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<div class="pod-document"><h1><a name="dancer2__logger__console__colored"></a>Dancer2::Logger::Console::Colored</h1>

<p>During development the console output of your app is often one of the most important tools.
But sometimes there is just too much noise, and changing the log settings all the time is not convenient.
Of course you can grep the log or scroll, but wouldn't it be nice to get visual clues for what you're looking for?</p>
<p>With <a href="https://metacpan.org/module/Dancer2::Logger::Console::Colored">Dancer2::Logger::Console::Colored</a> you can do that. It's a drop-in replacement for the default
console logger, but with color. It will make the message appear in color depending on the levels. You can turn
it on by setting your logger in your environment config file:</p>
<pre class="prettyprint">logger: "Console::Colored"</pre>

<p>Your log will instantly become cheerful and seasonal according to this default configuration:</p>
<pre class="prettyprint"># config.yml (these are the defaults)
engines:
  logger:
    Console::Colored:
      colored_origin: "cyan"
      colored_levels:
        core: "bold bright_white"
        debug: "bold bright_blue"
        info: "bold green"
        warning: "bold yellow"
        error: "bold yellow on_red"
      colored_messages:
        core: "bold bright_white"
        debug: "bold bright_blue"
        info: "bold green"
        warning: "bold yellow"
        error: "bold yellow on_red"</pre>

<img src="/images/2018/23/log-1.png">

<p>The <code>colored_origin</code> refers to the part of the message that shows the package that this
message originated in, as well as the file name and line.</p>
<pre class="prettyprint">&gt;&gt; Dancer2 v0.207000 server 28764 listening on http://0.0.0.0:3000
[main:28764] debug @2018-12-19 20:31:06&gt; Hello World in test.pl l. 6
 ^^^^                                                   ^^^^^^^    ^</pre>

<p>The <code>colored_levels</code> are the log levels themselves.</p>
<pre class="prettyprint">[main:28764] debug @2018-12-19 20:31:06&gt; Hello World in test.pl l. 6
             ^^^^^</pre>

<p>And the <code>colored_messages</code> refer to the actual message.</p>
<pre class="prettyprint">[main:28764] debug @2018-12-19 20:31:06&gt; Hello World in test.pl l. 6
                                         ^^^^^^^^^^^</pre>

<p>The colors are the same kind of color strings used by <a href="https://metacpan.org/module/Term::ANSIColor">Term::ANSIColor</a>. The first
color refers to the foreground, and the second one to the background. You can add an optional <code>bold</code>.</p>
<pre class="prettyprint">[bold] [foreground] [on_background]</pre>

<h2><a name="changing_the_log_message"></a>Changing the log message</h2>

<p>If you don't like the default log format, you can change it with the <code>log_format</code> setting, which is
documented in detail in <a href="https://metacpan.org/module/Dancer2::Core::Role::Logger">Dancer2::Core::Role::Logger</a>. You can just stick it in with the other configuration.</p>
<pre class="prettyprint"># config.yml (this is the default)
engines:
  logger:
    Console::Colored:
      log_format: "[%a:%P] %L @%T&gt; %m in %f l. %l"</pre>

<p>Usually you would run a single-worker server during development, so there is no need for request IDs.
And since the message is now colored, we can also drop the log level. How about a simple format like
the following:</p>
<pre class="prettyprint">%t %f:%l&gt; %m
# 20/Dec/2018 16:41:07 MyApp.pm:22&gt; Hello World</pre>

<h2><a name="i_know_regular_expressions_"></a>I know regular expressions!</h2>

<p>Sometimes just reading the log is not enough. You're looking for a specific piece of information. There
are three pages of log for a single request, and debugging is hard work. Grepping is an option,
but you need to look for a complex pattern. Maybe a product SKU, a date or some other piece of information.</p>
<p>With Dancer2::Logger::Console::Colored you can actually make it come out with a background color so you
can spot it easily, without having to change your code (or your added debugging log statements). Instead,
you can put a regular expression into your configuration file.</p>
<pre class="prettyprint"># config.yml
engines:
  logger:
    Console::Colored:
      colored_regex:
       - re: "customer number \d+"
         color: "bold red"</pre>

<p>This will find customer numbers according to the pattern and make them bold and red. You can supply
a regular expression pattern and a color setting.</p>
<img src="/images/2018/23/log-2.png">

<p>Note that there is a list under the <code>colored_regex</code> key. This means you can actually have
multiple patterns. Even really simple ones that make <code>print</code> style debugging easy
and attractive.</p>
<pre class="prettyprint"># config.yml
engines:
  logger:
    Console::Colored:
      colored_regex:
       - re: "customer number \d+"
         color: "bold red"
       - re: "\bhere\b"
         color: "white on_green"</pre>

<p>If you want to highlight an entire log message in a specific color, you can set a pattern that captures
everything. However, this works on the message only, and not on the entire formatted line of log output.
(Patches welcome!)</p>
<pre class="prettyprint"># config.yml
engines:
  logger:
    Console::Colored:
      colored_regex:
        - re: ".+here.+"
          color: "white on_red"</pre>

<img src="/images/2018/23/log-3.png">

<p>This opens up a lot of possibilities, for debugging as well as for general logging during development.</p>
<h2><a name="what_else"></a>What else?</h2>

<p>There are still some feature ideas in the backlog, but it's already pretty useful. If you would
like to see additional features, please feel free to
[open an issue on github](https://github.com/simbabque/Dancer2-Logger-Console-Colored/issues).</p>
<p>And if you happen to use Mojolicious as well and need something similar, take a look at
<a href="https://metacpan.org/module/Mojo::Log::Colored">Mojo::Log::Colored</a>, which is in the early stages of development, but works quite well.</p>
<h2><a name="author"></a>Author</h2>

<p>This article has been written by Julien Fiegehenn (simbabque) for the Perl Dancer 
Advent Calendar 2018.</p>
<h2><a name="copyright"></a>Copyright</h2>

<p>No copyright retained. Enjoy.</p>
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