AB(8)abAB(8)NAMEab - Apache HTTP server benchmarking tool
SYNOPSISab [ -A auth-username:password ] [ -b windowsize ] [ -c concurrency ] [
-C cookie-name=value ] [ -d ] [ -e csv-file ] [ -f protocol ] [ -g gnu‐
plot-file ] [ -h ] [ -H custom-header ] [ -i ] [ -k ] [ -n requests ] [
-p POST-file ] [ -P proxy-auth-username:password ] [ -q ] [ -r ] [ -s ]
[ -S ] [ -t timelimit ] [ -T content-type ] [ -u PUT-file ] [ -v ver‐
bosity] [ -V ] [ -w ] [ -x <table>-attributes ] [ -X proxy[:port] ] [
-y <tr>-attributes ] [ -z <td>-attributes ] [ -Z ciphersuite ]
SUMMARYab 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 serv‐
Supply BASIC Authentication credentials to the server. The user‐
name and password are separated by a single : and sent on the
wire base64 encoded. The string is sent regardless of whether
the server needs it (i.e., has sent an 401 authentication
Size of TCP send/receive buffer, in bytes.
Number of multiple requests to perform at a time. Default is one
request at a time.
Add a Cookie: line to the request. The argument is typically in
the form of a name=value pair. This field is repeatable.
-d Do not display the "percentage served within XX [ms] table".
Write a Comma separated value (CSV) file which contains for each
percentage (from 1% to 100%) the time (in milliseconds) it took
to serve that percentage of the requests. This is usually more
useful than the 'gnuplot' file; as the results are already
Specify SSL/TLS protocol (SSL2, SSL3, TLS1, or ALL).
Write all measured values out as a 'gnuplot' or TSV (Tab sepa‐
rate values) file. This file can easily be imported into pack‐
ages like Gnuplot, IDL, Mathematica, Igor or even Excel. The
labels are on the first line of the file.
-h Display usage information.
Append extra headers to the request. The argument is typically
in the form of a valid header line, containing a colon-separated
field-value pair (i.e., "Accept-Encoding: zip/zop;8bit").
-i Do HEAD requests instead of GET.
-k Enable the HTTP KeepAlive feature, i.e., perform multiple
requests within one HTTP session. Default is no KeepAlive.
Number of requests to perform for the benchmarking session. The
default is to just perform a single request which usually leads
to non-representative benchmarking results.
File containing data to POST. Remember to also set -T.
Supply BASIC Authentication credentials to a proxy en-route. The
username and password are separated by a single : and sent on
the wire base64 encoded. The string is sent regardless of
whether the proxy needs it (i.e., has sent an 407 proxy authen‐
-q When processing more than 150 requests, ab outputs a progress
count on stderr every 10% or 100 requests or so. The -q flag
will suppress these messages.
-r Don't exit on socket receive errors.
-s When compiled in (ab -h will show you) use the SSL protected
https rather than the http protocol. This feature is experimen‐
tal and very rudimentary. You probably do not want to use it.
-S Do not display the median and standard deviation values, nor
display the warning/error messages when the average and median
are more than one or two times the standard deviation apart. And
default to the min/avg/max values. (legacy support).
Maximum number of seconds to spend for benchmarking. This
implies a -n 50000 internally. Use this to benchmark the server
within a fixed total amount of time. Per default there is no
Content-type header to use for POST/PUT data, eg. application/x-
www-form-urlencoded. Default: text/plain.
File containing data to PUT. Remember to also set -T.
Set verbosity level - 4 and above prints information on headers,
3 and above prints response codes (404, 200, etc.), 2 and above
prints warnings and info.
-V Display version number and exit.
-w Print out results in HTML tables. Default table is two columns
wide, with a white background.
String to use as attributes for <table>. Attributes are inserted
<table here >.
Use a proxy server for the requests.
String to use as attributes for <tr>.
String to use as attributes for <td>.
Specify SSL/TLS cipher suite (See openssl ciphers).
DESCRIPTION OF OUTPUT
The following list describes the values returned by ab:
The value, if any, returned in the server HTTP header of the
first successful response. This includes all characters in the
header from beginning to the point a character with decimal
value of 32 (most notably: a space or CR/LF) is detected.
The DNS or IP address given on the command line
The port to which ab is connecting. If no port is given on the
command line, this will default to 80 for http and 443 for
The protocol parameters negotiated between the client and
server. This will only be printed if SSL is used.
The request URI parsed from the command line string.
This is size in bytes of the first succesfully returning docu‐
ment. If the document length changes during testing, the
response is considered an error.
The number of concurrent clients used during the test
Time taken for tests
This is the time taken from the moment the first socket connec‐
tion is created to the moment the last response is recieved
The number of successful responses recieved
The number of requests that were considered a failure. If the
number is greater than zero, another line will be printed show‐
ing the numer of requests that failed due to connecting, read‐
ing, incorrect content length, or exceptions.
The number of errors that failed during write (broken pipe).
The number of responses that were not in the 200 series of
response codes. If all responses were 200, this field is not
The number of connections that resulted in Keep-Alive requests
Total body sent
If configured to send data as part of the test, this is the
total number of bytes sent during the tests. This field is omit‐
ted if the test did not include a body to send.
The total number of bytes received from the server. This number
is essentially the number of bytes sent over the wire.
The total number of document bytes received from the server.
This number excludes bytes received in HTTP headers
Requests per second
This is the number of requests per second. This value is the
result of dividing the number of requests by the total time
Time per request
The average time spent per request. The first value is calcu‐
lated with the formula concurrency * timetaken * 1000 / done
while the second value is calculated with the formula timetaken
* 1000 / done
The rate of transfer as calculated by the formula totalread /
1024 / timetaken
There are various statically declared buffers of fixed length. Combined
with the lazy parsing of the command line arguments, the response head‐
ers from the server and other external inputs, this might bite you.
It does not implement HTTP/1.x fully; only accepts some 'expected'
forms of responses. The rather heavy use of strstr(3) shows up top in
profile, which might indicate a performance problem; i.e., you would
measure the ab performance rather than the server's.
Apache HTTP Server 2012-04-09 AB(8)