LWP::RobotUA - a class for well-behaved Web robots
use LWP::RobotUA; my $ua = LWP::RobotUA->new(my-robot/0.1, me@foo.com); $ua->delay(10); # be very nice -- max one hit every ten minutes! ... # Then just use it just like a normal LWP::UserAgent: my $response = $ua->get(http://whatever.int/...); ...
This class implements a user agent that is suitable for robot applications. Robots should be nice to the servers they visit. They should consult the /robots.txt file to ensure that they are welcomed and they should not make requests too frequently.
But before you consider writing a robot, take a look at <http://www.robotstxt.org/>.
When you use an LWP::RobotUA object as your user agent, then
you do not really have to think about these things yourself;
robots.txt files are automatically consulted and obeyed,
the server isn't queried too rapidly, and so on. Just send requests as
you do when you are using a normal LWP::UserAgent object (using
$ua->get(...), $ua->head(...),
$ua->request(...), etc.), and this special agent will
make sure you are nice.
The LWP::RobotUA is a sub-class of LWP::UserAgent and implements the same methods. In addition the following methods are provided:
my $ua = LWP::RobotUA->new( %options ) my $ua = LWP::RobotUA->new( $agent, $from ) my $ua = LWP::RobotUA->new( $agent, $from, $rules )
The LWP::UserAgent options agent and from
are mandatory. The options delay, use_sleep
and rules initialize attributes private to the RobotUA. If
rules are not provided, then WWW::RobotRules is
instantiated providing an internal database of robots.txt.
It is also possible to just pass the value of agent,
from and optionally rules as plain positional
arguments.
my $delay = $ua->delay; $ua->delay( $minutes );
Get/set the minimum delay between requests to the same server, in
minutes. The default is 1 minute. Note that this
number doesn't have to be an integer; for example, this sets the delay
to 10 seconds:
$ua->delay(10/60);
my $bool = $ua->use_sleep; $ua->use_sleep( $boolean );
Get/set a value indicating whether the UA should sleep in
LWP::RobotUA if requests arrive too fast, defined as
$ua->delay minutes not passed since last request to the
given server. The default is true. If this value is false then an
internal SERVICE_UNAVAILABLE response will be generated. It
will have a Retry-After header that indicates when it is OK
to send another request to this server.
my $rules = $ua->rules; $ua->rules( $rules );
Set/get which WWW::RobotRules object to use.
my $num = $ua->no_visits( $netloc )
Returns the number of documents fetched from this server host. Yeah I
know, this method should probably have been named
num_visits or something like that. :-(
my $num = $ua->host_wait( $netloc )
Returns the number of seconds (from now) you must wait before you can make a new request to this host.
my $string = $ua->as_string;
Returns a string that describes the state of the UA. Mainly useful for debugging.
LWP::UserAgent, WWW::RobotRules
Copyright 1996-2004 Gisle Aas.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.