Handlers

Log::Report class functionality to class messages (which can then be tested later):

  notice __x"Class me up", _class => 'label';
  ...
  if ($msg->inClass('label')) ...

Dancer2::Plugin::LogReport has a special message class, "no_session", which prevents the message from being saved to the messages session variable. This is useful, for example, if you are writing messages within the session hooks, in which case recursive loops can be experienced.

$obj->alert()

$obj->assert()

$obj->error()

$obj->failure()

$obj->fault()

$obj->info()

$obj->mistake()

$obj->notice()

$obj->panic()

$obj->success()

This is a special additional type, equivalent to "notice". The difference is that messages using this keyword will have the class "success" added, which can be used to color the messages differently to the end user. For example, Dancer2::Plugin::LogReport::Message#bootstrap_color uses this to display the message in green.

$obj->trace()

$obj->warning()

Larger example

  get '/route' => sub {
      # Stop execution, redirect, and display an error to the user
      $name or error "Please enter a name";
 
      # The same but translated
      $name or error __"Please enter a name";
  
      # The same but translated and with variables
      $name or error __x"{name} is not valid", name => $name;
 
      # Show the user a warning, but continue execution
      mistake "Not sure that's what you wanted";
 
      # Add debug information, can be caught in syslog by adding
      # the (for instance) syslog dispatcher
      trace "Hello world";
   };

Setup and Configuration

Dancer2::Logger::LogReport

Set up Dancer2::Logger::LogReport by adding it to your Dancer2 application configuration (see Dancer2::Config). By default, all messages will go to STDERR.

To get all message out "the Perl way" (using print, warn and die) just use

  logger: "LogReport"

At start, these are handled by a Log::Report::Dispatcher::Perl object, named 'default'. If you open a new dispatcher with the name 'default', the output via the perl mechanisms will be stopped.

To also send messages to your syslog:

  logger: "LogReport"

  engines:
    logger:
      LogReport:
        log_format: %a%i%m      # See Dancer2::Logger::LogReport
        app_name: MyApp
        dispatchers:
          default:              # Name
            type: SYSLOG        # Log::Reporter::dispatcher() options
            identity: myapp
            facility: local0
            flags: "pid ndelay nowait"
            mode: DEBUG

To send messages to a file:

  logger: "LogReport"

  engines:
    logger:
      LogReport:
        log_format: %a%i%m      # See Dancer2::Logger::LogReport
        app_name: MyApp
        dispatchers:
          logfile:              # "default" dispatcher stays open as well
            type: FILE
            to: /var/log/myapp.log
            charset: utf-8
            mode: DEBUG

See Log::Report::Dispatcher for full details of options.

Finally: a Dancer2 script may run many applications. Each application can have its own logger configuration. However, Log::Report dispatchers are global, so will be shared between Dancer2 applications. Any attempt to create a new Log::Report dispatcher by the same name (as will happen when a new Dancer2 application is started with the same configuration) will be ignored.

Dancer2::Plugin::LogReport

To use the plugin, you simply use it in your application:

  package MyApp;
  use Log::Report ();  # use early and minimal once
  use Dancer2;
  use Dancer2::Plugin::LogReport %config;

Dancer2::Plugin::LogReport takes the same %config options as Log::Report itself (see Log::Report::import()).

If you want to send messages from your modules/models, there is no need to use this specific plugin. Instead, you should simply "use Log::Report" to negate the need of loading all the Dancer2 specific code.

In use

In its simplest form, you can now use all the Log::Report logging functions to send messages to your dispatchers (as configured in the Logger configuration):

  trace "I'm here";

  warning "Something dodgy happened";

  panic "I'm bailing out";

  # Additional, special Dancer2 keyword
  success "Settings saved successfully";

Exceptions

Log::Report is a combination of a logger and an exception system. Messages to be logged are thrown to all listening dispatchers to be handled.

This module will also catch any unexpected exceptions:

  # This will be caught, the error will be logged (full stacktrace to STDOUT,
  # short message to the session messages), and the user will be forwarded
  # (default to /). This would also be sent to syslog with the appropriate
  # dispatcher.
  get 'route' => sub {
      my $foo = 1;
      my $bar = $foo->{x}; # whoops
  }

For a production application ("show_errors: 1"), the message saved in the session will be the generic text "An unexpected error has occurred". This can be customised in the configuration file, and will be translated.

Sending messages to the user

To make it easier to send messages to your users, messages at the following levels are also stored in the user's session: "notice", "warning", "mistake", "error", "fault", "alert", "failure" and "panic".

You can pass these to your template and display them at each page render:

  hook before_template => sub {
    my $tokens = shift;
    $tokens->{messages} = session 'messages';
    session 'messages' => []; # Clear the message queue
  }

Then in your template (for example the main layout):

  [% FOR message IN messages %]
    <div class="alert alert-[% message.bootstrap_color %]">
      [% message.toString | html_entity %]
    </div>
  [% END %]

The "bootstrap_color" of the message is compatible with Bootstrap contextual colors: "success", "info", "warning" or "danger".

Now, anywhere in your application that you have used Log::Report, you can

  warning "Hey user, you should now about this";

and the message will be sent to the next page the user sees.

Handling user errors

Sometimes we write a function in a model, and it would be nice to have a nice easy way to return from the function with an error message. One way of doing this is with a separate error message variable, but that can be messy code. An alternative is to use exceptions, but these can be a pain to deal with in terms of catching them. Here's how to do it with Log::Report.

In this example, we do use exceptions, but in a neat, easier to use manner.

First, your module/model:

  package MyApp::CD;

  sub update {
    my ($self, %values) = @_;
    $values{title} or error "Please enter a title";
    $values{description} or warning "No description entered";
  }

Then, in your controller:

  package MyApp;
  use Dancer2;

  post '/cd' => sub {
    my %values = (
      title       => param('title');
      description => param('description');
    );
    if (process sub { MyApp::CD->update(%values) } ) {
      success "CD updated successfully";
      redirect '/cd';
    }

    template 'cd' => { values => \%values };
  }

Now, when update() is called, any exceptions are caught. However, there is no need to worry about any error messages. Both the error and warning messages in the above code will have been stored in the messages session variable, where they can be displayed using the code in the previous section. The "error" will have caused the code to stop running, and process() will have returned false. "warning" will have simply logged the warning and not caused the function to stop running.

Logging DBIC database queries and errors

If you use DBIx::Class in your application, you can easily integrate its logging and exceptions. To log SQL queries:

  # Log all queries and execution time
  $schema->storage->debugobj(new Log::Report::DBIC::Profiler);
  $schema->storage->debug(1);

By default, exceptions from DBIC are classified at the level "error". This is normally a user level error, and thus may be filtered as normal program operation. If you do not expect to receive any DBIC exceptions, then it is better to class them at the level "panic":

  # panic() DBIC errors
  $schema->exception_action(sub { panic @_ });
  # Optionally get a stracktrace too
  $schema->stacktrace(1);

If you are occasionally running queries where you expect to naturally get exceptions (such as not inserting multiple values on a unique constraint), then you can catch these separately:

  try { $self->schema->resultset('Unique')->create() };
  # Log any messages from try block, but only as trace
  $@->reportAll(reason => 'TRACE');

Email alerts of exceptions

If you have an unexpected exception in your production application, then you probably want to be notified about it. One way to do so is configure rsyslog to send emails of messages at the panic level. Use the following configuration to do so:

  # Normal logging from LOCAL0
  local0.*                        -/var/log/myapp.log

  # Load the mail module
  $ModLoad ommail
  # Configure sender, receiver and mail server
  $ActionMailSMTPServer localhost
  $ActionMailFrom root
  $ActionMailTo root
  # Set up an email template
  $template mailSubject,"Critical error on %hostname%"
  $template mailBody,"RSYSLOG Alert\r\nmsg='%msg%'\r\nseverity='%syslogseverity-text%'"
  $ActionMailSubject mailSubject
  # Send an email no more frequently than every minute
  $ActionExecOnlyOnceEveryInterval 60
  # Configure the level of message to notify via email
  if $syslogfacility-text == 'local0' and $syslogseverity < 3 then :ommail:;mailBody
  $ActionExecOnlyOnceEveryInterval 0

With the above configuration, you will only be emailed of severe errors, but can view the full log information in /var/log/myapp.log