=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

=over 4

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

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

=over 2

=item expires => SECONDS

=item file => FILENAME

=item folder => FOLDER

=item log => LEVEL

=item method => STRING|CLASS|ARRAY

=item timeout => SECONDS|'NOTIMEOUT'

=item trace => LEVEL

=back

=back

=head2 The Locker

=over 4

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

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

=item $obj-E<gt>B<folder>([FOLDER])

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

=item $obj-E<gt>B<name>()

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

=back

=head2 Locking

=over 4

=item $obj-E<gt>B<hasLock>()

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

=item $obj-E<gt>B<isLocked>()

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

=item $obj-E<gt>B<lock>()

=item $obj-E<gt>B<unlock>()

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

=back

=head2 Error handling

=over 4

=item $obj-E<gt>B<AUTOLOAD>()

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

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

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

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

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

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

=item $obj-E<gt>B<errors>()

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

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

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

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

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

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

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

=item $obj-E<gt>B<logSettings>()

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

=item $obj-E<gt>B<notImplemented>()

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

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

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

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

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

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

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

=item $obj-E<gt>B<warnings>()

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

=back

=head2 Cleanup

=over 4

=item $obj-E<gt>B<DESTROY>()

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

=item $obj-E<gt>B<inGlobalDestruction>()

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

=back

=head1 DIAGNOSTICS

=over 4

=item Warning: Folder $folder already locked over nfs

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

=item Error: Package $package does not implement $method.

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.

=item Warning: Removed expired lockfile $filename.

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 successfully
removed.

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

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 2.106,
built on August 15, 2012. Website: F<http://perl.overmeer.net/mailbox/>

=head1 LICENSE

Copyrights 2001-2012 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>

