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1 non-PAUSE user(s).

Henry Van Styn

NAME

Catalyst::Controller::AutoAssets - Automatic asset serving via sha1-based URLs

SYNOPSIS

In your controller:

  package MyApp::Controller::Assets::MyCSS;
  use parent 'Catalyst::Controller::AutoAssets';
  
  1;

Then, in your .conf:

  <Controller::Assets::MyCSS>
    include   root/my_stylesheets/
    type      CSS
    minify    1
  </Controller::Assets::MyCSS>

And in your .tt files:

  <head>
    <link rel="stylesheet" type="text/css" href="[% c.controller('Assets::MyCSS').asset_path %]" />
  </head>

Or, to have the appropriate tags generated for you:

  <head>
    [% c.controller('Assets::MyCSS').html_head_tags %]
  </head>

Or, in static HTML:

  <head>
    <link rel="stylesheet" type="text/css" href="/assets/mycss/current.css" />
  </head>

PLUGIN INTERFACE

A Catalyst Plugin interface is also available for easy setup of multiple asset controllers at once. See

Catalyst::Plugin::AutoAssets

DESCRIPTION

Fast, convenient and extendable serving of assets (CSS, JavaScript, Images, etc) at URL path(s) containing sha1 checksums. This is an alternative/supplement to Catalyst::Plugin::Static::Simple or external/webserver for serving of an application's "nearly static" content.

The benefit of serving files through CAS paths ("content-addressable storage" - same design used by Git) is that it automatically alleviates client caching issues while simultaneously taking advantage of maximum aggressive HTTP cache settings. Because URL paths contain the sha1 checksum of the data, browsers can safely cache the content forever because "changes" automatically become new URLs. If the content (CSS, JavaScript or other) is modified later on, the client browsers instantly see the new version.

This is particularly useful when deploying new versions of an application where client browsers out in the network might have cached CSS, JavaScript and Images from previous versions. Instead of asking users to hit "F5", everyone gets the new content automagically, with no intervention required (and no sporadically broken user experiences when you forget to plan for cached data). All you have to do is change the content; the module handles the rest.

This module also provides some optional extra features that are useful in both development and production environments for automatically managing, minifying and deploying CSS, JavaScript, Image and Icon assets.

PERFORMANCE

Besides the performance benefits of aggressive HTTP caching (which can be significant, depending of the ratio of first-time visitors to returning visitors) this module has also been optimized to serve requests as fast as possible. On typical requests, all that happens besides returning the content from disk is one extra file stat and comparison of mtime. So, even with it's real-time content-change tracking and checksums, this module is essentially identical to Catalyst::Plugin::Static::Simple from a performance perspective (and may even be slightly faster because it caches guessed Content-Types instead of calculating on every request like Static::Simple).

When to use this module

This module is great for development, web applications, and any production site with a high percentage of returning users. If you want to take maximum advantage of HTTP caching without any work or planning, this module is for you. Or, if you just want an easy and flexible way to manage static content, performance benefits aside, this module is also for you.

When not to

The only cases where this module is not recommended is on very high-volume sites where most of the visits are unique (i.e. little benefit from HTTP caching), or where the scale is large enough that the marginal increase in speed of serving static content directly from the web server (like Apache), instead of through Catalyst, is worth manually - and correctly - doing all the things that this module does automatically. Unless you are carefully planning your HTTP caching strategy (such configuring Apache's cache settings) and coordinating all this with content changes/new releases, this module is likely to outperform your manual setup.

HANDLERS

Note: All config params and methods described below are actually delegated to the type handler specified in 'type' and some are specific (as noted below). For convenience, the core handlers Directory, CSS and JS are documented below but others are available (and custom handlers can also be written). To see other available type handlers and for information on writing custom handlers see:

Catalyst::Controller::AutoAssets::Handler

CONFIG PARAMS

type

Required - The asset type: Directory, CSS, JS, etc.

The asset type is a "Handler" class name, and the core built in types are covered below. Custom handlers can also be written. See Catalyst::Controller::AutoAssets::Handler for details.

The Directory asset type works in a similar manner as Static::Simple to make some directory structure accessible at a public URL. The root of the structure is made available at the URL path:

  <CONTROLLER_PATH>/<SHA1>/

MIME::Types is used to set the Content-Type HTTP header based on the file extension (same as Static::Simple does).

Because the sha1 checksum changes automatically and is unknown in advance, the above Asset Path is made available via the asset_path() controller method for use in TT files and throughout the application.

The CSS and JS types serve one automatically generated text file that is concatenated and optionally minified from the include files. The single, generated file is made available at the URL Path:

  <CONTROLLER_PATH>/<SHA1>.js    # for 'JS' type
  <CONTROLLER_PATH>/<SHA1>.css   # for 'CSS' type

The js/css types provide a bonus mode of operation to provide a simple and convenient way to manage groups of CSS and JavaScript files to be automatically deployed in the application. This is also particularly useful during development. Production applications with their own management and build process for CSS and JavaScript would simply use the Directory type.

no_logs

Defaults to true to suppress log messages in the same manner as Static::Simple.

include

Required - String or ArrayRef. The path(s) on the local filesystem containing the source asset files. For Directory type this must be exactly one directory, while for CSS and JS it can be a list of directories. The include directory becomes the root of the files hosted as-is for the Directory type, while for CSS and JS asset types it is the include files concatenated together (and possibly minified) to be served as the single file.

include_regex

Optional regex ($string) to require files to match to be included.

exclude_regex

Optional regex ($string) to use to exclude files from the includes.

regex_ignore_case

Whether or not to use case-insensitive regex (qr/$regex/i vs qr/$regex/) when evaluating include_regex/exclude_regex.

Defaults to false (0).

current_redirect

Whether or not to make the current asset available via 307 redirect to the real, current checksum/fingerprint asset path. This is a pure HTTP mechanism of resolving the asset path.

  <CONTROLLER_PATH>/current/      # for 'directory' type
  <CONTROLLER_PATH>/current.js    # for 'js' type
  <CONTROLLER_PATH>/current.css   # for 'css' type

For instance, you might reference a CSS file from a Directory asset Controller::Assets::ExtJS using this URL path (i.e. href in an HTML link tag):

  /assets/extjs/current/resources/css/ext-all.css

This path would redirect (HTTP 307) to the current asset/file path which would be something like:

  /assets/extjs/1512834162611db1fab246dfa87e3a37f68ed95f/resources/css/ext-all.css

The downside of this is that the server has to serve the non-cachable redirect every time, which partially defeats the performance benefits of this module (although the redirect is comparatively lightweight).

The other mechanism to find the current asset path is via the asset_path() method, which returns the current path outright and is the recommended usage, but is only available in locations where application controller methods can be called (like in TT files).

Defaults to true (1).

current_alias

Alias to use for the current_redirect. Defaults to 'current' (which also implies 'current.js'/'current.css' for JS and CSS asset types).

allow_static_requests

Whether or not to make the current asset available directly via a static path ('/static/'). This is like current_redirect except the asset is served directly. This is essentially only useful for debug purposes as it will make no use of caching.

See also 'use_etags' below.

Defaults to false (0).

current_response_headers

Extra headers to set in the response for 'current' requests. Cache-Control => 'no-cache' is always set unless it is overridden here.

Defaults to empty HashRef {}

static_alias

Alias to use for static requests if allow_static_requests is enabled. Defaults to 'static'.

static_response_headers

Extra headers to set in the response for 'static' requests. Cache-Control => 'no-cache' is always set unless it is overridden here.

Defaults to empty HashRef {}

use_etags

Whether or not to set 'Etag' ("Entity Tag") HTTP response headers and check 'If-None-Match' client request headers to return HTTP/304 'Not Modified' responses to clients that already have the current version of the requested asset/file. This is essentially the same default behavior as Apache.

Etags provide another content-based mechanism (built into HTTP 1.1) for cache validation. This module accomplishes even better cache validation than Etags because it avoids the validation request needed to check the current Etag in the first place, however, Etag functionality has also been included because it is very useful when enabling and using 'static' paths which do not make use of the checksum in the URL. Also, when Etags are present, most browsers will use them even when hitting "F5" to manually reload the page to avoid downloading the content again, so this feature further increases performance for the F5 use-case which many users may be in the habit of doing for various legit reasons.

Defaults to false (0).

minify

Whether or not to attempt to minify content for CSS or JS asset types. This is a purely optional convenience feature.

Defaults to false (0). Does not apply to the Directory asset type.

minifier

CodeRef used to minify the content when minify is true. The default code is a pass-through to CSS::Minifier::minify() for CSS assets and JavaScript::Minifier::minify() for JS. If you want to override you must follow the same API as in those modules, using the input and outfile filehandle interface. See JavaScript::Minifier and CSS::Minifier for more details.

Does not apply to the Directory asset type.

scopify

Applies only to the CSS asset type. CSS will be scopified using CSS::Scopifier. The scopify param should be an ArrayRef that will be used to pass to argument list of the scopify method. Note that scopify and minify are net yet supported together.

work_dir

The directory where asset-specific files are generated and stored. This contains the checksum/fingerprint file, the lock file, and the built file. In the case of Directory assets the built file contains a manifest of files and in the case of CSS and JS assets it contains the actual asset content (concatenated and possibly minified)

Defaults to:

  <APP_TMPDIR>/AutoAssets/<CONTROLLER_PATH>/

max_lock_wait

Number of seconds to wait to obtain an exclusive lock when recalculating/regenerating. For thread-safety, when the system needs to regenerate the asset (fingerprint and built file) it obtains an exclusive lock on the lockfile in the work_dir. If another thread/process already has a lock, the system will wait for up to max_lock_wait seconds before proceeding anyway.

Note that this is only relevant when the source/include content changes while the app is running (which should never happen in a production environment).

Defaults to 120 seconds.

Also, see BUGS for caveats about locking.

max_fingerprint_calc_age

Max number of seconds before recalculating the fingerprint of the content (sha1 checksum) regardless of whether or not the mtime has changed. 0 means infinite/disabled.

For performance, once the system has calculated the checksum of the asset content it caches the mtime of the include file(s) and verifies on each request to see if they have changed. If they have, it regenerates the asset on the fly (recalculates the checksum and concatenates and minifies (if enabled) for CSS and JS asset types). If max_fingerprint_calc_age is set to a non-zero value, it will force the system to regenerate at least every N seconds regardless of the mtime. This would only be needed in cases where you are worried the content could change without changing the mtime which shouldn't be needed in most cases.

Defaults to 0.

persist_state

For faster start-up, whether or not to persist and use state data (fingerprints and mtimes) across restarts to avoid rebuilding which may be expensive and unnecessary. The asset fingerprint is normally always recalculated at startup, but if this option is enabled it is loaded from a cache/state file maintained on disk. This is useful for assets that take a long time to build (such as big include libs) and is fine as long as you trust the state data stored on disk.

WARNING: Use this feature with caution for 'directory' type assets since the mtime check does not catch file content changes alone (only filename changes), and when this is enabled it may not catch changes even across app restarts which may not be expected.

No effect if max_fingerprint_calc_age is set.

Defaults to false (0).

asset_content_type

The content type returned in the 'Content-Type' header. Defaults to text/css or text/javascript for the CSS and JS types respectively.

Does not apply to Directory asset type. For files within Directory type assets, the Content-Type is set according to the file extension using MIME::Types.

cache_control_header

The HTTP 'Cache-Control' header to return when serving assets. Defaults to the maximum aggressive value that should be honored by most browsers (1 year):

  public, max-age=31536000, s-max-age=31536000

sha1_string_length

Optional custom length (truncated) for the SHA1 fingerprint/checksum hex string. The full 40 characters is probably overkill and so this option is provided if shorter URLs are desired. The lower the number the greater the chance of collision, so you just need to balance the risk with how much you want shorter URLs (not that under normal use cases these URLs need to be entered by a human in the first place). If you don't understand what this means then just leave this setting alone.

Must be a integer between 5 and 40.

Defaults to 40 (full SHA1 hex string).

include_relative_dir

The directory to use to resolve relative paths in the include param. Defaults to the Catalyst home directory.

METHODS

asset_path

Returns the current, public URL path to the asset:

  <CONTROLLER_PATH>/<SHA1>       # for 'Directory' type
  <CONTROLLER_PATH>/<SHA1>.js    # for 'JS' type
  <CONTROLLER_PATH>/<SHA1>.css   # for 'CSS' type

For Directory asset types, accepts an optional subpath argument to a specific file. For example, if there was a file images/logo.gif within the include directory, $c->controller('Foo::MyAsset')->asset_path('images/logo.gif') might return:

  /foo/myasset/1512834162611d99fab246dfa87345a37f68ed95f/images/logo.gif

html_head_tags

Convenience method to generate a set of tags, such as CSS <link> and JS <script>, suitable to drop into the <head> section of an HTML document. What this returns, if anything, is dependent on the asset type.

BUGS/TODO

Rebuilds assets on every request if they are empty (i.e. no files within the include_dir) FIXME
Newly added files within a subdirectory do not trigger a rebuild and cannot be accessed, even directly, because it does not change the mtime of the top directory. See 'all_dirs' option below for a possible fix for this problem. The other fix would be to always check the file system for an exact subfile path, even if it does not exist in the subfile_meta data.
Needs an 'mtime_check_mode' option to be able to control how thorough the mtime check on every request is. This mainly applies to Directory assets and could be tweaked according to the number of files. Possible modes could be 'top_dir' (only check the mtime of the top directory, default for Directory), 'all_dirs' (check all sub directories), 'all' (check all include files, default for CSS/JS) and 'none' to turn off the real-time mtime checks entirely.
Needs a 'require_checksum' option to be able to require a specific asset fingerprint (such as for included libs that should always have the same checksum, like the ExtJS 3.4.0 release, for instance)

BUGS

The AutoAssets handler uses a lock file to prevent simultaneous builds on the same resource. This lock file is implemented with flock() and also setting FD_CLOEXEC on the file handle, so there shouldn't be much danger of the lock leaking to a child process, UNLESS your system doesn't support FD_CLOEXEC, such as on Windows. So, if you're on Windows and shell out during the build_asset method, and your external program hangs, the lock won't get released until that program is killed, regardless of whether you restart your web service. (or, you can try to close all un-needed file descriptors before exec()ing the external program, and avoid the problem, which is a good policy anyway!)

SEE ALSO

Catalyst::Plugin::AutoAssets
Catalyst::Plugin::Assets
Catalyst::Controller::VersionedURI
Plack::Middleware::Assets
Plack::Middleware::JSConcat

AUTHOR

Henry Van Styn <vanstyn@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2013 by IntelliTree Solutions llc.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.