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README

version 0.56, stable, January 10, 2012, svn 589
 
2006 - 2012 Copyright (C)
  
Robert Iakobashvili,  <coroberti@gmail.com>, Ashdod, Israel
Michael Moser, <moser.michael@gmail.com>, Modiin, Israel
All rights reserved.

To skip bla-bla, please, refer to the QUICK-START file,
but mind, that tuning for a high load still is in the FAQs.



INTRODUCTION

The loader is an open-source community tool written in C-language, simulating 
application load and application behavior of thousands and tens of thousand 
HTTP/HTTPS and FTP/FTPS clients, each with its own source IP-address. In 
contrast to other tools, curl-loader is using real client protocol stacks, 
namely, HTTP and FTP stacks of libcurl, TLS/SSL of openssl, simulates user 
behavior and supports login and authentication flavors. 
The goal of the project is to deliver a powerful and flexible performance 
loading and testing tool as a reasonable substitute for Spirent Avalanche and 
IXIA IxLoad. 
The tool is useful for performance loading of various application services, 
using HTTP, HTTPS, FTP and FTPS, for testing web and ftp servers and traffic 
generation. Activities of each virtual client are logged and collected 
statistics include information about: resolving, connection establishment, 
sending of requests, receiving responses, headers and data received/sent, errors 
from network, TLS/SSL and application (HTTP, FTP) level events and errors. 
Virtual clients are grouped together to so-called batches of clients, performing 
the same sort of activities, like: 
- authentication login; 
- user activity simulation by fetching several URLs with configurable timeouts 
in between; 
- logoff. 
The tool can be easily extended to generate sftp, telnet, tftp, ldap, ssh, scp 
etc other application protocols, supported by the great libcurl library. 



FEATURES

- Virtual clients number. The tools runs depending on your HW and scenario 
5000-25000 and more simultaneously loading clients, all from a single 
curl-loader process. Actual number of clients may be several times higher (we 
tried 60 000) and is limited mainly by memory. Each client performs loading from 
its own source IP-address or, as an option, all clients share the same 
IP-address; 
- Rampup of the virtual clients number at loading start in either automatic or 
manual mode; 
- IPv4 and IPv6 addresses and URIs; 
- HTTP 1.1. GET, POST, PUT (including file upload), DELETE, HEAD; 
- HTTP user authentication login with POST or GET+POST methods. Unique 
configurable username and password for each virtual client as well as 
configurable posted string (post-forms) are the options. Another option is 
loading of users with credentials from a text file; 
- HTTP POST/GET forms with up to 16 tokens loaded from file; 
- HTTP user logoff with POST, GET+POST, or GET (cookies); POST logoff with 
configurable posted string (post-forms); 
- HTTP multipart form data POST-ing as in RFC1867; 
- HTTP Web and Proxy Authentication (HTTP 401 and 407 responses) with Basic, 
Digest (RFC2617) and NTLM supported; 
- HTTP 3xx redirections with unlimited number of redirections; 
- HTTP cookies and DNS caches; 
- FTP passive and active, FTP upload; 
- Full customization of client request HTTP/FTP headers ; 
- Transfer limit rate for each client download or upload operation on a per url 
bases; 
- URL fetching probability; 
- TCP connections reuse or re-establishment on a per url bases; 
- Unlimited configurable number of URLs. Mixing of HTTP, HTTPS, FTP and FTPS 
urls in a single batch (test plan) configuration;
- Thousands URLs configured from a template-URL and static tokens loaded from file;
- URLs configured from a template-URL and dynamic tokens fetched from responses; 
- Connection establishment timers for each URL; 
- URL completion timers monitoring and enforcement for each client; 
- Inter/after URL "sleeping" timers, including random timers taken from an 
interval; 
- Logfile with tracing activities for each virtual client. The logfile is 
automatically rewinded, when reaching configurable size preventing disk crashes; 

- Responses logging (headers and bodies) to files. 
- Pre-cooked batch configuration (test plan) examples; 
- Load Status GUI and load status output to file; 
- Status and statistics per each virtual client logged to file; 
- Detailed loading statistics at Load Status GUI and to file; 



LICENSE

curl-loader is licensed under GPL2.



AUTHORS

The tool is written and supported by Robert Iakobashvili and Michael Moser both 
from Israel, which are the copyright-holders for the project.
We are thankful to the great people, specified in THANKS file for their contributions.


SUPPORT

Please, use the link to the mailing list provided in Support section to contact 
us and to get support for the tool. Subscribe to the curl-loader-devel list and 
mail your filled PROBLEM-REPORTING form located in the curl-loader tarball to 
the list. Your suggestion, ideas and patches would be very much appreciated. 
The official language of the curl-loader-devel mailing list is English, whereas 
Russian and German written mails will be also responded. 


IGNORE_CONTENT_LENGTH - Ignore the Content-Length header on a per url basis. 
This is useful for Apache 1.x (and similar servers) which will report incorrect content 
length for files over 2 gigabytes. If this option is used, curl will not be able to 
accurately report progress, and will simply stop the download when the server ends 
the connection.
E.g. Add the following in the URL Section
IGNORE_CONTENT_LENGTH=1



FREQUENTLY ASKED QUESTIONS

  Questions 
    1. Basic Terminology 
      1.1. What is the batch? 
      1.2. What is the batch configuration file? 
    2. Hardware Requirements 
      2.1. What are the minimal HW requirements? 
      2.2. What is the recommended HW configuration? 
    3. Building curl-loader 
      3.1. Which operating systems are supported by curl-loader? 
      3.2. What are the building pre-requirements? 
      3.3. How to make (build) curl-loader? 
    4. Creating Loading Configuration 
      4.1. How can I create loading configuration file? 
      4.2. What are the loading configuration file tags and semantics? 
      4.3. What are the exact meanings of all these tags? 
      4.4. How does the loader support login, logoff and authentication flavors? 

    5. What about FTP load and mixed FTP/HTTP load? 
    6. Running Load 
      6.1. What are the running environment requirements? 
      6.2. How I can run the load? 
      6.3. Which loading modes are supported? 
      6.4. How I can monitor loading progress status? 
      6.5. Why I am getting "Connection time-out after 5108 ms" like errors in 
      the log file? 
      6.6. Where is the detaled log of all virtual clients activities and how to 
      read it? 
      6.7. Which statistics is collected and how to get to it? 
    7. Advanced Issues 
      7.1. What about performance? 
      7.2. How to run a really big load? 
      7.3. How to calculate CAPS numbers for a load? 


QUESTIONS:

1. Basic Terminology
1.1. What is the batch? 
^ 
Batch is a group of clients (virtual clients emulating real clients) with the 
same characteristics and loading behavior. 
1.2. What is the batch configuration file? 
^ 
Batch configuration file is a test plan for a batch of clients. 
2. Hardware Requirements
2.1. What are the minimal HW requirements? 
^ 
A PC with Pentium-III and 200 MB may be used for loads with hundreds 
simultaneous loading clients. 
2.2. What is the recommended HW configuration? 
^ 
Note, that each virtual client takes about 30-35 K memory in user-space plus 
some none-pageable memory in kernel mainly for send and recv buffers. 

Our PC with Pentium-4 2.4 GHz and 480 MB memory is capable to support 3000-4000 
simultaneously loading clients. To reach 10K simultaneously loading clients we 
would recommend a PC with a single 3.2 GHz Intel or 2.2 GHz AMD and 1.5-2 GB of 
memory.

When loading from a multi-CPU (or multi-core) systems, a loading model with the 
number of curl-loader threads equal to the number of logical CPUs seen in 
/proc/cpuinfo may be the most effective and deliver even higher numbers (than 
10K) of simultaneously loading clients from a single PC. To run a batch in 
several threads use the command line option -t <number-of-threads>.

If you are thinking, tuning, optimizing and getting our advise - the sky is the 
limit. 
3. Building curl-loader
3.1. Which operating systems are supported by curl-loader? 
^ 
You can use any operating system of your choice, providing that this is linux 
with kernel 2.4 or 2.6. 
3.2. What are the building pre-requirements? 
^ 
General C development environment with bash, gcc, make, etc on a linux machine 
is required.

Building pre-requirements are:
1. openssl binaries;
2. openssl development package with include files (on debian libssl-dev);

Adjust Makefile variables to point to the openssl headers and libraries. To 
specify an openssl development directory with include files (e.g. crypto.h), 
export environment variable OPENSSLDIR with the value of that directory.
For example:
$export OPENSSLDIR=the-full-path-to-the-directory

Another known issue is libidn.so, which means, that some linux distributions do 
have some libidn.so.11, but not libidn.so. Resolve it by creating a softlink or 
in some cases exclude -lidn from the linking string, which requires commenting a 
string in Makefile and uncommenting another.

Tarball of curl is included to the current release. When libcurl or curl-loader 
has building issues, correct them in the Makefile. 
3.3. How to make (build) curl-loader? 
^ 
Run the following commands from your bash linux shell:
$tar zxfv curl-loader-<version>.tar.gz
$cd curl-loader-<version>
$make

By default, we are building both libcurl and curl-loader without optimization 
and with debugging -g option. To build with optimization and without debugging, 
please, run:
$make cleanall
$make optimize=1 debug=0

Y can make optional installing of the loader by running as a root:
#make install

If still any building issues, please, fill you free to contact us for assistance 
using placed in download tarball PROBLEM-REPORTING form and its instructions.

4. Creating Loading Configuration 
4.1. How can I create loading configuration file? 
^ 
To run a load create your configuration file to be passed to curl-loader using 
-f command line option, e.g.

#curl-loader -f ./conf-examples/bulk.conf

For more examples, please, look at the files in "conf-examples" directory. You 
may copy an example file and edit it by using the next FAQ guidelines. 
4.2. What are the loading configuration file tags and semantics? 
^ 
Configuration file or "batch configuration file" consists from tag=value 
strings, grouped into the 2 sections:
- General;
- URLs;

Section General contains common for the batch parameters, whereas section URLs 
has one or more URL subsections each starting with a certain URL and containing 
more tags.

An example of a simple configuration file to be used for traffic generation 
client side against e.g. lighttpd web server: 
----------------------------------------------------------------------------
########### GENERAL SECTION ##################
BATCH_NAME= 10K-clients
CLIENTS_NUM_MAX=10000
CLIENTS_NUM_START=100
CLIENTS_RAMPUP_INC=50
INTERFACE =eth0
NETMASK=255.255.0.0 
IP_ADDR_MIN= 192.168.1.1
IP_ADDR_MAX= 192.168.53.255
CYCLES_NUM= -1
URLS_NUM= 1

########### URLs SECTION #######################

URL=http://localhost/index.html
URL_SHORT_NAME="local-index"
REQUEST_TYPE=GET
TIMER_URL_COMPLETION = 0
TIMER_AFTER_URL_SLEEP = 0


The name of the batch is "10K-clients" with the maximum number of clients to be 
10000; load will be started with initial 100 clients and each seconds will be 
added 50 more clients.

Network interface eth0 will be used for the load with unique IP-address for each 
client taken from 192.168.1.1 up to 192.168.53.255 with netmask 255.255.0.0. 
Number of cycles is to be performed by each client in not limited (CYCLES_NUM= 
-1) and load will proceed till user presses Cntl-C to stop it. Each client 
fetches a single url (URLS_NUM= 1) http://localhost/index.html.

The url was given a short name "local-index", and this name will appear at the 
Load Status GUI. The url will be fetched using HTTP GET request method and the 
download will not be limited by time (TIMER_URL_COMPLETION = 0). If we would 
like to limit this operation by time, we could place here some number in 
milli-seconds, e.g. TIMER_URL_COMPLETION=3000; the timer will be monitored, 
enforced and reported, if missed, at Load Status GUI and other statistics. By 
default all missed url-completion timers are considered as errors and added to 
statistics as T-err. Each client after accomplishing a url, including possible 
protocol redirections, waits/sleeps for 0 ms (TIMER_AFTER_URL_SLEEP = 0, which 
means, that actually client does not wait/sleep) and goes to the next URL, if 
any, to fetch. 


Yet a one more example of a configuration file used for login to a web-service, 
perform some activity and logoff, all in cycles, is presented below:

########### GENERAL SECTION ###################
#
BATCH_NAME=web-service
CLIENTS_NUM_MAX=100
CLIENTS_RAMPUP_INC=2
INTERFACE=eth0 
NETMASK=24 
IP_ADDR_MIN=192.168.0.2
IP_ADDR_MAX=192.168.0.2
URLS_NUM=4
CYCLES_NUM= 200

########### URLs SECTION #######################

### Login URL - cycling 

# GET-part
# 
URL=http://192.168.0.1:8888/vax/root/Admin
URL_SHORT_NAME="Login-GET"
REQUEST_TYPE=GET
TIMER_URL_COMPLETION = 10000
TIMER_AFTER_URL_SLEEP =5000

# POST-part
# 
URL=""
URL_SHORT_NAME="Login-POST"
URL_USE_CURRENT=1
USERNAME= admin
PASSWORD= admin-passphrase
REQUEST_TYPE=POST
FORM_USAGE_TYPE= SINGLE_USER
FORM_STRING= username=%s&password=%s 
TIMER_URL_COMPLETION = 4000 
TIMER_AFTER_URL_SLEEP =1000 

### Cycling URL 
# 
URL=http://192.168.0.1:8888/vax/Admin/ServiceList.do
URL_SHORT_NAME="Service List"
REQUEST_TYPE=GET
TIMER_URL_COMPLETION = 3000
TIMER_AFTER_URL_SLEEP =1000

### Logoff URL - cycling, uses GET and cookies to logoff.
#
URL=http://192.168.0.1:8888/vax/Admin/Logout.do
URL_SHORT_NAME="Logoff"
REQUEST_TYPE=GET
TIMER_URL_COMPLETION = 0
TIMER_AFTER_URL_SLEEP =1000


The name of the batch is "web-service", maximum number of clients 100, load will 
started with initial 2 clients and each seconds will be added 2 more clients.

Eth0 will be used with the same IP-address for each client 192.168.0.2 with 
netmask 255.255.255.0 (24 in CIDR notation). If we would like to assign to each 
client a unique IP, it could be done by providing a range of at least 100 
IP-address, e.g. IP_ADDR_MIN=192.168.0.10 and IP_ADDR_MAX=192.168.0.110. Number 
of cycles is to be performed by each client is limited to 200, and the load 
stops, when each client accomplishes 200 cycles. A client fetches up to 4 urls, 
specified in section URLs

The first URL operation, which is doing a simulated user/client, is login. Login 
is performed by GET-ing the page (with 3xx HTTP redirections handled inside) 
with the first url http://192.168.0.1:8888/vax/root/Admin, called shortly 
"Login-GET". Maximum time considered appropriate for this operation is 10000 
msecs. The 2000 msec "sleep" timer simulates here the time taken by a user to 
fill username and password to the POST-form received by the GET.

The second url is empty and is used for POST-ing to the "current" url, using the 
form. Such empty string urls are allowed only, when URL_USE_CURRENT=1 is 
specified. The url is named as "Login-POST". Username "admin" and password 
"admin-passphrase" are used as the single user type and "filled" to the 
FORM_STRING= username=%s&password=%s. The resulting form, which is sent to the 
web-service, is "username=admin&password=admin-passphrase". There are other 
options available for the tag FORM_STRING, such as unique generated users, 
unique generated passwords or credentials loaded from a file; these options will 
be described later. The maximum time allowed for this POST operation is 4000 
msecs, and the time of waiting/sleeping till the next url is 1000 msecs. Worth 
to mention, that when the authentication is accomplished successfully, server 
sets to client cookies and redirects the client to the service page, which is 
the next url (note, that all redirections are handled internally). 

The third url is http://192.168.0.1:8888/vax/Admin/ServiceList.do with a short 
name "Service List". After the url is fetched a client comes to the forth url 
http://192.168.0.1:8888/vax/Admin/Logout.do for logoff. This batch (testing 
plan) does not control and limit time for logoff as indicated by 
TIMER_URL_COMPLETION = 0. After 1000 msecs sleeping a client comes back to the 
first url to repeat the sequence till the number of cycles is expired. 

If we would like, that login and logoff to be done for each client only once, we 
would add to the first, second and forth url the tag URL_DONT_CYCLE=1 to mark 
the urls as not-cycled to be fetched only once. 

Note, that both quoted and non-quoted strings are supported as the tags values.

For more examples, please, look at the files in "conf-examples" directory.

4.3. What are the exact meanings of all these tags? 
^ 

Tags of the sections GENERAL:

BATCH_NAME requires a string value and is used to name the batch. This name is 
used for the display while the program is running, and also for the three 
generated log and statistics files.

CLIENTS_NUM_MAX - a maximum number of clients to be used for this load. Any 
positive number is valid here. Note, that each loading client requires about 30 
K of RAM plus some non-pageable memory in kernel. We have already tried loads 
with up to 60000 clients. Loads above 1000 client is recommended to start with a 
some lower starting number, managed by the next tag CLIENTS_NUM_START and 
ramped-up each second by adding CLIENTS_RAMPUP_INC clients to the load.

CLIENTS_NUM_START - number of clients to start the load with. If the tag is not 
present or zero CLIENTS_RAMPUP_INC value will be taken instead. If neither 
CLIENTS_NUM_START nor CLIENTS_RAMPUP_INC are present or have any positive value, 
the loader will take CLIENTS_NUM_MAX as the number of clients to start the load.

CLIENTS_RAMPUP_INC - number of clients to be added to the load in the auto mode 
every second till CLIENTS_NUM_MAX number will be reached. For machines with a 
single CPU we would recommend not to keep the number above 50-100, whereas for 
dual-CPU machines you can keep it as large as 200-300.

INTERFACE - name of the loading network interface. Find your interfaces by 
running /sbin/ifconfig.

NETMASK - netmask for the loading clients IP-addresses (from IP_ADDR_MIN to 
IP_ADDR_MAX). For IPv4 you can use either quad-dotted netmask string or CIDR 
number from 0-32. For IPv6 only CIDR values from 0 to 128 are supported.
To enable IPv6 change --disable-ipv6 to --enable-ipv6 in Makefile

IP-addresses from IP_ADDR_MIN up to IP_ADDR_MAX are the interval to be used for 
loading clients. The interval of the addresses should be large enough to supply 
a dedicated IP for each client. Another mode that can be used is "single IP 
address" for all clients. When IP_ADDR_MIN and IP_ADDR_MAX have the same valid 
IP-address, it will be used for all clients. If the IP-addresses specified by 
the tags do not exist, curl-loader adds them as the secondary IPs to the loading 
network interface.
Remember, that you should ensure smooth routing from the addresses used to 
server and from server back to the client addresses. Another route to ensure, 
when is appropriate, is to/from DNS server for resolving. Firewalling 
(netfilter/iptables) settings are also among those to check.

CYCLES_NUM is the number of cycles to be performed if the value is positive.
A zero or negative number means indefinite number of cycles, but see the
RUN_TIME tag below.  The default value is zero. Loading can be normally 
stopped at any moment by pressing Cntl-C; all statistics will be collected 
properly and files closed to contain necessary information. Note, that cycling 
relates only to the URLs not containing tag URL_DONT_CYCLE = 1. Curl-loader 
enables two optional non-cycling areas: the first before the cycling url/s area 
and the second after the cycling url/s area.

DUMP_OPSTATS is the flag indicating whether to write out a fairly voluminous
operational statistics file.  It takes values "yes" or "no".  The default
value is "yes".

RUN_TIME is the maximum time to run the load.  It is specified as up to
four numbers: hours, days, minutes and seconds separated by a colon (":").
When less than four numbers are specified, the senior categories are assumed
to be omitted.  That is 1:1:0:0 means one day and one hour, 1:1 means one
minute and 1 second, 10000 means 10000 seconds, etc.  A zero or negative
value means no limit to run time.  As noted above, the curl-loader may
stop before the maximum time, if any, is reached if either the number
of clycles to be performed runs out or the Cntl-C is pressed on the keyboard.

REQ_RATE is the desired fixed request rate per second, sometimes referred to
as offered load.  It is specified as an integer number.
The rate here means that of the effective URL requests, so if, for example,
each initial URL is redirected once with a 302 response, the rate of actual
requests will be double from the specified one.  Note that as many clients
as necessary are invoked in order to maintain the offered load.  If the total
response time to the effective URL exceeds 1 second, the CLIENTS_NUM_MAX
value must exceed the REQ_RATE value proportionately.  When the number of
clients is insufficient for the load, an error message "need free clients (X)"
is written to stderr, where X is the number of additional clients required.
That number may be used as a guide for increasing the CLIENTS_NUM_MAX value.

USER_AGENT provides an option to over-write the default MSIE-6-like HTTP header 
User-Agent. Place here a quoted string to emulate the browser that you need. The 
header is entered globally. If you need an option to customize it on a per-URL 
bases, please, use the tag HEADER="User-Agent: the string of my favorite 
browser".

URLS_NUM is the number of urls to be used in URLs Section.



Tags of the sections URLs:

URL - can be the first tag of each url-subsection and marks beginning of a new url.
Yet another option to start a new url (set of urls) is the tag URL_TEMPLATE.
Note, that the tags URL and URL_TEMPLATE are mutually exclusive.
URL tag should be either a valid url or an empty string, which is allowed only 
when URL_USE_CURRENT=1 also presents. "Current url" is used for example, when 
POST-ing at the url, resulting from the previous GET. HTTP redirections are 
handled internally and there is no need to use "current url" approach for that 
purpose. Note, that URL used for file uploading should include a filename and 
not only a directory.

URL_SHORT_NAME - an optional up to 12 ASCII string long name, which will appear 
on a Load Status GUI. It improves appearance of the current operational status 
at the console. We are recommending to configure it.

URL_USE_CURRENT - used in combination with an empty string URL="" to indicate, 
that the current url, fetched by the previous operation, should be used. 
"Current url" is useful e.g., when POST-ing at the url, resulting from the 
previous GET. Note, that HTTP redirections are handled internally and there is 
no need to use "current url" approach for that purpose. 

URL_DONT_CYCLE - marks a url as non-cycling. Curl-loader enables two optional 
non-cycling areas: the first before the cycling url/s area and the second after 
it. The first non-cycling area may be used for login, authentication, etc. 
single time operations, whereas the second non-cycling area is good for a single 
time logoff, for example.

REQUEST_TYPE - HTTP request method to be chosen from GET, POST, PUT,
DELETE or HEAD.

UPLOAD_FILE - filename, including path, to the file to be used for uploading. 
The path should be taken from the curl-loader place, e.g. 
./conf-examples/bax.conf 

HEADER - is assisting to customize/add/over-write HTTP/FTP headers. If a header 
already exits by default, the custom header over-writes it. USER_AGENT tag is 
for User-Agent header only, whereas by HEADER may be added or over-written any 
header (including User-Agent). Look for example at 
./conf-examples/custom_hdrs.conf.

USERNAME and PASSWORD are the tags to provide credentials for the login 
operations. The strings may be used either as is or as the base-words to append 
numbers and to generate some unique credentials. The behavior is governed by the 
tag FORM_USAGE_TYPE. Note, that PASSWORD may be an empty string.

FORM_USAGE_TYPE governs user login process. "UNIQUE_USERS_AND_PASSWORDS" is used 
to generate unique usernames and passwords by appending client sequence numbers 
(starting from 1) to USERNAME and PASSWORD tags within FORM_STRING template. 
"UNIQUE_USERS_SAME_PASSWORD" to be used when generating unique users with the 
same password. "SINGLE_USER" is useful, when all clients are making login using 
the same USERNAME and PASSWORD. "RECORDS_FROM_FILE" means, that user credentials 
to be loaded from the file specified by FORM_RECORDS_FILE value. "AS_IS" means, 
that the FORM_STRING template to be used just AS IS and without any usernames or 
passwords either from the relevant tags or from file.


FORM_STRING is the configurable template form to be used for POST-ing 
credentials or any other records.
To generate multiple unique users with unique passwords FORM_USAGE_TYPE= 
"UNIQUE_USERS_AND_PASSWORDS", and the FORM_STRING to be a template like 
"username=%s%d&password=%s%d". First '%s' will be substituted by the value of 
USERNAME tag and '%d' by the client number. Second '%s' will be substituted by 
PASSWORD tag value and second '%d' by the same client number. For example, if 
USERNAME=robert, PASSWORD=stam and FORM_STRING "username=%s%d&password=%s%d", 
the final POST string, used for the client number 1, will be 
"username=robert1&password=stam1".
In this case USERNAME and PASSWORD strings are used just as base-words for 
generating unique user credentials by appending a client sequence number. 
When FORM_USAGE_TYPE="UNIQUE_USERS_SAME_PASSWORD" template of FORM string to be 
something like "username=%s%d&password=%s", where only username will be unique 
using the same approach as described above. 
When FORM_USAGE_TYPE="SINGLE_USER", provide FORM_STRING without %d symbols, e.g. 
"user=%s&secret=%s". Thus, all clients will have the same POST credentials with 
the string looking like "user=robert&secret=stam". 
When FORM_USAGE_TYPE= "RECORDS_FROM_FILE" FORM_STRING to be also without %d 
symbols, because the credentials uniqueness is supposed to be ensured by the 
file content.
FORM_USAGE_TYPE="AS_IS" means, that FORM_STRING will not be validated and 
POST-ed indeed AS IS.


FORM_RECORDS_FILE specifies the path to the file with credentials or any other 
tokens. (full-path or relative to curl-loader location). A text file with 
usernames and passwords with the structure of each string like: 
<teken1><separator><token2> can be used as an input. According to RFC1738, only 
reserved ':', '@', '/' and probably ' ' (space) are safe to use as separators 
between username and password. An example of batch configuration is 
./conf-examples/post-form-token-fr-file.conf and an example of credentials is in 
./conf-examples/credentials.cred.
Next version will support up to 16 tokens (2 tokens now).

FORM_RECORDS_FILE_MAX_NUM allows to load not from a records file,
specified by tag FORM_RECORDS_FILE not the default number of records 
being the same as the maximum number of virtual clients CLIENTS_NUM_MAX,
but some larger number, required by FORM_RECORDS_RANDOM.

FORM_RECORDS_RANDOM allows to use for each virtual client not a pre-defined
record, but a randomly chosen record. One can load a 10000 records from a records file using
FORM_RECORDS_FILE tag and use the records in a random fashion for 1000 clients. 
The tag does not ensure uniquickness of the records used for each virtual client. To use the
tag properly, specify number of the records to be loaded, using tag
FORM_RECORDS_FILE_MAX_NUM

WEB_AUTH_METHOD to be configured from the "BASIC", "DIGEST", "GSS_NEGOTIATE", 
"NTLM" or "ANY". The configured method will be used for authentication on HTTP 
401 response. When "ANY" is configured, libcurl will choose a method. To use 
"GSS_NEGOTIATE" the libcurl should be re-compiled with support for GSS.

WEB_AUTH_CREDENTIALS to be provided in the form "user:password". If not 
configured, the loader uses USERNAME and PASSWORD tags value to synthesize the 
credentials.

PROXY_AUTH_METHOD to be configured from the "BASIC", "DIGEST", "GSS_NEGOTIATE", 
"NTLM" or "ANY". The configured method will be used for authentication on HTTP 
407 response. When "ANY" is configured, libcurl will choose a method. To use 
"GSS_NEGOTIATE" the libcurl should be re-compiled with support for GSS.

PROXY_AUTH_CREDENTIALS to be provided in the form "user:password". If not 
configured, the loader uses USERNAME and PASSWORD tags value to synthesize the 
credentials.

FRESH_CONNECT is used to define on a per url bases, whether the connection 
should be re-used or closed and re-connected after request-response cycle. When 
1, the TCP connection will be re-established. The system default is to keep the 
connection and re-use it as much as server and protocol allow it. Still the 
system default could be changed by the command-line option -r.

TIMER_TCP_CONN_SETUP is the time in seconds for DNS resolving and TCP connection 
setup on a per url bases. The global default is 5 seconds, which can be changed 
using -c command-line option.

TIMER_URL_COMPLETION is the time in milli-seconds to allow a url fetching 
operation, including all internal re-directions. The legal values are 0, which 
means no limit on url-completion time, or above 20 msecs. When a value of the 
tag is above 0, we are monitoring the url-fetching and canceling it, if above 
the specified milliseconds. The results are presented on the Load Status GUI as 
the operation "Timeouted" statistics and logged to all statistics files as T-Err 
number.

TIMER_AFTER_URL_SLEEP is the time in milli-seconds for client to sleep after 
fetching a URL prior to dealing with the next URL. Zero (0) means don't wait and 
schedule client after the URL immediately. Random timer values could be an 
option specified as e.g. 0-2000, which means, that a client will sleep for some 
random time from 0 to 2000 milliseconds.

FTP_ACTIVE, when defined as 1, is forcing FTP protocol to use an active mode 
(the default is passive).

LOG_RESP_HEADERS, when defined as 1, logs response headers to a file. Directory 
<batch-name> is created with subdirs url0, url1, url<n> Headers of responses are 
logged to the files named: cl-<client-num>-cycle-<cycle-num>.hdr

LOG_RESP_BODIES, when defined as 1, logs response headers to a file. Directory 
<batch-name> is created with subdirs url0, url1... url<n> Headers of responses 
are logged to the files named: cl-<client-num>-cycle-<cycle-num>.body

RESPONSE_STATUS_ERRORS supports changes to the default set of per-url responses 
considered as errors. By default 4xx without 401 and 407 and all 5xx response 
codes are treated as errors. Now you can either add a status to the errors set 
or remove it. Sign + (plus) adds, - (minus) removes. The syntax is a line of 
tokens separated by ',', where each tokens begins with either + or - and is 
followed by the response status number from 0 up to 600.
For example, the effect of RESPONSE_STATUS_ERRORS="+200,-404" is that 200 
responses will be considered for that url as errors, whereas 404 will be 
considered as success.


MULTIPART_FORM_DATA tag adds initial support for multipart form data POST-ing as 
in RFC1867. 
Several tags MULTIPART_FORM_DATA can be used for a url to post, e.g. as in 
./conf-examples/multipart-formdata-post.conf:

MULTIPART_FORM_DATA="yourname=Michael"
MULTIPART_FORM_DATA="filedescription=Cool text file with cool text inside"
MULTIPART_FORM_DATA="htmlcode=<HTML></HTML>;type=text/html"
MULTIPART_FORM_DATA="file=@cooltext.txt"
MULTIPART_FORM_DATA="coolfiles=@fil1.gif,fil2.txt,fil3.html"

The files to be copied are indicated by @ and to be located in the same 
directory as curl-loader. Currently, the feature uses the strings provided AS_IS 
and does not generate any unique users, unique passwords or loads tokens from 
file. To prevent from sending "Expect: 100-continue", pass as a custom HTTP 
header HEADER="Expect: "


TRANSFER_LIMIT_RATE limits client maximum throughput for a url. The value of the 
tag to be provided as bytes (not bits) per second.

FETCH_PROBABILITY allows to fetch a url not as a must, but with a certain 
run-time probability. The allowed values are in the range from 1 to 100 
percents.

FETCH_PROBABILITY_ONCE enables for a client to make the decision regarding 
wether to fetch a URL or not using FETCH_PROBABILITY to be done only once (at 
the first cycle). 
4.4. How does the loader support login, logoff and authentication flavors? 
^ 
curl-loader performs login and logoff operations using the following HTTP 
methods:
- GET+POST (server response to GET provides a post-form to be filled and posted 
by POST);
- POST only;
- GET only.
The loader also supports multipart form data POST-ing as in RFC1867.



URL_TEMPLATE  Yet another option to start a new url (set of urls) is the tag URL.
Note, that the tags URL and URL_TEMPLATE are mutually exclusive. 
An example of URL_TEMPLATE usage is: 
URL_TEMPLATE= http://www.foo.com/user/%s/group/%s.
URL_TEMPLATE allows an url to vary from client to client or from cycle to cycle. 
As in FORM_STRINGs, the %s markers will be replaced with appropriate strings 
before the URL is fetched. The replacement values can be obtained either 
statically from file (using URL_TOKEN_FILE) or fetched dynamically by fetching token 
from HTTP-responses (using RESPONSE_TOKENs and URL_TOKENs).


RESPONSE_TOKEN  (Example: RESPONSE_TOKEN = user_id) 
There can be any number of RESPONSE_TOKENs in an URL or URL_TEMPLATE subsection. 
When curl-loader fetches the url, it will scan the server's response for all the response tokens. 
If found, curl-loader will save the "value" of each response token for use in constructing 
later URL_TEMPLATEs (see URL_TOKEN below). For instance, if we specify 
RESPONSE_TOKEN = user_id, and if the server response contains ... user_id=1234 ..., 
then we will save the name-value pair "user_id, 1234". Different clients may well receive different 
responses and save different values, thus constructing different urls from later templates.
Note, that order of the RESPONSE_TOKENs in the url subsection is immaterial. Matches and values 
are collected across response-packet boundaries. Once a value is collected from a particular 
server response, the scanning for that token stops, and subsequent occurrences of that token in 
the response will not trigger a new value collection. Finally, a RESPONSE_TOKEN with the same 
name as one in a previous url will replace any previously collected value for that name.
See, the usage example in ./conf-examples/url-template-resp-dynamic.conf


URL_TOKEN Such tags may occur in an URL_TEMPLATE subsection. Each URL_TOKEN 
is taken in order and looked up in this client's bucket of saved RESPONSE_TOKENs. 
The value obtained is substituted for the next %s marker in the URL_TEMPLATE. 
Thus the order of the URL_TOKENs matters. There must be the same number of 
URL_TOKENs as %s makers, and each URL_TOKEN must have a corresponding saved 
RESPONSE_TOKEN value, or an error results. Note that not all these values need 
come from the same prior url the only requirement is that the needed value has 
been obtained from some prior server response by this client. URL_TOKEN is mutually 
exclusive with URL_TOKEN_FILE tag, where tokens are loaded from file statically.
See, the usage example in ./conf-examples/url-template-resp-dynamic.conf


URL_TOKEN_FILE - This tag may occur in an URL_TEMPLATE subsection, 
and is mutually exclusive with URL_TOKEN tag. It specifies a file from which the 
substitution tokens for the URL_TEMPLATE will be taken. The pathname must be 
absolute or relative to the curl-loader directory.
The syntax for token files is a bit more permissive than the rules for scanning 
server responses.
(1) Each remaining line is parsed to obtain the tokens for constructing one url, so there 
     must be as many tokens on each line as there are %s markers in the URL_TEMPLATE. 
(2) Tokens are runs of non-whitespace characters, or quoted strings, separated by whitespace. 
(3) Attention! If there is an extra token remaining in the line, it is saved as a cookie 
     to be sent when the url is fetched.
As the load runs, the pre-constructed urls are taken on demand, and if the 
demand is greater than the supply, we start over from the first url. Thus, if the 
number of urls is equal to the number of clients, each client will get the same 
unique url for each cycle.
See, the usage example in ./conf-examples/url-template-fr-file.conf


URL_RANDOM_RANGE - Specifies a range for random numbers to replace the token
specified in URL_RANDOM_TOKEN
E.g. URL_RANDOM_RANGE=0-2000
URL_RANDOM_TOKEN - Replace this token in the URL with a random number from the
range specified with URL_RANDOM_RANGE.
E.g. URL_RANDOM_TOKEN=JUNKSTR
For example config look at ./conf-examples/url-randomize.conf

RANDOM_SEED - this tags allows setting the random seed to a specified
non-negative value.  With the same seed the pseudo-random numbers used in
various parts of the curl-loader are generated in the same order, which
produces more consistent results.  If this tag is absent or the value is
negative, the random seed is generated based on the current time, i.e. it
is different from one run of the curl-loader to another.  The same seed is
used for all random numbers.  (Example, RANDOM_SEED = 10).
 

The loader supports HTTP Web Authentication and Proxy Authentication. The 
supported authentication methods are Basic, Digest (RFC2617) and NTLM. When 
responded 401 or 407, libcurl will choose the most safe method from those, 
supported by the server, unless the batch configuration (test plan) is 
explicitly indicating the method to be used by the tags WEB_AUTH_METHOD and/or 
PROXY_AUTH_METHOD.
To support GSS Web-Authentication, add in Makefile building of libcurl against 
appropriate GSS library, see libcurl pages for detailed instructions.



5. What about FTP load and mixed FTP/HTTP load? 
To generate FTP/FTPS load, please, pass user credentials via ftp-url according 
to the RFC 1738 like: ftp://username:password@hostname:port/etc-str
Tag FTP_ACTIVE serves to switch from the default passive FTP to active. Please, 
look at the examples in conf-examples directory, e.g. ftp.conf, ftp_http.conf, 
ftp_upload.conf.

6. Running Load
6.1. What are the running environment requirements? 
^ 
Running hundred and thousand of clients, please, do not forget:
- to increase limit of descriptors (sockets) by running e.g. 
#ulimit -n 100 000;
- optionally, to set reuse of sockets in time-wait state: by setting 
#echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle and/or
#echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse;

In some cases you may need to increase the system limits for open descriptors 
(sockets):
echo 150 000 > /proc/sys/fs/file-max 
Note, that your linux distribution may require editing of some other files like 
/etc/security/limits.conf, etc 
6.2. How I can run the load? 
^ 
Usage: run as a root user:
#./curl-loader -f <configuration filename> [other options]

Other possible options are:
-c[onnection establishment timeout, seconds]
-e[rror drop client. Client on error doesn't attempt to process the next cycle]
-d[etailed logging, hich outputs to logfile headers and bodies of requests/responses]
-h[elp]
-i[ntermediate (snapshot) statistics time interval (default 3 sec)]
-f[ilename of configuration to run (batches of clients)]
-l[ogfile max size in MB (default 1024). On the size reached, file pointer is 
rewinded]
-m[ode of loading, 0 - hyper (the default, epoll () based ), 1 - smooth (select 
() based)]
-r[euse connections disabled. Closes TCP-connections and re-open them. Try with 
and without]
-v[erbose output to the logfiles; includes info about headers sent/received. Increase the level of verbosity by using this option twice]
-u[rl logging - logs url names to logfile, when -v verbose option is used]
-w[arnings skip]
-x[set|unset proxy] "<proxy:port>"

Connection Reuse Disable Option (-r):
The default behavior of curl-loader after HTTP response is to re-use the 
tcp-connection for the next request. If you are specifying -r command-line 
option, the TCP connection will be closed and re-opened for the next request. 
Whether it is appropriate for you to work with -r option or without, it depends 
on your server support of Keep-Alive and the purpose of your testing. Try with 
and without -r and see, what you get.
Connection reuse (which is the default, without -r option) has advantages due to 
the decreased consumption of opened descriptors (sockets) and ports.

6.3. Which loading modes are supported? 
^ 
Hyper-mode (command line -m0) is the default mode . The mode is using for event 
demultiplexing epoll() or /dev/epoll. 

Another loading mode is called "smoothing" (-m1 command line) is basically the 
same as hyper, but uses poll() system call for demultiplexing. 

6.4. How I can monitor loading progress status? 
^ 
curl-loader outputs to the console loading status and statistics as the Load 
Status GUI output, where the left column is for the latest interval and the 
right is for the summary numbers since load start. A copy of the output is also 
saved in the file <batch-name>.txt

6.5. Why I am getting "Connection time-out after 5108 ms" like errors in the log 
file? 
^ 
This means, that the connections cannot be established within 5 seconds (which 
is the default). If some of clients are getting such errors, this means, that 
the server is overloaded and cannot establish TCP connection within the time. Y 
may wish to increase the connection timeout globally by e.g. -c 10 or to specify 
an increased timeout using tag TIMER_TCP_CONN_SETUP=10.

When all your clients have such errors, in most cases this is due either to 
resolving or routing problems or other network problems. Y can set any addresses 
to your clients in IP_ADDR_MIN and IP_ADDR_MAX tags, providing, that you ensure 
a smooth route from client and from server for the addresses you use.

Please, start with a single client and see that it works, than progress further. 
When you are specifying any addresses here, they are added by curl-loader 
initialization to the network interface of your choice and may be seen by the 
command:
#/sbin/ip addr

Command ping (man ping) has an option -I to force the ping to be issued from a 
certain ip-address. To test, that your routing is OK, you may use, e.g.:
#ping -I <the client address you wish to use> url-target
When it works - it will be OK. 
Please, also pay attention to the firewalling/NAT settings at your linux loading 
machine (netfilter/iptables), at the tested servers and through the whole 
packets route.

Y may also wish to read a bit about linux routing/networking/iptables and DNS 
resolving HOWTOS.


6.6. Where is the detailed log of all virtual clients activities and how to read 
it? 
^ 
Detailed log is written to the file named:
<batch-name>.log:

The semantics of logfile output, using command line options -v -v (very
verbose) and -u (url print) are as follows.

The first line is the time of the load start in milliseconds and in text
form:

# 1248743647809 Mon Jul 27 18:14:07 2009

The second line identifies log columns:

# msec_offset cycle_no url_no client_no (ip) indic info

That is the columns are:

   - time offset from start in milliseconds
   - cycle number
   - url number
   - client number
   - client ip address in parentheses
   - indicator, qualifies the message as setup (==), send (&gt;=),
     receive (&lt;=) or response (!!)
   - information string

Subsequent lines look as follows.

1234 4 3 39 (192.168.0.39) == Trying 10.30.6.42... : eff-url: http://10.30.6.42 :8888/server/Admin/ServiceList.do, url:

Which means: 1234 msec from start, cycle 4, url number 3, client number 39
with ipv4 address (192.168.0.39), type of the message is setup, eff-url -
is the url, used right now, "url:" is empty, which means, that it is the
same as effective.

Effective url may be a result of redirection and, thus, "url:" 
(target url, specified in batch configuration file) will be printed as well.

Please, note, that when the logfile reaches 1024 MB size, curl-loader rewinds it 
and starts to overwrite it from the beginning. Y may tune the rewinding file 
size by using command line option:
-l <log-filesize-in-MB>

6.7. Which statistics is collected and how to get to it? 
^ 
Currently HTTP/HTTPS statistics includes the following counters:
- run-time in seconds;
- requests num;
- 1xx success num;
- 2xx success num;
- 3xx redirects num;
- client 4xx errors num;
- server 5xx errors num;
- other errors num, like resolving, tcp-connect, server closing or empty 
responses number (Err);
- url completion time expiration errors (T-Err);
- average application server Delay (msec), estimated as the time between HTTP 
request and HTTP response without taking into the account network latency (RTT) 
(D);
- average application server Delay for 2xx (success) HTTP-responses, as above, 
but only for 2xx responses. The motivation for that is that 3xx redirections and 
5xx server errors/rejects may not necessarily provide a true indication of a 
testing server working functionality (D-2xx);
- throughput in, batch average, Bytes/sec (T-In);
- throughput out, batch average, Bytes/sec (T-Out);

The statistics goes to the screen (both the interval and the current summary 
statistics for the load) as well as to the file with name <batch_name>.txt When 
the load completes or when the user presses CTRL-C (sometimes some clients may 
stall), the final load report is printed at the console as well as to the 
statistics file.

Some strings from the file:
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Run-Time,Appl,Clients,Req,1xx,2xx,3xx,4xx,5xx,Err,T-Err,D,D-2xx,T-In,T-Out
2, Appl , 100, 155, 0, 0, 96, 0, 0, 0, 0, 1154, 1154, 2108414, 15538
2, Sec-Appl, 100, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
4, Appl, 100, 75, 0, 32, 69, 0, 0, 0, 0, 1267, 1559, 1634656, 8181
4, Sec-Appl, 100, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Cutted here

36, Appl , 39, 98, 0, 35, 58, 0, 0, 0, 0, 869, 851, 1339168, 11392
36, Sec-Appl, 39, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
38, Appl , 3, 91, 0, 44, 62, 0, 0, 0, 0, 530, 587, 1353899, 10136
38, Sec-Appl, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
*, *, *, *, *, *, *, *, *, *, *, *
Run-Time,Appl,Clients,Req,1xx,2xx,3xx,4xx,5xx,Err,T-Err,D,D-2xx,T-In,T-Out
38, Appl , 0, 2050, 0, 643, 1407, 0, 213, 0, 0, 725, 812, 1610688, 11706
38, Sec-Appl, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
The bottom strings after asterisks are for final averages.

At the same time a clients dump file with name <batch_name>.ctx is generated to 
provide detailed statistics about each client state and statistics counters.
One string from the file:
1 (192.168.0.1) 
,cycles:124,cstate:1,b-in:22722029,b-out:174605,req:745,2xx:497,3xx:248,4xx:0,5xx:0,err:0
where
1 (192.168.0.1)- is the index of the client and its ip-address;
cycles- number of loading cycles done;
cstate - is the number of the client state (-1 - error, 0 - init, 1- urls, 
2-final-ok);
b-in - bytes passed in;
b-out - bytes passed out;
req- number of requests done;
2xx, 3xx, 4xx, 5xx - number of responses Nxx received;
err - number of libcurl errors at the resolving, TCP/IP and TLS/SSL levels;


The following conditions are considered as errors:
- error at the level of libcurl, which includes resolving, TCP/IP and, when 
applicable, TLS/SSL errors;
- all HTTP 5xx server errors;
- most of HTTP 4xx client errors, excluding 401 and 407 authentication responses 
not considered real errors;
When the above error conditions occur, a virtual client is marked as being in 
the error state.

By default we "recover" such client by scheduling it to the next loading cycle, 
starting from the first operation of the cycle. You may use command line option 
-e to change the default behavior to another, so that clients once arriving at 
error state will not be scheduled for load any more. 


7. Advanced Issues
7.1. What about performance? 
^ 
HYPER mode (-m 0 command line option) was already used for loads with up to 
10000 clients, whereas HW issues, like CPU and memory resource, start to be 
counting. The mode uses epoll() syscall (via libevent library) for 
demultiplexing. 


7.2. How to run a really big load? 
^ 
0. Every big load starts with a small load. First, see, that you have a working 
configuration file. Run it with a 1-2-3 clients and commandline option -v, and 
look into the l<batch-name>.log logfile.
Look into the HW issues, discussed in the FAQs and mind, that each client 
requires 30-35 K of memory.

1. Compile with optimization;
Since you need performance compile with optimization and without debugging.
$make cleanall 
$make optimize=1 debug=0
Y may add to Makefile optimization for your particular processor by -match 
/-mcpu gcc option directives to OPT_FLAGS.

2. Login as a su;

3. Increase the default number of allowed open descriptors (sockets);

Run e.g. #ulimit -n 100 000

When running several instances of curl-loader, consider increase of system 
limits for open descriptors, if necessary. Take your own account of the socket 
usage in the system, considering sockets faster recycling (less time in the 
time-wait state), by setting, optionally, something like this:
#echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle and/or 
#echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse;

Correct, if required, the value of CURL_LOADER_FD_SETSIZE (set to 20000 in 
Makefile) to control the maximum fd, that may be used for select. This is not 
required to be cared about for the default hyper mode.

Increase the maximum number of open descriptors in your linux system, if 
required, using linux HOWTOS.
echo 65535 > /proc/sys/fs/file-max 
Note, that your linux distribution may require editing of some other files like 
/etc/security/limits.conf, etc

4. Relax routing checks;

Relax routing checks for your loading network interface. When "eth0" used for 
loading run:
echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter
echo 0 > /proc/sys/net/ipv4/conf/eth0/rp_filter

5. Increase memory available for kernel tcp;
Read the maximum available TCP memory and sysctl or echo as a root the number to 
the kernel tcp, e.g.:
cat /proc/sys/net/core/wmem_max - the output is 109568.
/sbin/sysctl net.ipv4.tcp_mem="109568 109568 109568" or 
echo "109568 109568 109568" > /proc/sys/net/ipv4/tcp_mem

6. Increase ARP thresholds;

echo 1024000 > /proc/sys/net/ipv4/neigh/default/gc_thresh1
echo 1024000 > /proc/sys/net/ipv4/neigh/default/gc_thresh2
echo 1024000 > /proc/sys/net/ipv4/neigh/default/gc_thresh3

Read:
http://txt.bitprocessor.be/2011/02/10/curl-loader-and-arp-cache-issues/


7. Create configuration files for each instance of curl-loader to run.

What is important is to give a unique value for tag BATCH_NAME, which is in use 
by a separate instance of curl-loader. Logfile, report file, etc have name, 
which are the derivatives of the BATCH_NAME value. Therefore, when several 
instances of curl-loader are writing to the same file, this is not helpful and 
may be even "crashful". Please, use in your configuration batch files 
non-overlapping ranges of IP-addresses, else libcurl virtual clients will 
compete for the IP-addresses to bind to.

Use CLIENTS_RAMPUP_INC tag in smooth or hyper mode to increase number of your 
clients gradually at start-up in order not boom the server and not to burn out 
the CPU at your loading machine. Addition of new clients is a CPU-expensive 
operation, therefore keep CLIENTS_RAMPUP_INC below 100 clients per second.

8. Connections re-use.

The default behavior of curl-loader now is to re-use the tcp-connection for the 
next request. This default decreases consumption of CPU and open sockets. If you 
are specifying -r command-line option, the connection will be closed and 
re-opened for the next request. 

9. Running curl-loader in multiple threads on several CPUs/cores.

SMP-support can be gained by using option -t <threads-num>. We can recommend to 
use number of threads as number of CPUs from /proc/cpuinfo. Sometimes 
curl-loader crashes on start with the option used due to suspected bugs in 
libevent library. Re-run it optionally changing/decreasing number of threads 
used. Note, that total statistics is written to the file $batch-name_0.txt, 
whereas logs are per-thread and are written to the files 
$batch-name_<thread-num>.log.

10. Troubleshooting.

Run the first loading attempt with a small number of clients using command-line 
options -v (verbose) and -u (url in logs). Grep to look for the errors and their 
reasons. If an error is "Connection timeout", you may try to increase the 
connection establishment timeout (the default is 5 seconds), using -c 
command-line option. When all your clients fail to connect with "Connection 
timeout" error, this may be due to routing or resolving problems.
If any assistance required, please, don't hesitate to contact us using 
PROBLEM-REPORTING form in the download tarball.

11. Logs and statistics.

After end of a run, or after SIGINT (Cntl-C), the final results are calculated 
and printed to the console as well as to the file <batch-name>.txt. Current 
results are presented in each row, and average summary as the last raws, 
separated from the rest by asterisks.

Pay attention, that <batch-name>.log log file may become huge, particularly, 
when using verbose output (-v -u). Command-line option -l <maxsize in MB> may be 
useful, whereas the default policy is to rewind the logfile (writing from the 
file start), when it reaches 1 GB. Do not use -v and -u options, when you have 
performance issues.

12. Monitoring of the loading PC.

Please, use top or vmstat commands to monitor the memory usage, swapping and 
CPU. Intensive swapping is a good indication, that your PC is short in 
user-space memory. If you see "memory pressure" counters in netstat -s output, 
this is a good indication, that the PC is short in kernel memory for TCP.
Zero idle CPU is not the show stopper, but when you see, that Load Status GUI on 
your console prints its output with delays higher than it should be (the default 
is 3 seconds and may be adjusted by -i command-line option), you need stronger 
CPU or run several curl-loader processes on a multi-CPU machine. Note, that for 
a load with several curl-loader processes you need to arrange different 
configuration files with different batch-names and not overlapping ranges of 
IP-addresses for each curl-loader process.

7.3. How to calculate CAPS numbers for a load? 
^ 
When number of clients is defined by CLIENTS_NUM_MAX tag, number of CAPS (call 
attempts per seconds) is resulting from the clients number and load duration for 
each cycle, comprising from url time for each url with possible redirections, 
intervals betwee urls and after url interval.

The actions and time intervals are configurable in batch file, whereas url 
retrival time is server and network dependent and not always easy to predict. 
The result is that number of clients/requests is a known parameter, and number 
of CAPS is something to be estimated from the time of test and number of 
requests.

LOAD STATUS GUI presents calculated current and average CAPS.



LIMITATIONS:
Please, see our TODO file for some of them.
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