title: Micrometer's Gauge - update ratio
body: <p>I'm wondering what's the update ratio of gauge meter in micrometer:</p>
  
  <pre><code>List&lt;String&gt; list = registry.gauge("listGauge", Collections.emptyList(), new ArrayList&lt;&gt;(), List::size);
  </code></pre>
  
  <p>now let's say that list is changing sometimes often, sometimes stays without a change for a long time. How often <code>aList.size()</code> will be called? </p>
  
  <p><strong><em>More general question:</em></strong></p>
  
  <p>Is gauge a good pick for reporting DB table state every x seconds? I've a table with date column and want to configure alert when date is older than t seconds. That requires DB query each time, so I don't want to be called too often. Appreciate any advice.</p>