Coro/Coro/LWP.pm

=head1 NAME

Coro::LWP - make LWP non-blocking - as much as possible

=head1 SYNOPSIS

 use Coro::LWP; # afterwards LWP should not block

=head1 DESCRIPTION

This module is an L<AnyEvent> user, you need to make sure that you use and
run a supported event loop.

This module tries to make L<LWP|LWP> non-blocking with respect to other
coroutines as much as possible, and with whatever means it takes.

LWP really tries very hard to be blocking (and relies on a lot of
undocumented functionality in IO::Socket), so this module had to be very
invasive and must be loaded very early to take the proper effect.

Note that the module L<AnyEvent::HTTP> might offer an alternative to the
full L<LWP> that is designed to be non-blocking.

Here is what it currently does (future versions of LWP might require
different tricks):

=over 4

=item It loads Coro::Select, overwriting the perl C<select> builtin I<globally>.

This is necessary because LWP calls select quite often for timeouts and
who-knows-what.

Impact: everybody else uses this (slower) version of select, too. It should be quite
compatible to perls builtin select, though.

=item It overwrites Socket::inet_aton with Coro::Util::inet_aton.

This is necessary because LWP might (and does) try to resolve hostnames
this way.

Impact: some code might not expect coroutine semantics, for example, when
you fork you might prefer the blocking variant because other coroutines
shouldn't actually run.

=item It replaces the base class of Net::HTTP, Net::FTP, Net::NNTP.

This is necessary because LWP does not always use select to see whether
a filehandle can be read/written without blocking, so the base class
C<IO::Socket::INET> needs to be replaced by C<Coro::Socket>.

Impact: Coro::Socket is not at all compatible to IO::Socket::INET. While
it duplicates some undocumented functionality required by LWP, it does not
have all the methods of IO::Socket::INET and might act quite differently
in practise. Also, protocols other than the above mentioned will still block,
at least some of the time.

=back

All this likely makes other libraries than just LWP not block, but thats
just a side effect you cannot rely on.

Increases parallelism is not supported by all libraries, some might cache
data globally.

=cut

package Coro::LWP;

use common::sense;

BEGIN {
   # suppress warnings
   local $^W = 0;
   require Net::Config;
}

# do it as early as possible
use Coro::Select;

# import these so they can grab Socket::inet_aton
use AnyEvent::Util ();
use AnyEvent::DNS ();

use Coro::Util ();
use Coro::Socket ();
use Coro::AnyEvent ();

use Socket ();

use IO::Socket::INET ();

use Net::HTTP ();
use Net::FTP ();
use Net::NNTP ();

our $VERSION = 5.2;

*Socket::inet_aton = \&Coro::Util::inet_aton;

for (@Net::HTTP::ISA, @Net::FTP::ISA, @Net::NTTP::ISA) {
   $_ = Coro::LWP::Socket:: if $_ eq IO::Socket::INET::;
}

package Coro::LWP::Socket;

no warnings;

use base Coro::Socket::;

sub new {
   my $self = shift;

   $self->SUPER::new (@_, partial => 1)
}

1;

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut


Revision:	1.47
Committed:	Fri Oct 2 19:55:59 2009 UTC (14 years, 8 months ago) by root
Branch:	MAIN
CVS Tags:	rel-5_2
Changes since 1.46:	+1 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			Coro::LWP - make LWP non-blocking - as much as possible
4
5			=head1 SYNOPSIS
6
7			use Coro::LWP; # afterwards LWP should not block
8
9			=head1 DESCRIPTION
10
11	root	1.6	This module is an L<AnyEvent> user, you need to make sure that you use and
12			run a supported event loop.
13
14	root	1.1	This module tries to make L<LWP\|LWP> non-blocking with respect to other
15			coroutines as much as possible, and with whatever means it takes.
16
17	root	1.7	LWP really tries very hard to be blocking (and relies on a lot of
18			undocumented functionality in IO::Socket), so this module had to be very
19	root	1.1	invasive and must be loaded very early to take the proper effect.
20
21	root	1.32	Note that the module L<AnyEvent::HTTP> might offer an alternative to the
22			full L<LWP> that is designed to be non-blocking.
23
24	root	1.1	Here is what it currently does (future versions of LWP might require
25			different tricks):
26
27			=over 4
28
29			=item It loads Coro::Select, overwriting the perl C<select> builtin I<globally>.
30
31			This is necessary because LWP calls select quite often for timeouts and
32			who-knows-what.
33
34			Impact: everybody else uses this (slower) version of select, too. It should be quite
35			compatible to perls builtin select, though.
36
37			=item It overwrites Socket::inet_aton with Coro::Util::inet_aton.
38
39	root	1.2	This is necessary because LWP might (and does) try to resolve hostnames
40			this way.
41	root	1.1
42	root	1.8	Impact: some code might not expect coroutine semantics, for example, when
43			you fork you might prefer the blocking variant because other coroutines
44			shouldn't actually run.
45	root	1.1
46	root	1.2	=item It replaces the base class of Net::HTTP, Net::FTP, Net::NNTP.
47	root	1.1
48	root	1.18	This is necessary because LWP does not always use select to see whether
49	root	1.2	a filehandle can be read/written without blocking, so the base class
50			C<IO::Socket::INET> needs to be replaced by C<Coro::Socket>.
51	root	1.1
52			Impact: Coro::Socket is not at all compatible to IO::Socket::INET. While
53			it duplicates some undocumented functionality required by LWP, it does not
54			have all the methods of IO::Socket::INET and might act quite differently
55	root	1.2	in practise. Also, protocols other than the above mentioned will still block,
56			at least some of the time.
57	root	1.1
58			=back
59
60			All this likely makes other libraries than just LWP not block, but thats
61			just a side effect you cannot rely on.
62
63			Increases parallelism is not supported by all libraries, some might cache
64			data globally.
65
66			=cut
67
68			package Coro::LWP;
69
70	root	1.46	use common::sense;
71	root	1.11
72			BEGIN {
73			# suppress warnings
74			local $^W = 0;
75			require Net::Config;
76			}
77	root	1.1
78	root	1.33	# do it as early as possible
79			use Coro::Select;
80
81			# import these so they can grab Socket::inet_aton
82	root	1.9	use AnyEvent::Util ();
83			use AnyEvent::DNS ();
84
85	root	1.8	use Coro::Util ();
86			use Coro::Socket ();
87	root	1.39	use Coro::AnyEvent ();
88	root	1.8
89			use Socket ();
90	root	1.11
91	root	1.8	use IO::Socket::INET ();
92
93			use Net::HTTP ();
94			use Net::FTP ();
95			use Net::NNTP ();
96	root	1.2
97	root	1.47	our $VERSION = 5.2;
98	root	1.3
99	root	1.1	*Socket::inet_aton = \&Coro::Util::inet_aton;
100
101	root	1.2	for (@Net::HTTP::ISA, @Net::FTP::ISA, @Net::NTTP::ISA) {
102			$_ = Coro::LWP::Socket:: if $_ eq IO::Socket::INET::;
103			}
104
105			package Coro::LWP::Socket;
106
107	root	1.11	no warnings;
108
109	root	1.2	use base Coro::Socket::;
110
111			sub new {
112			my $self = shift;
113
114			$self->SUPER::new (@_, partial => 1)
115			}
116
117			1;
118	root	1.1
119			=head1 AUTHOR
120
121			Marc Lehmann <schmorp@schmorp.de>
122			http://home.schmorp.de/
123
124			=cut
125
126