ab是apache自带的一个很好用的压力测试工具，当安装完apache的时候，就可以在bin下面找到ab
1 我们可以模拟100个并发用户，对一个页面发送1000个请求
./ab -n1000 -c100 http://vm1.jianfeng.com/a.html
其中-n代表请求数，-c代表并发数
返回结果:
##首先是apache的版本信息
This is ApacheBench, Version 2.3 <Revision:655654>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking vm1.jianfeng.com (be patient)
Server Software: Apache/2.2.19 ##apache版本
Server Hostname: vm1.jianfeng.com ##请求的机子
Server Port: 80 ##请求端口
Document Path: /a.html
Document Length: 25 bytes ##页面长度
Concurrency Level: 100 ##并发数
Time taken for tests: 0.273 seconds ##共使用了多少时间
Complete requests: 1000 ##请求数
Failed requests: 0 ##失败请求
Write errors: 0
Total transferred: 275000 bytes ##总共传输字节数，包含http的头信息等
HTML transferred: 25000 bytes ##html字节数，实际的页面传递字节数
Requests per second: 3661.60 [#/sec] (mean) ##每秒多少请求，这个是非常重要的参数数值，服务器的吞吐量
Time per request: 27.310 [ms] (mean) ##用户平均请求等待时间
Time per request: 0.273 [ms] (mean, across all concurrent requests) ##服务器平均处理时间，也就是服务器吞吐量的倒数
Transfer rate: 983.34 [Kbytes/sec] received ##每秒获取的数据长度
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 1 2.3 0 16
Processing: 6 25 3.2 25 32
Waiting: 5 24 3.2 25 32
Total: 6 25 4.0 25 48
Percentage of the requests served within a certain time (ms)
50% 25 ## 50%的请求在25ms内返回
66% 26 ## 60%的请求在26ms内返回
75% 26
80% 26
90% 27
95% 31
98% 38
99% 43
100% 48 (longest request)
2 ab也可以运行在windows中，如果在windows下安装apache,就可以在bin下找到ab.exe
直接就可以使用，不用依赖其他的dll
下面是我使用ab.exe 测试新浪一个页面的结果：
C:Users
ickyjfDesktopuseful>ab -n1000 -c100 http://sports.sina.com.cn/k/2011-05-24/12095590365.shtml
This is ApacheBench, Version 2.3 <Revision:655654>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking sports.sina.com.cn (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Completed 1000 requests
Finished 1000 requests
Server Software: Apache/2.0.63
Server Hostname: sports.sina.com.cn
Server Port: 80
Document Path: /k/2011-05-24/12095590365.shtml
Document Length: 86680 bytes
Concurrency Level: 100
Time taken for tests: 66.453 seconds
Complete requests: 1000
Failed requests: 0
Write errors: 0
Total transferred: 87135790 bytes
HTML transferred: 86680000 bytes
Requests per second: 15.05 [#/sec] (mean)
Time per request: 6645.294 [ms] (mean)
Time per request: 66.453 [ms] (mean, across all concurrent requests)
Transfer rate: 1280.51 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 1 56 398.3 2 3003
Processing: 89 6331 2603.7 6293 14626
Waiting: 2 1748 1485.9 1590 6284
Total: 90 6388 2615.0 6302 14627
Percentage of the requests served within a certain time (ms)
50% 6302
66% 7121
75% 8435
80% 9193
90% 9231
95% 9385
98% 11549
99% 12459
100% 14627 (longest request)
3 apache的ab工具也算是一种ddos攻击工具
下面是一个具体的例子：
在命令行下输出：
./ab -n number_of_total_requests -c number_of_simultaneous_requestshttp://your_web_server/your_php_app.php
例如：./ab -n 1000 -c 50 http://www.domain.com/myapp.php
AB将同时向http://www.domain.com/myapp.php发出50个并发请求，共发出1000次。
测试结果将可能是这样的：
Server Software: Apache/2.0.16
Server Hostname: localhost
Server Port: 80
Document Path: /myapp.php
Document Length: 1311 bytes
Concurrency Level: 50
Time taken for tests: 8.794 seconds
Complete requests: 1000
Failed requests: 0
Total transferred: 1754000 bytes
HTML transferred: 1311000 bytes
Requests per second: 113.71
Transfer rate: 199.45 kb/s received
Connection Times (ms)
min avg max
Connect: 0 0 5
Processing: 111 427 550
Total: 111 427 555
myapp.php每秒钟可以处理的请求数为113.71个。将请求数增加，看看服务器能否处理更大的压力。你也需要调节Apache的 MaxClients,ThreadsPerChild,MaxThreadsPerChild等参数，基于你的httpd.conf中的MPM模块选择。
如果你想得到更详细的信息，请到www.apache.org上查阅一些更深入的文档，包括模块和第三方的提高效率的工具。修改httpd.conf后，要重启Apache服务器，然后再用AB测试。你会看到每秒请求数增加或减少。记下每次的参数，最后选择最佳效率的那种配置。