hystrix（一） 簡單使用, 以及動態配置更新

本文轉載自https://my.oschina.net/u/1169457/blog/1787414

 

hystrix 簡單使用, 以及動態配置更新

概述

只介紹同步模式下簡單的使用, 有助於快速接入, 會有一些官方文檔中沒有涉及的細節.

默認方式

HelloWorld!

public class CommandHelloWorld extends HystrixCommand<String> {

    private final String name;

    // 構造方法中傳入需要用到的數據, run 方法處理邏輯.
    public CommandHelloWorld(String name) {
        // 構造 Setter 比較麻煩, 后面會進一步介紹
        super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"));
        this.name = name;
    }

    @Override
    protected String run() {
        // a real example would do work like a network call here
        return "Hello " + name + "!";
    }
    
    // fallback 方法可選, 如果沒有, 默認拋異常.
    @Override
    protected String getFallback() {
        return "fallback";
    }
}

 

構造Setter

Hystrix 講求的大而全, 設計的比較模式, 用起來不是很方便. 下面是一個構造 Setter 的實例:

Setter setter = Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey(site)) // groupKey 對command進行分組, 用於 reporting, alerting, dashboards, or team/library ownership, 也是 ThreadPool 的默認 key
        .andCommandKey(HystrixCommandKey.Factory.asKey(site)) // 可以根據 commandKey 具體的運行時參數
        .andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey(site))  // 指定 ThreadPool key, 這樣就不會默認使用 GroupKey
        .andCommandPropertiesDefaults(HystrixCommandProperties.Setter() // 初始化 Command 相關屬性
                .withMetricsRollingStatisticalWindowInMilliseconds(
                        100 * 1000) // 設置統計窗口為100秒
                .withCircuitBreakerSleepWindowInMilliseconds(
                        10 * 1000) // 設置熔斷以后, 試探間隔為10秒
                .withCircuitBreakerRequestVolumeThreshold(
                        10) // 設置判斷熔斷請求閾值為10
                .withCircuitBreakerErrorThresholdPercentage(
                        80) // 設置判斷熔斷失敗率為80%
                .withExecutionTimeoutInMilliseconds(3 * 1000)) // 設置每個請求超時時間為3秒
        .andThreadPoolPropertiesDefaults( // 設置和threadPool相關
                HystrixThreadPoolProperties.Setter().withCoreSize(20)); // 設置 threadPool 大小為20(最大20個並發)

 

另外 threadPool 還有個設置統計窗口的選項, 因為 Hystrix 統計維度會從主線程和線程池兩個維度來統計.

還有好多配置信息可以配置, 這里只提供了幾個重要的. 其他配置參考:hystrix-configuration

Spring cloud 注解方式

需要用到兩個注解: @EnableCircuitBreaker, @HystrixCommand(fallbackMethod = "reliable")

啟動類:

package hello;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.web.client.RestTemplate;

@EnableCircuitBreaker
@RestController
@SpringBootApplication
public class ReadingApplication {

  @Autowired
  private BookService bookService;

  @Bean
  public RestTemplate rest(RestTemplateBuilder builder) {
    return builder.build();
  }

  @RequestMapping("/to-read")
  public String toRead() {
    return bookService.readingList();
  }

  public static void main(String[] args) {
    SpringApplication.run(ReadingApplication.class, args);
  }
}
服務類:

package hello;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

import java.net.URI;

@Service
public class BookService {

  private final RestTemplate restTemplate;

  public BookService(RestTemplate rest) {
    this.restTemplate = rest;
  }

  @HystrixCommand(fallbackMethod = "reliable")
  public String readingList() {
    URI uri = URI.create("http://localhost:8090/recommended");

    return this.restTemplate.getForObject(uri, String.class);
  }

  public String reliable() {
    return "Cloud Native Java (O'Reilly)";
  }

}

 

動態更新配置

Hystrix 使用 Archaius 來實現動態配置. 使用 Spring 配置方式:

1. 創建配置獲取源
2. 配置並初始化自動配置

創建配置獲取源

實現接口 PolledConfigurationSource, 並返回一個 Map. 注意 Key 為 hystrix 配置key, 可以參考: Hystrix-configuration

package com.rh.config.hystrix;

import com.netflix.config.PollResult;
import com.netflix.config.PolledConfigurationSource;
import org.springframework.core.env.*;
import org.springframework.core.io.ResourceLoader;
import org.springframework.stereotype.Component;


import javax.annotation.Resource;
import java.util.*;

/**
 * @Auther: wangyunfei
 * @Date: 2019/12/10 14:12
 * @Description:
 */
@Component
/**
 * @Author wangyunfei
 * @Description 定期讀取配置文件中的hystrix配置
 * @Date 2019/12/10 14:13
 * @Param
 * @return
 **/
public class DegradeConfigSource implements PolledConfigurationSource {
    public final String HystrixPrefix = "hystrix";

    //spring的Environment
    private ConfigurableEnvironment environment;
    private PropertySourcesPropertyResolver resolver;

    DegradeConfigSource(ConfigurableEnvironment environment) {
        this.environment = environment;
        this.resolver = new PropertySourcesPropertyResolver(this.environment.getPropertySources());
        this.resolver.setIgnoreUnresolvableNestedPlaceholders(true);

    }
    
    @Override
    public PollResult poll(boolean initial, Object checkPoint) throws Exception {
        //Map<String, Object> complete = getHystrixConfig();
        Map<String, Object> complete = getProperties();
        return PollResult.createFull(complete);
    }

    @Resource
    private ResourceLoader resourceLoader;
    /**
     * @Author wangyunfei
     * @Description 獲取配置文件中的指定hystrix前綴信息
     * 缺點：1）不支持yml格式 只支持properties
     *       2）只能讀取某一個配置文件中的信息 如果配置是寫在不同配置文件則不支持
     * @Date 2019/12/20 14:58
     * @Param []
     * @return java.util.HashMap<java.lang.String,java.lang.String>
     **/
    public HashMap<String,Object> getHystrixConfig() throws Exception
    {
        HashMap<String,Object> hystrixMap = new  HashMap<String,Object>();
        org.springframework.core.io.Resource resource = resourceLoader.getResource("classpath:application-mod.properties");
        Properties props = new Properties();
        props.load(resource.getInputStream());
        Enumeration keys = props.propertyNames();
        while (keys.hasMoreElements()) {
            String key = (String) keys.nextElement();
            System.out.println(key + "=" + props.getProperty(key));
            if(key.contains(HystrixPrefix))
            {
                hystrixMap.put(key, props.getProperty(key));
            }
        }
        return hystrixMap;
    }

    /**
     * @Author wangyunfei
     * @Description 獲取所有配置信息
     * @Date 2019/12/20 15:06
     * @Param []
     * @return java.util.Map<java.lang.String,java.lang.Object>
     **/
    public Map<String, Object> getProperties() {
        Map<String, Object> properties = new LinkedHashMap<>();
        //spring env 里面也是多個source組合的
        for (Map.Entry<String, PropertySource<?>> entry : getPropertySources().entrySet()) {
            PropertySource<?> source = entry.getValue();
            if (source instanceof EnumerablePropertySource) {
                EnumerablePropertySource<?> enumerable = (EnumerablePropertySource<?>) source;
                for (String name : enumerable.getPropertyNames()) {
                    if (!properties.containsKey(name) && name.contains(HystrixPrefix)) {
                        properties.put(name, resolver.getProperty(name));
                    }
                }
            }
        }
        return properties;
    }

    //PropertySource也可能是組合的，通過遞歸獲取
    private Map<String, PropertySource<?>> getPropertySources() {
        Map<String, PropertySource<?>> map = new LinkedHashMap<String, PropertySource<?>>();
        MutablePropertySources sources = null;
        if (environment != null) {
            sources = environment.getPropertySources();
        } else {
            sources = new StandardEnvironment().getPropertySources();
        }
        for (PropertySource<?> source : sources) {
            extract("", map, source);
        }
        return map;
    }

    private void extract(String root, Map<String, PropertySource<?>> map,
                         PropertySource<?> source) {
        if (source instanceof CompositePropertySource) {
            for (PropertySource<?> nest : ((CompositePropertySource) source)
                    .getPropertySources()) {
                extract(source.getName() + ":", map, nest);
            }
        } else {
            map.put(root + source.getName(), source);
        }
    }
}

 

配置並初始化自動配置

創建一個 DynamicConfiguration, 並注冊一下就可以了. 注意, 我們使用了 FixedDelayPollingScheduler 來定期加載新的配置. 默認60秒加載一次.

@Configuration
public class DegradeDynamicConfig {

    @Bean
    public DynamicConfiguration dynamicConfiguration(@Autowired DegradeConfigSource degradeConfigSource) {
        AbstractPollingScheduler scheduler = new FixedDelayPollingScheduler(30 * 1000, 60 * 1000, false);
        DynamicConfiguration configuration = new DynamicConfiguration(degradeConfigSource, scheduler);
        ConfigurationManager.install(configuration); // must install to enable configuration
        return configuration;
    }

}

其中從配置文件獲取hystrix配置信息等參考如下代碼  http://techblog.ppdai.com/2018/05/08/20180508/

參考

Hystrix-how-to-use
Hystrix-configuration
Hystrix-change-config-dynamically
hystrix-archaius-to-dynamic-config
Spring-circuit-breaker