fix: issue of last partition not included for certain groups weightage

kafka-streams-partitioners/weighted-group-partitioner/src/main/java/org/hypertrace/core/kafkastreams/framework/partitioner/WeightedGroupProfile.java

@@ -41,11 +41,7 @@ public WeightedGroupProfile(PartitionerProfile profile) {
                 groupConfig ->
                     buildEntriesForEachMember(groupConfig, weightConsumedSoFar, totalWeight))
             .collect(Collectors.toUnmodifiableMap(Entry::getKey, Entry::getValue));
-    this.defaultGroup =
-        new WeightedGroup(
-            "[[default]]",
-            weightConsumedSoFar.get(),
-            weightConsumedSoFar.addAndGet(defaultGroupWeight / totalWeight));
+    this.defaultGroup = new WeightedGroup("[[default]]", weightConsumedSoFar.get(), 1.0);
 
     log.info(
         "partitioner default group config - weight range: {}, range end: {}",

kafka-streams-partitioners/weighted-group-partitioner/src/test/java/org/hypertrace/core/kafkastreams/framework/partitioner/WeightedGroupPartitionerTest.java

@@ -228,6 +228,75 @@ public void testWithNonMultipleWeightRatio() {
     }
   }
 
+  @Test
+  public void testWithNonMultipleRoundingWeightRatio() {
+
+    int numPartitions = 64;
+    int testCount = numPartitions * 2;
+    int lastPartitionSeen = -1;
+
+    WeightedGroupPartitioner<String, String> partitioner =
+        getPartitionerForTestWithNonMultipleRoundingWeightRatio();
+    int partition;
+
+    // Test case 1: tenant-1 belong to group-1 (partitions: [0 to 22])
+    for (int i = 1; i <= testCount; i++) {
+      partition = partitioner.partition("test-topic", "tenant-1", "span-" + i, numPartitions);
+      if (partition > lastPartitionSeen) lastPartitionSeen = partition;
+      assertTrue(
+          partition >= 0 && partition <= 22,
+          "actual partition not in expected range. partition: " + partition);
+    }
+
+    // Test case 2: tenant-2 belong to group-2 (partitions: [23 to 40])
+    for (int i = 1; i <= testCount; i++) {
+      partition = partitioner.partition("test-topic", "tenant-2", "span-" + i, numPartitions);
+      if (partition > lastPartitionSeen) lastPartitionSeen = partition;
+      assertTrue(
+          partition >= 23 && partition <= 40,
+          "actual partition not in expected range. partition: " + partition);
+    }
+
+    // Test case 3: tenant-3 belong to group-2 (partitions: [23 to 40])
+    for (int i = 1; i <= testCount; i++) {
+      partition = partitioner.partition("test-topic", "tenant-3", "span-" + i, numPartitions);
+      if (partition > lastPartitionSeen) lastPartitionSeen = partition;
+      assertTrue(
+          partition >= 23 && partition <= 40,
+          "actual partition not in expected range. partition: " + partition);
+    }
+
+    // Test case 4: groupKey=unknown should use default group [41 to 63]
+    for (int i = 1; i <= testCount; i++) {
+      partition = partitioner.partition("test-topic", "unknown", "span-" + i, numPartitions);
+      if (partition > lastPartitionSeen) lastPartitionSeen = partition;
+      assertTrue(
+          partition >= 41 && partition <= 63,
+          "actual partition not in expected range. partition: " + partition);
+    }
+    assertEquals(lastPartitionSeen, numPartitions - 1);
+  }
+
+  private WeightedGroupPartitioner<String, String>
+      getPartitionerForTestWithNonMultipleRoundingWeightRatio() {
+    PartitionerConfigServiceClient testClient =
+        (profileName) ->
+            new WeightedGroupProfile(
+                PartitionerProfile.newBuilder()
+                    .addGroups(newPartitionerGroup("group1", new String[] {"tenant-1"}, 37))
+                    .addGroups(
+                        newPartitionerGroup("group2", new String[] {"tenant-2", "tenant-3"}, 29))
+                    .addGroups(newPartitionerGroup("group3", new String[] {"tenant-4"}, 16))
+                    .setDefaultGroupWeight(20)
+                    .setName(profileName)
+                    .build());
+
+    WeightedGroupPartitioner<String, String> partitioner =
+        new WeightedGroupPartitioner<>(
+            "spans", testClient, groupKeyExtractor, roundRobinPartitioner);
+    return partitioner;
+  }
+
   private PartitionerConfigServiceClient getTestServiceClient() {
     return (profileName) ->
         new WeightedGroupProfile(