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 `<cpan at interactive.co.uk>'
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). You may obtain a copy
of the full license at:
http://www.perlfoundation.org/artistic_license_2_0
Any use, modification, and distribution of the Standard or Modified
Versions is governed by this Artistic License. By using, modifying or
distributing the Package, you accept this license. Do not use, modify,
or distribute the Package, if you do not accept this license.
If your Modified Version has been derived from a Modified Version made
by someone other than you, you are nevertheless required to ensure that
your Modified Version complies with the requirements of this license.
This license does not grant you the right to use any trademark, service
mark, tradename, or logo of the Copyright Holder.
This license includes the non-exclusive, worldwide, free-of-charge
patent license to make, have made, use, offer to sell, sell, import and
otherwise transfer the Package with respect to any patent claims
licensable by the Copyright Holder that are necessarily infringed by the
Package. If you institute patent litigation (including a cross-claim or
counterclaim) against any party alleging that the Package constitutes
direct or contributory patent infringement, then this Artistic License
to you shall terminate on the date that such litigation is filed.
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