plack::middleware::stacktrace(3pm) [debian man page]

Plack::Middleware::StackTrace(3pm)			User Contributed Perl Documentation			Plack::Middleware::StackTrace(3pm)

NAME

       Plack::Middleware::StackTrace - Displays stack trace when your app dies

SYNOPSIS

	 enable "StackTrace";

DESCRIPTION

       This middleware catches exceptions (run-time errors) happening in your application and displays nice stack trace screen. The stack trace is
       also stored in the environment as a plaintext and HTML under the key "plack.stacktrace.text" and "plack.stacktrace.html" respectively, so
       that middleware futher up the stack can reference it.

       This middleware is enabled by default when you run plackup in the default development mode.

       You're recommended to use this middleware during the development and use Plack::Middleware::HTTPExceptions in the deployment mode as a
       replacement, so that all the exceptions thrown from your application still get caught and rendered as a 500 error response, rather than
       crashing the web server.

       Catching errors in streaming response is not supported.

CONFIGURATION

       force
	     enable "StackTrace", force => 1;

	   Force display the stack trace when an error occurs within your application and the response code from your application is 500. Defaults
	   to off.

	   The use case of this option is that when your framework catches all the exceptions in the main handler and returns all failures in your
	   code as a normal 500 PSGI error response. In such cases, this middleware would never have a chance to display errors because it can't
	   tell if it's an application error or just random "eval" in your code. This option enforces the middleware to display stack trace even
	   if it's not the direct error thrown by the application.

       no_print_errors
	     enable "StackTrace", no_print_errors => 1;

	   Skips printing the text stacktrace to console ("psgi.errors"). Defaults to 0, which means the text version of the stack trace error is
	   printed to the errors handle, which usually is a standard error.

AUTHOR

       Tokuhiro Matsuno

       Tatsuhiko Miyagawa

SEE ALSO

       Devel::StackTrace::AsHTML Plack::Middleware Plack::Middleware::HTTPExceptions

perl v5.14.2							    2011-07-08					Plack::Middleware::StackTrace(3pm)

Plack::Builder(3pm)					User Contributed Perl Documentation				       Plack::Builder(3pm)

NAME

       Plack::Builder - OO and DSL to enable Plack Middlewares

SYNOPSIS

	 # in .psgi
	 use Plack::Builder;

	 my $app = sub { ... };

	 builder {
	     enable "Deflater";
	     enable "Session", store => "File";
	     enable "Debug", panels => [ qw(DBITrace Memory Timer) ];
	     enable "+My::Plack::Middleware";
	     $app;
	 };

	 # use URLMap

	 builder {
	     mount "/foo" => builder {
		 enable "Foo";
		 $app;
	     };

	     mount "/bar" => $app2;
	     mount "http://example.com/" => builder { $app3 };
	 };

	 # using OO interface

	 my $builder = Plack::Builder->new();
	 $builder->add_middleware('Foo', opt => 1);
	 $app = $builder->mount('/app' => $app);
	 $app = $builder->to_app($app);

DESCRIPTION

       Plack::Builder gives you a quick domain specific language (DSL) to wrap your application with Plack::Middleware subclasses. The middleware
       you're trying to use should use Plack::Middleware as a base class to use this DSL, inspired by Rack::Builder.

       Whenever you call "enable" on any middleware, the middleware app is pushed to the stack inside the builder, and then reversed when it
       actually creates a wrapped application handler. "Plack::Middleware::" is added as a prefix by default. So:

	 builder {
	     enable "Foo";
	     enable "Bar", opt => "val";
	     $app;
	 };

       is syntactically equal to:

	 $app = Plack::Middleware::Bar->wrap($app, opt => "val");
	 $app = Plack::Middleware::Foo->wrap($app);

       In other words, you're supposed to "enable" middleware from outer to inner.

INLINE MIDDLEWARE

       Plack::Builder allows you to code middleware inline using a nested code reference.

       If the first argument to "enable" is a code reference, it will be passed an $app and is supposed to return another code reference which is
       PSGI application that consumes $env in runtime. So:

	 builder {
	     enable sub {
		 my $app = shift;
		 sub {
		     my $env = shift;
		     # do preprocessing
		     my $res = $app->($env);
		     # do postprocessing
		     return $res;
		 };
	     };
	     $app;
	 };

       is equal to:

	 my $mw = sub {
	     my $app = shift;
	     sub { my $env = shift; $app->($env) };
	 };

	 $app = $mw->($app);

URLMap support
       Plack::Builder has a native support for Plack::App::URLMap with "mount" method.

	 use Plack::Builder;
	 my $app = builder {
	     mount "/foo" => $app1;
	     mount "/bar" => builder {
		 enable "Foo";
		 $app2;
	     };
	 };

       See Plack::App::URLMap's "map" method to see what they mean. With builder you can't use "map" as a DSL, for the obvious reason :)

       NOTE: Once you use "mount" in your builder code, you have to use "mount" for all the paths, including the root path ("/"). You can't have
       the default app in the last line of "builder" like:

	 my $app = sub {
	     my $env = shift;
	     ...
	 };

	 builder {
	     mount "/foo" => sub { ... };
	     $app; # THIS DOESN'T WORK
	 };

       You'll get warnings saying that your mount configuration will be ignored. Instead you should use "mount "/" => ..." in the last line to set
       the default fallback app.

	 builder {
	     mount "/foo" => sub { ... };
	     mount "/" => $app;
	 }

       Note that the "builder" DSL returns a whole new PSGI application, which means

       o   "builder { ... }" should normally the last statement of a ".psgi" file, because the return value of "builder" is the application that
	   actually is executed.

       o   You can nest your "builder" block, mixed with "mount" (see URLMap support above):

	     builder {
		 mount "/foo" => builder {
		     mount "/bar" => $app;
		 }
	     }

	   will locate the $app under "/foo/bar" since the inner "builder" block puts it under "/bar" and it results a new PSGI application which
	   is located under "/foo" because of the outer "builder" block.

CONDITIONAL MIDDLEWARE SUPPORT

       You can use "enable_if" to conditionally enable middleware based on the runtime environment. See Plack::Middleware::Conditional for
       details.

SEE ALSO

       Plack::Middleware Plack::App::URLMap Plack::Middleware::Conditional

perl v5.14.2							    2012-05-17						       Plack::Builder(3pm)