ab（apache bench）是apache下的一個工具，主要用於對web站點做壓力測試，
基礎用法：
其中-c選項為一次發送的請求數量，及並發量。
-n選項為請求次數。
實驗測試：
[dev@web ~]$ ab -c 20 -n 50000http://192.168.1.210/ 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 192.168.1.210 (be patient)
Completed 5000 requests
Completed 10000 requests
Completed 15000 requests
Completed 20000 requests
Completed 25000 requests
Completed 30000 requests
Completed 35000 requests
Completed 40000 requests
Completed 45000 requests
Completed 50000 requests
Finished 50000 requests
Server Software: nginx/1.6.2
Server Hostname: 192.168.1.210
Server Port: 80
Document Path: /
Document Length: 41005 bytes # 請求的頁面大小
Concurrency Level: 20 # 並發量
Time taken for tests: 1180.733 seconds # 測試總共耗時
Complete requests: 50000 # 完成的請求
Failed requests: 0 # 失敗的請求
Write errors: 0 # 錯誤
Total transferred: 2067550000 bytes # 總共傳輸數據量
HTML transferred: 2050250000 bytes
Requests per second: 42.35 [#/sec] (mean) # 每秒鐘的請求量。（僅僅是測試頁面的響應速度）
Time per request: 472.293 [ms] (mean) # 等於 Time taken for tests/(complete requests/concurrency level) 即平均請求等待時間（用戶等待的時間）
Time per request: 23.615 [ms] (mean, across all concurrent requests) # 等於 Time taken for tests/Complete requests 即服務器平均請求響應時間 在並發量為1時 用戶等待時間相同
Transfer rate: 1710.03 [Kbytes/sec] received # 平均每秒多少K，即帶寬速率
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 1 18.5 0 1001
Processing: 38 471 534.1 155 9269
Waiting: 37 456 524.6 147 9259
Total: 40 472 534.5 155 9269
Percentage of the requests served within a certain time (ms)
50% 155
66% 571
75% 783
80% 871
90% 1211
95% 1603
98% 1839
99% 2003
100% 9269 (longest request)
附錄：
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
-t timelimit Seconds to max. wait for responses
-b windowsize Size of TCP send/receive buffer, in bytes
#
-p postfile File containing data to POST. Remember also to set -T
-u putfile File containing data to PUT. Remember also to set -T
-T content-type Content-type header for POSTing, eg.
'application/x-www-form-urlencoded'
Default is 'text/plain'
-v verbosity How much troubleshooting info to print
-w Print out results in HTML tables
-i Use HEAD instead of GET
-x attributes String to insert as table attributes
-y attributes String to insert as tr attributes
-z attributes String to insert as td or th attributes
-C attribute Add cookie, eg. 'Apache=1234. (repeatable)
-H attribute Add Arbitrary header line, eg. 'Accept-Encoding: gzip'
Inserted after all normal header lines. (repeatable)
-A attribute Add Basic WWW Authentication, the attributes
are a colon separated username and password.
-P attribute Add Basic Proxy Authentication, the attributes
are a colon separated username and password.
-X proxy:port Proxyserver and port number to use
-V Print version number and exit
-k Use HTTP KeepAlive feature
-d Do not show percentiles served table.
-S Do not show confidence estimators and warnings.
-g filename Output collected data to gnuplot format file.
-e filename Output CSV file with percentages served
-r Don't exit on socket receive errors.
-h Display usage information (this message)
-Z ciphersuite Specify SSL/TLS cipher suite (See openssl ciphers)
-f protocol Specify SSL/TLS protocol (SSL2, SSL3, TLS1, or ALL)
