Improve Prometheus metrics using node_prefix as a label to help with Grafana variables

subsys/metrics/prometheus/src/main/java/org/commonjava/indy/metrics/prometheus/IndySampleBuilder.java

@@ -0,0 +1,36 @@
+package org.commonjava.indy.metrics.prometheus;
+
+import io.prometheus.client.Collector;
+import io.prometheus.client.dropwizard.samplebuilder.DefaultSampleBuilder;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class IndySampleBuilder
+        extends DefaultSampleBuilder
+{
+    private static final String NODE_NAME_LABEL = "node";
+
+    private String nodeName;
+
+    public IndySampleBuilder( String nodeName )
+    {
+        super();
+        this.nodeName = nodeName;
+    }
+
+    @Override
+    public Collector.MetricFamilySamples.Sample createSample( final String dropwizardName, final String nameSuffix,
+                                                              final List<String> additionalLabelNames,
+                                                              final List<String> additionalLabelValues,
+                                                              final double value )
+    {
+        List<String> labelNames = new ArrayList( additionalLabelNames );
+        labelNames.add( NODE_NAME_LABEL );
+
+        List<String> labelValues = new ArrayList( additionalLabelValues );
+        labelValues.add( nodeName );
+
+        return super.createSample( dropwizardName, nameSuffix, labelNames, labelValues, value );
+    }
+}

subsys/metrics/prometheus/src/main/java/org/commonjava/indy/metrics/prometheus/PrometheusDeployment.java

@@ -39,7 +39,7 @@ public DeploymentInfo getDeploymentInfo( String contextRoot, Application applica
             return null;
         }
 
-        CollectorRegistry.defaultRegistry.register( new DropwizardExports( metricRegistry ) );
+        CollectorRegistry.defaultRegistry.register( new DropwizardExports( metricRegistry, new IndySampleBuilder( config.getNodePrefix() ) ) );
 
         final ServletInfo servlet =
                 Servlets.servlet( "prometheus-metrics", MetricsServlet.class ).addMapping( "/metrics" );