/[fuse_dbi]/fuse-couchdb/DBI.pm
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revision 18 by dpavlin, Sun Sep 5 16:59:41 2004 UTC revision 36 by dpavlin, Tue Nov 16 15:34:25 2004 UTC
# Line 10  use POSIX qw(ENOENT EISDIR EINVAL ENOSYS Line 10  use POSIX qw(ENOENT EISDIR EINVAL ENOSYS
10  use Fuse;  use Fuse;
11  use DBI;  use DBI;
12  use Carp;  use Carp;
 use Proc::Simple;  
13  use Data::Dumper;  use Data::Dumper;
14    
15    
16  our $VERSION = '0.02';  our $VERSION = '0.05';
17    
18  =head1 NAME  =head1 NAME
19    
# Line 25  Fuse::DBI - mount your database as files Line 24  Fuse::DBI - mount your database as files
24    use Fuse::DBI;    use Fuse::DBI;
25    Fuse::DBI->mount( ... );    Fuse::DBI->mount( ... );
26    
27  See L<run> below for examples how to set parametars.  See C<run> below for examples how to set parameters.
28    
29  =head1 DESCRIPTION  =head1 DESCRIPTION
30    
31  This module will use L<Fuse> module, part of C<FUSE (Filesystem in USErspace)>  This module will use C<Fuse> module, part of C<FUSE (Filesystem in USErspace)>
32  available at L<http://sourceforge.net/projects/avf> to mount  available at L<http://fuse.sourceforge.net/> to mount
33  your database as file system.  your database as file system.
34    
35  That will give you posibility to use normal file-system tools (cat, grep, vi)  That will give you possibility to use normal file-system tools (cat, grep, vi)
36  to manipulate data in database.  to manipulate data in database.
37    
38  It's actually opposite of Oracle's intention to put everything into database.  It's actually opposite of Oracle's intention to put everything into database.
# Line 47  It's actually opposite of Oracle's inten Line 46  It's actually opposite of Oracle's inten
46    
47  Mount your database as filesystem.  Mount your database as filesystem.
48    
49    Let's suppose that your database have table C<files> with following structure:
50    
51     id:            int
52     filename:      text
53     size:          int
54     content:       text
55     writable:      boolean
56    
57    Following is example how to mount table like that to C</mnt>:
58    
59    my $mnt = Fuse::DBI->mount({    my $mnt = Fuse::DBI->mount({
60          filenames => 'select name from filenamefilenames,          'filenames' => 'select id,filename,size,writable from files',
61          read => 'sql read',          'read' => 'select content from files where id = ?',
62          update => 'sql update',          'update' => 'update files set content = ? where id = ?',
63          dsn => 'DBI:Pg:dbname=webgui',          'dsn' => 'DBI:Pg:dbname=test_db',
64          user => 'database_user',          'user' => 'database_user',
65          password => 'database_password'          'password' => 'database_password',
66            'invalidate' => sub { ... },
67    });    });
68    
69    Options:
70    
71    =over 5
72    
73    =item filenames
74    
75    SQL query which returns C<id> (unique id for that row), C<filename>,
76    C<size> and C<writable> boolean flag.
77    
78    =item read
79    
80    SQL query which returns only one column with content of file and has
81    placeholder C<?> for C<id>.
82    
83    =item update
84    
85    SQL query with two pace-holders, one for new content and one for C<id>.
86    
87    =item dsn
88    
89    C<DBI> dsn to connect to (contains database driver and name of database).
90    
91    =item user
92    
93    User with which to connect to database
94    
95    =item password
96    
97    Password for connecting to database
98    
99    =item invalidate
100    
101    Optional anonymous code reference which will be executed when data is updated in
102    database. It can be used as hook to delete cache (for example on-disk-cache)
103    which is created from data edited through C<Fuse::DBI>.
104    
105    =item fork
106    
107    Optional flag which forks after mount so that executing script will continue
108    running. Implementation is experimental.
109    
110    =back
111    
112  =cut  =cut
113    
114  my $dbh;  my $dbh;
# Line 63  my $sth; Line 116  my $sth;
116  my $ctime_start;  my $ctime_start;
117    
118  sub read_filenames;  sub read_filenames;
119    sub fuse_module_loaded;
120    
121    # evil, evil way to solve this. It makes this module non-reentrant. But, since
122    # fuse calls another copy of this script for each mount anyway, this shouldn't
123    # be a problem.
124    my $fuse_self;
125    
126  sub mount {  sub mount {
127          my $class = shift;          my $class = shift;
# Line 77  sub mount { Line 136  sub mount {
136          carp "mount needs 'mount' as mountpoint" unless ($arg->{'mount'});          carp "mount needs 'mount' as mountpoint" unless ($arg->{'mount'});
137    
138          # save (some) arguments in self          # save (some) arguments in self
139          $self->{$_} = $arg->{$_} foreach (qw(mount));          foreach (qw(mount invalidate)) {
140                    $self->{$_} = $arg->{$_};
141            }
142    
143          foreach (qw(filenames read update)) {          foreach (qw(filenames read update)) {
144                  carp "mount needs '$_' SQL" unless ($arg->{$_});                  carp "mount needs '$_' SQL" unless ($arg->{$_});
145          }          }
146    
147          $dbh = DBI->connect($arg->{'dsn'},$arg->{'user'},$arg->{'password'}, { AutoCommit => 0 }) || die $DBI::errstr;          $ctime_start = time();
148    
149            my $pid;
150            if ($arg->{'fork'}) {
151                    $self->{'mounted'} = 1;
152                    $pid = fork();
153                    die "fork() failed: $!" unless defined $pid;
154                    # child will return to caller
155                    if ($pid) {
156                            return $self;
157                    }
158            }
159    
160          print "start transaction\n";          $dbh = DBI->connect($arg->{'dsn'},$arg->{'user'},$arg->{'password'}, {AutoCommit => 0, RaiseError => 1}) || die $DBI::errstr;
         $dbh->begin_work || die $dbh->errstr;  
161    
162          $sth->{filenames} = $dbh->prepare($arg->{'filenames'}) || die $dbh->errstr();          $sth->{'filenames'} = $dbh->prepare($arg->{'filenames'}) || die $dbh->errstr();
163    
164          $sth->{'read'} = $dbh->prepare($arg->{'read'}) || die $dbh->errstr();          $sth->{'read'} = $dbh->prepare($arg->{'read'}) || die $dbh->errstr();
165          $sth->{'update'} = $dbh->prepare($arg->{'update'}) || die $dbh->errstr();          $sth->{'update'} = $dbh->prepare($arg->{'update'}) || die $dbh->errstr();
166    
         $ctime_start = time();  
167    
168          read_filenames;          $self->{'sth'} = $sth;
169    
170            $self->{'read_filenames'} = sub { $self->read_filenames };
171            $self->read_filenames;
172    
173          $self->{'proc'} = Proc::Simple->new();          $self->{'mounted'} = 1 unless ($arg->{'fork'});
         $self->{'proc'}->kill_on_destroy(1);  
174    
175          $self->{'proc'}->start( sub {          $fuse_self = \$self;
176                  Fuse::main(  
177                          mountpoint=>$arg->{'mount'},          Fuse::main(
178                          getattr=>\&e_getattr,                  mountpoint=>$arg->{'mount'},
179                          getdir=>\&e_getdir,                  getattr=>\&e_getattr,
180                          open=>\&e_open,                  getdir=>\&e_getdir,
181                          statfs=>\&e_statfs,                  open=>\&e_open,
182                          read=>\&e_read,                  statfs=>\&e_statfs,
183                          write=>\&e_write,                  read=>\&e_read,
184                          utime=>\&e_utime,                  write=>\&e_write,
185                          truncate=>\&e_truncate,                  utime=>\&e_utime,
186                          debug=>0,                  truncate=>\&e_truncate,
187                  );                  unlink=>\&e_unlink,
188          } );                  rmdir=>\&e_unlink,
189                    debug=>0,
190            );
191            
192            $self->{'mounted'} = 0;
193    
194          confess "Fuse::main failed" if (! $self->{'proc'}->poll);          exit(0) if ($arg->{'fork'});
195    
196            return 1;
197    
         $self ? return $self : return undef;  
198  };  };
199    
200  =head2 umount  =head2 umount
# Line 134  database to filesystem. Line 211  database to filesystem.
211  sub umount {  sub umount {
212          my $self = shift;          my $self = shift;
213    
214          confess "no process running?" unless ($self->{'proc'});          if ($self->{'mounted'}) {
215                    system "fusermount -u ".$self->{'mount'} || warn "umount error: $!" && return 0;
216            }
217    
218          system "fusermount -u ".$self->{'mount'} || croak "umount error: $!";          return 1;
219    }
220    
221          if ($self->{'proc'}->poll) {  $SIG{'INT'} = sub {
222                  $self->{'proc'}->kill;          print STDERR "umount called by SIG INT\n";
223                  return 1 if (! $self->{'proc'}->poll);          umount;
224          } else {  };
225    
226    sub DESTROY {
227            my $self = shift;
228            return if (! $self->{'mounted'});
229            print STDERR "umount called by DESTROY\n";
230            $self->umount;
231    }
232    
233    =head2 fuse_module_loaded
234    
235    Checks if C<fuse> module is loaded in kernel.
236    
237      die "no fuse module loaded in kernel"
238            unless (Fuse::DBI::fuse_module_loaded);
239    
240    This function in called by C<mount>, but might be useful alone also.
241    
242    =cut
243    
244    sub fuse_module_loaded {
245            my $lsmod = `lsmod`;
246            die "can't start lsmod: $!" unless ($lsmod);
247            if ($lsmod =~ m/fuse/s) {
248                  return 1;                  return 1;
249            } else {
250                    return 0;
251          }          }
252  }  }
253    
   
254  my %files;  my %files;
255  my %dirs;  my %dirs;
256    
257  sub read_filenames {  sub read_filenames {
258          my $self = shift;          my $self = shift;
259    
260            my $sth = $self->{'sth'} || die "no sth argument";
261    
262          # create empty filesystem          # create empty filesystem
263          (%files) = (          (%files) = (
264                  '.' => {                  '.' => {
# Line 237  sub e_getdir { Line 343  sub e_getdir {
343          my %out;          my %out;
344          foreach my $f (sort keys %files) {          foreach my $f (sort keys %files) {
345                  if ($dirname) {                  if ($dirname) {
346                          if ($f =~ s/^\E$dirname\Q\///) {                          if ($f =~ s/^\Q$dirname\E\///) {
347                                  $out{$f}++ if ($f =~ /^[^\/]+$/);                                  $out{$f}++ if ($f =~ /^[^\/]+$/);
348                          }                          }
349                  } else {                  } else {
# Line 252  sub e_getdir { Line 358  sub e_getdir {
358          return (keys %out),0;          return (keys %out),0;
359  }  }
360    
361    sub read_content {
362            my ($file,$id) = @_;
363    
364            die "read_content needs file and id" unless ($file && $id);
365    
366            $sth->{'read'}->execute($id) || die $sth->{'read'}->errstr;
367            $files{$file}{cont} = $sth->{'read'}->fetchrow_array;
368            # I should modify ctime only if content in database changed
369            #$files{$file}{ctime} = time() unless ($files{$file}{ctime});
370            print "file '$file' content [",length($files{$file}{cont})," bytes] read in cache\n";
371    }
372    
373    
374  sub e_open {  sub e_open {
375          # VFS sanity check; it keeps all the necessary state, not much to do here.          # VFS sanity check; it keeps all the necessary state, not much to do here.
376          my $file = filename_fixup(shift);          my $file = filename_fixup(shift);
# Line 260  sub e_open { Line 379  sub e_open {
379          return -ENOENT() unless exists($files{$file});          return -ENOENT() unless exists($files{$file});
380          return -EISDIR() unless exists($files{$file}{id});          return -EISDIR() unless exists($files{$file}{id});
381    
382          if (!exists($files{$file}{cont})) {          read_content($file,$files{$file}{id}) unless exists($files{$file}{cont});
383                  $sth->{'read'}->execute($files{$file}{id}) || die $sth->{'read'}->errstr;  
                 $files{$file}{cont} = $sth->{'read'}->fetchrow_array;  
                 print "file '$file' content read in cache\n";  
         }  
384          print "open '$file' ",length($files{$file}{cont})," bytes\n";          print "open '$file' ",length($files{$file}{cont})," bytes\n";
385          return 0;          return 0;
386  }  }
# Line 285  sub e_read { Line 401  sub e_read {
401          return -EINVAL() if ($off > $len);          return -EINVAL() if ($off > $len);
402          return 0 if ($off == $len);          return 0 if ($off == $len);
403    
404          $buf_len = $buf_len-$off if ($off+$buf_len > $len);          $buf_len = $len-$off if ($len - $off < $buf_len);
405    
406          return substr($files{$file}{cont},$off,$buf_len);          return substr($files{$file}{cont},$off,$buf_len);
407  }  }
# Line 296  sub clear_cont { Line 412  sub clear_cont {
412          print "invalidate all cached content\n";          print "invalidate all cached content\n";
413          foreach my $f (keys %files) {          foreach my $f (keys %files) {
414                  delete $files{$f}{cont};                  delete $files{$f}{cont};
415                    delete $files{$f}{ctime};
416          }          }
417          print "begin new transaction\n";          print "begin new transaction\n";
418          $dbh->begin_work || die $dbh->errstr;          #$dbh->begin_work || die $dbh->errstr;
419  }  }
420    
421    
# Line 307  sub update_db { Line 424  sub update_db {
424    
425          $files{$file}{ctime} = time();          $files{$file}{ctime} = time();
426    
427          if (!$sth->{'update'}->execute($files{$file}{cont},$files{$file}{id})) {          my ($cont,$id) = (
428                    $files{$file}{cont},
429                    $files{$file}{id}
430            );
431    
432            if (!$sth->{'update'}->execute($cont,$id)) {
433                  print "update problem: ",$sth->{'update'}->errstr;                  print "update problem: ",$sth->{'update'}->errstr;
434                  clear_cont;                  clear_cont;
435                  return 0;                  return 0;
# Line 318  sub update_db { Line 440  sub update_db {
440                          return 0;                          return 0;
441                  }                  }
442                  print "updated '$file' [",$files{$file}{id},"]\n";                  print "updated '$file' [",$files{$file}{id},"]\n";
443    
444                    $$fuse_self->{'invalidate'}->() if (ref $$fuse_self->{'invalidate'});
445          }          }
446          return 1;          return 1;
447  }  }
# Line 337  sub e_write { Line 461  sub e_write {
461    
462          $files{$file}{cont} .= substr($cont,0,$off) if ($off > 0);          $files{$file}{cont} .= substr($cont,0,$off) if ($off > 0);
463          $files{$file}{cont} .= $buffer;          $files{$file}{cont} .= $buffer;
464          $files{$file}{cont} .= substr($cont,-($off+length($buffer))) if ($off+length($buffer) > $len);          $files{$file}{cont} .= substr($cont,$off+length($buffer),$len-$off-length($buffer)) if ($off+length($buffer) < $len);
465    
466          $files{$file}{size} = length($files{$file}{cont});          $files{$file}{size} = length($files{$file}{cont});
467    
# Line 374  sub e_utime { Line 498  sub e_utime {
498    
499  sub e_statfs { return 255, 1, 1, 1, 1, 2 }  sub e_statfs { return 255, 1, 1, 1, 1, 2 }
500    
501    sub e_unlink {
502            my $file = filename_fixup(shift);
503    
504            if (exists( $dirs{$file} )) {
505                    print "unlink '$file' will re-read template names\n";
506                    print Dumper($fuse_self);
507                    $$fuse_self->{'read_filenames'}->();
508                    return 0;
509            } elsif (exists( $files{$file} )) {
510                    print "unlink '$file' will invalidate cache\n";
511                    read_content($file,$files{$file}{id});
512                    return 0;
513            }
514    
515            return -ENOENT();
516    }
517  1;  1;
518  __END__  __END__
519    
# Line 384  Nothing. Line 524  Nothing.
524  =head1 SEE ALSO  =head1 SEE ALSO
525    
526  C<FUSE (Filesystem in USErspace)> website  C<FUSE (Filesystem in USErspace)> website
527  L<http://sourceforge.net/projects/avf>  L<http://fuse.sourceforge.net/>
528    
529    Example for WebGUI which comes with this distribution in
530    directory C<examples/webgui.pl>. It also contains a lot of documentation
531    about design of this module, usage and limitations.
532    
533  =head1 AUTHOR  =head1 AUTHOR
534    
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