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.

Apache Manual URL

Usage: ab [options] [http://]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
-p postfile File containing data to POST
-T content-type Content-type header for POSTing
-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
-h Display usage information (this message)

Example:

1] ab -n 100 -c 10 www.celebrity.com/qna/qna.php?starid=1
– No table indexing
– No code optimization

This is ApacheBench, Version 2.0.41-dev <$Revision: 1.141 $> apache-2.0
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright (c) 1998-2002 The Apache Software Foundation, http://www.apache.org/

Benchmarking www.celebrity.com (be patient)…..done

Server Software: Apache/2.0.52
Server Hostname: www.celebrity.com
Server Port: 80

Document Path: /qna/qna.php?starid=1
Document Length: 8237 bytes

Concurrency Level: 10
Time taken for tests: 12.370747 seconds
Complete requests: 100
Failed requests: 0
Write errors: 0
Total transferred: 841100 bytes
HTML transferred: 823700 bytes
Requests per second: 8.08 [#/sec] (mean)
Time per request: 1237.075 [ms] (mean)
Time per request: 123.707 [ms] (mean, across all concurrent requests)
Transfer rate: 66.37 [Kbytes/sec] received

Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.0 0 0
Processing: 346 1169 1023.3 906 7490
Waiting: 345 1168 1023.3 905 7489
Total: 346 1169 1023.3 906 7490

Percentage of the requests served within a certain time (ms)
50% 906
66% 1064
75% 1240
80% 1363
90% 2402
95% 2618
98% 6031
99% 7490
100% 7490 (longest request)

2] ab -n 100 -c 10 www.celebrity.com/qna/qna.php?starid=1
– implemented table indexing
– code optimized

This is ApacheBench, Version 2.0.41-dev <$Revision: 1.141 $> apache-2.0
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright (c) 1998-2002 The Apache Software Foundation, http://www.apache.org/

Benchmarking www.celebrity.com (be patient)…..done

Server Software: Apache/2.0.52
Server Hostname: www.celebrity.com
Server Port: 80

Document Path: /qna/qna.php?starid=1
Document Length: 8237 bytes

Concurrency Level: 10
Time taken for tests: 10.537165 seconds
Complete requests: 100
Failed requests: 0
Write errors: 0
Total transferred: 841100 bytes
HTML transferred: 823700 bytes
Requests per second: 9.49 [#/sec] (mean)
Time per request: 1053.716 [ms] (mean)
Time per request: 105.372 [ms] (mean, across all concurrent requests)
Transfer rate: 77.91 [Kbytes/sec] received

Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.0 0 0
Processing: 354 1008 438.9 914 2314
Waiting: 353 1007 438.9 913 2313
Total: 354 1008 438.9 914 2314

Percentage of the requests served within a certain time (ms)
50% 914
66% 1104
75% 1261
80% 1353
90% 1590
95% 1913
98% 2296
99% 2314
100% 2314 (longest request)

In HTTP/0.9 and 1.0, the connection is closed after a single request/response pair. In HTTP/1.1 a keep-alive-mechanism was introduced, where a connection could be reused for more than one request.

Such persistent connections reduce lag perceptibly, because the client does not need to re-negotiate the TCP connection after the first request has been sent.

Version 1.1 of the protocol made bandwidth optimization improvements to HTTP/1.0. For example, HTTP/1.1 introduced chunked transfer encoding to allow content on persistent connections to be streamed, rather than buffered. HTTP pipelining further reduces lag time, allowing clients to send multiple requests before a previous response has been received to the first one. Another improvement to the protocol was byte serving, which is when a server transmits just the portion of a resource explicitly requested by a client.

Reference URL: http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol

The term Virtual Host refers to the practice of maintaining more than one server on one machine, as differentiated by their apparent hostname. For example, it is often desirable for companies sharing a web server to have their own domains, with web servers accessible as www.company1.com and www.company2.com, without requiring the user to know any extra path information.

Apache was one of the first servers to support IP-based virtual hosts right out of the box. Versions 1.1 and later of Apache support both, IP-based and name-based virtual hosts (vhosts). The latter variant of virtual hosts is sometimes also called host-based or non-IP virtual hosts.

Here is the example of how to add an virtual hosts entry in your httpd.conf (/etc/httpd/conf)

<VirtualHost *:80 >
DocumentRoot /var/www/html/wwwsitefolder
#ServerName 192.168.0.66
ServerName www.satishgaudo.com
RewriteEngine On
RewriteRule ^/image/(.*)$  /image.php?do=readfile&filepath=$1
SetEnvIfNoCase Request_URI \ \.(?:gif|jpg|jpe?g|png)$ no-gzip dont-vary
Header append Vary User-Agent env=!dont-vary
Header unset Pragma
FileETag None
<FilesMatch "\.(gif|js|css|jpg|jpe?g|png)$">
Header set Cache-Control "max-age=2592000, must-revalidate"
</FilesMatch>
CustomLog /var/log/httpd/satish_access_log combined
ErrorLog /var/log/httpd/satish_error.log
</VirtualHost>