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
<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