NAME

CHI::Driver::File - File-based cache using one file per entry in a multi-level directory structure

VERSION

version 0.61

SYNOPSIS

    use CHI;
    my $cache = CHI->new(
        driver         => 'File',
        root_dir       => '/path/to/cache/root',
        depth          => 3,
        max_key_length => 64
    );

DESCRIPTION

This cache driver stores data on the filesystem, so that it can be shared between processes on a single machine, or even on multiple machines if using NFS.

Each item is stored in its own file. By default, during a set, a temporary file is created and then atomically renamed to the proper file. While not the most efficient, it eliminates the need for locking (with multiple overlapping sets, the last one "wins") and makes this cache usable in environments like NFS where locking might normally be undesirable.

By default, the base filename is the key itself, with unsafe characters escaped similar to URL escaping. If the escaped key is larger than "max_key_length" (default 248 characters), it will be digested. You may want to lower "max_key_length" if you are storing a lot of items as long filenames can be more expensive to work with.

The files are evenly distributed within a multi-level directory structure with a customizable "depth", to minimize the time needed to search for a given entry.

CONSTRUCTOR OPTIONS

When using this driver, the following options can be passed to CHI->new() in addition to the CHI.

root_dir

The location in the filesystem that will hold the root of the cache. Defaults to a directory called 'chi-driver-file' under the OS default temp directory (e.g. '/tmp' on UNIX). This directory will be created as needed on the first cache set.

depth

The number of subdirectories deep to place cache files. Defaults to 2. This should be large enough that no leaf directory has more than a few hundred files. Each non-leaf directory contains up to 16 subdirectories (0-9, A-F).

dir_create_mode

Permissions mode to use when creating directories. Defaults to 0775.

file_create_mode

Permissions mode to use when creating files, modified by the current umask. Defaults to 0666.

file_extension

Extension to append to filename. Default is ".dat".

METHODS

path_to_key ( $key )

Returns the full path to the cache file representing $key, whether or not that entry exists. Returns the empty list if a valid path cannot be computed, for example if the key is too long.

path_to_namespace

Returns the full path to the directory representing this cache's namespace, whether or not it has any entries.

TEMPORARY FILE RENAME

By default, during a set, a temporary file is created and then atomically renamed to the proper file. This eliminates the need for locking. You can subclass and override method generate_temporary_filename to either change the path of the temporary filename, or skip the temporary file and rename altogether by having it return undef.

SEE ALSO

CHI

AUTHOR

Jonathan Swartz <swartz@pobox.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2021 by Jonathan Swartz.

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