/[fuse_dbi]/trunk/DBI.pm
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Revision 53 - (show annotations)
Sun Nov 28 20:20:36 2004 UTC (17 years, 10 months ago) by dpavlin
File size: 13460 byte(s)
fixed work-around for non-working fusermount, removed some debugging output

1 #!/usr/bin/perl
2
3 package Fuse::DBI;
4
5 use 5.008;
6 use strict;
7 use warnings;
8
9 use POSIX qw(ENOENT EISDIR EINVAL ENOSYS O_RDWR);
10 use Fuse;
11 use DBI;
12 use Carp;
13 use Data::Dumper;
14
15 our $VERSION = '0.07';
16
17 # block size for this filesystem
18 use constant BLOCK => 1024;
19
20 =head1 NAME
21
22 Fuse::DBI - mount your database as filesystem and use it
23
24 =head1 SYNOPSIS
25
26 use Fuse::DBI;
27 Fuse::DBI->mount( ... );
28
29 See C<run> below for examples how to set parameters.
30
31 =head1 DESCRIPTION
32
33 This module will use C<Fuse> module, part of C<FUSE (Filesystem in USErspace)>
34 available at L<http://fuse.sourceforge.net/> to mount
35 your database as file system.
36
37 That will give you possibility to use normal file-system tools (cat, grep, vi)
38 to manipulate data in database.
39
40 It's actually opposite of Oracle's intention to put everything into database.
41
42
43 =head1 METHODS
44
45 =cut
46
47 =head2 mount
48
49 Mount your database as filesystem.
50
51 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 my $mnt = Fuse::DBI->mount({
62 '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 });
70
71 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 =cut
115
116 my $dbh;
117 my $sth;
118 my $ctime_start;
119
120 sub read_filenames;
121 sub fuse_module_loaded;
122
123 # 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 sub mount {
129 my $class = shift;
130 my $self = {};
131 bless($self, $class);
132
133 my $arg = shift;
134
135 print Dumper($arg);
136
137 unless ($self->fuse_module_loaded) {
138 print STDERR "no fuse module loaded. Trying sudo modprobe fuse!\n";
139 system "sudo modprobe fuse" || die "can't modprobe fuse using sudo!\n";
140 }
141
142 carp "mount needs 'dsn' to connect to (e.g. dsn => 'DBI:Pg:dbname=test')" unless ($arg->{'dsn'});
143 carp "mount needs 'mount' as mountpoint" unless ($arg->{'mount'});
144
145 # save (some) arguments in self
146 foreach (qw(mount invalidate)) {
147 $self->{$_} = $arg->{$_};
148 }
149
150 foreach (qw(filenames read update)) {
151 carp "mount needs '$_' SQL" unless ($arg->{$_});
152 }
153
154 $ctime_start = time();
155
156 my $pid;
157 if ($arg->{'fork'}) {
158 $pid = fork();
159 die "fork() failed: $!" unless defined $pid;
160 # child will return to caller
161 if ($pid) {
162 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 }
173 }
174
175 $dbh = DBI->connect($arg->{'dsn'},$arg->{'user'},$arg->{'password'}, {AutoCommit => 0, RaiseError => 1}) || die $DBI::errstr;
176
177 $sth->{'filenames'} = $dbh->prepare($arg->{'filenames'}) || die $dbh->errstr();
178
179 $sth->{'read'} = $dbh->prepare($arg->{'read'}) || die $dbh->errstr();
180 $sth->{'update'} = $dbh->prepare($arg->{'update'}) || die $dbh->errstr();
181
182
183 $self->{'sth'} = $sth;
184
185 $self->{'read_filenames'} = sub { $self->read_filenames };
186 $self->read_filenames;
187
188 $fuse_self = \$self;
189
190 Fuse::main(
191 mountpoint=>$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 rmdir=>\&e_unlink,
202 debug=>0,
203 );
204
205 exit(0) if ($arg->{'fork'});
206
207 return 1;
208
209 };
210
211 =head2 is_mounted
212
213 Check if fuse filesystem is mounted
214
215 if ($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 =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 $self = shift;
250
251 if ($self->{'mount'} && $self->is_mounted) {
252 system "( fusermount -u ".$self->{'mount'}." 2>&1 ) >/dev/null";
253 if ($self->is_mounted) {
254 system "sudo umount ".$self->{'mount'} ||
255 return 0;
256 }
257 return 1;
258 }
259
260 return 0;
261 }
262
263 $SIG{'INT'} = sub {
264 if ($fuse_self && $$fuse_self->umount) {
265 print STDERR "umount called by SIG INT\n";
266 }
267 };
268
269 $SIG{'QUIT'} = sub {
270 if ($fuse_self && $$fuse_self->umount) {
271 print STDERR "umount called by SIG QUIT\n";
272 }
273 };
274
275 sub DESTROY {
276 my $self = shift;
277 if ($self->umount) {
278 print STDERR "umount called by DESTROY\n";
279 }
280 }
281
282 =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 This function in called by C<mount>, but might be useful alone also.
290
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 } else {
299 return 0;
300 }
301 }
302
303 my %files;
304
305 sub read_filenames {
306 my $self = shift;
307
308 my $sth = $self->{'sth'} || die "no sth argument";
309
310 # create empty filesystem
311 (%files) = (
312 '.' => {
313 type => 0040,
314 mode => 0755,
315 },
316 '..' => {
317 type => 0040,
318 mode => 0755,
319 },
320 # a => {
321 # cont => "File 'a'.\n",
322 # type => 0100,
323 # ctime => time()-2000
324 # },
325 );
326
327 # 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 }
358 }
359
360 print "found ",scalar(keys %files)," files\n";
361 }
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 my ($size) = $files{$file}{size} || BLOCK;
377 my ($dev, $ino, $rdev, $blocks, $gid, $uid, $nlink, $blksize) = (0,0,0,int(($size+BLOCK-1)/BLOCK),0,0,1,BLOCK);
378 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 #print "getattr($file) ",join(",",($dev,$ino,$modes,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks)),"\n";
386 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 foreach my $f (sort keys %files) {
396 if ($dirname) {
397 if ($f =~ s/^\Q$dirname\E\///) {
398 $out{$f}++ if ($f =~ /^[^\/]+$/);
399 }
400 } else {
401 $out{$f}++ if ($f =~ /^[^\/]+$/);
402 }
403 }
404 if (! %out) {
405 $out{'no files? bug?'}++;
406 }
407 print scalar keys %out," files in dir '$dirname'\n";
408 print "## ",join(" ",keys %out),"\n";
409 return (keys %out),0;
410 }
411
412 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} = $sth->{'read'}->fetchrow_array;
419 # I should modify ctime only if content in database changed
420 #$files{$file}{ctime} = time() unless ($files{$file}{ctime});
421 print "file '$file' content [",length($files{$file}{cont})," bytes] read in cache\n";
422 }
423
424
425 sub e_open {
426 # VFS sanity check; it keeps all the necessary state, not much to do here.
427 my $file = filename_fixup(shift);
428 my $flags = shift;
429
430 return -ENOENT() unless exists($files{$file});
431 return -EISDIR() unless exists($files{$file}{id});
432
433 read_content($file,$files{$file}{id}) unless exists($files{$file}{cont});
434
435 print "open '$file' ",length($files{$file}{cont})," bytes\n";
436 return 0;
437 }
438
439 sub e_read {
440 # return an error numeric, or binary/text string.
441 # (note: 0 means EOF, "0" will give a byte (ascii "0")
442 # to the reading program)
443 my ($file) = filename_fixup(shift);
444 my ($buf_len,$off) = @_;
445
446 return -ENOENT() unless exists($files{$file});
447
448 my $len = length($files{$file}{cont});
449
450 print "read '$file' [$len bytes] offset $off length $buf_len\n";
451
452 return -EINVAL() if ($off > $len);
453 return 0 if ($off == $len);
454
455 $buf_len = $len-$off if ($len - $off < $buf_len);
456
457 return substr($files{$file}{cont},$off,$buf_len);
458 }
459
460 sub clear_cont {
461 print "transaction rollback\n";
462 $dbh->rollback || die $dbh->errstr;
463 print "invalidate all cached content\n";
464 foreach my $f (keys %files) {
465 delete $files{$f}{cont};
466 delete $files{$f}{ctime};
467 }
468 print "begin new transaction\n";
469 #$dbh->begin_work || die $dbh->errstr;
470 }
471
472
473 sub update_db {
474 my $file = shift || die;
475
476 $files{$file}{ctime} = time();
477
478 my ($cont,$id) = (
479 $files{$file}{cont},
480 $files{$file}{id}
481 );
482
483 if (!$sth->{'update'}->execute($cont,$id)) {
484 print "update problem: ",$sth->{'update'}->errstr;
485 clear_cont;
486 return 0;
487 } else {
488 if (! $dbh->commit) {
489 print "ERROR: commit problem: ",$sth->{'update'}->errstr;
490 clear_cont;
491 return 0;
492 }
493 print "updated '$file' [",$files{$file}{id},"]\n";
494
495 $$fuse_self->{'invalidate'}->() if (ref $$fuse_self->{'invalidate'});
496 }
497 return 1;
498 }
499
500 sub e_write {
501 my $file = filename_fixup(shift);
502 my ($buffer,$off) = @_;
503
504 return -ENOENT() unless exists($files{$file});
505
506 my $cont = $files{$file}{cont};
507 my $len = length($cont);
508
509 print "write '$file' [$len bytes] offset $off length ",length($buffer),"\n";
510
511 $files{$file}{cont} = "";
512
513 $files{$file}{cont} .= substr($cont,0,$off) if ($off > 0);
514 $files{$file}{cont} .= $buffer;
515 $files{$file}{cont} .= substr($cont,$off+length($buffer),$len-$off-length($buffer)) if ($off+length($buffer) < $len);
516
517 $files{$file}{size} = length($files{$file}{cont});
518
519 if (! update_db($file)) {
520 return -ENOSYS();
521 } else {
522 return length($buffer);
523 }
524 }
525
526 sub e_truncate {
527 my $file = filename_fixup(shift);
528 my $size = shift;
529
530 print "truncate to $size\n";
531
532 $files{$file}{cont} = substr($files{$file}{cont},0,$size);
533 $files{$file}{size} = $size;
534 return 0
535 };
536
537
538 sub e_utime {
539 my ($atime,$mtime,$file) = @_;
540 $file = filename_fixup($file);
541
542 return -ENOENT() unless exists($files{$file});
543
544 print "utime '$file' $atime $mtime\n";
545
546 $files{$file}{time} = $mtime;
547 return 0;
548 }
549
550 sub e_statfs {
551
552 my $size = 0;
553 my $inodes = 0;
554
555 foreach my $f (keys %files) {
556 if ($f !~ /(^|\/)\.\.?$/) {
557 $size += $files{$f}{size} || 0;
558 $inodes++;
559 }
560 print "$inodes: $f [$size]\n";
561 }
562
563 $size = int(($size+BLOCK-1)/BLOCK);
564
565 my @ret = (255, $inodes, 1, $size, $size-1, BLOCK);
566
567 #print "statfs: ",join(",",@ret),"\n";
568
569 return @ret;
570 }
571
572 sub e_unlink {
573 my $file = filename_fixup(shift);
574
575 # if (exists( $dirs{$file} )) {
576 # print "unlink '$file' will re-read template names\n";
577 # print Dumper($fuse_self);
578 # $$fuse_self->{'read_filenames'}->();
579 # return 0;
580 if (exists( $files{$file} )) {
581 print "unlink '$file' will invalidate cache\n";
582 read_content($file,$files{$file}{id});
583 return 0;
584 }
585
586 return -ENOENT();
587 }
588 1;
589 __END__
590
591 =head1 EXPORT
592
593 Nothing.
594
595 =head1 BUGS
596
597 Size information (C<ls -s>) is wrong. It's a problem in upstream Fuse module
598 (for which I'm to blame lately), so when it gets fixes, C<Fuse::DBI> will
599 automagically pick it up.
600
601 =head1 SEE ALSO
602
603 C<FUSE (Filesystem in USErspace)> website
604 L<http://fuse.sourceforge.net/>
605
606 Example for WebGUI which comes with this distribution in
607 directory C<examples/webgui.pl>. It also contains a lot of documentation
608 about design of this module, usage and limitations.
609
610 =head1 AUTHOR
611
612 Dobrica Pavlinusic, E<lt>dpavlin@rot13.orgE<gt>
613
614 =head1 COPYRIGHT AND LICENSE
615
616 Copyright (C) 2004 by Dobrica Pavlinusic
617
618 This library is free software; you can redistribute it and/or modify
619 it under the same terms as Perl itself, either Perl version 5.8.4 or,
620 at your option, any later version of Perl 5 you may have available.
621
622
623 =cut
624

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