NAME

       File::Flock::Retry - Yet another flock module

VERSION

       This document describes version 0.632 of File::Flock::Retry (from Perl distribution File-
       Flock-Retry), released on 2021-08-10.

SYNOPSIS

        use File::Flock::Retry;

        # try to acquire exclusive lock. if fail to acquire lock within 60s, die.
        my $lock = File::Flock::Retry->lock($file);

        # explicitly unlock
        $lock->release;

        # automatically unlock if object is DESTROY-ed.
        undef $lock;

DESCRIPTION

       This is yet another flock module. It is a more lightweight alternative to File::Flock with
       some other differences:

       •   OO interface only

       •   Autoretry (by default for 60s) when trying to acquire lock

           I prefer this approach to blocking/waiting indefinitely or failing immediately.

METHODS

   lock
       Usage:

        $lock = File::Flock::Retry->lock($path, \%opts)

       Attempt to acquire an exclusive lock on $path. By default, $path will be created if not
       already exists (see "mode"). If $path is already locked by another process, will retry
       every second for a number of seconds (by default 60). Will die if failed to acquire lock
       after all retries.

       Will automatically unlock if $lock goes out of scope. Upon unlock, will remove $path if it
       is still empty (zero-sized).

       Available options:

       •   mode

           Integer. Default: O_CREAT | O_RDWR.

           File open mode, to be passed to Perl's "sysopen()". For example, if you want to avoid
           race condition between creating and locking the file, you might want to use "O_CREAT |
           O_EXCL | O_RDWR" to fail when the file already exists. Note that the constants are
           available after you do a "use Fcntl ':DEFAULT';".

       •   retries

           Integer. Default: 60.

           Number of retries (equals number of seconds, since retry is done every second).

       •   shared

           Boolean. Default: 0.

           By default, an exclusive lock (LOCK_EX) is attempted. However, if this option is set
           to true, a shared lock (LOCK_SH) is attempted.

   unlock
       Usage:

        $lock->unlock

       Unlock. will remove lock file if it is still empty.

   release
       Usage:

        $lock->release

       Synonym for "unlock".

   handle
       Usage:

        my $fh = $lock->handle;

       Return the file handle.

HOMEPAGE

       Please visit the project's homepage at <https://metacpan.org/release/File-Flock-Retry>.

SOURCE

       Source repository is at <https://github.com/perlancar/perl-File-Flock-Retry>.

BUGS

       Please report any bugs or feature requests on the bugtracker website
       <https://rt.cpan.org/Public/Dist/Display.html?Name=File-Flock-Retry>

       When submitting a bug or request, please include a test-file or a patch to an existing
       test-file that illustrates the bug or desired feature.

CAVEATS

       Not yet tested on Windows. Some filesystems do not support inode?

SEE ALSO

       File::Flock, a bit too heavy in terms of dependencies and startup overhead, for my taste.
       It depends on things like File::Slurp and Data::Structure::Util (which loads Digest::MD5,
       Storable, among others).

       File::Flock::Tiny which is also tiny, but does not have the autoremove and autoretry
       capability which I want. See also:
       <https://github.com/trinitum/perl-File-Flock-Tiny/issues/1>

       flock() Perl function.

       An alternative to flock() is just using sysopen() with O_CREAT|O_EXCL mode to create lock
       files. This is supported on more filesystems (particularly network filesystems which lack
       flock()).

AUTHOR

       perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2021, 2019, 2017, 2015, 2014 by perlancar
       <perlancar@cpan.org>.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.