A bit of documentation.

documentation/developer/Performance-Metrics.md

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+The Libresonic framework contains a convenient class (called MetricsManager) to add inner metrics that constructs in real time some performance indicators.
+
+The use of MetricsManager is illustrated in the org.libresonic.player.filter.MetricsFilter class. 
+
+The MetricsFilter adds a metric based on the time spent by each /main.view HTTP request. This is interesting as the main.view request is invoqued when something is displayed in the main Libresonic web frame.
+
+By default, the MetricsManager is deactivated; it does nothing. 
+It can be activated only by adding the following line inside the livresonic.properties configuration file :
+
+```
+Metrics=
+```
+
+Once the MetricsManager as been activated this way, each metric can be inspected using a jmx console like VisualVM.
+Each metric is registered as a MBean as shown below.
+
+![](metrics-visualvm-screenshot.png)