#!/usr/bin/perl
package Fuse::DBI;
use 5.008;
use strict;
use warnings;
use POSIX qw(ENOENT EISDIR EINVAL ENOSYS O_RDWR);
use Fuse;
use DBI;
use Carp;
use Data::Dumper;
our $VERSION = '0.08';
# block size for this filesystem
use constant BLOCK => 1024;
=head1 NAME
Fuse::DBI - mount your database as filesystem and use it
=head1 SYNOPSIS
use Fuse::DBI;
Fuse::DBI->mount( ... );
See C<run> below for examples how to set parameters.
=head1 DESCRIPTION
This module will use C<Fuse> module, part of C<FUSE (Filesystem in USErspace)>
available at L<http://fuse.sourceforge.net/> to mount
your database as file system.
That will give you possibility to use normal file-system tools (cat, grep, vi)
to manipulate data in database.
It's actually opposite of Oracle's intention to put everything into database.
=head1 METHODS
=cut
=head2 mount
Mount your database as filesystem.
Let's suppose that your database have table C<files> with following structure:
id: int
filename: text
size: int
content: text
writable: boolean
Following is example how to mount table like that to C</mnt>:
my $mnt = Fuse::DBI->mount({
'filenames' => 'select id,filename,size,writable from files',
'read' => 'select content from files where id = ?',
'update' => 'update files set content = ? where id = ?',
'dsn' => 'DBI:Pg:dbname=test_db',
'user' => 'database_user',
'password' => 'database_password',
'invalidate' => sub { ... },
});
Options:
=over 5
=item filenames
SQL query which returns C<id> (unique id for that row), C<filename>,
C<size> and C<writable> boolean flag.
=item read
SQL query which returns only one column with content of file and has
placeholder C<?> for C<id>.
=item update
SQL query with two pace-holders, one for new content and one for C<id>.
=item dsn
C<DBI> dsn to connect to (contains database driver and name of database).
=item user
User with which to connect to database
=item password
Password for connecting to database
=item invalidate
Optional anonymous code reference which will be executed when data is updated in
database. It can be used as hook to delete cache (for example on-disk-cache)
which is created from data edited through C<Fuse::DBI>.
=item fork
Optional flag which forks after mount so that executing script will continue
running. Implementation is experimental.
=back
=cut
my $dbh;
my $sth;
my $ctime_start;
sub read_filenames;
sub fuse_module_loaded;
# evil, evil way to solve this. It makes this module non-reentrant. But, since
# fuse calls another copy of this script for each mount anyway, this shouldn't
# be a problem.
my $fuse_self;
sub mount {
my $class = shift;
my $self = {};
bless($self, $class);
my $arg = shift;
print Dumper($arg);
unless ($self->fuse_module_loaded) {
print STDERR "no fuse module loaded. Trying sudo modprobe fuse!\n";
system "sudo modprobe fuse" || die "can't modprobe fuse using sudo!\n";
}
carp "mount needs 'dsn' to connect to (e.g. dsn => 'DBI:Pg:dbname=test')" unless ($arg->{'dsn'});
carp "mount needs 'mount' as mountpoint" unless ($arg->{'mount'});
# save (some) arguments in self
foreach (qw(mount invalidate)) {
$self->{$_} = $arg->{$_};
}
foreach (qw(filenames read update)) {
carp "mount needs '$_' SQL" unless ($arg->{$_});
}
$ctime_start = time();
my $pid;
if ($arg->{'fork'}) {
$pid = fork();
die "fork() failed: $!" unless defined $pid;
# child will return to caller
if ($pid) {
my $counter = 4;
while ($counter && ! $self->is_mounted) {
select(undef, undef, undef, 0.5);
$counter--;
}
if ($self->is_mounted) {
return $self;
} else {
return undef;
}
}
}
$dbh = DBI->connect($arg->{'dsn'},$arg->{'user'},$arg->{'password'}, {AutoCommit => 0, RaiseError => 1}) || die $DBI::errstr;
$sth->{'filenames'} = $dbh->prepare($arg->{'filenames'}) || die $dbh->errstr();
$sth->{'read'} = $dbh->prepare($arg->{'read'}) || die $dbh->errstr();
$sth->{'update'} = $dbh->prepare($arg->{'update'}) || die $dbh->errstr();
$self->{'sth'} = $sth;
$self->{'read_filenames'} = sub { $self->read_filenames };
$self->read_filenames;
$fuse_self = \$self;
Fuse::main(
mountpoint=>$arg->{'mount'},
getattr=>\&e_getattr,
getdir=>\&e_getdir,
open=>\&e_open,
statfs=>\&e_statfs,
read=>\&e_read,
write=>\&e_write,
utime=>\&e_utime,
truncate=>\&e_truncate,
unlink=>\&e_unlink,
rmdir=>\&e_unlink,
debug=>0,
);
exit(0) if ($arg->{'fork'});
return 1;
};
=head2 is_mounted
Check if fuse filesystem is mounted
if ($mnt->is_mounted) { ... }
=cut
sub is_mounted {
my $self = shift;
my $mounted = 0;
my $mount = $self->{'mount'} || confess "can't find mount point!";
if (open(MTAB, "/etc/mtab")) {
while(<MTAB>) {
$mounted = 1 if (/ $mount fuse /i);
}
close(MTAB);
} else {
warn "can't open /etc/mtab: $!";
}
return $mounted;
}
=head2 umount
Unmount your database as filesystem.
$mnt->umount;
This will also kill background process which is translating
database to filesystem.
=cut
sub umount {
my $self = shift;
if ($self->{'mount'} && $self->is_mounted) {
system "( fusermount -u ".$self->{'mount'}." 2>&1 ) >/dev/null";
if ($self->is_mounted) {
system "sudo umount ".$self->{'mount'} ||
return 0;
}
return 1;
}
return 0;
}
$SIG{'INT'} = sub {
if ($fuse_self && $$fuse_self->umount) {
print STDERR "umount called by SIG INT\n";
}
};
$SIG{'QUIT'} = sub {
if ($fuse_self && $$fuse_self->umount) {
print STDERR "umount called by SIG QUIT\n";
}
};
sub DESTROY {
my $self = shift;
if ($self->umount) {
print STDERR "umount called by DESTROY\n";
}
}
=head2 fuse_module_loaded
Checks if C<fuse> module is loaded in kernel.
die "no fuse module loaded in kernel"
unless (Fuse::DBI::fuse_module_loaded);
This function in called by C<mount>, but might be useful alone also.
=cut
sub fuse_module_loaded {
my $lsmod = `lsmod`;
die "can't start lsmod: $!" unless ($lsmod);
if ($lsmod =~ m/fuse/s) {
return 1;
} else {
return 0;
}
}
my %files;
sub read_filenames {
my $self = shift;
my $sth = $self->{'sth'} || die "no sth argument";
# create empty filesystem
(%files) = (
'.' => {
type => 0040,
mode => 0755,
},
'..' => {
type => 0040,
mode => 0755,
},
# a => {
# cont => "File 'a'.\n",
# type => 0100,
# ctime => time()-2000
# },
);
# fetch new filename list from database
$sth->{'filenames'}->execute() || die $sth->{'filenames'}->errstr();
# read them in with sesible defaults
while (my $row = $sth->{'filenames'}->fetchrow_hashref() ) {
$row->{'filename'} ||= 'NULL-'.$row->{'id'};
$files{$row->{'filename'}} = {
size => $row->{'size'},
mode => $row->{'writable'} ? 0644 : 0444,
id => $row->{'id'} || 99,
};
my $d;
foreach (split(m!/!, $row->{'filename'})) {
# first, entry is assumed to be file
if ($d) {
$files{$d} = {
mode => 0755,
type => 0040
};
$files{$d.'/.'} = {
mode => 0755,
type => 0040
};
$files{$d.'/..'} = {
mode => 0755,
type => 0040
};
}
$d .= "/" if ($d);
$d .= "$_";
}
}
print "found ",scalar(keys %files)," files\n";
}
sub filename_fixup {
my ($file) = shift;
$file =~ s,^/,,;
$file = '.' unless length($file);
return $file;
}
sub e_getattr {
my ($file) = filename_fixup(shift);
$file =~ s,^/,,;
$file = '.' unless length($file);
return -ENOENT() unless exists($files{$file});
my ($size) = $files{$file}{size} || 0;
my ($dev, $ino, $rdev, $blocks, $gid, $uid, $nlink, $blksize) = (0,0,0,int(($size+BLOCK-1)/BLOCK),0,0,1,BLOCK);
my ($atime, $ctime, $mtime);
$atime = $ctime = $mtime = $files{$file}{ctime} || $ctime_start;
my ($modes) = (($files{$file}{type} || 0100)<<9) + $files{$file}{mode};
# 2 possible types of return values:
#return -ENOENT(); # or any other error you care to
#print "getattr($file) ",join(",",($dev,$ino,$modes,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks)),"\n";
return ($dev,$ino,$modes,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks);
}
sub e_getdir {
my ($dirname) = shift;
$dirname =~ s!^/!!;
# return as many text filenames as you like, followed by the retval.
print((scalar keys %files)." files total\n");
my %out;
foreach my $f (sort keys %files) {
if ($dirname) {
if ($f =~ s/^\Q$dirname\E\///) {
$out{$f}++ if ($f =~ /^[^\/]+$/);
}
} else {
$out{$f}++ if ($f =~ /^[^\/]+$/);
}
}
if (! %out) {
$out{'no files? bug?'}++;
}
print scalar keys %out," files in dir '$dirname'\n";
print "## ",join(" ",keys %out),"\n";
return (keys %out),0;
}
sub read_content {
my ($file,$id) = @_;
die "read_content needs file and id" unless ($file && $id);
$sth->{'read'}->execute($id) || die $sth->{'read'}->errstr;
$files{$file}{cont} = $sth->{'read'}->fetchrow_array;
# I should modify ctime only if content in database changed
#$files{$file}{ctime} = time() unless ($files{$file}{ctime});
print "file '$file' content [",length($files{$file}{cont})," bytes] read in cache\n";
}
sub e_open {
# VFS sanity check; it keeps all the necessary state, not much to do here.
my $file = filename_fixup(shift);
my $flags = shift;
return -ENOENT() unless exists($files{$file});
return -EISDIR() unless exists($files{$file}{id});
read_content($file,$files{$file}{id}) unless exists($files{$file}{cont});
$files{$file}{cont} ||= '';
print "open '$file' ",length($files{$file}{cont})," bytes\n";
return 0;
}
sub e_read {
# return an error numeric, or binary/text string.
# (note: 0 means EOF, "0" will give a byte (ascii "0")
# to the reading program)
my ($file) = filename_fixup(shift);
my ($buf_len,$off) = @_;
return -ENOENT() unless exists($files{$file});
my $len = length($files{$file}{cont});
print "read '$file' [$len bytes] offset $off length $buf_len\n";
return -EINVAL() if ($off > $len);
return 0 if ($off == $len);
$buf_len = $len-$off if ($len - $off < $buf_len);
return substr($files{$file}{cont},$off,$buf_len);
}
sub clear_cont {
print "transaction rollback\n";
$dbh->rollback || die $dbh->errstr;
print "invalidate all cached content\n";
foreach my $f (keys %files) {
delete $files{$f}{cont};
delete $files{$f}{ctime};
}
print "begin new transaction\n";
#$dbh->begin_work || die $dbh->errstr;
}
sub update_db {
my $file = shift || die;
$files{$file}{ctime} = time();
my ($cont,$id) = (
$files{$file}{cont},
$files{$file}{id}
);
if (!$sth->{'update'}->execute($cont,$id)) {
print "update problem: ",$sth->{'update'}->errstr;
clear_cont;
return 0;
} else {
if (! $dbh->commit) {
print "ERROR: commit problem: ",$sth->{'update'}->errstr;
clear_cont;
return 0;
}
print "updated '$file' [",$files{$file}{id},"]\n";
$$fuse_self->{'invalidate'}->() if (ref $$fuse_self->{'invalidate'});
}
return 1;
}
sub e_write {
my $file = filename_fixup(shift);
my ($buffer,$off) = @_;
return -ENOENT() unless exists($files{$file});
my $cont = $files{$file}{cont};
my $len = length($cont);
print "write '$file' [$len bytes] offset $off length ",length($buffer),"\n";
$files{$file}{cont} = "";
$files{$file}{cont} .= substr($cont,0,$off) if ($off > 0);
$files{$file}{cont} .= $buffer;
$files{$file}{cont} .= substr($cont,$off+length($buffer),$len-$off-length($buffer)) if ($off+length($buffer) < $len);
$files{$file}{size} = length($files{$file}{cont});
if (! update_db($file)) {
return -ENOSYS();
} else {
return length($buffer);
}
}
sub e_truncate {
my $file = filename_fixup(shift);
my $size = shift;
print "truncate to $size\n";
$files{$file}{cont} = substr($files{$file}{cont},0,$size);
$files{$file}{size} = $size;
return 0
};
sub e_utime {
my ($atime,$mtime,$file) = @_;
$file = filename_fixup($file);
return -ENOENT() unless exists($files{$file});
print "utime '$file' $atime $mtime\n";
$files{$file}{time} = $mtime;
return 0;
}
sub e_statfs {
my $size = 0;
my $inodes = 0;
foreach my $f (keys %files) {
if ($f !~ /(^|\/)\.\.?$/) {
$size += $files{$f}{size} || 0;
$inodes++;
}
print "$inodes: $f [$size]\n";
}
$size = int(($size+BLOCK-1)/BLOCK);
my @ret = (255, $inodes, 1, $size, $size-1, BLOCK);
#print "statfs: ",join(",",@ret),"\n";
return @ret;
}
sub e_unlink {
my $file = filename_fixup(shift);
# if (exists( $dirs{$file} )) {
# print "unlink '$file' will re-read template names\n";
# print Dumper($fuse_self);
# $$fuse_self->{'read_filenames'}->();
# return 0;
if (exists( $files{$file} )) {
print "unlink '$file' will invalidate cache\n";
read_content($file,$files{$file}{id});
return 0;
}
return -ENOENT();
}
1;
__END__
=head1 EXPORT
Nothing.
=head1 BUGS
Size information (C<ls -s>) is wrong. It's a problem in upstream Fuse module
(for which I'm to blame lately), so when it gets fixes, C<Fuse::DBI> will
automagically pick it up.
=head1 SEE ALSO
C<FUSE (Filesystem in USErspace)> website
L<http://fuse.sourceforge.net/>
Example for WebGUI which comes with this distribution in
directory C<examples/webgui.pl>. It also contains a lot of documentation
about design of this module, usage and limitations.
=head1 AUTHOR
Dobrica Pavlinusic, E<lt>dpavlin@rot13.orgE<gt>
=head1 COPYRIGHT AND LICENSE
Copyright (C) 2004 by Dobrica Pavlinusic
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.8.4 or,
at your option, any later version of Perl 5 you may have available.
=cut