NAME
AnyEvent::Net::Curl::Queued - Any::Moose wrapper for queued downloads via Net::Curl & AnyEvent
VERSION
version 0.017
SYNOPSIS
#!/usr/bin/env perl
package CrawlApache;
use common::sense;
use HTML::LinkExtor;
use Any::Moose;
extends 'AnyEvent::Net::Curl::Queued::Easy';
after finish => sub {
my ($self, $result) = @_;
say $result . "\t" . $self->final_url;
if (
not $self->has_error
and $self->getinfo('content_type') =~ m{^text/html}
) {
my @links;
HTML::LinkExtor->new(sub {
my ($tag, %links) = @_;
push @links,
grep { $_->scheme eq 'http' and $_->host eq 'localhost' }
values %links;
}, $self->final_url)->parse(${$self->data});
for my $link (@links) {
$self->queue->prepend(sub {
CrawlApache->new({ initial_url => $link });
});
}
}
};
no Any::Moose;
__PACKAGE__->meta->make_immutable;
1;
package main;
use common::sense;
use AnyEvent::Net::Curl::Queued;
my $q = AnyEvent::Net::Curl::Queued->new;
$q->append(sub {
CrawlApache->new({ initial_url => 'http://localhost/manual/' })
});
$q->wait;
DESCRIPTION
Efficient and flexible batch downloader with a straight-forward interface:
create a queue;
append/prepend URLs;
wait for downloads to end (retry on errors).
Download init/finish/error handling is defined through Moose's method modifiers.
MOTIVATION
I am very unhappy with the performance of LWP. It's almost perfect for properly handling HTTP headers, cookies & stuff, but it comes at the cost of speed. While this doesn't matter when you make single downloads, batch downloading becomes a real pain.
When I download large batch of documents, I don't care about cookies or headers, only content and proper redirection matters. And, as it is clearly an I/O bottleneck operation, I want to make as many parallel requests as possible.
So, this is what CPAN offers to fulfill my needs:
Net::Curl: Perl interface to the all-mighty libcurl, is well-documented (opposite to WWW::Curl);
AnyEvent: the DBI of event loops. Net::Curl also provides a nice and well-documented example of AnyEvent usage (03-multi-event.pl);
MooseX::NonMoose: Net::Curl uses a Pure-Perl object implementation, which is lightweight, but a bit messy for my Moose-based projects. MooseX::NonMoose patches this gap.
AnyEvent::Net::Curl::Queued is a glue module to wrap it all together. It offers no callbacks and (almost) no default handlers. It's up to you to extend the base class AnyEvent::Net::Curl::Queued::Easy so it will actually download something and store it somewhere.
ATTRIBUTES
allow_dups
Allow duplicate requests (default: false). By default, requests to the same URL (more precisely, requests with the same signature are issued only once. To seed POST parameters, you must extend the AnyEvent::Net::Curl::Queued::Easy class. Setting allow_dups
to true value disables request checks.
completed
Count completed requests.
cv
AnyEvent condition variable. Initialized automatically, unless you specify your own. Also reset automatically after "wait", so keep your own reference if you really need it!
max
Maximum number of parallel connections (default: 4; minimum value: 1).
multi
Net::Curl::Multi instance.
queue
ArrayRef
to the queue. Has the following helper methods:
queue_push: append item at the end of the queue;
queue_unshift: prepend item at the top of the queue;
dequeue: shift item from the top of the queue;
count: number of items in queue.
share
Net::Curl::Share instance.
stats
AnyEvent::Net::Curl::Queued::Stats instance.
timeout
Timeout (default: 60 seconds).
unique
Signature cache.
watchdog
The last resort against the non-deterministic chaos of evil lurking sockets.
METHODS
start()
Populate empty request slots with workers from the queue.
empty()
Check if there are active requests or requests in queue.
add($worker)
Activate a worker.
append($worker)
Put the worker (instance of AnyEvent::Net::Curl::Queued::Easy) at the end of the queue. For lazy initialization, wrap the worker in a sub { ... }
, the same way you do with the Moose default => sub { ... }
:
$queue->append(sub {
AnyEvent::Net::Curl::Queued::Easy->new({ initial_url => 'http://.../' })
});
prepend($worker)
Put the worker (instance of AnyEvent::Net::Curl::Queued::Easy) at the beginning of the queue. For lazy initialization, wrap the worker in a sub { ... }
, the same way you do with the Moose default => sub { ... }
:
$queue->prepend(sub {
AnyEvent::Net::Curl::Queued::Easy->new({ initial_url => 'http://.../' })
});
wait()
Process queue.
CAVEAT
The "Attempt to free unreferenced scalar: SV 0xdeadbeef during global destruction." message on finalization is mostly harmless.
SEE ALSO
AUTHOR
Stanislaw Pusep <stas@sysd.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2012 by Stanislaw Pusep.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.