[Java知识库]使用sentinel核心库进行流量控制

一、用代码方式进行流量控制

1. 添加依赖

<dependency>
     <groupId>com.alibaba.csp</groupId>
     <artifactId>sentinel-core</artifactId>
     <version>1.8.0</version>
</dependency>

2. 定义资源名称

import com.alibaba.csp.sentinel.Entry;
import com.alibaba.csp.sentinel.EntryType;
import com.alibaba.csp.sentinel.SphU;
import com.alibaba.csp.sentinel.Tracer;
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.degrade.DegradeRule;
import com.alibaba.csp.sentinel.slots.block.degrade.DegradeRuleManager;
import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
import com.alibaba.csp.sentinel.slots.block.flow.FlowRuleManager;
import com.demo.sentinel.User;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.PostConstruct;
import java.util.ArrayList;
import java.util.List;

private static final String RESOURCE_NAME = "hello";

3. 对资源定义流控规则

@PostConstruct
    private static void initFlowRules()
    {
        List<FlowRule> rules = new ArrayList<>();

        # 定义流控规则
        FlowRule rule = new FlowRule();
        rule.setResource(RESOURCE_NAME);
        # QPS流控规则
        rule.setGrade(RuleConstant.FLOW_GRADE_QPS);
        # 每秒次数
        rule.setCount(1);
        rules.add(rule);

        FlowRule ruleUser = new FlowRule();
        ruleUser.setResource(USER_RESOURCE_NAME);
        ruleUser.setGrade(RuleConstant.FLOW_GRADE_QPS);
        ruleUser.setCount(1);
        rules.add(ruleUser);

        FlowRuleManager.loadRules(rules);
    }

4. 业务执行过程中应用规则

@RequestMapping(value="/hello")
    public String hello()
    {
        Entry entry = null;
        try {
             entry = SphU.entry(RESOURCE_NAME);
             String  str = "hello world";
             return str;

        }catch (BlockException e){
            return "被流控了";
        }
        catch (Exception e){
            e.printStackTrace();
        }
        finally {
            if(entry != null){
                entry.exit();
            }
        }
        return null;
    }

如果访问QPS大于每秒1次时，就会抛出流控异常。

二、用注解方式进行流量控制

1. 添加依赖

<dependency>
            <groupId>com.alibaba.csp</groupId>
            <artifactId>sentinel-annotation-aspectj</artifactId>
            <version>1.8.0</version>
        </dependency>

2. 在启动类或者配置类配置bean

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

3. 添加注解

@RequestMapping("/user")
    @SentinelResource(value = USER_RESOURCE_NAME,   // 设置资源名称
            fallback = "fallbackForUser",           // 当方法调用出现异常时的降级方法
            blockHandler = "blockHanderForUser")    // 设置流控处理方法
    public User getUser(String id)
    {
        // int i = 1 / 0;
        return new User("test");
    }

4. 添加流控处理

public User blockHanderForUser(String id, BlockException ex)
    {
        ex.printStackTrace();
        return new User("流控了");
    }

流控方法应该与资源方法保持一致的参数和返回值，只是在参数列表中，增加一个流控异常参数 。

5. 异常降级方法

public User fallbackForUser(String id, Throwable ex)
    {
        return new User("异常降级了");
    }