1 files changed, 138 insertions, 0 deletions
diff --git a/container-core/src/main/java/com/yahoo/container/jdisc/state/GaugeMetric.java b/container-core/src/main/java/com/yahoo/container/jdisc/state/GaugeMetric.java
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index 00000000000..da8c318f055
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+++ b/container-core/src/main/java/com/yahoo/container/jdisc/state/GaugeMetric.java
@@ -0,0 +1,138 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.container.jdisc.state;
+
+import java.util.List;
+import java.util.Optional;
+
+import com.yahoo.collections.Tuple2;
+
+/**
+ * A metric which contains a gauge value, i.e a value which represents the magnitude of something
+ * measured at a point in time. This metric value contains some additional information about the distribution
+ * of this gauge value in the time interval this metric is for.
+ *
+ * @author <a href="mailto:simon@yahoo-inc.com">Simon Thoresen Hult</a>
+ */
+public final class GaugeMetric extends MetricValue {
+
+    private double last;
+    private double max;
+    private double min;
+    private double sum;
+    private long count;
+    private Optional<List<Tuple2<String, Double>>> percentiles;
+
+    private GaugeMetric(double last, double max, double min, double sum, long count, Optional<List<Tuple2<String, Double>>> percentiles) {
+        this.last = last;
+        this.max = max;
+        this.min = min;
+        this.sum = sum;
+        this.count = count;
+        this.percentiles = percentiles;
+    }
+
+    @Override
+    void add(Number val) {
+        double dval = val.doubleValue();
+        last = dval;
+        if (dval > max) {
+            max = dval;
+        }
+        if (dval < min) {
+            min = dval;
+        }
+        sum += dval;
+        ++count;
+    }
+
+    @Override
+    void add(MetricValue val) {
+        GaugeMetric rhs = (GaugeMetric)val;
+        last = rhs.last;
+        if (rhs.max > max) {
+            max = rhs.max;
+        }
+        if (rhs.min < min) {
+            min = rhs.min;
+        }
+        sum += rhs.sum;
+        count += rhs.count;
+    }
+
+    /**
+     * Returns the average reading of this value in the time interval, or--if no
+     * value has been set within this period--the value of 'last' from the
+     * most recent interval where this metric was set.
+     */
+    public double getAverage() {
+        return count != 0 ? (sum / count) : last;
+    }
+
+    /**
+     * Returns the most recent assignment of this metric in the time interval,
+     * or--if no value has been set within this period--the value of 'last'
+     * from the most recent interval where this metric was set.
+     */
+    public double getLast() { return last; }
+
+    /**
+     * Returns the max value of this metric in the time interval, or--if no
+     * value has been set within this period--the value of 'last' from the
+     * most recent interval where this metric was set.
+     */
+    public double getMax() {
+        return (count == 0) ? last : max;
+    }
+
+    /**
+     * Returns the min value of this metric in the time interval, or--if no
+     * value has been set within this period--the value of 'last' from the
+     * most recent interval where this metric was set.
+     */
+    public double getMin() {
+        return (count == 0) ? last : min;
+    }
+
+    /** Returns the sum of all assignments of this metric in the time interval */
+    public double getSum() {
+        return sum;
+    }
+
+    /** Returns the number of assignments of this value in the time interval */
+    public long getCount() {
+        return count;
+    }
+
+    /** Returns the 95th percentile value for this time interval */
+    public Optional<List<Tuple2<String, Double>>> getPercentiles() {
+        return percentiles;
+    }
+
+    /**
+     * Create a partial clone of this gauge where the value of 'last' is
+     * carried over to the new gauge with all other fields left at defaults
+     * (0 for count and sum, biggest possible double for min, smallest possible
+     * double for max). Note that since count is 0, these extreme values will
+     * never be output from the min/max getters as these will return 'last'
+     * in this case.
+     * @return A new gauge instance
+     */
+    public GaugeMetric newWithPreservedLastValue() {
+        // min/max set to enforce update of these values on first call to add()
+        return new GaugeMetric(last, Double.MIN_VALUE, Double.MAX_VALUE, 0, 0, Optional.empty());
+    }
+
+    public static GaugeMetric newSingleValue(Number val) {
+        double dval = val.doubleValue();
+        return new GaugeMetric(dval, dval, dval, dval, 1, Optional.empty());
+    }
+
+    public static GaugeMetric newInstance(double last, double max, double min, double sum, long count) {
+        return new GaugeMetric(last, max, min, sum, count, Optional.empty());
+    }
+
+    public static GaugeMetric newInstance(double last, double max, double min, double sum, long count, Optional<List<Tuple2<String, Double>>> percentiles) {
+        return new GaugeMetric(last, max, min, sum, count, percentiles);
+    }
+
+}