ab的原理：ab命令会创建多个并发访问线程，模拟多个访问者同时对摸一个URL地址进行访问。它的测试目标是基于URL的，因此它既可以用来测试apache的负载压力，也可以测试nginx、lighthtt
ab的原理：ab命令会创建多个并发访问线程，模拟多个访问者同时对摸一个URL地址进行访问。它的测试目标是基于URL的，因此它既可以用来测试apache的负载压力，也可以测试nginx、lighthttp、tomcat、IIS等其他web服务器的压力。
$ ab -n1000 -c10 http://localhost:3000/
1000条请求，10个并发
相关参数：
-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-l Accept variable document length (use this for dynamic pages)-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.-m method Method name-h Display usage information (this message)-Z ciphersuite Specify SSL/TLS cipher suite (See openssl ciphers)-f protocol Specify SSL/TLS protocol
