Encode sketch average explicitly

To avoid numeric stability issues when computing it as sum/cnt.

Author: vickenty

dogstatsd-http-serializer/src/main/java/com/datadoghq/dogstatsd/http/serializer/SketchMetric.java

@@ -9,7 +9,7 @@
 
 /** Builder for sketch timeseries. */
 public class SketchMetric extends Metric<SketchMetric> {
-    private static final int VALUES_PER_SKETCH_POINT = 3;
+    private static final int VALUES_PER_SKETCH_POINT = 4;
 
     SketchMetric(PayloadBuilder pb, int type, String name) {
         super(pb, type, name);
@@ -25,6 +25,7 @@ protected SketchMetric self() {
      *
      * @param timestamp Timestamp of the point in seconds since Unix epoch.
      * @param sum Total sum of all observed values.
+     * @param avg Average of all observed values.
      * @param min Minimum observed value.
      * @param max Maximum observed value.
      * @param cnt Number of observed values.
@@ -35,6 +36,7 @@ protected SketchMetric self() {
     public SketchMetric addPoint(
             long timestamp,
             double sum,
+            double avg,
             double min,
             double max,
             long cnt,
@@ -47,6 +49,7 @@ public SketchMetric addPoint(
 
         pb.timestamps.put(timestamp);
         pb.values.put(sum);
+        pb.values.put(avg);
         pb.values.put(min);
         pb.values.put(max);
         pb.counts.put(cnt);
@@ -85,6 +88,9 @@ void encodeValues(ValueType valueType) {
                     r.putSint64(
                             Column.valsSint64,
                             (long) pb.values.get(VALUES_PER_SKETCH_POINT * i + 2));
+                    r.putSint64(
+                            Column.valsSint64,
+                            (long) pb.values.get(VALUES_PER_SKETCH_POINT * i + 3));
                     r.putSint64(Column.valsSint64, pb.counts.get(i));
                 }
                 break;
@@ -98,6 +104,9 @@ void encodeValues(ValueType valueType) {
                     r.putFloat32(
                             Column.valsFloat32,
                             (float) pb.values.get(VALUES_PER_SKETCH_POINT * i + 2));
+                    r.putFloat32(
+                            Column.valsFloat32,
+                            (float) pb.values.get(VALUES_PER_SKETCH_POINT * i + 3));
                     r.putSint64(Column.valsSint64, pb.counts.get(i));
                 }
                 break;
@@ -108,6 +117,8 @@ void encodeValues(ValueType valueType) {
                             Column.valsFloat64, pb.values.get(VALUES_PER_SKETCH_POINT * i + 1));
                     r.putFloat64(
                             Column.valsFloat64, pb.values.get(VALUES_PER_SKETCH_POINT * i + 2));
+                    r.putFloat64(
+                            Column.valsFloat64, pb.values.get(VALUES_PER_SKETCH_POINT * i + 3));
                     r.putSint64(Column.valsSint64, pb.counts.get(i));
                 }
                 break;

dogstatsd-http-serializer/src/test/java/com/datadoghq/dogstatsd/http/serializer/PayloadBuilderTest.java

@@ -44,8 +44,17 @@ public void handle(byte[] p) {
 
         b.sketch("ijk")
                 .setTags(Arrays.asList(new String[] {"foo", "baz"}))
-                .addPoint(100, 4.75, 1.25, 1.75, 3, new int[] {1351, 1373}, new int[] {1, 2})
-                .addPoint(110, 6.5, 2.25, 2.75, 5, new int[] {1389, 1402}, new int[] {2, 3})
+                .addPoint(
+                        100,
+                        4.75,
+                        4.75 / 3,
+                        1.25,
+                        1.75,
+                        3,
+                        new int[] {1351, 1373},
+                        new int[] {1, 2})
+                .addPoint(
+                        110, 6.5, 6.5 / 5, 2.25, 2.75, 5, new int[] {1389, 1402}, new int[] {2, 3})
                 .close();
 
         b.rate("lm").setInterval(10).addPoint(100, 3.14).close();
@@ -60,7 +69,7 @@ public void handle(byte[] p) {
                 new int[] {
                     // MetricData
                     (3 << 3) | 2,
-                    188,
+                    196,
                     1,
                     // dictNameStr
                     (1 << 3) | 2,
@@ -194,14 +203,19 @@ public void handle(byte[] p) {
                     4,
                     6,
                     10,
-                    // valsFloat32, list(pack('<ffffff', 4.75, 1.25, 1.75, 6.5, 2.25, 2.75))
+                    // valsFloat32, list(pack('<ffffffff', 4.75, 4.75/3, 1.25, 1.75, 6.5, 6.5/5,
+                    // 2.25, 2.75))
                     (18 << 3) | 2,
                     1,
-                    24,
+                    32,
                     0,
                     0,
                     152,
                     64,
+                    171,
+                    170,
+                    202,
+                    63,
                     0,
                     0,
                     160,
@@ -214,6 +228,10 @@ public void handle(byte[] p) {
                     0,
                     208,
                     64,
+                    102,
+                    102,
+                    166,
+                    63,
                     0,
                     0,
                     16,