SpringCloud实战四十：fallback服务降级

I.FALLBACK

1、准备两个提供者9003、9004，和一个服务消费者

配置参照：https://www.aimaboge.com/article/717

2、编写接口

• 服务提供者：

package com.laoxu.springcloud.controller;

import com.laoxu.springcloud.entities.CommonResult;
import com.laoxu.springcloud.entities.Payment;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;

@RestController
public class PaymentController {

    @Value("${server.port}")
    public String serverPort;

    public static HashMap<Long, Payment> hashMap = new HashMap<Long, Payment>();
    static
    {
        hashMap.put(1L, new Payment(1L, "a"));
        hashMap.put(2L, new Payment(2L, "b"));
        hashMap.put(3L, new Payment(3L, "c"));
    }

    @GetMapping("/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id){
        Payment payment = hashMap.get(id);
        CommonResult<Payment> result = new CommonResult<Payment>(200, "from mysql, serverPort: " + serverPort, payment);
        return result;
    }

}

• 服务消费者

package com.laoxu.springcloud.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.laoxu.springcloud.entities.CommonResult;
import com.laoxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@Slf4j
public class CircleBreakerController {

    public static final String SERVICE_URL = "http://nacos-payment-provider";

    @Autowired
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
    @SentinelResource(value = "fallback", fallback = "handleFallback")
    public CommonResult<Payment> fallback(@PathVariable("id") Long id){
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/" + id, CommonResult.class);
        if(id == 4){
            throw new IllegalArgumentException("IllegalArgumentException， 非法参数异常。。。");
        }else if(id > 4 && id < 8){
            throw new NullPointerException("NullPointerException, 该id没有对应的记录，空指针异常");
        }
        return result;
    }

    public CommonResult<Payment> handleFallback(@PathVariable("id") Long id, Throwable e){
        Payment payment = new Payment(id, "null");
        return new CommonResult<Payment>(444, "fallback异常, 异常内容："+ e.getMessage(), payment);
    }


}

3、测试访问：http://localhost:84/consumer/fallback/1

负载均衡配置完成。

4、测试访问：http://localhost:84/consumer/fallback/4

5、测试访问：http://localhost:84/consumer/fallback/5

II.BLOCKEXCEPTION

1、服务提供者接口不变

package com.laoxu.springcloud.controller;

import com.laoxu.springcloud.entities.CommonResult;
import com.laoxu.springcloud.entities.Payment;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;

@RestController
public class PaymentController {

    @Value("${server.port}")
    public String serverPort;

    public static HashMap<Long, Payment> hashMap = new HashMap<Long, Payment>();
    static
    {
        hashMap.put(1L, new Payment(1L, "a"));
        hashMap.put(2L, new Payment(2L, "b"));
        hashMap.put(3L, new Payment(3L, "c"));
    }

    @GetMapping("/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id){
        Payment payment = hashMap.get(id);
        CommonResult<Payment> result = new CommonResult<Payment>(200, "from mysql, serverPort: " + serverPort, payment);
        return result;
    }

}

2、消费者改变

package com.laoxu.springcloud.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.laoxu.springcloud.entities.CommonResult;
import com.laoxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@Slf4j
public class CircleBreakerController {

    public static final String SERVICE_URL = "http://nacos-payment-provider";

    @Autowired
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
//    @SentinelResource(value = "fallback", fallback = "handleFallback")
    @SentinelResource(value = "fallback", blockHandler = "blockHandler")
    public CommonResult<Payment> fallback(@PathVariable("id") Long id){
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/" + id, CommonResult.class);
        if(id == 4){
            throw new IllegalArgumentException("IllegalArgumentException， 非法参数异常。。。");
        }else if(id > 4 && id < 8){
            throw new NullPointerException("NullPointerException, 该id没有对应的记录，空指针异常");
        }
        return result;
    }

    public CommonResult<Payment> handleFallback(@PathVariable("id") Long id, Throwable e){
        Payment payment = new Payment(id, "null");
        return new CommonResult<Payment>(444, "fallback异常, 异常内容："+ e.getMessage(), payment);
    }
    public CommonResult<Payment> blockHandler(@PathVariable Long id, BlockException exception){
        Payment payment = new Payment(id, "null");
        return new CommonResult<Payment>(445, "blockHandler-sentinel限流, 无此流水 异常内容："+ exception.getMessage(), payment);
    }

}

3、配置sentinel限流

4、测试访问：http://localhost:84/consumer/fallback/4

会看到error page，java运行报错页面，blockException只管配置违规，不管java报错

当2s内访问次数超过2次那么触发blockException

III.BLOCKEXCEPTION && FALLBACK

1、服务提供者接口不变

package com.laoxu.springcloud.controller;

import com.laoxu.springcloud.entities.CommonResult;
import com.laoxu.springcloud.entities.Payment;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;

@RestController
public class PaymentController {

    @Value("${server.port}")
    public String serverPort;

    public static HashMap<Long, Payment> hashMap = new HashMap<Long, Payment>();
    static
    {
        hashMap.put(1L, new Payment(1L, "a"));
        hashMap.put(2L, new Payment(2L, "b"));
        hashMap.put(3L, new Payment(3L, "c"));
    }

    @GetMapping("/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id){
        Payment payment = hashMap.get(id);
        CommonResult<Payment> result = new CommonResult<Payment>(200, "from mysql, serverPort: " + serverPort, payment);
        return result;
    }

}

2、消费者改变

package com.laoxu.springcloud.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.laoxu.springcloud.entities.CommonResult;
import com.laoxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@Slf4j
public class CircleBreakerController {

    public static final String SERVICE_URL = "http://nacos-payment-provider";

    @Autowired
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
//    @SentinelResource(value = "fallback", fallback = "handleFallback")
//    @SentinelResource(value = "fallback", blockHandler = "blockHandler")
    @SentinelResource(value = "fallback", fallback = "handleFallback", blockHandler = "blockHandler")
    public CommonResult<Payment> fallback(@PathVariable("id") Long id){
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/" + id, CommonResult.class);
        if(id == 4){
            throw new IllegalArgumentException("IllegalArgumentException， 非法参数异常。。。");
        }else if(id > 4 && id < 8){
            throw new NullPointerException("NullPointerException, 该id没有对应的记录，空指针异常");
        }
        return result;
    }

    public CommonResult<Payment> handleFallback(@PathVariable("id") Long id, Throwable e){
        Payment payment = new Payment(id, "null");
        return new CommonResult<Payment>(444, "fallback异常, 异常内容："+ e.getMessage(), payment);
    }
    public CommonResult<Payment> blockHandler(@PathVariable Long id, BlockException exception){
        Payment payment = new Payment(id, "null");
        return new CommonResult<Payment>(445, "blockHandler-sentinel限流, 无此流水 异常内容："+ exception.getMessage(), payment);
    }

}

3、配置sentinel限流

4、测试访问：http://localhost:84/consumer/fallback/4

当没有达到限流规则的条件的情况下，走fallback异常

当达到限流规则的条件的情况下，走blockException异常

结论：sentinel平台违规优先级大于java报错

5、异常忽略

• 修改接口

异常忽略：exceptionsToIgnore = IllegalArgumentException.class

加上后，出现IllegalArgumentException后不会走handleFallback

@RestController
@Slf4j
public class CircleBreakerController {

    public static final String SERVICE_URL = "http://nacos-payment-provider";

    @Autowired
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
//    @SentinelResource(value = "fallback", fallback = "handleFallback")
//    @SentinelResource(value = "fallback", blockHandler = "blockHandler")
//    @SentinelResource(value = "fallback", fallback = "handleFallback", blockHandler = "blockHandler")
    @SentinelResource(value = "fallback", fallback = "handleFallback",
            blockHandler = "blockHandler", exceptionsToIgnore = IllegalArgumentException.class)
    public CommonResult<Payment> fallback(@PathVariable("id") Long id){
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/" + id, CommonResult.class);
        if(id == 4){
            throw new IllegalArgumentException("IllegalArgumentException， 非法参数异常。。。");
        }else if(id > 4 && id < 8){
            throw new NullPointerException("NullPointerException, 该id没有对应的记录，空指针异常");
        }
        return result;
    }

    public CommonResult<Payment> handleFallback(@PathVariable("id") Long id, Throwable e){
        Payment payment = new Payment(id, "null");
        return new CommonResult<Payment>(444, "fallback异常, 异常内容："+ e.getMessage(), payment);
    }
    public CommonResult<Payment> blockHandler(@PathVariable Long id, BlockException exception){
        Payment payment = new Payment(id, "null");
        return new CommonResult<Payment>(445, "blockHandler-sentinel限流, 无此流水 异常内容："+ exception.getMessage(), payment);
    }

}

6、测试访问：http://localhost:84/consumer/fallback/4