官网：https://github.com/alibaba/Sentinel
官网中文：https://github.com/alibaba/Sentinel/wiki/%E4%BB%8B%E7%BB%8D
下载地址：https://github.com/alibaba/Sentinel/releases
安装Sentinel控制台
前提：java8环境OK，8080端口不能被占用
命令：java -jar sentinel-dashboard-1.7.0.jar
访问sentinel管理界 http://localhost:8080，登录账号密码均为sentinel
二、初始化演示工程（1）新建工程进行配置
pom依赖
com.alibaba.cloud spring-cloud-starter-alibaba-nacos-discovery com.alibaba.csp sentinel-datasource-nacos com.alibaba.cloud spring-cloud-starter-alibaba-sentinel org.springframework.cloud spring-cloud-starter-openfeign org.springframework.boot spring-boot-starter-web org.springframework.boot spring-boot-starter-actuator org.springframework.boot spring-boot-devtools runtime true cn.hutool hutool-all 4.6.3 org.projectlombok lombok true org.springframework.boot spring-boot-starter-test test
yml配置
server:
port: 8401
spring:
application:
name: cloudalibaba-sentinel-service
cloud:
nacos:
discovery:
server-addr: localhost:8848
sentinel:
transport:
dashboard: localhost:8080
port: 8719 #默认8719，假如被占用了会自动从8719开始依次+1扫描。直至找到未被占用的端口
management:
endpoints:
web:
exposure:
include: '*'
主启动
@EnableDiscoveryClient
@SpringBootApplication
public class MainApp8401
{
public static void main(String[] args) {
SpringApplication.run(MainApp8401.class, args);
}
}
业务类FlowLimitController
@RestController
public class FlowLimitController
{
@GetMapping("/testA")
public String testA() {
return "------testA";
}
@GetMapping("/testB")
public String testB() {
return "------testB";
}
}
（2）启动8401微服务后查看sentienl控制台
Sentinel采用的懒加载说明，执行一次访问即可
http://localhost:8401/testA
http://localhost:8401/testB
效果
（1）直接（默认）
系统默认：直接->快速失败
配置及说明
测试
快速点击访问http://localhost:8401/testA
（2）关联
当与A关联的资源B达到阈值后，就限流自己
配置A
postman模拟并发密集访问testB
大批量线程高并发访问B，导致A失效了
（3）链路
快速请求A，请求阻塞，一秒一次，请求成功
（4）预热
默认coldFactor为3，即请求QPS从threshold/3开始，经预热时长逐渐升至设定的QPS阈值。
官网说明：https://github.com/alibaba/Sentinel/wiki/%E9%99%90%E6%B5%81—%E5%86%B7%E5%90%AF%E5%8A%A8
源码：com.alibaba.csp.sentinel.slots.block.flow.controller.WarmUpController
配置：
（5）排队等待
官网：
源码：com.alibaba.csp.sentinel.slots.block.flow.controller.RateLimiterController
四、降级规则
（1）RT配置
代码
@GetMapping("/testD")
public String testD()
{
try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); }
log.info("testD 测试RT");
return "------testD";
}
配置
jmeter压测，结论
（2）异常比例
代码
@GetMapping("/testD")
public String testD()
{
log.info("testD 测试RT");
int age = 10/0;
return "------testD";
}
配置
jmeter
结论
（3）异常数
代码
@GetMapping("/testE")
public String testE()
{
log.info("testE 测试异常数");
int age = 10/0;
return "------testE 测试异常数";
}
配置
官网：https://github.com/alibaba/Sentinel/wiki/热点参数限流
核心注解：@SentinelResource
代码：com.alibaba.csp.sentinel.slots.block.BlockException
@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";
}
//兜底方法
public String deal_testHotKey (String p1, String p2, BlockException exception){
return "------deal_testHotKey,o(╥﹏╥)o";
}
方法testHostKey里面第一个参数只要QPS超过每秒1次，马上降级处理
具体配置：
系统规则：
（1）按资源名称限流+后续处理
@RestController
public class RateLimitController
{
@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");
}
（2）按照Url地址限流+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"));
}
（3）客户自定义限流处理逻辑
创建customerBlockHandler类用于自定义限流处理逻辑
public class CustomerBlockHandler {
public static CommonResult handleException(BlockException exception) {
return new CommonResult(2020, "自定义限流处理信息....CustomerBlockHandler");
}
}
业务RateLimitController
@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"));
}
（4）原理说明
Sentinel主要有三个核心API：
SphU定义资源
Tracer定义统计
ContextUtil定义了上下文
sentinel整合ribbon+openFeign+fallback
（1）Ribbon系列
@RestController
@Slf4j
public class CircleBreakerController {
public static final String SERVICE_URL = "http://nacos-payment-provider";
@Resource
private RestTemplate restTemplate;
@RequestMapping("/consumer/fallback/{id}")
//@SentinelResource(value = "fallback") //没有配置
//@SentinelResource(value = "fallback",fallback = "handlerFallback") //fallback只负责业务异常
//@SentinelResource(value = "fallback",blockHandler = "blockHandler") //blockHandler只负责sentinel控制台配置违规
@SentinelResource(value = "fallback",fallback = "handlerFallback",blockHandler = "blockHandler",
exceptionsToIgnore = {IllegalArgumentException.class})
public CommonResult fallback(@PathVariable Long id) {
CommonResult 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;
}
//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);
}
//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);
}
}
fallback管运行异常，blockHandler管配置违规
fallback和blockHandler都配置，正常报错进入fallback，异常次数过多满足block配置则进入block
（2）Feign系列
yml配置
server:
port: 84
spring:
application:
name: nacos-order-consumer
cloud:
nacos:
discovery:
server-addr: 192.168.40.128:8848
sentinel:
transport:
dashboard: localhost:8080
port: 8719
service-url:
nacos-user-service: http://nacos-payment-provider
#对Feign的支持
feign:
sentinel:
enabled: true
业务类
带@FeignClient注解的业务接口
@FeignClient(value = "nacos-payment-provider",fallback = PaymentFallbackService.class)
public interface PaymentService
{
@GetMapping(value = "/paymentSQL/{id}")
public CommonResult paymentSQL(@PathVariable("id") Long id);
}
PaymentFallbackService实现类
@Component
public class PaymentFallbackService implements PaymentService
{
@Override
public CommonResult paymentSQL(Long id)
{
return new CommonResult<>(44444,"服务降级返回,---PaymentFallbackService",new Payment(id,"errorSerial"));
}
}
Controller
// OpenFeign
@Resource
private PaymentService paymentService;
@GetMapping(value = "/consumer/paymentSQL/{id}")
public CommonResult paymentSQL(@PathVariable("id") Long id) {
return paymentService.paymentSQL(id);
}
主启动，添加@EnableFeignClients启动Feign的功能
@EnableDiscoveryClient
@SpringBootApplication
@EnableFeignClients
public class OrderNacosMain84
{
public static void main(String[] args) {
SpringApplication.run(OrderNacosMain84.class, args);
}
}
（3）熔断框架比较
POM依赖
com.alibaba.csp sentinel-datasource-nacos
YML配置
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: #配置nocos数据源，将sentinel配置持久化到nacos中
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
