NAME Catalyst::Plugin::Cache::HTTP::Preempt - preemptive HTTP cache control VERSION v0.1.3 REQUIREMENTS This module requires Perl v5.10 or later. The following non-core Perl modules are required: Catalyst DateTime HTTP::Message 6.06 Moose Readonly Additional modules may be required for running tests: DateTime::Format::HTTP Digest::MD5 ok Test::WWW::Mechanize::Catalyst URI DESCRIPTION This is a Catalyst plugin handles HTTP 1.1 cache-control queries. The functionality is similar to Catalyst::Plugin::Cache::HTTP, except that it processes the cache control queries before data-intensive queries, rather rather than delaying processing until the view is generated. SYNOPSIS use Catalyst qw/ Cache::HTTP::Preempt /; __PACKAGE__->config( 'Plugin::Cache::HTTP::Preempt' => { no_preempt_head => 0, etag_generator => sub { my ($c, $config) = @_; return "W/" . sprintf("%x", $c->res->headers->last_modified); }, }, ); CONFIGURATION OPTIONS no_preempt_head By default, the not_cached method will return `false' for `HEAD' requests (even though it will still process cache control headers). If you still want to handle `HEAD' requests, then set this option to a `true' value. no_etag Do not set the `ETag' header. no_last_modified Do not set the `Last-Modified' header. no_expires Do not set the `Expires' header. etag_generator You can change how the `ETag' is generated by using the `etag_generator' option: sub etag_generator { my ($c, $config) = @_; my $mtime = $c->req->headers->last_modified; return sprintf( $config->{strong} ? "%x" : "W/%x" , $mtime); } if ($c->not_cached({ etag_generator => \&etag_generator }) { ... } This is useful if you want to use something other than the modification date of an entity for generating the `ETag'. The purpose of this function is to *only* generate the `ETag'. No headers should be changed. Returning an `undef' value corresponds to not setting an `ETag'. strong Generate a strong `ETag'. By default, a weak `ETag' is used, since the `ETag' is based on the `Last-Modified' time rather than the content. As per the HTTP 1.1 specification, weak `ETags' will not work with the `If-Match' header. check_if_range When this option, is true, it will check for the `If-Range' and `Range' headers. The controller is responsible for sending the correct response. (See the discussion for the not_cached method below.) METHODS not_cached $c->res->headers->last_modified( $obj->mtime ); ... if ($c->not_cached(\%options)) { # The response is not cached, so should be generated ... } else { ... } Checks the requests for HTTP 1.1 cache control headers and handles them accordingly. This method sets the `ETag' header based on the `Last-Modified' header (unless one is already set) and checks for the `If-Modified-Since', `If-Unmodified-Since', `If-Match' and `If-None-Match' request headers to see if generating the entity can be preempted. If the entity can be preempted (i.e. if it has not been modified since the given date), then the status is set appropriately, and this method returns false. Otherwise it returns true. This allows you to avoid reading data from a database or otherwise data-intensive processing when it's not actually needed. If `%options' are given, then they will override the global options. If the `Last-Modified' header is unset, then this function will assume the last-modification time is the current time. If no `Expires' header is set and the function will return a true value, then it will set it to the current time. (This is important for web browsers that aggressively cache responses, such as Firefox.) Cache control options will be processed for `HEAD' requests, but this method will always return false, unless the `no_preempt_head' option is true. If the status is already set to something other than `2xx' when this method is called, then the the `If-Match', `If-None-Match' and `If-Unmodified-Since' headers will be ignored. However, the `ETag', `Expires' and `Last-Modified' headers will still be set. (Ideally, you would not be calling the not_cached method if there is an error.) If the `check_if_range' option is true, then you *must* check whether the status code has been set to `206' or `200', and respond accordingly: if ($c->not_cached( { check_if_range => 1 }) { if ($c->res->code == 206) { # Return partial content as per the Range header. ... } else { # Return full content. Note that the status is set to 200, so # it must be updated if there are other errors ... } } Using with Catalyst::Plugin::Cache::HTTP This module can be used with Catalyst::Plugin::Cache::HTTP in a Catalyst application, although it is not recommended that you use it in the same method. If you are using both plugins, then you should modify the view processing method to check if an `ETag' header has already been set: sub process { my $self = shift; my $c = $_[0]; $self->next::method(@_) or return 0; my $method = $c->req->method; return 1 if ((($method ne 'GET') and ($method ne 'HEAD')) or $c->stash->{nocache}); # disable caching explicitely unless ($c->res->headers->etag || $c->stash->{no_etag}) { ... } } Using with Catalyst::Controller::REST Catalyst::Controller::REST does not have status helpers for "304 Not Modified" and and "412 Precondition Failed" responses. To work around this, you need to manually set the entity using an undocumented method: $c->res->headers->last_modified( $obj->mtime ); if ($c->modified) { # Do more processing to generate the page } else { $self->_set_entity($c, { error => "Not Modified" }); return 1; } SEE ALSO * Catalyst * Catalyst::Plugin::Cache::HTTP * HTTP 1.1 AUTHOR Interactive Information, Ltd `' SUPPORT You can find documentation for this module with the perldoc command. perldoc Catalyst::Plugin::Cache::HTTP::Preempt You can also find information at: * RT: CPAN's request tracker (report bugs here) http://rt.cpan.org/NoAuth/Bugs.html?Dist=Catalyst-Plugin-Cache-HTTP- Preempt * AnnoCPAN: Annotated CPAN documentation http://annocpan.org/dist/Catalyst-Plugin-Cache-HTTP-Preempt * CPAN Ratings http://cpanratings.perl.org/d/Catalyst-Plugin-Cache-HTTP-Preempt * Search CPAN http://search.cpan.org/dist/Catalyst-Plugin-Cache-HTTP-Preempt/ LICENSE AND COPYRIGHT Copyright (c) 2012-2013 Interactive Information, Ltd This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0). 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