NAME
Plack::App::MCCS - Minify, Compress, Cache-control and Serve static
files from Plack applications
VERSION
version 0.004
EXTENDS
Plack::Component
SYNOPSIS
# in your app.psgi:
use Plack::Builder;
use Plack::App::MCCS;
my $app = sub { ... };
# be happy with the defaults:
builder {
mount '/static' => Plack::App::MCCS->new(root => '/path/to/static_files');
mount '/' => $app;
};
# or tweak the app to suit your needs:
builder {
mount '/static' => Plack::App::MCCS->new(
root => '/path/to/static_files',
defaults => {
valid_for => 86400,
cache_control => ['private'],
},
types => {
'.htc' => {
content_type => 'text/x-component',
valid_for => 360,
cache_control => ['no-cache', 'must-revalidate'],
},
},
);
mount '/' => $app;
};
DESCRIPTION
"Plack::App::MCCS" is a Plack application that serves static files from
a directory. It will prefer serving precompressed versions of files if
they exist and the client supports it, and also prefer minified versions
of CSS/JS files if they exist.
If IO::Compress::Gzip is installed, "MCCS" will also automatically
compress files that do not have a precompressed version and save the
compressed versions to disk (so it only happens once and not on every
request to the same file).
If CSS::Minifier::XS and/or JavaScript::Minifier::XS are installed, it
will also automatically minify CSS/JS files that do not have a
preminified version and save them to disk (once again, will only happen
once per file).
This means "MCCS" needs to have write privileges to the static files
directory. It would be better if files are preminified and
precompressed, say automatically in your build process (if such a
process exists). However, at some projects where you don't have an
automatic build process, it is not uncommon to forget to
minify/precompress. That's where automic minification/compression is
useful.
Most importantly, "MCCS" will generate proper Cache Control headers for
every file served, including "Last-Modified", "Expires", "Cache-Control"
and even "ETag" (ETags are created automatically, once per file, and
saved to disk for future requests). It will appropriately respond with
"304 Not Modified" for requests with headers "If-Modified-Since" or
"If-None-Match" when these cache validations are fulfilled, without
actually having to read the files' contents again.
"MCCS" is active by default, which means that if there are some things
you *don't* want it to do, you have to *tell* it not to. This is on
purpose, because doing these actions is the whole point of "MCCS".
WAIT, AREN'T THERE EXISTING PLACK MIDDLEWARES FOR THAT?
Yes and no. A similar functionality can be added to an application by
using the following Plack middlewares:
* Plack::Middleware::Static or Plack::App::File - will serve static
files
* Plack::Middleware::Static::Minifier - will minify CSS/JS
* Plack::Middleware::Precompressed - will serve precompressed .gz
files
* Plack::Middleware::Deflater - will compress representations with
gzip/deflate algorithms
* Plack::Middleware::ETag - will create ETags for files
* Plack::Middleware::ConditionalGET - will handle "If-None-Match" and
"If-Modified-Since"
* Plack::Middleware::Header - will allow you to add cache control
headers manually
So why wouldn't I just use these middlewares? Here are my reasons:
* "Static::Minifier" will not minify to disk, but will minify on every
request, even to the same file (unless you provide it with a cache,
which is not that better). This pointlessly increases the load on
the server.
* "Precompressed" is nice, but it relies on appending ".gz" to every
request and sending it to the app. If the app returns "404 Not
Found", it sends the request again without the ".gz" part. This
might pollute your logs and I guess two requests to get one file is
not better than one request. You can circumvent that with regex
matching, but that isn't very comfortable.
* "Deflater" will not compress to disk, but do that on every request.
So once again, this is a big load on the server for no real reason.
It also has a long standing bug where deflate responses fail on
Firefox, which is annoying.
* "ETag" will calculate the ETag again on every request.
* "ConditionalGET" does not prevent the requested file to be opened
for reading even if "304 Not Modified" is to be returned (since that
check is performed later). I'm not sure if it affects performance in
anyway, probably not.
* No possible combination of any of the aformentioned middlewares
seems to return proper (and configurable) Cache Control headers, so
you need to do that manually, possibly with
Plack::Middleware::Header, which is not just annoying if different
file types have different cache settings, but doesn't even seem to
work.
* I don't really wanna use so many middlewares just for this
functionality.
"Plack::App::MCCS" attempts to perform all of this faster and better.
Read the next section for more info.
HOW DOES MCCS HANDLE REQUESTS?
When a request is handed to "Plack::App::MCCS", the following process is
performed:
1. Discovery:
"MCCS" will try to find the requested path in the root directory. If
the path is not found, "404 Not Found" is returned. If the path
exists but is a directory, "403 Forbidden" is returned (directory
listings might be supported in the future).
2. Examination:
"MCCS" will try to find the content type of the file, either by its
extension (relying on Plack::MIME for that), or by a specific
setting provided to the app by the user (will take precedence). If
not found (or file has no extension), "text/plain" is assumed (which
means you should give your files proper extensions if possible).
"MCCS" will also determine for how long to allow browsers/proxy
caches/whatever caches to cache the file. By default, it will set a
representation as valid for 86400 seconds (i.e. one day). However,
this can be changed in two ways: either by setting a different
default when creating an instance of the application (see more info
at the "new()" method's documentation below), or by setting a
specific value for certain file types. Also, "MCCS" by default sets
the "public" option for the "Cache-Control" header, meaning caches
are allowed to save responses even when authentication is performed.
You can change that the same way.
3. Minification
If the content type is "text/css" or "application/javascript",
"MCCS" will try to find a preminified version of it on disk
(directly, not with a second request). If found, this version will
be marked for serving. If not found, and CSS::Minifier::XS or
JavaScript::Minifier:XS are installed, "MCCS" will minify the file,
save the minified version to disk, and mark it as the version to
serve. Future requests to the same file will see the minified
version and not minify again.
"MCSS" searches for files that end with ".min.css" and ".min.js",
and that's how it creates them too. So if a request comes to
"style.css", "MCSS" will look for "style.min.css", possibly creating
it if not found. The request path remains the same ("style.css")
though, even internally. If a request comes to "style.min.css"
(which you don't really want when using "MCCS"), the app will not
attempt to minify it again (so you won't get things like
"style.min.min.css").
4. Compression
If the client supports gzip encoding (deflate to be added in the
future, probably), as noted with the "Accept-Encoding" header,
"MCCS" will try to find a precompressed version of the file on disk.
If found, this version is marked for serving. If not found, and
IO::Compress::Gzip is installed, "MCCS" will compress the file, save
the gzipped version to disk, and mark it as the version to serve.
Future requests to the same file will see the compressed version and
not compress again.
"MCSS" searches for files that end with ".gz", and that's how it
creates them too. So if a request comes to "style.css" (and it was
minified in the previous step), "MCSS" will look for
"style.min.css.gz", possibly creating it if not found. The request
path remains the same ("style.css") though, even internally.
5. Cache Validation
If the client provided the "If-Modified-Since" header, "MCCS" will
determine if the file we're serving has been modified after the
supplied date, and return "304 Not Modified" immediately if not.
Unless the file has the 'no-store' cache control option, and if the
client provided the "If-None-Match" header, "MCCS" will look for a
file that has the same name as the file we're going to serve, plus
an ".etag" prefix, such as "style.min.css.gz.etag" for example. If
found, the contents of this file is read and compared with the
provided ETag. If the two values are equal, "MCCS" will immediately
return "304 Not Modified".
6. ETagging
If an ".etag" file wasn't found in the previous step (and the file
we're serving doesn't have the 'no-store' cache control option),
"MCCS" will create one from the file's inode, last modification date
and size. Future requests to the same file will see this ETag file,
so it is not created again.
7. Headers and Cache-Control
"MCCS" now sets headers, especially cache control headers, as
appropriate:
"Content-Encoding" is set to <gzip> if a compressed version is
returned.
"Content-Length" is set with the size of the file in bytes.
"Content-Type" is set with the type of the file (if a text file,
charset string is appended, e.g. "text/css; charset=UTF-8").
"Last-Modified" is set with the last modification date of the file
in HTTP date format.
"Expires" is set with the date in which the file will expire
(determined in stage 2), in HTTP date format.
"Cache-Control" is set with the number of seconds the representation
is valid for (unless caching of the file is not allowed) and other
options (determined in stage 2).
"Etag" is set with the ETag value (if exists).
"Vary" is set with "Accept-Encoding".
8. Serving
The file handle is returned to the Plack handler/server for serving.
HOW DO WEB CACHES WORK ANYWAY?
If you need more information on how caches work and cache control
headers, read this great article <http://www.mnot.net/cache_docs/>.
CLASS METHODS
new( %opts )
Creates a new instance of this module. %opts *must* have the following
keys:
root - the path to the root directory where static files reside.
%opts *may* have the following keys:
encoding - the character set to append to content-type headers when text
files are returned. Defaults to UTF-8.
defaults - a hash-ref with some global defaults, the following options
are supported:
* valid_for: the default number of seconds caches are allowed to save
a response.
* cache_control: takes an array-ref of options for the "Cache-Control"
header (all except for "max-age", which is automatically calculated
from the resource's "valid_for" setting).
* minify: give this option a false value (0, empty string, "undef") if
you don't want "MCCS" to automatically minify CSS/JS files (it will
still look for preminified versions though).
* compress: like "minify", give this option a false value if you don't
want "MCCS" to automatically compress files (it will still look for
precompressed versions).
types - a hash-ref with file extensions that may be served (keys must
begin with a dot, so give '.css' and not 'css'). Every extension takes a
hash-ref that might have valid_for and cache_control as with the
"defaults" option, but also content_type with the content type to return
for files with this extension (useful when Plack::MIME doesn't know the
content type of a file).
If you don't want something to be cached, you need to give the valid_for
option (either in "defaults" or for a specific file type) a value of
either zero, or preferably any number lower than zero, which will cause
"MCCS" to set an "Expires" header way in the past. You should also pass
the cache_control option "no_store" and probably "no_cache". When "MCCS"
encounteres the "no_store" option, it does not automatically add the
"max-age" option to the "Cache-Control" header.
OBJECT METHODS
call( \%env )
Plack automatically calls this method to handle a request. This is where
the magic (or disaster) happens.
CAVEATS AND THINGS TO CONSIDER
* You can't tell "MCCS" to not minify/compress a specific file type
yet but only disable minification/compression altogether (in the
"defaults" setting for the "new()" method).
* Directory listings are not supported yet (not sure if they will be).
* Deflate compression is not supported yet (just gzip).
* Caching middlewares such as Plack::Middleware::Cache and
Plack::Middleware::Cached don't rely on Cache-Control headers (or so
I understand) for their expiration values, which makes them less
useful for applications that rely on "MCCS". You'll probably be
better off with an external cache like Varnish
<https://www.varnish-cache.org/> if you want a cache on your
application server. Even without a server cache, your application
should still appear faster for users due to browser caching (and
also server load should be decreased).
* "Range" requests are not supported. See Plack::App::File::Range if
you need that.
* An "MCCS" middleware is not provided yet, just a Plack::App, so you
need to use something like "mount" with Plack::Builder to use it.
* "MCCS" is mounted on a directory and can't be set to only serve
requests that match a certain regex.
DIAGNOSTICS
This module doesn't throw any exceptions, instead returning HTTP errors
for the client and possibly issuing some "warn"s. The following list
should help you to determine some potential problems with "MCCS":
"failed gzipping %s: %s"
This warning is issued when IO::Compress::Gzip fails to gzip a file.
When it happens, "MCCS" will simply not return a gzipped
representation.
"Can't open ETag file %s.etag for reading"
This warning is issued when "MCCS" can't read an ETag file, probably
because it does not have enough permissions. The request will still
be fulfilled, but it won't have the "ETag" header.
"Can't open ETag file %s.etag for writing"
Same as before, but when "MCCS" can't write an ETag file.
"403 Forbidden" is returned for files that exist
If a request for a certain file results in a "403 Forbidden" error,
it probably means "MCCS" has no read permissions for that file.
CONFIGURATION AND ENVIRONMENT
"Plack::App::MCCS" requires no configuration files or environment
variables.
DEPENDENCIES
"Plack::App::MCCS" depends on the following CPAN modules:
* parent
* Cwd
* Fcntl
* File::Spec::Unix
* HTTP::Date
* Module::Load::Conditional
* Plack (obviously)
"Plack::App::MCCS" will use the following modules if they exist, in
order to minify/compress files (if they are not installed, "MCCS" will
not be able to minify/compress on its own):
* CSS::Minifier::XS
* JavaScript::Minifier::XS
* IO::Compress::Gzip
INCOMPATIBILITIES WITH OTHER MODULES
None reported.
BUGS AND LIMITATIONS
No bugs have been reported.
Please report any bugs or feature requests to
"bug-Plack-App-MCCS@rt.cpan.org", or through the web interface at
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Plack-App-MCCS>.
SEE ALSO
Plack::Middleware::Static, Plack::App::File, Plack::Builder.
ACKNOWLEDGMENTS
Some of this module's code is based on Plack::App::File by Tatsuhiko
Miyagawa and Plack::Middleware::ETag by Franck Cuny.
AUTHOR
Ido Perlmuter <ido@ido50.net>
LICENSE AND COPYRIGHT
Copyright (c) 2011-2012, Ido Perlmuter "ido@ido50.net".
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself, either version 5.8.1 or any later
version. See perlartistic and perlgpl.
The full text of the license can be found in the LICENSE file included
with this module.
DISCLAIMER OF WARRANTY
BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
NECESSARY SERVICING, REPAIR, OR CORRECTION.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE
TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
DAMAGES.