package LWP::RobotUA;
require LWP::UserAgent;
@ISA = qw(LWP::UserAgent);
$VERSION = "6.03";
require WWW::RobotRules;
require HTTP::Request;
require HTTP::Response;
use Carp ();
use HTTP::Status ();
use HTTP::Date qw(time2str);
use strict;
#
# Additional attributes in addition to those found in LWP::UserAgent:
#
# $self->{'delay'} Required delay between request to the same
# server in minutes.
#
# $self->{'rules'} A WWW::RobotRules object
#
sub new
{
my $class = shift;
my %cnf;
if (@_ < 4) {
# legacy args
@cnf{qw(agent from rules)} = @_;
}
else {
%cnf = @_;
}
Carp::croak('LWP::RobotUA agent required') unless $cnf{agent};
Carp::croak('LWP::RobotUA from address required')
unless $cnf{from} && $cnf{from} =~ m/\@/;
my $delay = delete $cnf{delay} || 1;
my $use_sleep = delete $cnf{use_sleep};
$use_sleep = 1 unless defined($use_sleep);
my $rules = delete $cnf{rules};
my $self = LWP::UserAgent->new(%cnf);
$self = bless $self, $class;
$self->{'delay'} = $delay; # minutes
$self->{'use_sleep'} = $use_sleep;
if ($rules) {
$rules->agent($cnf{agent});
$self->{'rules'} = $rules;
}
else {
$self->{'rules'} = WWW::RobotRules->new($cnf{agent});
}
$self;
}
sub delay { shift->_elem('delay', @_); }
sub use_sleep { shift->_elem('use_sleep', @_); }
sub agent
{
my $self = shift;
my $old = $self->SUPER::agent(@_);
if (@_) {
# Changing our name means to start fresh
$self->{'rules'}->agent($self->{'agent'});
}
$old;
}
sub rules {
my $self = shift;
my $old = $self->_elem('rules', @_);
$self->{'rules'}->agent($self->{'agent'}) if @_;
$old;
}
sub no_visits
{
my($self, $netloc) = @_;
$self->{'rules'}->no_visits($netloc) || 0;
}
*host_count = \&no_visits; # backwards compatibility with LWP-5.02
sub host_wait
{
my($self, $netloc) = @_;
return undef unless defined $netloc;
my $last = $self->{'rules'}->last_visit($netloc);
if ($last) {
my $wait = int($self->{'delay'} * 60 - (time - $last));
$wait = 0 if $wait < 0;
return $wait;
}
return 0;
}
sub simple_request
{
my($self, $request, $arg, $size) = @_;
# Do we try to access a new server?
my $allowed = $self->{'rules'}->allowed($request->uri);
if ($allowed < 0) {
# Host is not visited before, or robots.txt expired; fetch "robots.txt"
my $robot_url = $request->uri->clone;
$robot_url->path("robots.txt");
$robot_url->query(undef);
# make access to robot.txt legal since this will be a recursive call
$self->{'rules'}->parse($robot_url, "");
my $robot_req = HTTP::Request->new('GET', $robot_url);
my $parse_head = $self->parse_head(0);
my $robot_res = $self->request($robot_req);
$self->parse_head($parse_head);
my $fresh_until = $robot_res->fresh_until;
my $content = "";
if ($robot_res->is_success && $robot_res->content_is_text) {
$content = $robot_res->decoded_content;
$content = "" unless $content && $content =~ /^\s*Disallow\s*:/mi;
}
$self->{'rules'}->parse($robot_url, $content, $fresh_until);
# recalculate allowed...
$allowed = $self->{'rules'}->allowed($request->uri);
}
# Check rules
unless ($allowed) {
my $res = HTTP::Response->new(
&HTTP::Status::RC_FORBIDDEN, 'Forbidden by robots.txt');
$res->request( $request ); # bind it to that request
return $res;
}
my $netloc = eval { local $SIG{__DIE__}; $request->uri->host_port; };
my $wait = $self->host_wait($netloc);
if ($wait) {
if ($self->{'use_sleep'}) {
sleep($wait)
}
else {
my $res = HTTP::Response->new(
&HTTP::Status::RC_SERVICE_UNAVAILABLE, 'Please, slow down');
$res->header('Retry-After', time2str(time + $wait));
$res->request( $request ); # bind it to that request
return $res;
}
}
# Perform the request
my $res = $self->SUPER::simple_request($request, $arg, $size);
$self->{'rules'}->visit($netloc);
$res;
}
sub as_string
{
my $self = shift;
my @s;
push(@s, "Robot: $self->{'agent'} operated by $self->{'from'} [$self]");
push(@s, " Minimum delay: " . int($self->{'delay'}*60) . "s");
push(@s, " Will sleep if too early") if $self->{'use_sleep'};
push(@s, " Rules = $self->{'rules'}");
join("\n", @s, '');
}
1;
__END__
=head1 NAME
LWP::RobotUA - a class for well-behaved Web robots
=head1 SYNOPSIS
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/...');
...
=head1 DESCRIPTION
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 F</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
<URL:http://www.robotstxt.org/>.
When you use a I<LWP::RobotUA> object as your user agent, then you do not
really have to think about these things yourself; C<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 I<LWP::UserAgent>
object (using C<< $ua->get(...) >>, C<< $ua->head(...) >>,
C<< $ua->request(...) >>, etc.), and this
special agent will make sure you are nice.
=head1 METHODS
The LWP::RobotUA is a sub-class of LWP::UserAgent and implements the
same methods. In addition the following methods are provided:
=over 4
=item $ua = LWP::RobotUA->new( %options )
=item $ua = LWP::RobotUA->new( $agent, $from )
=item $ua = LWP::RobotUA->new( $agent, $from, $rules )
The LWP::UserAgent options C<agent> and C<from> are mandatory. The
options C<delay>, C<use_sleep> and C<rules> initialize attributes
private to the RobotUA. If C<rules> are not provided, then
C<WWW::RobotRules> is instantiated providing an internal database of
F<robots.txt>.
It is also possible to just pass the value of C<agent>, C<from> and
optionally C<rules> as plain positional arguments.
=item $ua->delay
=item $ua->delay( $minutes )
Get/set the minimum delay between requests to the same server, in
I<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);
=item $ua->use_sleep
=item $ua->use_sleep( $boolean )
Get/set a value indicating whether the UA should sleep() 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 an Retry-After header that indicates when it is OK to
send another request to this server.
=item $ua->rules
=item $ua->rules( $rules )
Set/get which I<WWW::RobotRules> object to use.
=item $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. :-(
=item $ua->host_wait( $netloc )
Returns the number of I<seconds> (from now) you must wait before you can
make a new request to this host.
=item $ua->as_string
Returns a string that describes the state of the UA.
Mainly useful for debugging.
=back
=head1 SEE ALSO
L<LWP::UserAgent>, L<WWW::RobotRules>
=head1 COPYRIGHT
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.