架构师训练营第七周作业

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发布于: 2020 年 11 月 09 日
性能压测的时候，随着并发压力的增加，系统响应时间和吞吐量如何变化，为什么？随着并发压力增加，系统响应时间会逐渐增大，压力到达一定阈值后，响应时间会急剧增加，直至系统崩溃
随着并发压力增加，吞吐量首先会逐渐增加，增加幅度会逐渐放缓，压力到达一定阈值后吞吐量会逐渐减小，幅度会越来越大，直至系统崩溃
导致以上变化的原因为：
并发数较小时，系统资源足够，系统收到请求后无需等待或等待时间较短，所以响应时间变化不大，而吞吐量 = (1000 / 响应时间ms) x 并发数，所以吞吐量随并发数增加而增加；
并发数较大时，系统资源不足以分配给每个请求，CPU需要调度系统资源，如在内存耗尽的情况下使用虚拟内存，虚拟内存的读写速度远低于内存的读写速度，响应时间相应变长，另一方面，线程之间切换也有时间开销，因此吞吐量会逐渐减小
﻿
性能压测工具开发语言为Java，使用CloseableHttpClient完成请求
package com.colin.benchmarker;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.http.ConnectionReuseStrategy;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.protocol.HttpContext;
public class CustomBenchMarker {
    /**
     * 返回时间
     */
    List<Long> responseTimes;
    /**
     * 测试地址
     */
    String url;
    /**
     * 并发数
     */
    int concurrency;
    /**
     * 总请求次数
     */
    AtomicInteger totalRequests;
    CloseableHttpClient httpClient;
    HttpGet httpGet;
    ExecutorService executorService;
    
    public CustomBenchMarker(String url, int concurrency, int total) {
        this.url = url;
        this.concurrency = concurrency;
        totalRequests = new AtomicInteger(total);
        List<Long> list = new LinkedList<Long>();
        this.responseTimes = Collections.synchronizedList(list);
        executorService = Executors.newFixedThreadPool(concurrency);
        httpClient = HttpClients.custom().setMaxConnPerRoute(concurrency)
                .setConnectionReuseStrategy(new ConnectionReuseStrategy() {
                    @Override
                    public boolean keepAlive(HttpResponse response, HttpContext context) {
                        return true;
                    }
                }).build();
         httpGet = new HttpGet(url);
    }
    public void startTest() throws Exception {
        for (int i = 0; i < concurrency; ++i) {
            executorService.execute(() -> {
                try {
                    test();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
        }
        executorService.awaitTermination(10, TimeUnit.SECONDS);
        System.out.println(responseTimes.size());
    }
    
    public void report() {
        int requestCounts = responseTimes.size();
        responseTimes.sort((a, b) -> a.compareTo(b));
        Long p50 = responseTimes.get((int) (requestCounts * 0.5));
        Long p95 = responseTimes.get((int) (requestCounts * 0.95));
        Long p99 = responseTimes.get((int) (requestCounts * 0.99));
    
        long avgResponseTime = 0;
        for (int i = 0; i < requestCounts; ++i) {
            avgResponseTime += responseTimes.get(i);
        }
        
        System.out.println(String.format("average response time: %d", avgResponseTime / requestCounts));
        System.out.println(String.format("50%% response time: %d", p50));
        System.out.println(String.format("95%% response time: %d", p95));
        System.out.println(String.format("99%% response time: %d", p99));
    }
    public void test() throws Exception {
        Long responseTime = 0l;
        Long taskStart;
        while (totalRequests.decrementAndGet() > 0) {
            taskStart = System.currentTimeMillis();
            CloseableHttpResponse response = httpClient.execute(httpGet);
            response.close();
            responseTime = System.currentTimeMillis() - taskStart;
            responseTimes.add(responseTime);
        }
    }
    public static void main(String[] args) throws Exception {
        CustomBenchMarker benchMarker = new CustomBenchMarker("https://www.baidu.com", 10, 100);
        benchMarker.startTest();
        benchMarker.report();
    }
}
输出示例：
average response time: 57
50% response time: 44
95% response time: 183
99% response time: 184
﻿
发布于: 2020 年 11 月 09 日阅读数: 30
原文链接:【http://xie.infoq.cn/article/e262c630fed40bde8598bd871】。未经作者许可，禁止转载。
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