ApacheBench (ab) Load Testing

ab is a tool for benchmarking your Apache Hypertext Transfer Protocol (HTTP) server. It is designed to give you an impression of how your current Apache installation performs. This especially shows you how many requests per second your Apache installation is capable of serving.

  • You can increase the total requests. It should always be more than number of concurrent requests.
  • You can also add -H “Accept-Encoding: gzip,deflate” to more closely emulate real requests. But as we are on same server and there is no network overhead, it will not matter too much.
  • For such high number of request the test should be done locally or on same LAN (Local Area Network). Otherwise you may get bad results due to network latency and you may think its your server problem. In reality all you concurrent users won’t come from one machine.
  • This tests does not emulate the real environment fully. But it is good enough to help you find out most of the major problems in your site.


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.
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)


[root@gopal ~]# ab -n 100 -c 20 -g http://gnutoolbox.com/
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 gnutoolbox.com (be patient)…..done

Server Software:        Apache
Server Hostname:        gnutoolbox.com
Server Port:            80

Document Path:          /
Document Length:        0 bytes

Concurrency Level:      20
Time taken for tests:   14.082 seconds
Complete requests:      100
Failed requests:        0
Write errors:           0
Non-2xx responses:      100
Total transferred:      31300 bytes
HTML transferred:       0 bytes
Requests per second:    7.10 [#/sec] (mean)
Time per request:       2816.460 [ms] (mean)
Time per request:       140.823 [ms] (mean, across all concurrent requests)
Transfer rate:          2.17 [Kbytes/sec] received

Connection Times (ms)
min  mean[+/-sd] median   max
Connect:      359  377  15.2    374     426
Processing:  1329 2316 474.0   2195    3631
Waiting:     1329 2315 474.0   2193    3627
Total:       1734 2693 476.8   2580    4008

Percentage of the requests served within a certain time (ms)
50%   2580
66%   2779
75%   2962
80%   3029
90%   3420
95%   3719
98%   3900
99%   4008
100%   4008 (longest request)