[GitHub] [incubator-pinot] npawar commented on a change in pull request #4211: StreamPartitionAssignmentStrategy interface to plug in various partition assignment strategies (uniform, replica group based)

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npawar commented on a change in pull request #4211: StreamPartitionAssignmentStrategy interface to plug in various partition assignment strategies (uniform, replica group based)
URL: https://github.com/apache/incubator-pinot/pull/4211#discussion_r284880484
 
 

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 File path: pinot-common/src/main/java/org/apache/pinot/common/partition/ReplicaGroupBasedStreamPartitionAssignmentStrategy.java
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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.pinot.common.partition;
+
+import com.google.common.annotations.VisibleForTesting;
+import java.util.ArrayList;
+import java.util.List;
+import javax.annotation.Nonnull;
+import org.apache.helix.HelixManager;
+import org.apache.pinot.common.exception.InvalidConfigException;
+
+
+/**
+ * Replica group based partition assignment strategy for realtime partitions
+ */
+public class ReplicaGroupBasedStreamPartitionAssignmentStrategy implements StreamPartitionAssignmentStrategy {
+
+  /**
+   * Fetches the replica group partition assignment znode and assigns partitions across the replica groups.
+   * A vertical slice will be picked form the replica group sets for a partition, based on the formula:
+   * vertical slice = partition % numInstancesPerReplicaGroup
+   */
+  @Override
+  public PartitionAssignment getStreamPartitionAssignment(HelixManager helixManager, @Nonnull String tableNameWithType,
+      @Nonnull List<String> partitions, int numReplicas, List<String> instances) throws InvalidConfigException {
+
+    ReplicaGroupPartitionAssignment replicaGroupPartitionAssignment =
+        getReplicaGroupPartitionAssignment(helixManager, tableNameWithType);
+    if (replicaGroupPartitionAssignment == null) {
+      throw new InvalidConfigException("ReplicaGroupPartitionAssignment is null for table:" + tableNameWithType);
+    }
+    int numReplicaGroups = replicaGroupPartitionAssignment.getNumReplicaGroups();
+    if (numReplicaGroups != numReplicas) {
+      throw new InvalidConfigException(
+          "numReplicas:" + numReplicas + " is not equal to numReplicaGroups:" + numReplicaGroups
+              + " from znode for table:" + tableNameWithType);
+    }
+    int numInstancesPerReplicaGroup = replicaGroupPartitionAssignment.getInstancesFromReplicaGroup(0, 0).size();
 
 Review comment:
   That would be a good extension. Will add a TODO indicating that we might want to do this if we want to remove strict requirement that numInstancesPerReplicaGroup is same across all replica groups

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