=head1 NAME

Mail::Box::Locker::NFS - lock a folder with a separate file, NFS-safe

=head1 INHERITANCE

 Mail::Box::Locker::NFS
   is a Mail::Box::Locker
   is a Mail::Reporter

=head1 SYNOPSIS

 See Mail::Box::Locker

=head1 DESCRIPTION

Like the C<::DotLock> locker, but then in an NFS-safe fashion.  Over NFS,
the creation of a file is not atomic.  The C<::DotLock> locker depends
on an atomic C<open> system call, hence in not usable to lock a folder
which accessed over NFS.  The C<::NFS>
locker is therefore more complicated (so therefore slower), but will work
for NFS --and for local disks as well.

=head1 METHODS

=head2 Constructors

Mail::Box::Locker::NFS-E<gt>B<new>(OPTIONS)

=over 4

 Option --Defined in     --Default
 expires  Mail::Box::Locker  1 hour
 file     Mail::Box::Locker  undef
 folder   Mail::Box::Locker  <required>
 log      Mail::Reporter   'WARNINGS'
 method   Mail::Box::Locker  'NFS'
 timeout  Mail::Box::Locker  10 seconds
 trace    Mail::Reporter   'WARNINGS'

. expires => SECONDS

. file => FILENAME

. folder => FOLDER

. log => LEVEL

. method => STRING|CLASS|ARRAY

. timeout => SECONDS|'NOTIMEOUT'

. trace => LEVEL

=back

=head2 The Locker

$obj-E<gt>B<filename>([FILENAME])

=over 4

See L<Mail::Box::Locker/"The Locker">

=back

$obj-E<gt>B<folder>

=over 4

See L<Mail::Box::Locker/"The Locker">

=back

$obj-E<gt>B<name>

=over 4

See L<Mail::Box::Locker/"The Locker">

=back

=head2 Locking

$obj-E<gt>B<hasLock>

=over 4

See L<Mail::Box::Locker/"Locking">

=back

$obj-E<gt>B<isLocked>

=over 4

See L<Mail::Box::Locker/"Locking">

=back

$obj-E<gt>B<lock>

=over 4

=back

$obj-E<gt>B<unlock>

=over 4

See L<Mail::Box::Locker/"Locking">

=back

=head2 Error handling

$obj-E<gt>B<AUTOLOAD>

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<addReport>(OBJECT)

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<defaultTrace>([LEVEL]|[LOGLEVEL, TRACELEVEL]|[LEVEL, CALLBACK])

Mail::Box::Locker::NFS-E<gt>B<defaultTrace>([LEVEL]|[LOGLEVEL, TRACELEVEL]|[LEVEL, CALLBACK])

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<errors>

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<log>([LEVEL [,STRINGS]])

Mail::Box::Locker::NFS-E<gt>B<log>([LEVEL [,STRINGS]])

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<logPriority>(LEVEL)

Mail::Box::Locker::NFS-E<gt>B<logPriority>(LEVEL)

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<logSettings>

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<notImplemented>

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<report>([LEVEL])

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<reportAll>([LEVEL])

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<trace>([LEVEL])

=over 4

See L<Mail::Reporter/"Error handling">

=back

$obj-E<gt>B<warnings>

=over 4

See L<Mail::Reporter/"Error handling">

=back

=head2 Cleanup

$obj-E<gt>B<DESTROY>

=over 4

See L<Mail::Box::Locker/"Cleanup">

=back

$obj-E<gt>B<inGlobalDestruction>

=over 4

See L<Mail::Reporter/"Cleanup">

=back

=head1 DIAGNOSTICS

Warning: Folder $folder already locked over nfs

=over 4

Do not try to lock the folder when the application already has the
lock: it will give you dead-locks.

=back

Error: Package $package does not implement $method.

=over 4

Fatal error: the specific package (or one of its superclasses) does not
implement this method where it should. This message means that some other
related classes do implement this method however the class at hand does
not.  Probably you should investigate this and probably inform the author
of the package.

=back

Warning: Removed expired lockfile $filename.

=over 4

A lock file was found which was older than the expiration period as
specified with L<new(timeout)|Mail::Box::Locker/"METHODS">.  The lock file was succesfully
removed.

=back

Error: Unable to remove expired lockfile $lockfile: $!

=over 4

A lock file was found which was older than the expiration period as
specified with the L<new(timeout)|Mail::Box::Locker/"METHODS"> option.  It is impossible to remove that
lock file, so we need to wait until it vanishes by some external cause.

=back

=head1 SEE ALSO

This module is part of Mail-Box distribution version 2.079,
built on November 28, 2007. Website: F<http://perl.overmeer.net/mailbox/>

=head1 LICENSE

Copyrights 2001-2007 by Mark Overmeer. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See F<http://www.perl.com/perl/misc/Artistic.html>