hystrix具体配置——演示超时熔断过程

分手后的思念是犯贱 2022-05-22 11:40 200阅读 0赞

1、引入maven依赖

<dependency>
                <groupId>com.netflix.hystrix</groupId>
                <artifactId>hystrix-core</artifactId>
                <version>1.5.12</version>
            </dependency>

2、编写一个动态出现超时异常的继承HystrixCommand的类

package com.xueyou.hystrixdemo.v3;
    
    import com.netflix.hystrix.HystrixCommand;
    
    import java.util.Arrays;
    import java.util.List;
    
    public class CommandHelloworldWithFallBack extends HystrixCommand<String> {
        public static List<Integer> times = Arrays.asList(100, 200, 300, 400, 500, 600,
                700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100);
        private String name;
        private int timeIndex;
    
        public CommandHelloworldWithFallBack(Setter setter, String name, int timeIndex) {
            super(setter);
            this.name = name;
            this.timeIndex = timeIndex;
        }
    
        @Override
        protected String getFallback() {
            return "fall back timeMillSeconds is :" + times.get(timeIndex);
        }
    
        @Override
        protected String run() {
            try {
                Thread.currentThread().sleep(times.get(this.getTimeIndex()));
            } catch (InterruptedException e) {
            }
            return "ok timeMillSeconds is :" + times.get(timeIndex);
        }
    
        public int getTimeIndex() {
            return timeIndex;
        }
    
        public void setTimeIndex(int timeIndex) {
            this.timeIndex = timeIndex;
        }
    }

3、编写一些测试类进行测试

package com.xueyou.hystrixdemo.v3;
    
    import com.netflix.hystrix.*;
    
    public class HelloWorldFallBack {
        public static void main(String[] args) {
            int count = 0;
            while (true) {
                String s = new CommandHelloworldWithFallBack(HystrixCommand.Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"))
                        .andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey("threadpoolwithfallback"))
                        .andThreadPoolPropertiesDefaults(HystrixThreadPoolProperties.Setter()
                                .withCoreSize(10)
                                .withMaximumSize(10))
                        .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                                .withExecutionTimeoutInMilliseconds(1000)
                                .withCircuitBreakerSleepWindowInMilliseconds(5000)
                                .withCircuitBreakerErrorThresholdPercentage(50)
                                .withCircuitBreakerRequestVolumeThreshold(1))
                        , "ccc", count % 20).execute();
                System.out.println(s);
                count++;
                try {
                    Thread.currentThread().sleep(50);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                }
            }
    
        }
    }

4、运行结果：

ok timeMillSeconds is :100

ok timeMillSeconds is :200

ok timeMillSeconds is :300

ok timeMillSeconds is :400

ok timeMillSeconds is :500

ok timeMillSeconds is :600

ok timeMillSeconds is :700

ok timeMillSeconds is :800

ok timeMillSeconds is :900

ok timeMillSeconds is :1000

fall back timeMillSeconds is :1100

fall back timeMillSeconds is :1200

fall back timeMillSeconds is :1300

fall back timeMillSeconds is :1400

fall back timeMillSeconds is :1500

fall back timeMillSeconds is :1600

fall back timeMillSeconds is :1700

fall back timeMillSeconds is :1800

fall back timeMillSeconds is :1900

fall back timeMillSeconds is :2000

fall back timeMillSeconds is :100

fall back timeMillSeconds is :200

fall back timeMillSeconds is :300

fall back timeMillSeconds is :400

fall back timeMillSeconds is :500

fall back timeMillSeconds is :600

fall back timeMillSeconds is :700

fall back timeMillSeconds is :800

fall back timeMillSeconds is :900

fall back timeMillSeconds is :1000

fall back timeMillSeconds is :1100

fall back timeMillSeconds is :1200

fall back timeMillSeconds is :1300

fall back timeMillSeconds is :1400

fall back timeMillSeconds is :1500

fall back timeMillSeconds is :1600

fall back timeMillSeconds is :1700

fall back timeMillSeconds is :1800

fall back timeMillSeconds is :1900

fall back timeMillSeconds is :2000

fall back timeMillSeconds is :100

fall back timeMillSeconds is :200

fall back timeMillSeconds is :300

fall back timeMillSeconds is :400

fall back timeMillSeconds is :500

fall back timeMillSeconds is :600

fall back timeMillSeconds is :700

fall back timeMillSeconds is :800

fall back timeMillSeconds is :900

fall back timeMillSeconds is :1000

fall back timeMillSeconds is :1100

fall back timeMillSeconds is :1200

fall back timeMillSeconds is :1300

fall back timeMillSeconds is :1400

fall back timeMillSeconds is :1500

fall back timeMillSeconds is :1600

fall back timeMillSeconds is :1700

fall back timeMillSeconds is :1800

fall back timeMillSeconds is :1900

fall back timeMillSeconds is :2000

fall back timeMillSeconds is :100

fall back timeMillSeconds is :200

fall back timeMillSeconds is :300

fall back timeMillSeconds is :400

fall back timeMillSeconds is :500

fall back timeMillSeconds is :600

fall back timeMillSeconds is :700

fall back timeMillSeconds is :800

fall back timeMillSeconds is :900

fall back timeMillSeconds is :1000

fall back timeMillSeconds is :1100

fall back timeMillSeconds is :1200

fall back timeMillSeconds is :1300

fall back timeMillSeconds is :1400

fall back timeMillSeconds is :1500

fall back timeMillSeconds is :1600

fall back timeMillSeconds is :1700

fall back timeMillSeconds is :1800

fall back timeMillSeconds is :1900

fall back timeMillSeconds is :2000

fall back timeMillSeconds is :100

fall back timeMillSeconds is :200

fall back timeMillSeconds is :300

fall back timeMillSeconds is :400

fall back timeMillSeconds is :500

fall back timeMillSeconds is :600

fall back timeMillSeconds is :700

fall back timeMillSeconds is :800

fall back timeMillSeconds is :900

fall back timeMillSeconds is :1000

fall back timeMillSeconds is :1100

fall back timeMillSeconds is :1200

fall back timeMillSeconds is :1300

fall back timeMillSeconds is :1400

fall back timeMillSeconds is :1500

fall back timeMillSeconds is :1600

fall back timeMillSeconds is :1700

fall back timeMillSeconds is :1800

fall back timeMillSeconds is :1900

fall back timeMillSeconds is :2000

fall back timeMillSeconds is :100

fall back timeMillSeconds is :200

fall back timeMillSeconds is :300

fall back timeMillSeconds is :400

fall back timeMillSeconds is :500

fall back timeMillSeconds is :600

fall back timeMillSeconds is :700

ok timeMillSeconds is :800

ok timeMillSeconds is :900

ok timeMillSeconds is :1000

fall back timeMillSeconds is :1100

fall back timeMillSeconds is :1200

fall back timeMillSeconds is :1300

fall back timeMillSeconds is :1400

结果分析：

1、首先在run()方法没有超时的时候，是正常返回的，没有走getFallback()。

然后，时间超时了，这是时候会走getFallback()。

2、那么什么时候发生熔断呢，或者说熔断的触发条件是什么呢？（这里先不讨论线程是满了的情况，也就是说假设线程池足够用）

*  withExecutionTimeoutInMilliseconds(1000)==>run()方法的执行时间超过最大阈值毫秒数。如果超过了，那么hystrix会当做本次为一次错误。

官网解释：

execution.isolation.thread.timeoutInMilliseconds

This property sets the time in milliseconds after which the caller will observe a timeout and walk away from the command execution. Hystrix marks the  HystrixCommand  as a TIMEOUT, and performs fallback logic. Note that there is configuration for turning off timeouts per-command, if that is desired (see command.timeout.enabled).

*  withCircuitBreakerRequestVolumeThreshold(1)==>代表在一个rolling window内发生的所有请求的个数。如果这个个数很少，那么不会触发熔断，只有大于这阈值，才有可能触发熔断。

官网的解释是这样的：

circuitBreaker.requestVolumeThreshold

This property sets the minimum number of requests in a rolling window that will trip the circuit.

For example, if the value is 20, then if only 19 requests are received in the rolling window (say a window of 10 seconds) the circuit will not trip open even if all 19 failed.

*  withCircuitBreakerErrorThresholdPercentage(50) ==>发生问题的请求占所有请求的百分比阈值（在一个rolling window内的所有请求里）。

这个是官网的解释：

circuitBreaker.errorThresholdPercentage

This property sets the error percentage at or above which the circuit should trip open and start short-circuiting requests to fallback logic.

从上面的解释我们能够看到熔断的触发条件首先在指定rolling window内请求的个数大于设定的阈值；同时，出现错误的请求个数占总请求数的百分比大于设置的百分比。

补充一下，rolling window这么关键，那么如何设置rolling window的大小呢？

metrics.rollingStats.timeInMilliseconds

3、什么时候熔断会自动恢复呢（也就是说什么条件才会触发熔断自动恢复呢）？

*  withCircuitBreakerSleepWindowInMilliseconds(5000)==>当已经熔断的时候经过设定的毫秒数后，会重新走一次run()方法（熔断开始后，所有的请求会直接走getFallback()，不会走run()方法的）。也就是说，如果熔断了，没隔5秒会执行一下run()方法，看一下是否能够正常执行，如果能够正常执行，那么熔断自动恢复，否则继续处于熔断状态。

下面是官网的解释：

circuitBreaker.sleepWindowInMilliseconds

This property sets the amount of time, after tripping the circuit, to reject requests before allowing attempts again to determine if the circuit should again be closed.

最后附上异常hystrix的流程图

![70][]

[70]: /images/20220522/f41db21ab069496f87ed97c5874c1336.png