sentinel篇2-资源注解使用-结合SpringAOP

前言

• 上篇进行了快速的入门使用，可以知道的是：
  • 使用 sentinel 主要就是 定义资源、配置资源规则、验证配置的有效性
  • 资源在 sentinel 中，“可以是任何东西，服务，服务里的方法，甚至是一段代码。”
• 本篇将使用 sentinel 注解进行资源的定义，这需要引入切面相关依赖。流控的监控和规则配置则是通过 sentinel-dashboard。

springboot应用集成sentinel

• pom依赖

<dependency>
	<groupId>com.alibaba.csp</groupId>
	<artifactId>sentinel-core</artifactId>
	<version>${sentinel.version}</version>
</dependency>
<dependency>
	<groupId>com.alibaba.csp</groupId>
	<artifactId>sentinel-annotation-aspectj</artifactId>
	<version>${sentinel.version}</version>
</dependency>
<dependency>
	<groupId>com.alibaba.csp</groupId>
	<artifactId>sentinel-transport-simple-http</artifactId>
	<version>${sentinel.version}</version>
</dependency>

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>

• 注入sentinel资源注册切面 SentinelResourceAspect

@Configuration
public class SentinelAspectConfiguration {

    @Bean
    public SentinelResourceAspect sentinelResourceAspect() {
        return new SentinelResourceAspect();
    }
}

• 使用 @SentinelResource 定义资源

@Service
public class TestService {
	@SentinelResource(value = "resource1")
	public String resource1() {
		System.out.println("resource1");
		return "resource1";
	}
	
	public String notResource() {
		System.out.println("notResource");
		return "resource1";
	}
}

@RestController
public class Demo1Controller {
	@Autowired
    private TestService service;
	
	@GetMapping("/resource1")
    public String resource1() {
		
        return service.resource1() + " " + LocalDateTime.now().toString();
    }
	
	@GetMapping("/notResource")
    public String notResource() {
		
        return service.notResource() + " " + LocalDateTime.now().toString();
    }
}

• 启动应用（启动参数配置-Dcsp.sentinel.dashboard.server=localhost:8080或者springboot启动类main方法设置系统参数System.setProperty("csp.sentinel.dashboard.server", "localhost:8080");）
• 密集请求目标资源，观察dashboard资源请求情况，因为没有配置任何流控规则，所以只是监控，没有阻断效果，图示 ↓
  
• dashboard 配置资源的流控规则（FlowRule），限制为QPS=1，密集请求查看效果，图示 ↓
  
  
• 代码配置资源的阻断处理（blockHandler）和或降级处理（fallback）并进行验证

  @Service
  public class TestService {
  	@SentinelResource(value = "resource1", blockHandler = "handleException", blockHandlerClass = { ExceptionUtil2.class })
  	public String resource1() {
  		System.out.println("resource1");
  		return "resource1";
  	}
  	
  	public String notResource() {
  		System.out.println("notResource");
  		return "notResource";
  	}
  
  	@SentinelResource(value = "test", blockHandler = "handleException", blockHandlerClass = { ExceptionUtil.class })
  	public void test() {
  		System.out.println("Test");
  	}
  
  	@SentinelResource(value = "hello", fallback = "helloFallback")
  	public String hello(long s) {
  		if (s < 0) {
  			throw new IllegalArgumentException("invalid arg");
  		}
  		return String.format("Hello at %d", s);
  	}
  
  	@SentinelResource(value = "helloAnother", defaultFallback = "defaultFallback", exceptionsToIgnore = {
  			IllegalStateException.class })
  	public String helloAnother(String name) {
  		if (name == null || "bad".equals(name)) {
  			throw new IllegalArgumentException("oops");
  		}
  		if ("foo".equals(name)) {
  			throw new IllegalStateException("oops");
  		}
  		return "Hello, " + name;
  	}
  
  	public String helloFallback(long s, Throwable ex) {
  		// Do some log here.
  		ex.printStackTrace();
  		return "Oops, error occurred at " + s;
  	}
  
  	public String defaultFallback() {
  		System.err.println("Go to default fallback");
  		return "default_fallback";
  	}
  }
  
  public final class ExceptionUtil2 {
  	public static String handleException(BlockException ex) {
          // Handler method that handles BlockException when blocked.
          // The method parameter list should match original method, with the last additional
          // parameter with type BlockException. The return type should be same as the original method.
          // The block handler method should be located in the same class with original method by default.
          // If you want to use method in other classes, you can set the blockHandlerClass
          // with corresponding Class (Note the method in other classes must be static).
          System.err.println("Oops: " + ex.getClass().getCanonicalName());
          
          return ex.getClass().getSimpleName();
      }
  }
  

  • 踩坑注意点：
  • 1）blockHandler的方法必须为静态方法，且返回值和“资源”相同
  • 2）fallback的方法需要和“资源”在同一个类中（除非再指定 fallbackClass），且参数和返回类型都要一致
  • 3）同时配置 blockHandler 和 fallback 的话，只会 blockHandler 起作用
  • 4）从使用上看，blockHandler 针对限流，强调快速异常（明确告诉调用端这样不可用）；fallback 针对降级，强调友好的备用响应（保持调用链路完整性）。归根到底都是对目标资源进行高可用保护！（PS：blockHandler 使用下来的话，感觉用全局异常处理-ControllerAdvice代替更加方便）
  • 官方说明参考：https://sentinelguard.io/zh-cn/docs/annotation-support.html

有效参考

• Java启动参数及调优
• 官方sentinel-annotation文档
• 本文原文地址
• 博客也会同步更新
• 本系列demo源码Gitte仓库

标签：return,String,class,sentinel,SpringAOP,注解,resource1,public
来源： https://www.cnblogs.com/noodlerkun/p/15541115.html