一、ab的原理
ab是apachebench命令的縮寫。
ab的原理：ab命令會創建多個併發訪問線程，模擬多個訪問者同時對某一URL地址進行訪問。它的測試目標是基於URL的，因此，它既可以用來測試apache的負載壓力，也可以測試nginx、lighthttp、tomcat、IIS等其它Web服務器的壓力。
ab命令對發出負載的計算機要求很低，它既不會佔用很高CPU，也不會佔用很多內存。但卻會給目標服務器造成巨大的負載，其原理類似CC攻擊。自己測試使用也需要注意，否則一次上太多的負載。可能造成目標服務器資源耗完，嚴重時甚至導致死機。
二、ab的安裝
yum -y install httpd-tools
ab -V
三、ab參數說明
[root@myhost vhost]# ab --help
ab: wrong number of arguments
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
-s timeout Seconds to max. wait for each response
Default is 30 seconds
-b windowsize Size of TCP send/receive buffer, in bytes
-B address Address to bind to when making outgoing connections
-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 to use for POST/PUT data, 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.
-q Do not show progress when doing more than 150 requests
-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
(SSL3, TLS1, TLS1.1, TLS1.2 or ALL)
四、ab實際使用
ab的命令參數比較多，我們經常使用的是-c和-n參數。
[root@myhost vhost]# ab -c 10000 -n 100000 http://www.baidu.com
-c表示併發用戶數
-n表示請求總數
五、輸出結果
Server Software: nginx
Server Hostname: 127.0.0.1
Server Port: 80
Document Path: /wordpress
Document Length: 178 bytes #請求大小
Concurrency Level: 10000 #併發請求量
Time taken for tests: 7.926 seconds #整個測試持續時間
Complete requests: 100000 #完成的請求數
Failed requests: 0 #失敗的請求數
Write errors: 0
Non-2xx responses: 100000
Total transferred: 36800000 bytes #整個場景中網絡傳輸量
HTML transferred: 17800000 bytes #整個場景中的HTML內容傳輸量
Requests per second: 12615.91 [#/sec] (mean) #吞吐速率，大家最關心的指標之一
Time per request: 792.650 [ms] (mean) #用戶平均請求等待時間，大家最關心的指標之二
Time per request: 0.079 [ms] (mean, across all concurrent requests) #服務器平均請求處理的時間，大家最關心的指標之三
Transfer rate: 4533.84 [Kbytes/sec] received #平均每秒網絡上的流量，可以幫助排除是否有存在網絡流量過大導致響應時間延長的問題
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 510 1056.6 3 7026
Processing: 3 28 89.9 8 1889
Waiting: 0 25 89.4 6 1887
Total: 7 538 1079.8 12 7240
Percentage of the requests served within a certain time (ms)
50% 12
66% 22
75% 1016
80% 1022
90% 1231
95% 3027
98% 3232
99% 3828
100% 7240 (longest request)