【Spring Cloud】服务容错中间件Sentinel入门

import com.alibaba.csp.sentinel.Entry;
import com.alibaba.csp.sentinel.SphU;
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.slots.block.RuleConstant;
import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
import com.alibaba.csp.sentinel.slots.block.flow.FlowRuleManager;
 
import java.util.ArrayList;
import java.util.List;
 
public class SentinelExample {
 
    static {
        initFlowRules();
    }
 
    private static void initFlowRules() {
        List<FlowRule> rules = new ArrayList<>();
        FlowRule rule = new FlowRule();
        rule.setResource("test");
        rule.setGrade(RuleConstant.FLOW_GRADE_QPS);
        // Set limit to 20 calls per second.
        rule.setCount(20);
        rules.add(rule);
        FlowRuleManager.loadRules(rules);
    }
 
    @SentinelResource(value = "test", blockHandler = "handleException")
    public void test() {
        System.out.println("Test resource invoking...");
    }
 
    public void handleException(BlockException ex) {
        System.err.println("Test resource handled exception: " + ex.getClass().getCanonicalName());
    }
 
    public static void main(String[] args) {
        while (true) {
            Entry entry = null;
            try {
                entry = SphU.entry("test");
                // Your business logic here.
                test();
            } catch (BlockException ex) {
                // Handle blocked exception.
                System.err.println("Blocked!");
            } finally {
                if (entry != null) {
                    entry.exit();
                }
            }
        }
    }
}

这段代码演示了如何使用Sentinel的注解和API来实现服务的限流。首先，我们初始化了一条流量控制规则，设置了资源名为"test"的QPS阈值为20。接着，我们定义了一个带有Sentinel资源注解的test方法，并指定了异常处理方法handleException。在main方法中，我们持续尝试进入名为"test"的资源，如果被限流，会触发BlockException异常，并调用handleException方法处理。这个例子简单地打印出了异常信息，实际应用中可以根据需要进行更复杂的异常处理。