SpringCloud学习笔记

最新推荐文章于 2024-05-16 13:29:10 发布

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最新推荐文章于 2024-05-16 13:29:10 发布

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文章标签： spring cloud 学习笔记

本文链接：https://blog.youkuaiyun.com/Programmer_czw/article/details/130997461

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文章讲述了SpringCloud中的微服务模块构建，包括创建module、配置pom、编写yml、启动服务和业务类。重点讨论了基于余数的负载均衡算法，并手写了使用JUCCAS的轮询负载均衡实现。同时，文章提到了OpenFeign的服务调用和Hystrix熔断器的作用，如防止级联故障、服务降级和限流。在实施过程中遇到了Hystrix配置错误和Gateway找不到路由工厂的问题。

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微服务模块

1.建module

2.改pom

3.写yml

4.主启动

5.业务类

负载均衡

**负载均衡算法：**rest接口第几次请求数 % 服务器集群总数量 = 实际调用服务器位置下表，每次服务重启后rest接口计数从1开始。在这里插入图片描述
如图：服务器集群总数量：2台
List = 2 instance
第一次请求：1 % 2 = 1 —》 index = 1 list.get(index);
第二次请求：2 % 2 = 0 —》 index = 0 list.get(index)

手写一个负载的算法，原理+JUC（CAS+自旋锁的复习）

package com.atguigu.springcloud.lb;

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

/**
 1. 轮询算法
 */
@Component
public class MyLB implements LoadBalancer{

    private AtomicInteger atomicInteger = new AtomicInteger(0);

    public final int getAndIncrement() {
        int current;
        int next;
        do {
            current = this.atomicInteger.get();
            next = current >= 2147483467 ? 0 : current + 1;
        } while (!this.atomicInteger.compareAndSet(current, next));
        System.out.println("********next" + next);
        return next;
    }


    @Override
    public ServiceInstance instances(List<ServiceInstance> serviceInstances) {

        int index = getAndIncrement() % serviceInstances.size();
        return serviceInstances.get(index);
    }
}

OpenFeign服务调用

1.yml
在这里插入图片描述
2.启动类

3.业务
在这里插入图片描述

4.详细日志

Hystrix熔断器

能保证一个依赖出问题的情况下，不会导致整体服务失败，避免级联故障，以提高分布式系统的弹性

服务熔断
服务降级
接近实时的监控

Hystrix重要概念

服务降级：服务器忙，请稍后再试，不让客户端等待并立刻返回一个友好提示，fallback
哪些情况会触发服务降级：程序运行异常、超时、服务熔断触发服务降级、线程池/信号量打满也会导致服务降级
服务熔断：类比保险丝达到最大服务访问后，直接拒绝访问，拉闸限电，然后调用服务降级的方法并返回友好提示，相当于保险丝。break。服务的降级—> 进而熔断—> 恢复调用链路
服务限流：秒杀高并发等操作，严禁一窝蜂的过来拥挤，大家排队，一秒钟N个，有序进行

服务降级

服务熔断

遇到的问题

控制台报错：Failed to set Command properties. groupKey: ‘PaymentServiceImpl’, commandKey: 'paymentCircuitBreaker
错误代码：在这里插入图片描述

 protected HystrixCommandProperties(HystrixCommandKey key, HystrixCommandProperties.Setter builder, String propertyPrefix) {
        this.key = key;
        this.circuitBreakerEnabled = getProperty(propertyPrefix, key, "circuitBreaker.enabled", builder.getCircuitBreakerEnabled(), default_circuitBreakerEnabled);
        this.circuitBreakerRequestVolumeThreshold = getProperty(propertyPrefix, key, "circuitBreaker.requestVolumeThreshold", builder.getCircuitBreakerRequestVolumeThreshold(), default_circuitBreakerRequestVolumeThreshold);
        this.circuitBreakerSleepWindowInMilliseconds = getProperty(propertyPrefix, key, "circuitBreaker.sleepWindowInMilliseconds", builder.getCircuitBreakerSleepWindowInMilliseconds(), default_circuitBreakerSleepWindowInMilliseconds);
        this.circuitBreakerErrorThresholdPercentage = getProperty(propertyPrefix, key, "circuitBreaker.errorThresholdPercentage", builder.getCircuitBreakerErrorThresholdPercentage(), default_circuitBreakerErrorThresholdPercentage);
        this.circuitBreakerForceOpen = getProperty(propertyPrefix, key, "circuitBreaker.forceOpen", builder.getCircuitBreakerForceOpen(), default_circuitBreakerForceOpen);
        this.circuitBreakerForceClosed = getProperty(propertyPrefix, key, "circuitBreaker.forceClosed", builder.getCircuitBreakerForceClosed(), default_circuitBreakerForceClosed);
        this.executionIsolationStrategy = getProperty(propertyPrefix, key, "execution.isolation.strategy", builder.getExecutionIsolationStrategy(), default_executionIsolationStrategy);
        //this property name is now misleading.  //TODO figure out a good way to deprecate this property name
        this.executionTimeoutInMilliseconds = getProperty(propertyPrefix, key, "execution.isolation.thread.timeoutInMilliseconds", builder.getExecutionIsolationThreadTimeoutInMilliseconds(), default_executionTimeoutInMilliseconds);
        this.executionTimeoutEnabled = getProperty(propertyPrefix, key, "execution.timeout.enabled", builder.getExecutionTimeoutEnabled(), default_executionTimeoutEnabled);
        this.executionIsolationThreadInterruptOnTimeout = getProperty(propertyPrefix, key, "execution.isolation.thread.interruptOnTimeout", builder.getExecutionIsolationThreadInterruptOnTimeout(), default_executionIsolationThreadInterruptOnTimeout);
        this.executionIsolationThreadInterruptOnFutureCancel = getProperty(propertyPrefix, key, "execution.isolation.thread.interruptOnFutureCancel", builder.getExecutionIsolationThreadInterruptOnFutureCancel(), default_executionIsolationThreadInterruptOnFutureCancel);
        this.executionIsolationSemaphoreMaxConcurrentRequests = getProperty(propertyPrefix, key, "execution.isolation.semaphore.maxConcurrentRequests", builder.getExecutionIsolationSemaphoreMaxConcurrentRequests(), default_executionIsolationSemaphoreMaxConcurrentRequests);
        this.fallbackIsolationSemaphoreMaxConcurrentRequests = getProperty(propertyPrefix, key, "fallback.isolation.semaphore.maxConcurrentRequests", builder.getFallbackIsolationSemaphoreMaxConcurrentRequests(), default_fallbackIsolationSemaphoreMaxConcurrentRequests);
        this.fallbackEnabled = getProperty(propertyPrefix, key, "fallback.enabled", builder.getFallbackEnabled(), default_fallbackEnabled);
        this.metricsRollingStatisticalWindowInMilliseconds = getProperty(propertyPrefix, key, "metrics.rollingStats.timeInMilliseconds", builder.getMetricsRollingStatisticalWindowInMilliseconds(), default_metricsRollingStatisticalWindow);
        this.metricsRollingStatisticalWindowBuckets = getProperty(propertyPrefix, key, "metrics.rollingStats.numBuckets", builder.getMetricsRollingStatisticalWindowBuckets(), default_metricsRollingStatisticalWindowBuckets);
        this.metricsRollingPercentileEnabled = getProperty(propertyPrefix, key, "metrics.rollingPercentile.enabled", builder.getMetricsRollingPercentileEnabled(), default_metricsRollingPercentileEnabled);
        this.metricsRollingPercentileWindowInMilliseconds = getProperty(propertyPrefix, key, "metrics.rollingPercentile.timeInMilliseconds", builder.getMetricsRollingPercentileWindowInMilliseconds(), default_metricsRollingPercentileWindow);
        this.metricsRollingPercentileWindowBuckets = getProperty(propertyPrefix, key, "metrics.rollingPercentile.numBuckets", builder.getMetricsRollingPercentileWindowBuckets(), default_metricsRollingPercentileWindowBuckets);
        this.metricsRollingPercentileBucketSize = getProperty(propertyPrefix, key, "metrics.rollingPercentile.bucketSize", builder.getMetricsRollingPercentileBucketSize(), default_metricsRollingPercentileBucketSize);
        this.metricsHealthSnapshotIntervalInMilliseconds = getProperty(propertyPrefix, key, "metrics.healthSnapshot.intervalInMilliseconds", builder.getMetricsHealthSnapshotIntervalInMilliseconds(), default_metricsHealthSnapshotIntervalInMilliseconds);
        this.requestCacheEnabled = getProperty(propertyPrefix, key, "requestCache.enabled", builder.getRequestCacheEnabled(), default_requestCacheEnabled);
        this.requestLogEnabled = getProperty(propertyPrefix, key, "requestLog.enabled", builder.getRequestLogEnabled(), default_requestLogEnabled);
 
        // threadpool doesn't have a global override, only instance level makes sense
        this.executionIsolationThreadPoolKeyOverride = forString().add(propertyPrefix + ".command." + key.name() + ".threadPoolKeyOverride", null).build();
    }