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
吞吐率：单位时间内服务器处理的请求数，通常使用 "reqs/s" (服务器每秒处理请求的数量)表示ab工具的参数比较多，常用的有以下几个：-n:表示测试请求总数,默认执行一个请求-c:要创建的并发用户数,默认创建一个用户-t:等待Web服务器相应的最大时间（单位：秒），默认没有时间限制-k:使用Keep-Alive 特性(一) 在windows 执行一次压力测试C:\Documents and Settings\Administrator>ab -c10 -n 1000 http://localhost/abtest.phpThis 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 localhost (be patient)Completed 100 requestsCompleted 200 requestsCompleted 300 requestsCompleted 400 requestsCompleted 500 requestsCompleted 600 requestsCompleted 700 requestsCompleted 800 requestsCompleted 900 requestsCompleted 1000 requestsFinished 1000 requestsServer Software: Apache/2.2.22 #表示被测试的Web服务器软件名称Server Hostname: localhost #表示请求的URL主机名Server Port: 80 #表示被测试的Web服务器软件的监听端口Document Path: /abtest.php #表示请求的URL中的根绝对路径，通过该文件的后缀名，我们一般可以了解该请求的类型Document Length: 698 bytes #表示HTTP响应数据的正文长度Concurrency Level: 10 #表示并发用户数，这是我们设置的参数之一，即-c参数中的指定Time taken for tests: 0.563 seconds #表示所有这些请求被处理完成所花费的总时间Complete requests: 1000 #表示总请求数量，这是我们设置的参数之一Failed requests: 1 #表示失败的请求数量，这里的失败是指请求在连接服务器、发送数据等环节发生异常，以及无响应后超时的情况。如果接收到的HTTP响应数据的头信息中含有2XX以外的状态码，则会在测试结果中显示另一个名为 “Non-2xx responses”的统计项，用于统计这部分请求数，这些请求并不算在失败的请求中。 (Connect: 1, Receive: 0, Length: 0, Exceptions: 0)Write errors: 0Total transferred: 887000 bytes # 表示所有请求的响应数据长度总和，包括每个HTTP响应数据的头信息和正文数据的长度。注意这里不包括HTTP请求数据的长度，仅仅为web服务器流向用户PC的应用层数据总长度。HTML transferred: 698000 bytes # 表示所有请求的响应数据中正文数据的总和，也就是减去了Total transferred中HTTP响应数据中的头信息的长度Requests per second: 1777.78 [#/sec] (mean) # 吞吐率，计算公式：Complete requests / Time taken for tests Time per request: 5.625 [ms] (mean) # 用户平均请求等待时间，计算公式：Time token for tests/（Complete requests/Concurrency Level） 如果加大并发用户的数量这个等待时间相应会加长Time per request: 0.563 [ms] (mean, across all concurrent requests) # 服务器平均请求等待时间，计算公式：Time taken for tests/Complete requests，正好是吞吐率的倒数。也可以这么统计：Time per request/Concurrency LevelTransfer rate: 1539.93 [Kbytes/sec] received # 表示这些请求在单位时间内从服务器获取的数据长度，计算公式：Total trnasferred/ Time taken for tests，这个统计很好的说明服务器的处理能力达到极限时，其出口宽带的需求量。Connection Times (ms) min mean[+/-sd] median maxConnect: 0 0 1.2 0 16Processing: 0 5 7.4 0 16Waiting: 0 5 7.4 0 16Total: 0 6 7.5 0 16Percentage of the requests served within a certain time (ms) # 这部分数据用于描述每个请求处理时间的分布情况，比如以上测试，80%的请求处理时间都不超过6ms，这个处理时间是指前面的Time per request，即对于单个用户而言，平均每个请求的处理时间。 50% 0 66% 16 75% 16 80% 16 90% 16 95% 16 98% 16 99% 16 100% 16 (longest request)
(二) 使用长连接的一次测试
C:\Documents and Settings\Administrator>ab -c10 -n 1000 -k http://localhost/abtest.phpThis 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 localhost (be patient)Completed 100 requestsCompleted 200 requestsCompleted 300 requestsCompleted 400 requestsCompleted 500 requestsCompleted 600 requestsCompleted 700 requestsCompleted 800 requestsCompleted 900 requestsCompleted 1000 requestsFinished 1000 requestsServer Software: Apache/2.2.22Server Hostname: localhostServer Port: 80Document Path: /abtest.phpDocument Length: 698 bytesConcurrency Level: 10Time taken for tests: 0.391 seconds # 使用长连接时间明显变短Complete requests: 1000Failed requests: 0Write errors: 0Keep-Alive requests: 995 # 长连接时间Total transferred: 922782 bytesHTML transferred: 698000 bytesRequests per second: 2560.00 [#/sec] (mean) # 吞吐量明显变大Time per request: 3.906 [ms] (mean)Time per request: 0.391 [ms] (mean, across all concurrent requests)Transfer rate: 2306.95 [Kbytes/sec] receivedConnection Times (ms) min mean[+/-sd] median maxConnect: 0 0 0.0 0 0Processing: 0 4 7.2 0 47Waiting: 0 4 7.2 0 47Total: 0 4 7.2 0 47Percentage of the requests served within a certain time (ms) 50% 0 66% 0 75% 0 80% 16 90% 16 95% 16 98% 16 99% 16 100% 47 (longest request)