package Brackup::DigestCache;
use strict;
use warnings;
sub new {
my ($class, $root, $rconf) = @_;
my $self = bless {}, $class;
my $file = $rconf->value('digestdb_file') ||
($root->path . '/' . default_filename());
my $type = $rconf->value('digestdb_type') || 'SQLite';
my $dict_class = "Brackup::Dict::$type";
eval "require $dict_class";
$self->{dict} = $dict_class->new(
table => "digest_cache",
file => $file,
);
return $self;
}
sub default_filename { ".brackup-digest.db" };
# proxy through to underlying dictionary
sub get { shift->{dict}->get(@_) }
sub set { shift->{dict}->set(@_) }
sub each { shift->{dict}->each(@_) }
sub delete { shift->{dict}->delete(@_) }
sub count { shift->{dict}->count(@_) }
sub backing_file { shift->{dict}->backing_file(@_) }
1;
__END__
=head1 NAME
Brackup::DigestCache - cache digests of file and chunk contents
=head1 DESCRIPTION
The brackup DigestCache caches the digests (currently SHA1) of files
and file chunks, to prevent untouched files from needing to be re-read
on subsequent, iterative backups.
The digest cache is I<purely> a cache. It has no critical data in it,
so if you lose it, subsequent backups will just take longer while the
digest cache is re-built.
Note that you don't need the digest cache to do a restore.
=head1 DETAILS
=head2 Storage type
The digest cache makes use of Dictionary modules (Brackup::Dict::*) to
handle the storage of the cache. The default dictionary used is
L<Brackup::Dict::SQLite>, which stores the cache as an SQLite database
in a single file. The schema is created automatically as needed... no
database maintenance is required.
The dictionary type can be specified in the [SOURCE] declaration in
your brackup.conf file, using the 'digestdb_type' property e.g.:
[SOURCE:home]
path = /home/bradfitz/
# specify the lighter/slower Brackup::Dict::SQLite2 instead of the default
digestdb_type = SQLite2
=head2 File location
The cache database file is stored in either the location specified in
a L<Brackup::Root>'s [SOURCE] declaration in ~/.brackup.conf, as:
[SOURCE:home]
path = /home/bradfitz/
# be explicit if you want:
digestdb_file = /var/cache/brackup-brad/digest-cache-bradhome.db
Or, more commonly (and recommended), is to not specify it and accept
the default location, which is ".brackup-digest.db" in the root's
root directory.
[SOURCE:home]
path = /home/bradfitz/
# this is the default:
# digestdb_file = /home/bradfitz/.brackup-digest.db
=head2 Keys & Values stored in the cache
B<Files digests keys> (see L<Brackup::File>)
[rootname]path/to/file.txt:<ctime>,<mtime>,<size>,<inodenum>
B<Chunk digests keys> (see L<Brackup::PositionedChunk>)
[rootname]path/to/file.txt:<ctime>,<mtime>,<size>,<inodenum>;o=<offset>;l=<length>
B<Values>
In both cases, the values are the digest of the chunk/file, in form:
sha1:e23c4b5f685e046e7cc50e30e378ab11391e528e
=head1 SEE ALSO
L<brackup>
L<Brackup>
L<Brackup::Dict::SQLite>
L<Brackup::Dict::SQLite2>