使用ab接口压力测试

由于最近在开发前端日志监控系统，对接口负载有较高的要求。
我们需要模拟高并发的环境下，接口承受的最大负载。

后端接口使用nodejs部署，服务器为1核2G腾讯云。
如果是ubuntu系统，可以用下面命令安装

sudo apt install apache2-utils

// 下面为输入ab后的帮助命令
Usage: ab [options] [http[s]://]hostname[:port]/path
Options are:
    -n requests     Number of requests to perform
    -c concurrency  Number of multiple requests to make at a time
    -t timelimit    Seconds to max. to spend on benchmarking
                    This implies -n 50000

-n 表示请求的次数，-c 表示并发数，-t 表示持续的时间

模拟500个客户端，进行20000次的请求。

ab -c 500 -c 20000 'http://127.0.0.1'

下面为压测的结果

Concurrency Level:      500 // 发送的并发数
Time taken for tests:   3.301 seconds
Complete requests:      10000 // 总的请求数
Failed requests:        0
Total transferred:      980000 bytes
HTML transferred:       0 bytes
Requests per second:    3029.78 [#/sec] (mean)  // 每秒处理的请求数
Time per request:       165.028 [ms] (mean) //  接口平均用时
Time per request:       0.330 [ms] (mean, across all concurrent requests)
Transfer rate:          289.96 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0   28 162.8      0    1002
Processing:    41   76  30.3     74     880
Waiting:       41   76  30.3     74     880
Total:         41  104 176.4     75    1279

Percentage of the requests served within a certain time (ms)
  50%     75
  66%     77
  75%     79
  80%     81
  90%     84
  95%     87
  98%   1071
  99%   1241
 100%   1279 (longest request)

结果显示，500个请求没什么压力，那我们换成3000个并发呢
如果执行请求提示

socket: Too many open files (24)

表示连接数被限制了，可以用下面命令修改

ulimit -n 65535

以下为3000并发时的测试结果

Concurrency Level:      3000
Time taken for tests:   27.179 seconds
Complete requests:      30000
Failed requests:        0
Total transferred:      2940000 bytes
HTML transferred:       0 bytes
Requests per second:    1103.80 [#/sec] (mean)
Time per request:       2717.874 [ms] (mean) // 处理时间变长
Time per request:       0.906 [ms] (mean, across all concurrent requests)
Transfer rate:          105.64 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0  400 1872.4      0   15037
Processing:    23  209 519.4    132   26165
Waiting:       23  209 519.4    132   26165
Total:         45  609 2043.7    141   27168

Percentage of the requests served within a certain time (ms)
  50%    141
  66%    194
  75%    216
  80%    246
  90%    495
  95%   3095
  98%   7318
  99%  15102
 100%  27168 (longest request)

可以看到处理能力出现了明显下降。

为了了解服务器瓶颈，需要看下云服务器的资源使用情况
cpu是满载了，还是内存用完了，还是硬盘io有问题，或者是程序没写好，出错了。进行逐一排查，榨干性能。

image.png

上图可以看出cpu出现了100%，导致处理能力下降。

由于我用的是单核处理器，所以我只开了一个进程，如果你是用多核处理器，可以用pm2开多个进程提高cpu的利用率。