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.