，预热方式就是为了保护系统，可慢慢的把流量放进来，慢慢的把阈值增长到设置的阈值。
  • 排队等待：匀速排队，让请求以匀速通过，阈值类型必须设置为QPS，否则无效
    
    

降级规则

RT

异常比例

异常数

热点key限流

配置

@GetMapping("/testHotKey")
@SentinelResource(value = "testHotKey")
public String testHotKey(@RequestParam(value = "p1",required = false) String p1,
                         @RequestParam(value = "p2",required = false) String p2)
{
    //int age = 10/0;
    return "------testHotKey";
}

返回异常不友好界面，blocked by sentinel

@GetMapping("/testHotKey")
@SentinelResource(value = "testHotKey",blockHandler = "deal_testHotKey")
public String testHotKey(@RequestParam(value = "p1",required = false) String p1,
                         @RequestParam(value = "p2",required = false) String p2)
{
    //int age = 10/0;
    return "------testHotKey";
}
public String deal_testHotKey (String p1, String p2, BlockException exception)
{
    return "------deal_testHotKey,o(╥﹏╥)o";  //sentinel系统默认的提示：Blocked by Sentinel (flow limiting)
    }

自定义blockHandler，处理异常。

参数例外项

假如当p1的值等于5时，它的阈值可以达到200：

参数类型仅限于基本数据类型或者String

系统规则

系统配置管辖太宽泛，可能引起全局范围内的问题，不使用，危险。

@SentinelResource

按照资源名称+流控规则限流+后续处理

@GetMapping("/byResource")
@SentinelResource(value = "byResource",blockHandler = "handleException")
public CommonResult byResource()
{
    return new CommonResult(200,"按资源名称限流测试OK",new Payment(2020L,"serial001"));
}
public CommonResult handleException(BlockException exception)
{
    return new CommonResult(444,exception.getClass().getCanonicalName()+"\t 服务不可用");
}

按照url+流控规则限流+后续处理

@GetMapping("/rateLimit/byUrl")
@SentinelResource(value = "byUrl")
public CommonResult byUrl()
{
    return new CommonResult(200,"按url限流测试OK",new Payment(2020L,"serial002"));
}

现阶段问题

• 系统默认，没有体现特定的业务要求
• 自定义Handler与业务逻辑耦合
• 每个业务逻辑都需要独自的兜底Handler，代码膨胀
• 没有全局统一的处理方法

自定义限流处理逻辑

• 自定义限流处理类

public class CustomerBlockHandler
{
    public static CommonResult handlerException(BlockException exception)
    {
        return new CommonResult(4444,"按客戶自定义,global handlerException----1");
    }
    public static CommonResult handlerException2(BlockException exception)
    {
        return new CommonResult(4444,"按客戶自定义,global handlerException----2");
    }
}

• 修改@SentinelResource

@GetMapping("/rateLimit/customerBlockHandler")
@SentinelResource(value = "customerBlockHandler",
        blockHandlerClass = CustomerBlockHandler.class,
        blockHandler = "handlerException2")
public CommonResult customerBlockHandler()
{
    return new CommonResult(200,"按客戶自定义",new Payment(2020L,"serial003"));
}

服务熔断

消费侧Sentinel整合Ribbon+OpenFeign+FallBack

• pom

<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-openfeignartifactId>
dependency>

<dependency>
    <groupId>com.alibaba.cloudgroupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
dependency>

<dependency>
    <groupId>com.alibaba.cloudgroupId>
    <artifactId>spring-cloud-starter-alibaba-sentinelartifactId>
dependency>

• yml

server:
  port: 84

spring:
  application:
    name: nacos-order-consumer
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
    sentinel:
      transport:
        #配置Sentinel dashboard地址
        dashboard: localhost:8080
        #默认8719端口，假如被占用会自动从8719开始依次+1扫描,直至找到未被占用的端口
        port: 8719

#消费者将要去访问的微服务名称(注册成功进nacos的微服务提供者)
service-url:
  nacos-user-service: http://nacos-payment-provider

# 激活Sentinel对Feign的支持
feign:
  sentinel:
    enabled: true

Ribbon

• 配置RestTemplate

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

• 业务逻辑

@RequestMapping("/consumer/fallback/{id}")
//fallback只负责业务异常
//blockHandler只负责sentinel控制台配置违规
@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

• Service

@FeignClient(value = "nacos-payment-provider",fallback = PaymentFallbackService.class)
public interface PaymentService
{
    @GetMapping(value = "/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id);
}

• FallBackService

@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

@Resource
private PaymentService paymentService;

@GetMapping(value = "/consumer/paymentSQL/{id}")
@SentinelResource(value = "fallback",blockHandler = "blockHandler")
public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id)
{
    return paymentService.paymentSQL(id);
}

规则持久化

一旦重启应用,sentinel规则消失,生产环境需要将配置规则进行持久化。
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得到,只要Nacos里面的配置不删除,针对8401上的流控规则持续有效

• pom

<!--SpringCloud ailibaba nacos -->
<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>
<!--SpringCloud ailibaba sentinel-datasource-nacos 后续做持久化用到-->
<dependency>
    <groupId>com.alibaba.csp</groupId>
    <artifactId>sentinel-datasource-nacos</artifactId>
</dependency>
<!--SpringCloud ailibaba sentinel -->
<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>

• yaml

server:
  port: 8401

spring:
  application:
    name: cloudalibaba-sentinel-service
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848 #Nacos服务注册中心地址
    sentinel:
      transport:
        dashboard: localhost:8080 #配置Sentinel dashboard地址
        port: 8719
      datasource:
        ds1:
          nacos:
            server-addr: localhost:8848
            dataId: cloudalibaba-sentinel-service
            groupId: DEFAULT_GROUP
            data-type: json
            rule-type: flow

management:
  endpoints:
    web:
      exposure:
        include: '*'

feign:
  sentinel:
    enabled: true # 激活Sentinel对Feign的支持

• 添加Nacos业务规则配置