Coro/Coro/Storable.pm

=head1 NAME

Coro::Storable - offer a more fine-grained Storable interface

=head1 SYNOPSIS

 use Coro::Storable;

=head1 DESCRIPTION

This module implements a few functions from the Storable module in a way
so that it cede's more often. Some applications (such as the Deliantra
game server) sometimes need to load large Storable objects without
blocking the server for a long time.

This is being implemented by using a perlio layer that feeds only small
amounts of data (512 bytes per call) into Storable, and C<Coro::cede>'ing
regularly (at most 100 times per second by default, though).

As it seems that Storable is not reentrant, this module also wraps most
functions of the Storable module so that only one freeze or thaw is done
at any one moment (recursive invocations are not currently supported).

=head1 FUNCTIONS

=over 4

=item $ref = thaw $pst

Retrieve an object from the given $pst, which must have been created with
C<Coro::Storable::freeze> or C<Storable::store_fd>/C<Storable::store>
(sorry, but Storable uses incompatible formats for disk/mem objects).

This works by calling C<Coro::cede> for every 4096 bytes read in.

=item $pst = freeze $ref

Freeze the given scalar into a Storable object. It uses the same format as
C<Storable::store_fd>.

This works by calling C<Coro::cede> for every write that Storable
issues. Unfortunately, Storable often makes many very small writes, so it
is rather inefficient. But it does keep the latency low.

=item $pst = nfreeze $ref

Same as C<freeze> but is compatible to C<Storable::nstore_fd> (note the
C<n>).

=item $pst = blocking_freeze $ref

Same as C<freeze> but is guaranteed to block. This is useful e.g. in
C<Coro::Util::fork_eval> when you want to serialise a data structure
for use with the C<thaw> function for this module. You cannot use
C<Storable::freeze> for this as Storable uses incompatible formats for
memory and file images.

=item $pst = blocking_nfreeze $ref

Same as C<blocking_freeze> but uses C<nfreeze> internally.

=item $guard = guard

Acquire the Storable lock, for when you want to call Storable yourself.

Note that this module already wraps the Storable functions, so there is
rarely the need to do this yourself.

=back

=cut

package Coro::Storable;

use strict qw(subs vars);
no warnings;

use Coro ();
use Coro::Semaphore ();

BEGIN {
   # suppress warnings
   local $^W = 0;
   require Storable;
}

use Storable;
use base "Exporter";

our $VERSION = 4.746;
our @EXPORT = qw(thaw freeze nfreeze blocking_thaw blocking_freeze blocking_nfreeze);

my $lock = new Coro::Semaphore;

sub guard {
   $lock->guard
}

# wrap xs functions
for (qw(net_pstore mstore net_mstore pretrieve mretrieve dclone)) {
   my $orig = \&{"Storable::$_"};
   *{"Storable::$_"} = sub {
      my $guard = $lock->guard;
      &$orig
   };
   die if $@;
}

sub thaw($) {
   open my $fh, "<:via(CoroCede)", \$_[0]
      or die "cannot open pst via CoroCede: $!";
   Storable::fd_retrieve $fh
}

sub freeze($) {
   open my $fh, ">:via(CoroCede)", \my $buf
      or die "cannot open pst via CoroCede: $!";
   Storable::store_fd $_[0], $fh;
   $buf
}

sub nfreeze($) {
   open my $fh, ">:via(CoroCede)", \my $buf
      or die "cannot open pst via CoroCede: $!";
   Storable::nstore_fd $_[0], $fh;
   $buf
}

sub blocking_thaw($) {
   open my $fh, "<", \$_[0]
      or die "cannot open pst: $!";
   Storable::fd_retrieve $fh
}

sub blocking_freeze($) {
   open my $fh, ">", \my $buf
         or die "cannot open pst: $!";
   Storable::store_fd $_[0], $fh;
   close $fh;

   $buf
}

sub blocking_nfreeze($) {
   open my $fh, ">", \my $buf
         or die "cannot open pst: $!";
   Storable::nstore_fd $_[0], $fh;
   close $fh;

   $buf
}

package PerlIO::via::CoroCede;

# generic cede-on-read/write filtering layer

use Time::HiRes ("time");

our $GRANULARITY = 0.01;

my $next_cede;

sub PUSHED {
   __PACKAGE__
}

sub FILL {
   if ($next_cede <= time) {
      $next_cede = time + $GRANULARITY; # calling time() twice usually is a net win
      Coro::cede ();
   }

   read $_[1], my $buf, 512
      or return undef;

   $buf
}

sub WRITE {
   if ($next_cede <= time) {
      $next_cede = time + $GRANULARITY;
      Coro::cede ();
   }

   (print {$_[2]} $_[1]) ? length $_[1] : -1
}

1;

=head1 AUTHOR

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

=cut


Revision:	1.23
Committed:	Sun Sep 21 01:23:26 2008 UTC (15 years, 8 months ago) by root
Branch:	MAIN
CVS Tags:	rel-4_746
Changes since 1.22:	+1 -1 lines
Log Message:	4.746
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			Coro::Storable - offer a more fine-grained Storable interface
4
5			=head1 SYNOPSIS
6
7			use Coro::Storable;
8
9			=head1 DESCRIPTION
10
11			This module implements a few functions from the Storable module in a way
12	root	1.22	so that it cede's more often. Some applications (such as the Deliantra
13	root	1.1	game server) sometimes need to load large Storable objects without
14			blocking the server for a long time.
15
16	root	1.6	This is being implemented by using a perlio layer that feeds only small
17			amounts of data (512 bytes per call) into Storable, and C<Coro::cede>'ing
18	root	1.21	regularly (at most 100 times per second by default, though).
19	root	1.6
20	root	1.22	As it seems that Storable is not reentrant, this module also wraps most
21			functions of the Storable module so that only one freeze or thaw is done
22			at any one moment (recursive invocations are not currently supported).
23	root	1.2
24	root	1.1	=head1 FUNCTIONS
25
26			=over 4
27
28			=item $ref = thaw $pst
29
30			Retrieve an object from the given $pst, which must have been created with
31			C<Coro::Storable::freeze> or C<Storable::store_fd>/C<Storable::store>
32			(sorry, but Storable uses incompatible formats for disk/mem objects).
33
34	root	1.4	This works by calling C<Coro::cede> for every 4096 bytes read in.
35	root	1.1
36			=item $pst = freeze $ref
37
38			Freeze the given scalar into a Storable object. It uses the same format as
39	root	1.6	C<Storable::store_fd>.
40	root	1.1
41			This works by calling C<Coro::cede> for every write that Storable
42			issues. Unfortunately, Storable often makes many very small writes, so it
43			is rather inefficient. But it does keep the latency low.
44
45	root	1.6	=item $pst = nfreeze $ref
46
47	root	1.7	Same as C<freeze> but is compatible to C<Storable::nstore_fd> (note the
48	root	1.6	C<n>).
49
50			=item $pst = blocking_freeze $ref
51
52			Same as C<freeze> but is guaranteed to block. This is useful e.g. in
53			C<Coro::Util::fork_eval> when you want to serialise a data structure
54			for use with the C<thaw> function for this module. You cannot use
55	root	1.7	C<Storable::freeze> for this as Storable uses incompatible formats for
56	root	1.6	memory and file images.
57
58			=item $pst = blocking_nfreeze $ref
59
60			Same as C<blocking_freeze> but uses C<nfreeze> internally.
61
62	root	1.22	=item $guard = guard
63	root	1.8
64			Acquire the Storable lock, for when you want to call Storable yourself.
65
66	root	1.22	Note that this module already wraps the Storable functions, so there is
67			rarely the need to do this yourself.
68
69	root	1.1	=back
70
71			=cut
72
73			package Coro::Storable;
74
75	root	1.22	use strict qw(subs vars);
76	root	1.13	no warnings;
77	root	1.1
78			use Coro ();
79	root	1.2	use Coro::Semaphore ();
80	root	1.1
81	root	1.13	BEGIN {
82			# suppress warnings
83			local $^W = 0;
84			require Storable;
85			}
86
87	root	1.1	use Storable;
88			use base "Exporter";
89
90	root	1.23	our $VERSION = 4.746;
91	root	1.9	our @EXPORT = qw(thaw freeze nfreeze blocking_thaw blocking_freeze blocking_nfreeze);
92	root	1.1
93	root	1.2	my $lock = new Coro::Semaphore;
94
95	root	1.8	sub guard {
96			$lock->guard
97			}
98
99	root	1.22	# wrap xs functions
100			for (qw(net_pstore mstore net_mstore pretrieve mretrieve dclone)) {
101			my $orig = \&{"Storable::$_"};
102			*{"Storable::$_"} = sub {
103			my $guard = $lock->guard;
104			&$orig
105			};
106			die if $@;
107			}
108
109	root	1.6	sub thaw($) {
110			open my $fh, "<:via(CoroCede)", \$_[0]
111			or die "cannot open pst via CoroCede: $!";
112			Storable::fd_retrieve $fh
113			}
114
115	root	1.1	sub freeze($) {
116			open my $fh, ">:via(CoroCede)", \my $buf
117			or die "cannot open pst via CoroCede: $!";
118	root	1.6	Storable::store_fd $_[0], $fh;
119	root	1.1	$buf
120			}
121
122	root	1.6	sub nfreeze($) {
123			open my $fh, ">:via(CoroCede)", \my $buf
124	root	1.1	or die "cannot open pst via CoroCede: $!";
125	root	1.6	Storable::nstore_fd $_[0], $fh;
126			$buf
127			}
128
129	root	1.10	sub blocking_thaw($) {
130	root	1.9	open my $fh, "<", \$_[0]
131			or die "cannot open pst: $!";
132			Storable::fd_retrieve $fh
133			}
134
135	root	1.10	sub blocking_freeze($) {
136	root	1.6	open my $fh, ">", \my $buf
137			or die "cannot open pst: $!";
138			Storable::store_fd $_[0], $fh;
139			close $fh;
140
141			$buf
142			}
143
144	root	1.10	sub blocking_nfreeze($) {
145	root	1.6	open my $fh, ">", \my $buf
146			or die "cannot open pst: $!";
147			Storable::nstore_fd $_[0], $fh;
148			close $fh;
149
150			$buf
151	root	1.1	}
152
153			package PerlIO::via::CoroCede;
154
155			# generic cede-on-read/write filtering layer
156
157	root	1.6	use Time::HiRes ("time");
158
159	root	1.21	our $GRANULARITY = 0.01;
160	root	1.6
161			my $next_cede;
162
163	root	1.1	sub PUSHED {
164			__PACKAGE__
165			}
166
167			sub FILL {
168	root	1.6	if ($next_cede <= time) {
169			$next_cede = time + $GRANULARITY; # calling time() twice usually is a net win
170	root	1.16	Coro::cede ();
171	root	1.6	}
172
173	root	1.5	read $_[1], my $buf, 512
174	root	1.3	or return undef;
175	root	1.6
176	root	1.1	$buf
177			}
178
179			sub WRITE {
180	root	1.21	if ($next_cede <= time) {
181			$next_cede = time + $GRANULARITY;
182	root	1.20	Coro::cede ();
183	root	1.6	}
184
185	root	1.1	(print {$_[2]} $_[1]) ? length $_[1] : -1
186			}
187
188			1;
189
190			=head1 AUTHOR
191
192			Marc Lehmann <schmorp@schmorp.de>
193			http://home.schmorp.de/
194
195			=cut
196
197