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Catalyst::Plugin::PageUsereContributed Perl DocuCatalyst::Plugin::PageCache(3)

NAME
       Catalyst::Plugin::PageCache - Cache the output of entire	pages

SYNOPSIS
	   use Catalyst;
	   MyApp->setup( qw/Cache::FileCache PageCache/	);

	   __PACKAGE__->config(
	       'Plugin::PageCache' => {
		   expires => 300,
		   set_http_headers => 1,
		   auto_cache => [
		       '/view/.*',
		       '/list',
		   ],
		   debug => 1,

		   # Optionally, a cache hook method to	be called prior	to dispatch to
		   # determine if the page should be cached.  This is called both
		   # before dispatch, and before finalize.
		   cache_hook => 'some_method',

		   # You may alternatively set different methods to be used as hooks
		   # for dispatch and finalize.	The dispatch method will determine
		   # whether the currently cached page will be displayed to the	user,
		   # and the finalize hook will	determine whether to save the newly
		   # created page.
		   cache_dispatch_hook => 'some_method_for_dispatch',
		   cache_finalize_hook => 'some_method_for_finalize',
	       }
	   );

	   sub some_method {
	       my $c = shift;
	       if ( $c->user_exists and	$c->user->some_field ) {
		   return 0; # Don't cache
	       }
	       return 1; # Cache
	   }

	   # in	a controller method
	   $c->cache_page( '3600' );

	   $c->clear_cached_page( '/list' );

	   # Expire at a specific time
	   $c->cache_page( $datetime_object );

	   # Fine control
	   $c->cache_page(
	       last_modified   => $last_modified,
	       cache_seconds   => 24 * 60 * 60,	   # once a day
	       expires	       => 300,		   # allow client caching
	   );

DESCRIPTION
       Many dynamic websites perform heavy processing on most pages, yet this
       information may rarely change from request to request.  Using the
       PageCache plugin, you can cache the full	output of different pages so
       they are	served to your visitors	as fast	as possible.  This method of
       caching is very useful for withstanding a Slashdotting, for example.

       This plugin requires that you also load a Cache plugin.	Please see the
       Known Issues when choosing a cache backend.

WARNINGS
       PageCache should	be placed at the end of	your plugin list.

       You should only use the page cache on pages which have NO user-specific
       or customized content.  Also, be	careful	if caching a page which	may
       forward to another controller.  For example, if you cache a page	behind
       a login screen, the logged-in version may be cached and served to
       unauthenticated users.

       Note that pages that result from	POST requests will never be cached.

PERFORMANCE
       On my Athlon XP 1800+ Linux server, a cached page is served in 0.008
       seconds when using the HTTP::Daemon server and any of the Cache
       plugins.

CONFIGURATION
       Configuration is	optional.  You may define the following	configuration
       values:

	   expires => $seconds

       This will set the default expiration time for all page caches.  If you
       do not specify this, expiration defaults	to 300 seconds (5 minutes).

	   cache_headers => 1

       Enable this value if you	need your cached responses to include custom
       HTTP headers set	by your	application.  This may be necessary if you
       operate behind an edge cache such as Akamai.  This option is disabled
       by default.

	   set_http_headers => 1

       Enabling	this value will	cause Catalyst to set the correct HTTP headers
       to allow	browsers and proxy servers to cache your page.	This will
       further reduce the load on your server.	The headers are	set in such a
       way that	the browser/proxy cache	will expire at the same	time as	your
       cache.  The Last-Modified header	will be	preserved if you have already
       specified it.  This option is disabled by default.

	   auto_cache => [
	       $uri,
	   ]

       To automatically	cache certain pages, or	all pages, you can specify
       auto-cache URIs as an array reference.  Any controller within your
       application that	matches	one of the auto_cache URIs will	be cached
       using the default expiration time.  URIs	may be specified as absolute:
       '/list' or as a regex: '/view/.*'

	   disable_index => 1

       To support the "clear_cached_page" method, PageCache attempts keep an
       index of	all cached pages. This adds overhead by	performing extra cache
       reads and writes	to maintain the	(possibly very large) page index. It's
       also not	reliable, see "KNOWN ISSUES".

       If you don't intend to use "clear_cached_page", you should enable this
       config option to	avoid the overhead of creating and updating the	cache
       index.  This option is currently	disabled (i.e. the page	index is
       enabled)	by default but that may	change in a future release.

	   index_page_key => '...'

       The key string used for the index, Defaults to a	string that includes
       the name	of the Catalyst	app class.

	   busy_lock =>	10

       On a high traffic site where page re-generation may take	many seconds,
       a common	problem	encountered is the "dog-pile" effect, where many
       concurrent connections all hit a	page where the cache has expired and
       all perform the same expensive operation	to rebuild the cache.  To
       prevent this situation, you can set the busy_lock option	to the maximum
       number of seconds any of	your pages can be expected to take to rebuild
       the cache.  Then, when the cache	expires, the first request will
       rebuild the cache while also extending the expiration time by the
       number of seconds specified, allowing other requests that arrive	before
       the cache has been rebuilt to use the previously	cached page.  This
       option is disabled by default.

	   debug => 1

       This will print additional debugging information	to the Catalyst	log.
       You will	need to	have -Debug enabled to see these messages.

	   auto_check_user => 1

       If this option is enabled, automatic caching is disabled	for logged in
       users i.e., if the app class has	a user_exists()	method and it returns
       true.

	   cache_hook => 'cache_hook_method'
	   cache_finalize_hook => 'cache_finalize_hook_method'
	   cache_dispatch_hook => 'cache_dispatch_hook_method'

       Calls a method on the application that is expected to return a true or
       false.  This method is called before dispatch, and before finalize so
       you can short circuit the pagecache behavior.  As an example, if	you
       want to disable PageCache while running under debug mode:

	   package MyApp;

	   ...

	   sub cache_hook_method { return shift->debug;	}

       Or, if you want to not cache for	certain	roles, say "admin":

	   sub cache_hook_method {
	       my ( $c ) = @_;
	       return !$c->check_user_roles('admin');
	   }

       Note that this is called	BEFORE auto_check_user,	so you have more
       flexibility to determine	what to	do for not logged in users.

       To override the generation of page keys:

	   __PACKAGE__->config(
	       'Plugin::PageCache' => {
		   key_maker =>	sub {
		       my $c = shift;
		       return $c->req->base . '/' . $c->req->path;
		   }
	       }
	   );

       "key_maker" can also be the name	of a method, which will	be invoked as
       "<$c-"$key_maker>>.

       In most cases you would use a single cache_hook method for consistency.

       It is possible to achieve background refreshing of content by disabling
       caching in cache_dispatch_hook and enabling caching in
       cache_finalize_hook for a specific IP address (say 127.0.0.1).

       A cron of wget "http://localhost/foo.html" would	cause the content to
       be generated fresh and cached for future	viewers. Useful	for content
       which takes a very long time to build or	pages which should be
       refreshed at a specific time such as always rolling over	content	at
       midnight.

METHODS
   cache_page
       Call cache_page in any controller method	you wish to be cached.

	   $c->cache_page( $expire );

       The page	will be	cached for $expire seconds.  Every user	who visits the
       URI(s) referenced by that controller will receive the page directly
       from cache.  Your controller will not be	processed again	until the
       cache expires.  You can set this	value to a low value, such as 60
       seconds,	if you have heavy traffic, to greatly improve site
       performance.

       Pass in a DateTime object to make the cache expire at a given point in
       time.

	   $two_hours =	DateTime->now->add( hours => 2 );
	   $c->cache_page( $two_hours );

       The page	will be	stored in the page cache until this time.

       If set_http_headers is set then Expires and Cache-Control headers will
       also be set to expire at	the given date as well.

       Pass in a list or hash reference	for finer control.

	   $c->cache_page(
	       last_modified   => $last_modified,
	       cache_seconds   => 24 * 60 * 60,
	       expires	       => 30,
	   );

       This allows separate control of the page	cache and the header cache
       values sent to the client.

       Possible	options	are:

       cache_seconds
	   This	is the number of seconds to keep the page in the page cache,
	   which may be	different (normally longer) than the time that client
	   caches may store the	page.  This is the value set when only a
	   single parameter is passed.

       expires
	   This	is the length of time in seconds that a	client may cache the
	   page	before revalidating (by	asking the server if the document has
	   changed).

	   Unlike above, this is a fixed setting that each client will see.
	   Regardless of how much longer the page will be cached in the	page
	   cache the client still sees the same	expires	time.

	   Setting zero	(0) for	expires	will result in the page	being cached,
	   but headers will be sent telling the	client to not cache the	page.
	   Allows caching expensive content to generate, but any changes will
	   be seen right away.

       last_modified
	   Last	modified time in epoch seconds.	 If not	set will use either
	   the current Last-Modified header, or	if not set, the	current	time.

   clear_cached_page
       To clear	the cached pages for a URI, you	may call clear_cached_page.

	   $c->clear_cached_page( '/view/userlist' );
	   $c->clear_cached_page( '/view/.*' );
	   $c->clear_cached_page( '/view/.*\?.*\bparam=value\b'	);

       This method takes an absolute path or regular expression.  Returns the
       number of matching entries found	in the index.  A warning will be
       generated if the	page index is disabled (see "CONFIGURATION").

       The argument is matched against all the keys in the page	index.	The
       page index keys include the request path	and query string, if any.

       Typically you'd call this from a	different controller than the cached
       controller. You may for example wish to build an	admin page that	lets
       you clear page caches.

INTERNAL EXTENDED METHODS
   dispatch
       "dispatch" decides whether or not to serve a particular request from
       the cache.

   finalize
       "finalize" caches the result of the current request if needed.

   setup
       "setup" initializes all default values.

I18N SUPPORT
       If your application uses	Catalyst::Plugin::I18N for localization, a
       separate	cache key will be used for each	language a page	is displayed
       in.

KNOWN ISSUES
       The page	index, used to support the "clear_cached_page" method is
       unreliable because it uses a read-modify-write approach which will
       loose data if more than one process attempts to update the page index
       at the same time.

       It is not currently possible to cache pages served from the Static
       plugin.	If you're concerned enough about performance to	use this
       plugin, you should be serving static files directly from	your web
       server anyway.

       Cache::FastMmap does not	have the ability to specify different
       expiration times	for cached data.  Therefore, if	your
       MyApp->config->{cache}->{expires} value is set to anything other	than
       0, you may experience problems with the clear_cached_page method,
       because the cache index may be removed.	For best results, you may wish
       to use Cache::FileCache or Cache::Memcached as your cache backend.

SEE ALSO
       Catalyst, Catalyst::Plugin::Cache::FastMmap,
       Catalyst::Plugin::Cache::FileCache, Catalyst::Plugin::Cache::Memcached

AUTHOR
       Andy Grundman, <andy@hybridized.org>

THANKS
       Bill Moseley, <mods@hank.org>, for many patches and tests.

       Roberto HenrAquez, <roberto@freekeylabs.com>, for i18n support.

COPYRIGHT
       This program is free software, you can redistribute it and/or modify it
       under the same terms as Perl itself.

POD ERRORS
       Hey! The	above document had some	coding errors, which are explained
       below:

       Around line 835:
	   Non-ASCII character seen before =encoding in	'HenrAquez,'. Assuming
	   UTF-8

perl v5.32.1			  2016-08-18	Catalyst::Plugin::PageCache(3)

NAME | SYNOPSIS | DESCRIPTION | WARNINGS | PERFORMANCE | CONFIGURATION | METHODS | INTERNAL EXTENDED METHODS | I18N SUPPORT | KNOWN ISSUES | SEE ALSO | AUTHOR | THANKS | COPYRIGHT | POD ERRORS

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