Added optional "timestamp" value as part of metric sample (#337)

Author: felipe-conde-benavides

simpleclient/src/main/java/io/prometheus/client/Collector.java

@@ -77,12 +77,18 @@ public static class Sample {
       public final List<String> labelNames;
       public final List<String> labelValues;  // Must have same length as labelNames.
       public final double value;
+      public final Long timestampMs;  // It's an epoch format with milliseconds value included (this field is subject to change).
 
-      public Sample(String name, List<String> labelNames, List<String> labelValues, double value) {
+      public Sample(String name, List<String> labelNames, List<String> labelValues, double value, Long timestampMs) {
         this.name = name;
         this.labelNames = labelNames;
         this.labelValues = labelValues;
         this.value = value;
+        this.timestampMs = timestampMs;
+      }
+
+      public Sample(String name, List<String> labelNames, List<String> labelValues, double value) {
+    	  this(name, labelNames, labelValues, value, null);
       }
 
       @Override
@@ -91,8 +97,10 @@ public boolean equals(Object obj) {
           return false;
         }
         Sample other = (Sample) obj;
+
         return other.name.equals(name) && other.labelNames.equals(labelNames)
-          && other.labelValues.equals(labelValues) && other.value == value;
+          && other.labelValues.equals(labelValues) && other.value == value
+          && ((timestampMs == null && other.timestampMs == null) || (other.timestampMs != null) && (other.timestampMs.equals(timestampMs)));
       }
 
       @Override
@@ -103,13 +111,16 @@ public int hashCode() {
         hash = 37 * hash + labelValues.hashCode();
         long d = Double.doubleToLongBits(value);
         hash = 37 * hash + (int)(d ^ (d >>> 32));
+        if (timestampMs != null) {
+          hash = 37 * hash + timestampMs.hashCode();
+        }
         return hash;
       }
 
       @Override
       public String toString() {
         return "Name: " + name + " LabelNames: " + labelNames + " labelValues: " + labelValues +
-          " Value: " + value;
+          " Value: " + value + " TimestampMs: " + timestampMs;
       }
     }
   }

simpleclient/src/main/java/io/prometheus/client/Gauge.java

@@ -136,6 +136,7 @@ public static class Child {
     private final DoubleAdder value = new DoubleAdder();
 
     static TimeProvider timeProvider = new TimeProvider();
+
     /**
      * Increment the gauge by 1.
      */
@@ -287,7 +288,6 @@ public double get() {
     return noLabelsChild.get();
   }
 
-
   @Override
   public List<MetricFamilySamples> collect() {
     List<MetricFamilySamples.Sample> samples = new ArrayList<MetricFamilySamples.Sample>(children.size());

simpleclient/src/test/java/io/prometheus/client/GaugeTest.java

@@ -138,5 +138,4 @@ public void testCollect() {
     assertEquals(1, mfs.size());
     assertEquals(mfsFixture, mfs.get(0));
   }
-
 }

simpleclient_common/src/main/java/io/prometheus/client/exporter/common/TextFormat.java

@@ -46,6 +46,10 @@ public static void write004(Writer writer, Enumeration<Collector.MetricFamilySam
         }
         writer.write(' ');
         writer.write(Collector.doubleToGoString(sample.value));
+        if (sample.timestampMs != null){
+          writer.write(' ');
+          writer.write(sample.timestampMs.toString());
+        }
         writer.write('\n');
       }
     }

simpleclient_common/src/test/java/io/prometheus/client/exporter/common/TextFormatTest.java

@@ -4,10 +4,13 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
+import java.util.ArrayList;
+import java.util.List;
 
 import org.junit.Before;
 import org.junit.Test;
 
+import io.prometheus.client.Collector;
 import io.prometheus.client.CollectorRegistry;
 import io.prometheus.client.Counter;
 import io.prometheus.client.Gauge;
@@ -54,6 +57,29 @@ public void testCounterOutput() throws IOException {
                  + "nolabels 1.0\n", writer.toString());
   }
 
+  @Test
+  public void testMetricOutputWithTimestamp() throws IOException {
+
+    class CustomCollector extends Collector {
+      public List<MetricFamilySamples> collect() {
+        List<MetricFamilySamples> mfs = new ArrayList<MetricFamilySamples>();
+        ArrayList<String> labelNames = new ArrayList<String>();
+        ArrayList<String> labelValues = new ArrayList<String>();
+        ArrayList<MetricFamilySamples.Sample> samples = new ArrayList<Collector.MetricFamilySamples.Sample>();
+        MetricFamilySamples.Sample sample = new MetricFamilySamples.Sample("nolabels", labelNames, labelValues, 1.0, 1518123456L);
+        samples.add(sample);
+        mfs.add(new MetricFamilySamples("nolabels", Collector.Type.UNTYPED, "help", samples));
+        return mfs;
+      }
+    }
+    
+    new CustomCollector().register(registry);
+    TextFormat.write004(writer, registry.metricFamilySamples());
+    assertEquals("# HELP nolabels help\n"
+                 + "# TYPE nolabels untyped\n"
+                 + "nolabels 1.0 1518123456\n", writer.toString());
+  }
+
   @Test
   public void testSummaryOutput() throws IOException {
     Summary noLabels = Summary.build().name("nolabels").help("help").register(registry);