常用linux命令:ab压力测试

ab是apache自带的压力测试工具。ab命令会创建多个并发访问线程，模拟多个访问者同时对某一URL地址进行访问

// 安装(如果不安装apache但是又想使用ab命令，可以直接安装apache的工具包httpd-tools)
$ yum -y install httpd-tools

// 查看是否安装成功
$ ab -V
This is ApacheBench, Version 2.3 <$Revision: 1430300 gt;
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

// 常用参数
-n 执行的请求数量
-c 并发请求个数

// 示例
$ ab -n10 -c3 https://www.baidu.com
This is ApacheBench, Version 2.3 <$Revision: 1430300 gt;
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking www.baidu.com (be patient).....done
Server Software:        BWS/1.1                                             // 服务器版本
Server Hostname:        www.baidu.com                                       // 服务器主机名
Server Port:            443                                                 // 服务器端口
SSL/TLS Protocol:       TLSv1.2,ECDHE-RSA-AES128-GCM-SHA256,2048,128
Document Path:          /                                                   // 文件路径
Document Length:        227 bytes                                           // 页面字节数
Concurrency Level:      3                                                   // 并发数
Time taken for tests:   0.271 seconds                                       // 总访问时间
Complete requests:      10                                                  // 请求成功数量
Failed requests:        0                                                   // 请求失败数量
Write errors:           0
Total transferred:      10820 bytes                                         // 请求总数据大小(包括header头信息)
HTML transferred:       2270 bytes                                          // HTML传输字节数
Requests per second:    36.86 [#/sec] (mean)                                // 每秒处理请求数，mean表示这是一个平均值
Time per request:       81.385 [ms] (mean)                                  // 用户平均请求等待时间
Time per request:       27.128 [ms] (mean, across all concurrent requests)  // 服务器平均处理时间
Transfer rate:          38.95 [Kbytes/sec] received                         // 传输速率
Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:       38   49   5.5     49      57
Processing:    13   16   1.7     16      19
Waiting:       13   16   1.7     16      19
Total:         51   65   7.0     65      76
Percentage of the requests served within a certain time (ms)
  50%     65                                                                // 50%用户请求在65ms内返回
  66%     66
  75%     66
  80%     74
  90%     76
  95%     76
  98%     76
  99%     76                                                                // %99用户请求在76ms内返回
 100%     76 (longest request)