/[fuse_dbi]/fuse-couchdb/DBI.pm
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Annotation of /fuse-couchdb/DBI.pm

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Revision 54 - (hide annotations)
Tue Apr 26 19:57:51 2005 UTC (18 years, 11 months ago) by dpavlin
Original Path: trunk/DBI.pm
File size: 13485 byte(s)
better support for zero-sized files

1 dpavlin 1 #!/usr/bin/perl
2    
3 dpavlin 9 package Fuse::DBI;
4    
5     use 5.008;
6     use strict;
7     use warnings;
8    
9 dpavlin 7 use POSIX qw(ENOENT EISDIR EINVAL ENOSYS O_RDWR);
10 dpavlin 1 use Fuse;
11     use DBI;
12 dpavlin 11 use Carp;
13     use Data::Dumper;
14 dpavlin 1
15 dpavlin 47 our $VERSION = '0.07';
16 dpavlin 1
17 dpavlin 52 # block size for this filesystem
18     use constant BLOCK => 1024;
19    
20 dpavlin 9 =head1 NAME
21 dpavlin 1
22 dpavlin 9 Fuse::DBI - mount your database as filesystem and use it
23 dpavlin 1
24 dpavlin 9 =head1 SYNOPSIS
25 dpavlin 6
26 dpavlin 9 use Fuse::DBI;
27 dpavlin 11 Fuse::DBI->mount( ... );
28 dpavlin 1
29 dpavlin 28 See C<run> below for examples how to set parameters.
30 dpavlin 1
31 dpavlin 9 =head1 DESCRIPTION
32 dpavlin 1
33 dpavlin 23 This module will use C<Fuse> module, part of C<FUSE (Filesystem in USErspace)>
34 dpavlin 36 available at L<http://fuse.sourceforge.net/> to mount
35 dpavlin 9 your database as file system.
36 dpavlin 1
37 dpavlin 28 That will give you possibility to use normal file-system tools (cat, grep, vi)
38 dpavlin 9 to manipulate data in database.
39 dpavlin 1
40 dpavlin 9 It's actually opposite of Oracle's intention to put everything into database.
41 dpavlin 1
42    
43 dpavlin 9 =head1 METHODS
44    
45     =cut
46    
47 dpavlin 11 =head2 mount
48 dpavlin 9
49     Mount your database as filesystem.
50    
51 dpavlin 28 Let's suppose that your database have table C<files> with following structure:
52    
53     id: int
54     filename: text
55     size: int
56     content: text
57     writable: boolean
58    
59     Following is example how to mount table like that to C</mnt>:
60    
61 dpavlin 11 my $mnt = Fuse::DBI->mount({
62 dpavlin 28 'filenames' => 'select id,filename,size,writable from files',
63     'read' => 'select content from files where id = ?',
64     'update' => 'update files set content = ? where id = ?',
65     'dsn' => 'DBI:Pg:dbname=test_db',
66     'user' => 'database_user',
67     'password' => 'database_password',
68     'invalidate' => sub { ... },
69 dpavlin 9 });
70    
71 dpavlin 28 Options:
72    
73     =over 5
74    
75     =item filenames
76    
77     SQL query which returns C<id> (unique id for that row), C<filename>,
78     C<size> and C<writable> boolean flag.
79    
80     =item read
81    
82     SQL query which returns only one column with content of file and has
83     placeholder C<?> for C<id>.
84    
85     =item update
86    
87     SQL query with two pace-holders, one for new content and one for C<id>.
88    
89     =item dsn
90    
91     C<DBI> dsn to connect to (contains database driver and name of database).
92    
93     =item user
94    
95     User with which to connect to database
96    
97     =item password
98    
99     Password for connecting to database
100    
101     =item invalidate
102    
103     Optional anonymous code reference which will be executed when data is updated in
104     database. It can be used as hook to delete cache (for example on-disk-cache)
105     which is created from data edited through C<Fuse::DBI>.
106    
107     =item fork
108    
109     Optional flag which forks after mount so that executing script will continue
110     running. Implementation is experimental.
111    
112     =back
113    
114 dpavlin 9 =cut
115    
116     my $dbh;
117     my $sth;
118     my $ctime_start;
119    
120 dpavlin 11 sub read_filenames;
121 dpavlin 21 sub fuse_module_loaded;
122 dpavlin 9
123 dpavlin 24 # evil, evil way to solve this. It makes this module non-reentrant. But, since
124     # fuse calls another copy of this script for each mount anyway, this shouldn't
125     # be a problem.
126     my $fuse_self;
127    
128 dpavlin 11 sub mount {
129     my $class = shift;
130     my $self = {};
131     bless($self, $class);
132 dpavlin 9
133 dpavlin 11 my $arg = shift;
134 dpavlin 9
135 dpavlin 11 print Dumper($arg);
136    
137 dpavlin 51 unless ($self->fuse_module_loaded) {
138     print STDERR "no fuse module loaded. Trying sudo modprobe fuse!\n";
139     system "sudo modprobe fuse" || die "can't modprobe fuse using sudo!\n";
140     }
141    
142 dpavlin 11 carp "mount needs 'dsn' to connect to (e.g. dsn => 'DBI:Pg:dbname=test')" unless ($arg->{'dsn'});
143     carp "mount needs 'mount' as mountpoint" unless ($arg->{'mount'});
144    
145 dpavlin 12 # save (some) arguments in self
146 dpavlin 24 foreach (qw(mount invalidate)) {
147     $self->{$_} = $arg->{$_};
148     }
149 dpavlin 12
150 dpavlin 9 foreach (qw(filenames read update)) {
151 dpavlin 11 carp "mount needs '$_' SQL" unless ($arg->{$_});
152 dpavlin 9 }
153    
154 dpavlin 21 $ctime_start = time();
155 dpavlin 9
156 dpavlin 22 my $pid;
157 dpavlin 21 if ($arg->{'fork'}) {
158 dpavlin 22 $pid = fork();
159 dpavlin 21 die "fork() failed: $!" unless defined $pid;
160     # child will return to caller
161     if ($pid) {
162 dpavlin 47 my $counter = 4;
163     while ($counter && ! $self->is_mounted) {
164     select(undef, undef, undef, 0.5);
165     $counter--;
166     }
167     if ($self->is_mounted) {
168     return $self;
169     } else {
170     return undef;
171     }
172 dpavlin 21 }
173     }
174 dpavlin 9
175 dpavlin 21 $dbh = DBI->connect($arg->{'dsn'},$arg->{'user'},$arg->{'password'}, {AutoCommit => 0, RaiseError => 1}) || die $DBI::errstr;
176    
177 dpavlin 26 $sth->{'filenames'} = $dbh->prepare($arg->{'filenames'}) || die $dbh->errstr();
178 dpavlin 9
179     $sth->{'read'} = $dbh->prepare($arg->{'read'}) || die $dbh->errstr();
180     $sth->{'update'} = $dbh->prepare($arg->{'update'}) || die $dbh->errstr();
181    
182 dpavlin 26
183     $self->{'sth'} = $sth;
184    
185     $self->{'read_filenames'} = sub { $self->read_filenames };
186 dpavlin 21 $self->read_filenames;
187 dpavlin 9
188 dpavlin 26 $fuse_self = \$self;
189    
190 dpavlin 22 Fuse::main(
191 dpavlin 21 mountpoint=>$arg->{'mount'},
192     getattr=>\&e_getattr,
193     getdir=>\&e_getdir,
194     open=>\&e_open,
195     statfs=>\&e_statfs,
196     read=>\&e_read,
197     write=>\&e_write,
198     utime=>\&e_utime,
199     truncate=>\&e_truncate,
200     unlink=>\&e_unlink,
201 dpavlin 26 rmdir=>\&e_unlink,
202 dpavlin 21 debug=>0,
203     );
204 dpavlin 26
205 dpavlin 22 exit(0) if ($arg->{'fork'});
206    
207     return 1;
208    
209 dpavlin 9 };
210    
211 dpavlin 47 =head2 is_mounted
212    
213     Check if fuse filesystem is mounted
214    
215     if ($mnt->is_mounted) { ... }
216    
217     =cut
218    
219     sub is_mounted {
220     my $self = shift;
221    
222     my $mounted = 0;
223     my $mount = $self->{'mount'} || confess "can't find mount point!";
224     if (open(MTAB, "/etc/mtab")) {
225     while(<MTAB>) {
226     $mounted = 1 if (/ $mount fuse /i);
227     }
228     close(MTAB);
229     } else {
230     warn "can't open /etc/mtab: $!";
231     }
232    
233     return $mounted;
234     }
235    
236    
237 dpavlin 11 =head2 umount
238    
239     Unmount your database as filesystem.
240    
241     $mnt->umount;
242    
243     This will also kill background process which is translating
244     database to filesystem.
245    
246     =cut
247    
248     sub umount {
249     my $self = shift;
250    
251 dpavlin 47 if ($self->{'mount'} && $self->is_mounted) {
252 dpavlin 53 system "( fusermount -u ".$self->{'mount'}." 2>&1 ) >/dev/null";
253     if ($self->is_mounted) {
254 dpavlin 51 system "sudo umount ".$self->{'mount'} ||
255     return 0;
256 dpavlin 53 }
257 dpavlin 47 return 1;
258     }
259 dpavlin 40
260 dpavlin 47 return 0;
261 dpavlin 21 }
262    
263 dpavlin 26 $SIG{'INT'} = sub {
264 dpavlin 40 if ($fuse_self && $$fuse_self->umount) {
265     print STDERR "umount called by SIG INT\n";
266     }
267 dpavlin 26 };
268 dpavlin 24
269 dpavlin 40 $SIG{'QUIT'} = sub {
270     if ($fuse_self && $$fuse_self->umount) {
271     print STDERR "umount called by SIG QUIT\n";
272     }
273     };
274    
275 dpavlin 24 sub DESTROY {
276     my $self = shift;
277 dpavlin 40 if ($self->umount) {
278     print STDERR "umount called by DESTROY\n";
279     }
280 dpavlin 24 }
281    
282 dpavlin 21 =head2 fuse_module_loaded
283    
284     Checks if C<fuse> module is loaded in kernel.
285    
286     die "no fuse module loaded in kernel"
287     unless (Fuse::DBI::fuse_module_loaded);
288    
289 dpavlin 28 This function in called by C<mount>, but might be useful alone also.
290 dpavlin 21
291     =cut
292    
293     sub fuse_module_loaded {
294     my $lsmod = `lsmod`;
295     die "can't start lsmod: $!" unless ($lsmod);
296     if ($lsmod =~ m/fuse/s) {
297     return 1;
298 dpavlin 12 } else {
299 dpavlin 21 return 0;
300 dpavlin 12 }
301 dpavlin 11 }
302    
303 dpavlin 9 my %files;
304 dpavlin 1
305 dpavlin 9 sub read_filenames {
306 dpavlin 11 my $self = shift;
307    
308 dpavlin 26 my $sth = $self->{'sth'} || die "no sth argument";
309    
310 dpavlin 9 # create empty filesystem
311     (%files) = (
312     '.' => {
313     type => 0040,
314     mode => 0755,
315     },
316 dpavlin 40 '..' => {
317     type => 0040,
318     mode => 0755,
319     },
320 dpavlin 9 # a => {
321     # cont => "File 'a'.\n",
322     # type => 0100,
323     # ctime => time()-2000
324     # },
325     );
326 dpavlin 1
327 dpavlin 9 # fetch new filename list from database
328     $sth->{'filenames'}->execute() || die $sth->{'filenames'}->errstr();
329    
330     # read them in with sesible defaults
331     while (my $row = $sth->{'filenames'}->fetchrow_hashref() ) {
332     $files{$row->{'filename'}} = {
333     size => $row->{'size'},
334     mode => $row->{'writable'} ? 0644 : 0444,
335     id => $row->{'id'} || 99,
336     };
337    
338     my $d;
339     foreach (split(m!/!, $row->{'filename'})) {
340     # first, entry is assumed to be file
341     if ($d) {
342     $files{$d} = {
343     mode => 0755,
344     type => 0040
345     };
346     $files{$d.'/.'} = {
347     mode => 0755,
348     type => 0040
349     };
350     $files{$d.'/..'} = {
351     mode => 0755,
352     type => 0040
353     };
354     }
355     $d .= "/" if ($d);
356     $d .= "$_";
357 dpavlin 1 }
358     }
359 dpavlin 9
360 dpavlin 51 print "found ",scalar(keys %files)," files\n";
361 dpavlin 1 }
362    
363    
364     sub filename_fixup {
365     my ($file) = shift;
366     $file =~ s,^/,,;
367     $file = '.' unless length($file);
368     return $file;
369     }
370    
371     sub e_getattr {
372     my ($file) = filename_fixup(shift);
373     $file =~ s,^/,,;
374     $file = '.' unless length($file);
375     return -ENOENT() unless exists($files{$file});
376 dpavlin 54 my ($size) = $files{$file}{size} || 0;
377 dpavlin 52 my ($dev, $ino, $rdev, $blocks, $gid, $uid, $nlink, $blksize) = (0,0,0,int(($size+BLOCK-1)/BLOCK),0,0,1,BLOCK);
378 dpavlin 1 my ($atime, $ctime, $mtime);
379     $atime = $ctime = $mtime = $files{$file}{ctime} || $ctime_start;
380    
381     my ($modes) = (($files{$file}{type} || 0100)<<9) + $files{$file}{mode};
382    
383     # 2 possible types of return values:
384     #return -ENOENT(); # or any other error you care to
385 dpavlin 53 #print "getattr($file) ",join(",",($dev,$ino,$modes,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks)),"\n";
386 dpavlin 1 return ($dev,$ino,$modes,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks);
387     }
388    
389     sub e_getdir {
390     my ($dirname) = shift;
391     $dirname =~ s!^/!!;
392     # return as many text filenames as you like, followed by the retval.
393     print((scalar keys %files)." files total\n");
394     my %out;
395 dpavlin 13 foreach my $f (sort keys %files) {
396 dpavlin 1 if ($dirname) {
397 dpavlin 32 if ($f =~ s/^\Q$dirname\E\///) {
398 dpavlin 13 $out{$f}++ if ($f =~ /^[^\/]+$/);
399     }
400 dpavlin 1 } else {
401     $out{$f}++ if ($f =~ /^[^\/]+$/);
402     }
403     }
404     if (! %out) {
405     $out{'no files? bug?'}++;
406     }
407 dpavlin 8 print scalar keys %out," files in dir '$dirname'\n";
408 dpavlin 13 print "## ",join(" ",keys %out),"\n";
409 dpavlin 1 return (keys %out),0;
410     }
411    
412 dpavlin 21 sub read_content {
413     my ($file,$id) = @_;
414    
415     die "read_content needs file and id" unless ($file && $id);
416    
417     $sth->{'read'}->execute($id) || die $sth->{'read'}->errstr;
418     $files{$file}{cont} = $sth->{'read'}->fetchrow_array;
419 dpavlin 31 # I should modify ctime only if content in database changed
420     #$files{$file}{ctime} = time() unless ($files{$file}{ctime});
421 dpavlin 21 print "file '$file' content [",length($files{$file}{cont})," bytes] read in cache\n";
422     }
423    
424    
425 dpavlin 1 sub e_open {
426     # VFS sanity check; it keeps all the necessary state, not much to do here.
427 dpavlin 6 my $file = filename_fixup(shift);
428     my $flags = shift;
429    
430 dpavlin 1 return -ENOENT() unless exists($files{$file});
431     return -EISDIR() unless exists($files{$file}{id});
432 dpavlin 6
433 dpavlin 21 read_content($file,$files{$file}{id}) unless exists($files{$file}{cont});
434    
435 dpavlin 54 $files{$file}{cont} ||= '';
436 dpavlin 3 print "open '$file' ",length($files{$file}{cont})," bytes\n";
437 dpavlin 1 return 0;
438     }
439    
440     sub e_read {
441 dpavlin 3 # return an error numeric, or binary/text string.
442     # (note: 0 means EOF, "0" will give a byte (ascii "0")
443     # to the reading program)
444 dpavlin 1 my ($file) = filename_fixup(shift);
445 dpavlin 8 my ($buf_len,$off) = @_;
446 dpavlin 3
447 dpavlin 1 return -ENOENT() unless exists($files{$file});
448 dpavlin 3
449     my $len = length($files{$file}{cont});
450    
451 dpavlin 8 print "read '$file' [$len bytes] offset $off length $buf_len\n";
452 dpavlin 3
453     return -EINVAL() if ($off > $len);
454     return 0 if ($off == $len);
455    
456 dpavlin 21 $buf_len = $len-$off if ($len - $off < $buf_len);
457 dpavlin 3
458 dpavlin 8 return substr($files{$file}{cont},$off,$buf_len);
459 dpavlin 1 }
460    
461 dpavlin 6 sub clear_cont {
462 dpavlin 7 print "transaction rollback\n";
463     $dbh->rollback || die $dbh->errstr;
464 dpavlin 6 print "invalidate all cached content\n";
465     foreach my $f (keys %files) {
466     delete $files{$f}{cont};
467 dpavlin 31 delete $files{$f}{ctime};
468 dpavlin 6 }
469 dpavlin 7 print "begin new transaction\n";
470 dpavlin 21 #$dbh->begin_work || die $dbh->errstr;
471 dpavlin 6 }
472    
473    
474     sub update_db {
475     my $file = shift || die;
476    
477 dpavlin 8 $files{$file}{ctime} = time();
478    
479 dpavlin 21 my ($cont,$id) = (
480     $files{$file}{cont},
481     $files{$file}{id}
482     );
483    
484     if (!$sth->{'update'}->execute($cont,$id)) {
485 dpavlin 9 print "update problem: ",$sth->{'update'}->errstr;
486 dpavlin 6 clear_cont;
487     return 0;
488     } else {
489 dpavlin 7 if (! $dbh->commit) {
490 dpavlin 9 print "ERROR: commit problem: ",$sth->{'update'}->errstr;
491 dpavlin 6 clear_cont;
492     return 0;
493     }
494     print "updated '$file' [",$files{$file}{id},"]\n";
495 dpavlin 24
496 dpavlin 26 $$fuse_self->{'invalidate'}->() if (ref $$fuse_self->{'invalidate'});
497 dpavlin 6 }
498     return 1;
499     }
500    
501     sub e_write {
502     my $file = filename_fixup(shift);
503 dpavlin 18 my ($buffer,$off) = @_;
504 dpavlin 6
505     return -ENOENT() unless exists($files{$file});
506    
507 dpavlin 18 my $cont = $files{$file}{cont};
508     my $len = length($cont);
509 dpavlin 6
510 dpavlin 18 print "write '$file' [$len bytes] offset $off length ",length($buffer),"\n";
511 dpavlin 6
512 dpavlin 18 $files{$file}{cont} = "";
513 dpavlin 6
514 dpavlin 18 $files{$file}{cont} .= substr($cont,0,$off) if ($off > 0);
515     $files{$file}{cont} .= $buffer;
516 dpavlin 21 $files{$file}{cont} .= substr($cont,$off+length($buffer),$len-$off-length($buffer)) if ($off+length($buffer) < $len);
517 dpavlin 18
518     $files{$file}{size} = length($files{$file}{cont});
519    
520 dpavlin 6 if (! update_db($file)) {
521     return -ENOSYS();
522     } else {
523 dpavlin 18 return length($buffer);
524 dpavlin 6 }
525     }
526    
527     sub e_truncate {
528     my $file = filename_fixup(shift);
529     my $size = shift;
530    
531 dpavlin 18 print "truncate to $size\n";
532    
533 dpavlin 6 $files{$file}{cont} = substr($files{$file}{cont},0,$size);
534 dpavlin 18 $files{$file}{size} = $size;
535 dpavlin 6 return 0
536     };
537    
538    
539     sub e_utime {
540     my ($atime,$mtime,$file) = @_;
541     $file = filename_fixup($file);
542    
543     return -ENOENT() unless exists($files{$file});
544    
545 dpavlin 8 print "utime '$file' $atime $mtime\n";
546    
547 dpavlin 6 $files{$file}{time} = $mtime;
548     return 0;
549     }
550    
551 dpavlin 51 sub e_statfs {
552 dpavlin 1
553 dpavlin 51 my $size = 0;
554     my $inodes = 0;
555    
556     foreach my $f (keys %files) {
557     if ($f !~ /(^|\/)\.\.?$/) {
558     $size += $files{$f}{size} || 0;
559     $inodes++;
560     }
561     print "$inodes: $f [$size]\n";
562     }
563    
564 dpavlin 52 $size = int(($size+BLOCK-1)/BLOCK);
565 dpavlin 51
566 dpavlin 52 my @ret = (255, $inodes, 1, $size, $size-1, BLOCK);
567 dpavlin 51
568 dpavlin 53 #print "statfs: ",join(",",@ret),"\n";
569 dpavlin 51
570     return @ret;
571     }
572    
573 dpavlin 21 sub e_unlink {
574     my $file = filename_fixup(shift);
575    
576 dpavlin 51 # if (exists( $dirs{$file} )) {
577     # print "unlink '$file' will re-read template names\n";
578     # print Dumper($fuse_self);
579     # $$fuse_self->{'read_filenames'}->();
580     # return 0;
581     if (exists( $files{$file} )) {
582 dpavlin 26 print "unlink '$file' will invalidate cache\n";
583     read_content($file,$files{$file}{id});
584     return 0;
585     }
586 dpavlin 21
587 dpavlin 26 return -ENOENT();
588 dpavlin 21 }
589 dpavlin 9 1;
590     __END__
591    
592     =head1 EXPORT
593    
594     Nothing.
595    
596 dpavlin 40 =head1 BUGS
597    
598     Size information (C<ls -s>) is wrong. It's a problem in upstream Fuse module
599     (for which I'm to blame lately), so when it gets fixes, C<Fuse::DBI> will
600     automagically pick it up.
601    
602 dpavlin 9 =head1 SEE ALSO
603    
604     C<FUSE (Filesystem in USErspace)> website
605 dpavlin 36 L<http://fuse.sourceforge.net/>
606 dpavlin 9
607 dpavlin 28 Example for WebGUI which comes with this distribution in
608 dpavlin 30 directory C<examples/webgui.pl>. It also contains a lot of documentation
609 dpavlin 28 about design of this module, usage and limitations.
610    
611 dpavlin 9 =head1 AUTHOR
612    
613     Dobrica Pavlinusic, E<lt>dpavlin@rot13.orgE<gt>
614    
615     =head1 COPYRIGHT AND LICENSE
616    
617     Copyright (C) 2004 by Dobrica Pavlinusic
618    
619     This library is free software; you can redistribute it and/or modify
620     it under the same terms as Perl itself, either Perl version 5.8.4 or,
621     at your option, any later version of Perl 5 you may have available.
622    
623    
624     =cut
625    

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