Cap sampleWeight at 50%

2 files changed, 12 insertions, 5 deletions

diff --git a/container-search/src/main/java/com/yahoo/search/dispatch/LoadBalancer.java b/container-search/src/main/java/com/yahoo/search/dispatch/LoadBalancer.java
index 99960be5d65..8736f612fc1 100644
--- a/container-search/src/main/java/com/yahoo/search/dispatch/LoadBalancer.java
+++ b/container-search/src/main/java/com/yahoo/search/dispatch/LoadBalancer.java
@@ -246,7 +246,7 @@ public class LoadBalancer {
             public void decay(RequestDuration duration) {
                 double searchTime = Math.max(duration.duration().toMillis()/1000.0, MIN_QUERY_TIME);
                 double decayRate = LATENCY_DECAY_TIME;
-                double sampleWeight = toDouble(duration.timeSince(prev));
+                double sampleWeight = Math.min(decayRate/2, toDouble(duration.timeSince(prev)));
                 averageSearchTime = (sampleWeight*searchTime + (decayRate - sampleWeight) * averageSearchTime) / decayRate;
                 prev = duration;
             }
diff --git a/container-search/src/test/java/com/yahoo/search/dispatch/LoadBalancerTest.java b/container-search/src/test/java/com/yahoo/search/dispatch/LoadBalancerTest.java
index 1499a4bb324..283c2bc743a 100644
--- a/container-search/src/test/java/com/yahoo/search/dispatch/LoadBalancerTest.java
+++ b/container-search/src/test/java/com/yahoo/search/dispatch/LoadBalancerTest.java
@@ -27,7 +27,7 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
  * @author ollivir
  */
 public class LoadBalancerTest {
-
+    private static final double delta = 0.0000001;
     @Test
     void requireThatLoadBalancerServesSingleNodeSetups() {
         Node n1 = new Node(0, "test-node1", 0);
@@ -212,7 +212,6 @@ public class LoadBalancerTest {
 
     @Test
     public void requireDecayByTimeToDependOnlyOnTime() {
-        double delta = 0.0000001;
         GroupStatus.Decayer decayer = new AdaptiveScheduler.DecayByTime(Duration.ofMillis(2), RequestDuration.of(Instant.EPOCH, Duration.ZERO));
         assertEquals(0.002, decayer.averageSearchTime(), delta);
         decayer.decay(RequestDuration.of(Instant.ofEpochMilli(1000), Duration.ofMillis(10)));
@@ -227,13 +226,21 @@ public class LoadBalancerTest {
         assertEquals(0.0059959552, decayer.averageSearchTime(), delta);
         decayer.decay(RequestDuration.of(Instant.ofEpochMilli(3000), Duration.ofMillis(10)));
         assertEquals(0.006076036096, decayer.averageSearchTime(), delta);
-        decayer.decay(RequestDuration.of(Instant.ofEpochMilli(6000), Duration.ofMillis(10)));
-        assertEquals(0.0084304144384, decayer.averageSearchTime(), delta);
+        decayer.decay(RequestDuration.of(Instant.ofEpochMilli(5000), Duration.ofMillis(10)));
+        assertEquals(0.0076456216576000005, decayer.averageSearchTime(), delta);
         assertEquals(110, countRequestsToReach90p(Duration.ofMillis(100), Duration.ofMillis(10)));
         assertEquals(55, countRequestsToReach90p(Duration.ofMillis(200), Duration.ofMillis(10)));
         assertEquals(11, countRequestsToReach90p(Duration.ofMillis(1000), Duration.ofMillis(10)));
     }
 
+    @Test
+    public void requireDecayByTimeToNotJumpTooFar() {
+        GroupStatus.Decayer decayer = new AdaptiveScheduler.DecayByTime(Duration.ofMillis(2), RequestDuration.of(Instant.EPOCH, Duration.ZERO));
+        assertEquals(0.002, decayer.averageSearchTime(), delta);
+        decayer.decay(RequestDuration.of(Instant.ofEpochMilli(10000), Duration.ofMillis(10)));
+        assertEquals(0.006, decayer.averageSearchTime(), delta); // Capped at 50% sampleWeight
+    }
+
     private static void updateSearchTime(GroupStatus gs, RequestDuration time) {
         gs.allocate();
         gs.release(true, time);