default error pages

[Jonathan Swartz]

The default behavior for errors, e.g. 404 Not Found, 403 Forbidden, on plack servers is a blank page (unless I've got something misconfigured). For a new development environment this seems a poor and confusing default, compared with say Apache's default error pages. I'm always a little surprised the first time I see that blank page on a new project.

I see Plack::Middleware::ErrorDocument, which lets you create your own error pages. Is there a middleware that adds standard error pages? If not, would it be legitimate for us to steal Apache's default error pages and write a middleware that serves them? What would be the best way to structure this in relation to Plack::Middleware::ErrorDocument?

Thanks
Jon

[Tatsuhiko Miyagawa]

On Friday, May 18, 2012 at 6:27 AM, Jonathan Swartz wrote:

The default behavior for errors, e.g. 404 Not Found, 403 Forbidden, on plack servers is a blank page (unless I've got something misconfigured).

Unlike Apache, Plack is not a document server - it's totally up to the PSGI application what kind of content it serves up, even including the error cases. There's no "configuration" per se for this.

For a new development environment this seems a poor and confusing default, compared with say Apache's default error pages. I'm always a little surprised the first time I see that blank page on a new project.

I'm puzzled what you really mean by "pages". If you use Catalyst, Dancer or Mojolicious with Plack, when you hit a URL that doesn't match/exist, you'll see error pages generated by the framework.

Also, if you *really* use a document server such as Plack::App::File/Directory, you'll see a minimum error page like "404 Not Found" if you hit a page that doesn't exist. 

I see Plack::Middleware::ErrorDocument, which lets you create your own error pages. Is there a middleware that adds standard error pages? If not, would it be legitimate for us to steal Apache's default error pages and write a middleware that serves them? What would be the best way to structure this in relation to Plack::Middleware::ErrorDocument?

Thanks

Jon

--

Tatsuhiko Miyagawa

[Jakob Voss]

Jonathan Swartz wrote:

> The default behavior for errors, e.g. 404 Not Found, 403 Forbidden, on

> plack servers is a blank page (unless I've got something
misconfigured).

What do you mean by plack servers? There are PSGI applications and
there are PSGI servers, but Plack is only a toolkit including some PSGI
applications and middleware. Furthermore all errors should be generated
by PSGI applications, not by any PSGI server (unless there is a bug in
the server).

> For a new development environment this seems a poor and confusing
> default, compared with say Apache's default error pages. I'm always a
> little surprised the first time I see that blank page on a new
project.

Which "new development environment" produces blank error pages? For
instance Plack::App::File produces plain test messages or if your
application
dies, there is a stack trace in the 500 error document by default.

> I see Plack::Middleware::ErrorDocument, which lets you create your own

> error pages. Is there a middleware that adds standard error pages? If
not,
> would it be legitimate for us to steal Apache's default error pages
and write
> a middleware that serves them? What would be the best way to structure
> this in relation to Plack::Middleware::ErrorDocument?

There is also an Plack::Middleware::ErrorDocument::App (not at CPAN):


https://github.com/jamadam/Plack-Middleware-ErrorDocument-App/blob/master/lib/Plack/Middleware/ErrorDocument/App.pm


I think the best is to fork the latter and add the following feature:


* support error code ranges, such as 4xx, 5xx, and 'all'
* pass the actual error code as second argument to the error app
* rename the module to Plack::Middleware::ErrorApp


Now you can implement your favorite "default error page" layout:


builder {
enable 'Plack::Middleware::ErrorApp',
4xx => sub {
my ($env, $code) = @_;
my $html = "..."; # use status_message from HTTP::Status
[ $code, "Content-Type" => "text/html", [ $html ] ];
};
$app;
};


You could also implement a set of default error pages in
Plack::Middleware::ErrorApp for convenience to allow:


enable 'Plack::Middleware::ErrorApp', all => 'plain';
enable 'Plack::Middleware::ErrorApp', all => 'html';


Each error page layout could be implemented as module that
is loaded automatically if a string is provided as app:


Plack::Middleware::ErrorApp::Plain
Plack::Middleware::ErrorApp::Html
Plack::Middleware::ErrorApp::Debug
...


Cheers,
Jakob




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jakob...@gbv.de

[Jonathan Swartz]

On May 18, 2012, at 8:48 AM, Tatsuhiko Miyagawa wrote:

On Friday, May 18, 2012 at 6:27 AM, Jonathan Swartz wrote:

The default behavior for errors, e.g. 404 Not Found, 403 Forbidden, on plack servers is a blank page (unless I've got something misconfigured).

Unlike Apache, Plack is not a document server - it's totally up to the PSGI application what kind of content it serves up, even including the error cases. There's no "configuration" per se for this.

For a new development environment this seems a poor and confusing default, compared with say Apache's default error pages. I'm always a little surprised the first time I see that blank page on a new project.

I'm puzzled what you really mean by "pages". If you use Catalyst, Dancer or Mojolicious with Plack, when you hit a URL that doesn't match/exist, you'll see error pages generated by the framework.

Also, if you *really* use a document server such as Plack::App::File/Directory, you'll see a minimum error page like "404 Not Found" if you hit a page that doesn't exist. 

Fair enough. I'm still working out what does and does not belong in Plack.

Plack::Middleware::StackTrace is enabled in dev mode, so there's at least *some* justification for thinking that certain kinds of error messages would be auto-generated.

Anyway, as the creator of a framework (Poet) I guess it is up to me to generate these error pages. :)

Thanks

Jon