=head1 DESCRIPTION
-This chapter of the tutorial takes a brief look at the primary options
+This chapter of the tutorial takes a brief look at the primary options
available for troubleshooting Catalyst applications.
+Source code for the tutorial in included in the F</home/catalyst/Final>
+directory of the Tutorial Virtual machine (one subdirectory per
+chapter). There are also instructions for downloading the code in
+L<Catalyst::Manual::Tutorial::01_Intro>.
+
+
Note that when it comes to debugging and troubleshooting, there are two
camps:
=over 4
-=item *
+=item *
Fans of C<log> and C<print> statements embedded in the code.
-=item *
+=item *
Fans of interactive debuggers.
=head1 LOG STATEMENTS
-Folks in the former group can use Catalyst's C<$c-E<gt>log> facility.
-(See L<Catalyst::Log|Catalyst::Log> for more detail.) For example, if
-you add the following code to a controller action method:
+Folks in the former group can use Catalyst's C<< $c->log >> facility.
+(See L<Catalyst::Log> for more detail.) For example, if you add the
+following code to a controller action method:
$c->log->info("Starting the foreach loop here");
[% c.log.debug("This is a test log message") %]
-As with many other logging facilities, a method is defined for
-each of the following "logging levels" (in increasing order of
+As with many other logging facilities, a method is defined for each of
+the following "logging levels" (in increasing order of
severity/importance):
$c->log->debug
$c->log->error
$c->log->fatal
-You can also use L<Data::Dumper|Data::Dumper> in both Catalyst code
-(C<use Data::Dumper; $c-E<gt>log-E<gt>debug("\$var is: ".Dumper($var));)>)
-and TT templates (C<[% Dumper.dump(book) %]>.
+You can also use Data::Dumper in both Catalyst code and in TT templates.
+For use in Catalyst code:
+
+ use Data::Dumper;
+ $c->log->debug("\$var is: ".Dumper($c->stash->{something}));
+
+and TT templates:
+
+ [% USE Dumper ; Dumper.dump(c.stash.something) %].
+
+B<NOTE:> Whether you are a logging fanatic or not, we strongly recommend
+that you take advantage of L<Log::Log4perl> or L<Log::Dispatch>. It's
+easy to use L<Catalyst::Log> with either of these and they will provide
+a huge amount of extra functionality that you will want in virtually
+every production application you run or support.
=head1 RUNNING CATALYST UNDER THE PERL DEBUGGER
# 'Context' that's used to 'glue together' the various components
# that make up the application
my ($self, $c) = @_;
-
+
$DB::single=1;
-
+
# Retrieve all of the book records as book model objects and store in the
# stash where they can be accessed by the TT template
$c->stash->{books} = [$c->model('DB::Book')->all];
-
+
# Set the TT template to use. You will almost always want to do this
# in your action methods.
$c->stash->{template} = 'books/list.tt2';
}
-This causes the Perl Debugger to enter "single step mode" when this command is
-encountered (it has no effect when Perl is run without the C<-d> flag).
+This causes the Perl Debugger to enter "single step mode" when this
+command is encountered (it has no effect when Perl is run without the
+C<-d> flag).
B<NOTE:> The C<DB> here is the Perl Debugger, not the DB model.
$ export DBIC_TRACE=1
-To now run the Catalyst development server under the Perl debugger, simply
-prepend C<perl -d> to the front of C<script/myapp_server.pl>:
+To now run the Catalyst development server under the Perl debugger,
+simply prepend C<perl -d> to the front of C<script/myapp_server.pl>:
$ perl -d script/myapp_server.pl
This will start the interactive debugger and produce output similar to:
- $ perl -d script/myapp_server.pl
-
+ $ perl -d script/myapp_server.pl
+
Loading DB routines from perl5db.pl version 1.3
Editor support available.
-
+
Enter h or `h h' for help, or `man perldebug' for more help.
-
+
main::(script/myapp_server.pl:16): my $debug = 0;
-
- DB<1>
+
+ DB<1>
Press the C<c> key and hit C<Enter> to continue executing the Catalyst
development server under the debugger. Although execution speed will be
C<MyApp::Controller::list> method, the console session running the
development server will drop to the Perl debugger prompt:
- MyApp::Controller::Books::list(/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm:48):
+ MyApp::Controller::Books::list(/home/catalyst/MyApp/script/../lib/MyApp/Controller/Books.pm:48):
48: $c->stash->{books} = [$c->model('DB::Book')->all];
-
+
DB<1>
You now have the full Perl debugger at your disposal. First use the
DB<1> n
SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me:
- MyApp::Controller::Books::list(/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm:53):
+ MyApp::Controller::Books::list(/home/catalyst/MyApp/script/../lib/MyApp/Controller/Books.pm:53):
53: $c->stash->{template} = 'books/list.tt2';
-
+
DB<1>
This takes you to the next line of code where the template name is set.
-Notice that because we enabled C<DBIC_TRACE=1> earlier, SQL debug
-output also shows up in the development server debug information.
+Notice that because we enabled C<DBIC_TRACE=1> earlier, SQL debug output
+also shows up in the development server debug information.
Next, list the methods available on our C<Book> model:
_calculate_score
_collapse_cond
<lines removed for brevity>
-
+
DB<2>
We can also play with the model directly:
Finally, press C<Ctrl+C> to break out of the development server.
Because we are running inside the Perl debugger, you will drop to the
-debugger prompt.
+debugger prompt.
^CCatalyst::Engine::HTTP::run(/usr/local/share/perl/5.10.0/Catalyst/Engine/HTTP.pm:260):
260: while ( accept( Remote, $daemon ) ) {
DB<4>
-Finally, press C<q> to exit the debugger and return to your OS
-shell prompt:
+Finally, press C<q> to exit the debugger and return to your OS shell
+prompt:
DB<4> q
$
You can also type C<h> or C<h h> at the debugger prompt to view the
built-in help screens.
-For an excellent book covering all aspects of the Perl debugger, we highly
-recommend reading 'Pro Perl Debugging' by Richard Foley.
+For an excellent book covering all aspects of the Perl debugger, we
+highly recommend reading 'Pro Perl Debugging' by Richard Foley.
-Oh yeah, before you forget, be sure to remove the C<DB::single=1> line you
-added above in C<lib/MyApp/Controller/Books.pm>.
+Oh yeah, before you forget, be sure to remove the C<DB::single=1> line
+you added above in C<lib/MyApp/Controller/Books.pm>.
=head1 DEBUGGING MODULES FROM CPAN
-Although the techniques discussed above work well for code you are
-writing, what if you want to use print/log/warn messages or set
-breakpoints in code that you have installed from CPAN (or in module that
-ship with Perl)? One helpful approach is to place a copy of the module
-inside the C<lib> directory of your Catalyst project. When Catalyst
-loads, it will load from inside your C<lib> directory first, only
-turning to the global modules if a local copy cannot be found. You can
-then make modifications such as adding a C<$DB::single=1> to the local
-copy of the module without risking the copy in the original location.
-This can also be a great way to "locally override" bugs in modules while
+Although the techniques discussed above work well for code you are
+writing, what if you want to use print/log/warn messages or set
+breakpoints in code that you have installed from CPAN (or in module that
+ship with Perl)? One helpful approach is to place a copy of the module
+inside the C<lib> directory of your Catalyst project. When Catalyst
+loads, it will load from inside your C<lib> directory first, only
+turning to the global modules if a local copy cannot be found. You can
+then make modifications such as adding a C<$DB::single=1> to the local
+copy of the module without risking the copy in the original location.
+This can also be a great way to "locally override" bugs in modules while
you wait for a fix on CPAN.
-
-Matt Trout has suggested the following shortcut to create a local
-copy of an installed module:
+Matt Trout has suggested the following shortcut to create a local copy
+of an installed module:
mkdir -p lib/Module; cp `perldoc -l Module::Name` lib/Module/
-Note: If you are following along in Debian 5 or Ubuntu, you will
-need to install the C<perl-doc> package to use the C<perldoc> command.
-Use C<sudo aptitude install perl-doc> to do that.
+Note: If you are following along in Debian 6 or Ubuntu, you will need to
+install the C<perl-doc> package to use the C<perldoc> command. Use
+C<sudo aptitude install perl-doc> to do that.
-For example, you could make a copy of
-L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>
-with the following command:
+For example, you could make a copy of
+L<Catalyst::Plugin::Authentication> with the following command:
mkdir -p lib/Catalyst/Plugin; cp \
`perldoc -l Catalyst::Plugin::Authentication` lib/Catalyst/Plugin
You can then use the local copy inside your project to place logging
messages and/or breakpoints for further study of that module.
-B<Note:> Matt has also suggested the following tips for Perl
-debugging:
+B<Note:> Matt has also suggested the following tips for Perl debugging:
=over 4
-=item *
+=item *
Check the version of an installed module:
or die qq(module \"\$m\" is not installed\\n); \
print \$m->VERSION'"
-=item *
+=item *
Check if a modules contains a given method:
=head1 TT DEBUGGING
-If you run into issues during the rendering of your template, it might
-be helpful to enable TT C<DEBUG> options. You can do this in a Catalyst
-environment by adding a C<DEBUG> line to the C<__PACKAGE__->config>
+If you run into issues during the rendering of your template, it might
+be helpful to enable TT C<DEBUG> options. You can do this in a Catalyst
+environment by adding a C<DEBUG> line to the C<__PACKAGE__->config>
declaration in C<lib/MyApp/View/HTML.pm>:
__PACKAGE__->config({
DEBUG => 'undef',
});
-There are a variety of options you can use, such as 'undef', 'all',
-'service', 'context', 'parser' and 'provider'. See
-L<Template::Constants|Template::Constants> for more information
-(remove the C<DEBUG_> portion of the name shown in the TT docs and
-convert to lower case for use inside Catalyst).
+There are a variety of options you can use, such as 'undef', 'all',
+'service', 'context', 'parser' and 'provider'. See
+L<Template::Constants> for more information (remove the C<DEBUG_>
+portion of the name shown in the TT docs and convert to lower case for
+use inside Catalyst).
-B<NOTE:> B<Please be sure to disable TT debug options before continuing
-with the tutorial> (especially the 'undef' option -- leaving this
-enabled will conflict with several of the conventions used by this
+B<NOTE:> B<Please be sure to disable TT debug options before continuing
+with the tutorial> (especially the 'undef' option -- leaving this
+enabled will conflict with several of the conventions used by this
tutorial to leave some variables undefined on purpose).
Happy debugging.
+
+You can jump to the next chapter of the tutorial here:
+L<Testing|Catalyst::Manual::Tutorial::08_Testing>
+
+
=head1 AUTHOR
Kennedy Clark, C<hkclark@gmail.com>
-Please report any errors, issues or suggestions to the author. The
-most recent version of the Catalyst Tutorial can be found at
-L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
+Feel free to contact the author for any errors or suggestions, but the
+best way to report issues is via the CPAN RT Bug system at
+L<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
-Copyright 2006-2008, Kennedy Clark, under Creative Commons License
+Copyright 2006-2011, Kennedy Clark, under the
+Creative Commons Attribution Share-Alike License Version 3.0
(L<http://creativecommons.org/licenses/by-sa/3.0/us/>).
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