ApacheBench 简称ab， 是 Apache 附带的一个小工具 ， 专门用测试网站服务器的运行想能，特别是针对Apache网站服务器的效能分析。专门用于 HTTP Server 的 benchmark testing ， 可以同时模拟多个并发请求。
windows下在安装完apache的时候，就可以在bin下面找到ab
linux一般会安装在/usr/bin目录下，一般安装完apache后就有了。
在windows下显示如下：
1、ab经常使用命令：ab -c 20 -n 1000 http://www.imudges.com/
-c：并发数
-n：总请求数
2、结果显示
我们再windows下测试http://www.imudges.com/
This is ApacheBench, Version 2.3 <$Revision: 1528965 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking http://www.imudges.com/ (be patient).....done
Server Software: GWS/2.1
Server Hostname: www.imudges.com
Server Port: 80
Document Path: /
Document Length: 11648 bytes
Concurrency Level: 10
/* 整个测试持续的时间 * /
Time taken for tests: 0.711 seconds
/* 完成的请求数量 */
Complete requests: 10
/* 失败的请求数量 */
Failed requests: 0
Write errors: 0
Non-2xx responses: 10
Keep-Alive requests: 10
/* 整个场景中的网络传输量 */
Total transferred: 6020 bytes
/* 整个场景中的 HTML 内容传输量 */
HTML transferred: 2300 bytes
/* 大家最关心的指标之一，相当于 LR 中的 每秒事务数 ，后面括号中的 mean 表示这是一个平均值 */
Requests per second: 3.09 [#/sec] (mean)
/* 大家最关心的指标之二，相当于 LR 中的 平均事务响应时间 ，后面括号中的 mean 表示这是一个平均值 */
Time per request: 3234.651 [ms] (mean)
/* 这个还不知道是什么意思，有知道的朋友请留言，谢谢 ^_^ */
Time per request: 323.465 [ms] (mean, across all concurrent requests)
/* 平均每秒网络上的流量，可以帮助排除是否存在网络流量过大导致响应时间延长的问题 */
Transfer rate: 1.55 [Kbytes/sec] received
/* 网络上消耗的时间的分解，各项数据的具体算法还不是很清楚 */
Connection Times (ms)
min mean[+/-sd] median max
Connect: 20 318 926.1 30 2954
Processing: 40 2160 1462.0 3034 3154
Waiting: 40 2160 1462.0 3034 3154
Total: 60 2479 1276.4 3064 3184
/* 下面的内容为整个场景中所有请求的响应情况。在场景中每个请求都有一个响应时间，其中 50 ％ 的用户响应时间小于 3064 毫秒， 60 ％ 的用户响应时间小于 3094 毫秒，最大的响应时间小于 3184 毫秒 */
Percentage of the requests served within a certain time (ms)
50% 3064
66% 3094
75% 3124
80% 3154
90% 3184
95% 3184
98% 3184
99% 3184
100% 3184 (longest request)
3、在测试过程中会出现以下这些错误
1）
ab并发数不能大于请求数，会提示
ab: Cannot use concurrency level greater than total number of requests
2）
请求数默认不能超过1024个，会提示
socket: Too many open files (24)
可用ulimit -n命令修改，例如：ulimit -n 8192 （设置用户可以同时打开的最大文件数）。
3）
并发数默认不能大于20000个，会提示
ab: Invalid Concurrency [Range 0..20000]
需要修改apache源代码support目录下ab.c文件，找到：
#define MAX_CONCURRENCY 20000
将宏定义的值改大，重新编译安装apache。
4）
提示
apr_socket_recv: Connection reset by peer (104)
网上说是apr-util有些问题，不太稳定，多试几次就好了。
更多信息
ab 不像 LR 那么强大，但是它足够轻便，如果只是在开发过程中想检查一下某个模块的响应情况，或者做一些场景比较简单的测试， ab 还是一个不错的选择——至少不用花费很多时间去学习 LR 那些复杂的功能，就更别说那 License 的价格了。
下面是 ab 的详细参数解释，大家有兴趣的可以研究一下，最近没有足够多的时间研究，如果哪位朋友有兴趣希望可以帮忙翻译一下每个参数的含义，有问题讨论也欢迎在这里回帖 ^_^
ab [ - A auth-username : password ] [ - c concurrency ] [ - C cookie-name = value ] [ - d ] [ - ecsv-file ] [ - g gnuplot-file ] [ - h ] [ - H custom-header ] [ - i ] [ - k ] [ - n requests ] [ - pPOST-file ] [ - P proxy-auth-username : password ] [ - q ] [ - s ] [ - S ] [ - t timelimit ] [ - Tcontent-type ] [ - v verbosity ] [ - V ] [ - w ] [ - x <table>-attributes ] [ - X proxy [: port ] ] [ - y<tr>-attributes ] [ - z <td>-attributes ] [http://] hostname [: port ]/ path
-A auth-username : password
Supply BASIC Authentication credentials to the server. The username and password are separated by a single : and sent on the wire base64 encoded. The string is sent regardless of whether the server needs it (i.e. , has sent an 401 authentication needed).
-c concurrency
Number of multiple requests to perform at a time. Default is one request at a time.
-C cookie-name = value
Add a Cookie: line to the request. The argument is typically in the form of a name = value pair. This field is repeatable.
-d
Do not display the "percentage served within XX [ms] table". (legacy support).
-e csv-file
Write a Comma separated value (CSV) file which contains for each percentage (from 1% to 100%) the time (in milliseconds) it took to serve that percentage of the requests. This is usually more useful than the 'gnuplot' file; as the results are already 'binned'.
-g gnuplot-file
Write all measured values out as a 'gnuplot' or TSV (Tab separate values) file. This file can easily be imported into packages like Gnuplot, IDL, Mathematica, Igor or even Excel. The labels are on the first line of the file.
-h
Display usage information.
-H custom-header
Append extra headers to the request. The argument is typically in the form of a valid header line, containing a colon-separated field-value pair (i.e. , "Accept-Encoding: zip/zop;8bit" ).
-i
Do HEAD requests instead of GET .
-k
Enable the HTTP KeepAlive feature, i.e. , perform multiple requests within one HTTP session. Default is no KeepAlive.
-n requests
Number of requests to perform for the benchmarking session. The default is to just perform a single request which usually leads to non-representative benchmarking results.
-p POST-file
File containing data to POST.
-P proxy-auth-username : password
Supply BASIC Authentication credentials to a proxy en-route. The username and password are separated by a single : and sent on the wire base64 encoded. The string is sent regardless of whether the proxy needs it (i.e. , has sent an 407 proxy authentication needed).
-q
When processing more than 150 requests, ab outputs a progress count on stderr every 10% or 100 requests or so. The -q flag will suppress these messages.
-s
When compiled in ( ab -h will show you) use the SSL protected https rather than the http protocol. This feature is experimental and very rudimentary. You probably do not want to use it.
-S
Do not display the median and standard deviation values, nor display the warning/error messages when the average and median are more than one or two times the standard deviation apart. And default to the min/avg/max values. (legacy support).
-t timelimit
Maximum number of seconds to spend for benchmarking. This implies a -n 50000 internally. Use this to benchmark the server within a fixed total amount of time. Per default there is no timelimit.
-T content-type
Content-type header to use for POST data.
-v verbosity
Set verbosity level - 4 and above prints information on headers, 3 and above prints response codes (404, 200, etc.), 2 and above prints warnings and info.
-V
Display version number and exit.
-w
Print out results in HTML tables. Default table is two columns wide, with a white background.
-x <table>-attributes
String to use as attributes for <table> . Attributes are inserted <table here > .
-X proxy [: port ]
Use a proxy server for the requests.
-y <tr>-attributes
String to use as attributes for <tr> .
-z <td>-attributes
String to use as attributes for <td>
