title: Why are performance metric libraries needed for metric implementations?
body: <p>I have this primitive doubt. There are many metrics libraries for Java such as <a href="http://metrics.dropwizard.io/3.1.0/getting-started/" rel="nofollow">http://metrics.dropwizard.io/3.1.0/getting-started/</a> How are these different from having primitive data types and doing the metrics ourselves? For example, this  provides a feature called counters which could be used for measurements for counting. But how does this differ from having a local integer variable and incrementing and decrementing it ourselves? This is not just related to this library, but to all the performance metrics libraries out there. Another feature is health check. How does it differ from having a simple boolean variable for the same purpose? Please advice.</p>