WWW::Mechanize::Cached(3)

NAME
WWW::Mechanize::Cached - Cache response to be polite

VERSION
version 1.56

SYNOPSIS
    use WWW::Mechanize::Cached;

    my $cacher = WWW::Mechanize::Cached->new;
    $cacher->get( 'https://metacpan.org' );

    # or, with your own Cache object
    use CHI;
    use WWW::Mechanize::Cached;

    my $cache = CHI->new(
        driver   => 'File',
        root_dir => '/tmp/mech-example'
    );

    my $mech = WWW::Mechanize::Cached->new( cache => $cache );
    $mech->get("http://www.wikipedia.org");

DESCRIPTION
Uses the Cache::Cache hierarchy by default to implement a caching Mech. This lets one perform repeated requests without hammering a server impolitely. Please note that Cache::Cache has been superseded by CHI, but the default has not been changed here for reasons of backwards compatibility. For this reason, you are encouraged to provide your own CHI caching object to override the default.

CONSTRUCTOR

  new
Behaves like, and calls, WWW::Mechanize's "new" method. Any params, other than those explicitly listed here are passed directly to WWW::Mechanize's constructor.

You may pass in a "cache => $cache_object" if you wish. The $cache_object must have get() and set() methods like the "Cache::Cache" family.

The default Cache object is set up with the following params:

    my $cache_params = {
        default_expires_in => "1d", namespace => 'www-mechanize-cached',
    };

    $cache = Cache::FileCache->new( $cache_params );

This should be fine if you only want to use a disk-based cache, you only want to cache results for 1 day and you're not in a shared hosting environment. If any of this presents a problem for you, you should pass in your own Cache object. These defaults will remain unchanged in order to maintain backwards compatibility.

For example, you may want to try something like this:

    use WWW::Mechanize::Cached;
    use CHI;

    my $cache = CHI->new(
        driver   => 'File',
        root_dir => '/tmp/mech-example'
    );

    my $mech = WWW::Mechanize::Cached->new( cache => $cache );
    $mech->get("http://www.wikipedia.org");

METHODS
Most methods are provided by WWW::Mechanize. See that module's documentation for details.

  cache( $cache_object )
Requires an caching object which has a get() and a set() method. Using the CHI module to create your cache is the recommended way. See new() for examples.

  is_cached()
Returns true if the current page is from the cache, or false if not. If it returns "undef", then you don't have any current request.

  positive_cache( 0|1 )
As of v1.36 positive caching is enabled by default. Up to this point, this module had employed a negative cache, which means it cached 404 responses, temporary redirects etc. In most cases, this is not what you want, so the default behaviour now better reflects this. You can revert to the negative cache quite easily:

    # cache everything (404s, all 300s etc)
    $mech->positive_cache( 0 );

  ref_in_cache_key( 0|1 )
Allow the referring URL to be used when creating the cache key. This is off by default. In almost all cases, you will not want to enable this, but it is available to you for reasons of backwards compatibility and giving you enough rope to hang yourself.

Previous to v1.36 the following was in the "BUGS AND LIMITATIONS" section:

    It may sometimes seem as if it's not caching something. And this may well
    be true. It uses the HTTP request, in string form, as the key to the cache
    entries, so any minor changes will result in a different key. This is most
    noticable when following links as L<WWW::Mechanize> adds a C<Referer>
    header.

See RT #56757 for a detailed example of the bugs this functionality can trigger.

  cache_undef_content_length( 0 | 'warn' | 1 )
This is configuration option which adjusts how caching behaviour performs when the Content-Length header is not specified by the server.

Default behaviour is 0, which is not to cache.

Setting this value to 1, will cache pages even if the Content-Length header is missing, which was the default behaviour prior to the addition of this feature.

And thirdly, you can set the value to the string 'warn', to warn if this scenario occurs, and then not cache it.

  cache_zero_content_length( 0 | 'warn' | 1 )
This is configuration option which adjusts how caching behaviour performs when the Content-Length header is equal to 0.

Default behaviour is 0, which is not to cache.

Setting this value to 1, will cache pages even if the Content-Length header is 0, which was the default behaviour prior to the addition of this feature.

And thirdly, you can set the value to the string 'warn', to warn if this scenario occurs, and then not cache it.

  cache_mismatch_content_length( 0 | 'warn' | 1 )
This is configuration option which adjusts how caching behaviour performs when the Content-Length header differs from the length of the content itself. ( Which usually indicates a transmission error )

Setting this value to 0, will silently not cache pages with a Content-Length mismatch.

Setting this value to 1, will cache pages even if the Content-Length header conflicts with the content length, which was the default behaviour prior to the addition of this feature.

And thirdly, you can set the value to the string 'warn', to warn if this scenario occurs, and then not cache it. ( This is the default behaviour )

  invalidate_last_request()
Remove the last request from the cache.

The return value reveals whether the request was successfully removed from the cache. 1 means it's still cached, 0 means it was removed, and undef means there was nothing to remove (there was no request or it wasn't cached).

UPGRADING FROM 1.40 OR EARLIER
Caching behaviour has changed since 1.40, and this may result in pages that were previously cached start failing to cache, and in some cases, emit warnings.

To return to the 1.40 behaviour:

    $mech->cache_undef_content_length(1);  # Default is 0
    $mech->cache_zero_content_length(1);   # Default is 0
    $mech->cache_mismatch_content_length(1); # Default is 'warn'

THANKS
Iain Truskett for writing this in the first place. Andy Lester for graciously handing over maintainership. Kent Fredric for adding content length handling.

SUPPORT
You can find documentation for this module with the perldoc command.

    perldoc WWW::Mechanize::Cached

•   Search CPAN

    <https://metacpan.org/module/WWW::Mechanize::Cached>

SEE ALSO
WWW::Mechanize, WWW::Mechanize::Cached::GZip.

AUTHORS

•   Iain Truskett (original author)

•   Andy Lester <petdance@cpan.org> (2004 - July 2009)

•   Olaf Alders <olaf@wundercounter.com> (current maintainer)

COPYRIGHT AND LICENSE
This software is copyright (c) 2004 by Iain Truskett and Andy Lester.

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