Catalyst::Plugin::PageUsereContributed Perl DocuCatalyst::Plugin::PageCache(3)NAMECatalyst::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 HenrA~quez, <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.
perl v5.14.1 2010-11-09 Catalyst::Plugin::PageCache(3)
