Wallflower::Tutorial - Turn your Plack app into a static site
# do cool stuff using Plack-aware frameworks, # to generate static web sites
Static websites have a lot of advantages, when serving data that changes rarely:
The point of saving URLs from a PSGI application to files is not simply to make a static version of a fully dynamic site.
Unlike many static website generators, wallflower does not enforce any conventions on its users.
wallflower makes it very easy to write a static website using the web framework of your choice.
To make the most of a static website, there are a few simple rules to follow, listed below:
A PSGI/Plack application can specify the
Content-Type returned for any URL content.
On the other hand, static servers use the file extension to decide what
Content-Type to send for a given file. When unable to decide what the file content is, servers usually send
application/octet-stream as the
Since the goal of a Wallflower application is to generate a static website, all URL pathnames should have an extension.
Similarly, wallflower decides to check the body of a response for links it may contain based on its
Content-Type header, as links only make sense for HTML and CSS files.
If the response has no
Content-Type header, wallflower will miss some of the links, and thus not properly crawl the whole site.
Because the website can be written with any modern web framework, it's also very easy to have URLs that reply to
POST requests. Obviously, these pages cannot be saved on the static destination.
It's therefore possible to hide the dynamic parts of the application in the
development environment, while only the static elements are reachable from the
By default, wallflower starts by loading
/, and automatically and repeatedly follows all URLs found in HTML and CSS documents, until all reachable URLs have been processed.
The simplest way to generate the full static site is to make sure that all URLs can be reached by repeatedly following links from the root.
When using the
--url option to "mount" your application under some path, don't forget to call wallflower with that path as the root:
wallflower --application myapp.psgi --url http://localhost/myapp /myapp/
A Plack application deals with URLs. Nothing prevents the application from treating /thunk and /thunk/ differently and returning different content bodies for them.
From the perspective of a filesystem, however, if thunk is a directory, then it is semantically equivalent to thunk/. And it is impossible to have both a file and a directory with the same name inside the same parent directory.
When dealing with a static site, the server maps the URLs to the filesystem. If thunk is a directory, the server usually redirects the client to thunk/ (using a
301 Moved Permanently response). Then the default file is picked for the content, traditionally thunk/index.html.
Because Wallflower does not know the conventions used by the Plack application it calls, it cannot decide if /thunk should be understood as a "file" or as a "directory" when generating the file name that will receive the content for that URL.
So, if your application treats /thunk and /thunk/ as identical, you should:
301 Moved Permanentlyto requests for thunk. This is what a well-behaved web server serving static pages will do when a user-agent requests a "directory" without a final
At this point, you know that an application that treats /thunk ("file") and /thunk/ ("directory") differently will not work with wallflower.
wallflower will show a status code of
999 (not a valid HTTP status) in the following two cases:
Can't open thunk/pam for writing: Not a directory)
Can't open thunk for writing: Is a directory)
See also the section "All URLs should have an extension", for why you should avoid extensionless URLs.
A few articles about wallflower have been published, and are listed below:
The wallflower announcement on http://blogs.perl.org/.
Wallflower in the Perl Advent Calendar 2012.
A presentation of Wallflower by one of its users.
A comparison of using Wget and Wallflower to generate static web sites.
Philippe Bruhat (BooK) <email@example.com>
Copyright 2012-2015 by Philippe Bruhat (BooK).
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.