drupal_module__munin_api/help/what-is-munin-api.html

<p>This module is designed to allow Munin reporting of Drupal-related information.</p>

<p><a href="http://munin-monitoring.org/">Munin</a> itself is an Open Source 
  monitoring solution able to track just about any time-series information using 
  the <a href="http://www.mrtg.org/rrdtool/">RRDtool</a> graphing package 
  originally made popular by the MRTG monitoring system.</p>

<p>It is generally used by system and network administrators for low-level 
  technical information, but the Munin API module enables it to go beyond
  such system-level monitoring, to include Drupal-level, or even business-level 
  monitoring.</p>
 
<h3>Bundled graph providers</h3>

<p>Munin API is provided with a number of graph providers by default, each of them providing several graphs</p>

<p><img src="&path&munin_api.png" alt="Screenshot of various Drupal graphs in Munin" style="float: right; width: 50%; margin: 0 0 1em 1em" /></p>

<ul>
  <li>drupal_apc
    <ul>
      <li>APC memory use: allocated, used</li>
      <li>APC entries: hits, misses, insertions, entries, deleted entries.</li>
      <li>APC uptime</li>
      <li>Due to APC architecture, this plugin can only work if the module is
        running in normal Drupal mode, not from a CLI SAPI, as will happen when
        using a Drush plugin to query the Munin API module. Other bundled graph
        providers do not have this limitation.</li>
      </ul>
    </li>
  <li>drupal_core
    <ul>
      <li>core content: nodes (published vs unpublished), comments (published vs unpublished)</li>
      <li>core taxonomy: vocabularies, terms</li>
      <li>core users: users (active vs blocked), sessions (anonymous vs logged)</li>
      </ul>
    </li>
  <li>drupal_munin
    <ul>
      <li>This provider is wired into the Munin API module itself. It periodically checks whether Munin came to gets its data, making it able to warn in case of anomalous Munin probing like missed probes or probes coming in too fast.</li> 
      </ul>
    </li>
  </ul>

<h3>Non-bundled graph providers</h3>

<p>The Munin API module has been designed to be extended by custom graph providers,
created for the specific needs of any specific site.</p>

<p>New graph providers can be added by just implementing two hooks:</p>
<ul>
  <li><code style="display: inline">hook_munin_api_info()</code> to declare a graph provider</li>
  <li><code style="display: inline">hook_munin_api_fetch($graph_name)</code> to return the data for a specific graph</li> 
  </ul>
  
<h3>Graph providers vs Munin plugins</h3>

<p>Technically, Munin API serves data from its graph providers as just one Munin-level 
multiple graph plugin.</p>

<p>A default Munin-level plugin is provided in the <code style="display: inline">plugins/</code>
directory. Most sites will likely expand on this sample.</p>