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https://github.com/robrwo/catalyst-plugin-detachifnotmodified

Short-circuit requests with If-Modified-Since headers
https://github.com/robrwo/catalyst-plugin-detachifnotmodified

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Short-circuit requests with If-Modified-Since headers

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# NAME



Catalyst::Plugin::DetachIfNotModified - Short-circuit requests with If-Modified-Since headers



# VERSION



version v0.3.1



# SYNOPSIS



In your Catalyst class:



```perl

use Catalyst qw/

    DetachIfNotModified

  /;

```



In a controller method:



```perl

my $item = ...



$c->detach_if_not_modified_since( $item->timestamp );



# Do some CPU-intensive stuff or generate response body here.

```



# DESCRIPTION



This plugin will allow your [Catalyst](https://metacpan.org/pod/Catalyst) app to handle requests with

`If-Modified-Since` headers.



If the content of a web page has not been modified since a given date,

you can quickly bail out and avoid generating a web page that you do

not need to.



This can improve the performance of your website.



This should be used with [Plack::Middleware::ConditionalGET](https://metacpan.org/pod/Plack%3A%3AMiddleware%3A%3AConditionalGET).



# METHODS



## detach\_if\_not\_modified\_since



```

$c->detach_if_not_modified_since( @timestamps );

```



This sets the `Last-Modified` header in the response to the

maximum timestamp, and checks if the request contains a

`If-Modified-Since` header that not less than the maximum timestamp.  If it

does, then it will set the response status code to `304` (Not

Modified) and detach.



The `@timestamps` is a list of unix epochs or objects with an `epoch`

method, such as a [DateTime](https://metacpan.org/pod/DateTime) object.



This should only be used with GET or HEAD requests.



If you later need to reset the `Last-Modified` header after calling

this method, you can use



```

$c->res->headers->remove_header('Last-Modified');

```



# CAVEATS



Be careful when aggregating a collection of objects into a single

timestamp, e.g. the maximum timestamp from a list.  If a member is

removed from that collection, then the maximum timestamp won't be

affected, and the result is that an outdated web page may be cached by

user agents.



# SUPPORT FOR OLDER PERL VERSIONS



Since v0.3.0, the this module requires Perl v5.14 or later.



Future releases may only support Perl versions released in the last ten years.



If you need this module on earlier Perls, please use one of the v0.2.x

versions of this module.  Significant bug or security fixes may be

backported to those versions.



# SEE ALSO



[Catalyst](https://metacpan.org/pod/Catalyst)



[Catalyst::Plugin::Cache::HTTP::Preempt](https://metacpan.org/pod/Catalyst%3A%3APlugin%3A%3ACache%3A%3AHTTP%3A%3APreempt)



[Plack::Middleware::ConditionalGET](https://metacpan.org/pod/Plack%3A%3AMiddleware%3A%3AConditionalGET)



[RFC 7232 Section 3.3](https://tools.ietf.org/html/rfc7232#section-3.3)



# SOURCE



The development version is on github at [https://github.com/robrwo/Catalyst-Plugin-DetachIfNotModified](https://github.com/robrwo/Catalyst-Plugin-DetachIfNotModified)

and may be cloned from [git://github.com/robrwo/Catalyst-Plugin-DetachIfNotModified.git](git://github.com/robrwo/Catalyst-Plugin-DetachIfNotModified.git)



# BUGS



Please report any bugs or feature requests on the bugtracker website

[https://github.com/robrwo/Catalyst-Plugin-DetachIfNotModified/issues](https://github.com/robrwo/Catalyst-Plugin-DetachIfNotModified/issues)



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.



# AUTHOR



Robert Rothenberg 



This module is based on code created for Science Photo Library

[https://www.sciencephoto.com](https://www.sciencephoto.com).



# COPYRIGHT AND LICENSE



This software is Copyright (c) 2020-2023 by Robert Rothenberg.



This is free software, licensed under:



```

The Artistic License 2.0 (GPL Compatible)

```