1 files changed, 68 insertions, 0 deletions
diff --git a/tenant-cd/src/main/java/ai/vespa/hosted/cd/metric/Statistic.java b/tenant-cd/src/main/java/ai/vespa/hosted/cd/metric/Statistic.java
new file mode 100644
index 00000000000..fc52900bdac
--- /dev/null
+++ b/tenant-cd/src/main/java/ai/vespa/hosted/cd/metric/Statistic.java
@@ -0,0 +1,68 @@
+package ai.vespa.hosted.cd.metric;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.StringJoiner;
+
+import static java.util.Map.copyOf;
+
+/**
+ * Known statistic about a metric, at a certain point.
+ *
+ * @author jonmv
+ */
+public class Statistic {
+
+    private final Map<Type, Double> data;
+
+    /** Creates a new Statistic with a copy of the given data. */
+    private Statistic(Map<Type, Double> data) {
+        this.data = data;
+    }
+
+    public static Statistic of(Map<Type, Double> data) {
+        return new Statistic(copyOf(data));
+    }
+
+    /** Returns the value of the given type, or throws a NoSuchElementException if this isn't known. */
+    public double get(Type key) {
+        if ( ! data.containsKey(key))
+            throw new NoSuchElementException("No value with key '" + key + "' is known.");
+
+        return data.get(key);
+    }
+
+    /** Returns the underlying, unmodifiable Map. */
+    public Map<Type, Double> asMap() {
+        return data;
+    }
+
+    Statistic mergedWith(Statistic other) {
+        if (data.keySet().equals(other.data.keySet()))
+            throw new IllegalArgumentException("Incompatible key sets '" + data.keySet() + "' and '" + other.data.keySet() + "'.");
+
+        Map<Type, Double> merged = new HashMap<>();
+        double n1 = get(Type.count), n2 = other.get(Type.count);
+        for (Type type : data.keySet()) switch (type) {
+            case count: merged.put(type, n1 + n2); break;
+            case rate: merged.put(type, get(Type.rate) + other.get(Type.rate)); break;
+            case max: merged.put(type, Math.max(get(Type.max), other.get(Type.max))); break;
+            case min: merged.put(type, Math.min(get(Type.min), other.get(Type.min))); break;
+            case average: merged.put(type, (n1 * get(Type.average) + n2 * other.get(Type.average)) / (n1 + n2)); break;
+            case last:
+            case percentile95:
+            case percentile99: break;
+            default: throw new IllegalArgumentException("Unexpected type '" + type + "'.");
+        }
+        return of(merged);
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", Statistic.class.getSimpleName() + "[", "]")
+                .add("data=" + data)
+                .toString();
+    }
+
+}