Skip to content

Embed URL

HTTPS clone URL

Subversion checkout URL

You can clone with
or
.
Download ZIP
Simple web crawler/scraper implemented using Mojolicious
#!/usr/bin/env perl
use 5.010;
use open qw(:locale);
use strict;
use utf8;
use warnings qw(all);
use Mojo::UserAgent;
# FIFO queue
my @urls = map { Mojo::URL->new($_) } qw(
http://sysd.org/page/1/
http://sysd.org/page/2/
http://sysd.org/page/3/
);
# Limit parallel connections to 4
my $max_conn = 4;
# User agent following up to 5 redirects
my $ua = Mojo::UserAgent->new(max_redirects => 5);
$ua->proxy->detect;
# Keep track of active connections
my $active = 0;
Mojo::IOLoop->recurring(
0 => sub {
for ($active + 1 .. $max_conn) {
# Dequeue or halt if there are no active crawlers anymore
return ($active or Mojo::IOLoop->stop)
unless my $url = shift @urls;
# Fetch non-blocking just by adding
# a callback and marking as active
++$active;
$ua->get($url => \&get_callback);
}
}
);
# Start event loop if necessary
Mojo::IOLoop->start unless Mojo::IOLoop->is_running;
sub get_callback {
my (undef, $tx) = @_;
# Deactivate
--$active;
# Parse only OK HTML responses
return
if not $tx->res->is_status_class(200)
or $tx->res->headers->content_type !~ m{^text/html\b}ix;
# Request URL
my $url = $tx->req->url;
say $url;
parse_html($url, $tx);
return;
}
sub parse_html {
my ($url, $tx) = @_;
say $tx->res->dom->at('html title')->text;
# Extract and enqueue URLs
for my $e ($tx->res->dom('a[href]')->each) {
# Validate href attribute
my $link = Mojo::URL->new($e->{href});
next if 'Mojo::URL' ne ref $link;
# "normalize" link
$link = $link->to_abs($tx->req->url)->fragment(undef);
next unless grep { $link->protocol eq $_ } qw(http https);
# Don't go deeper than /a/b/c
next if @{$link->path->parts} > 3;
# Access every link only once
state $uniq = {};
++$uniq->{$url->to_string};
next if ++$uniq->{$link->to_string} > 1;
# Don't visit other hosts
next if $link->host ne $url->host;
push @urls, $link;
say " -> $link";
}
say '';
return;
}
__DATA__
Featured at:
http://blogs.perl.org/users/stas/2013/01/web-scraping-with-modern-perl-part-1.html
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Something went wrong with that request. Please try again.