[GitHub] [incubator-pinot] Jackie-Jiang commented on a change in pull request #4269: Add interface and implementations for the new segment assignment

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Jackie-Jiang commented on a change in pull request #4269: Add interface and implementations for the new segment assignment
URL: https://github.com/apache/incubator-pinot/pull/4269#discussion_r290125924
 
 

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 File path: pinot-controller/src/main/java/org/apache/pinot/controller/helix/core/assignment/InstancePartitionsUtils.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.controller.helix.core.assignment;
+
+import java.util.Collections;
+import java.util.List;
+import org.apache.helix.AccessOption;
+import org.apache.helix.HelixManager;
+import org.apache.helix.ZNRecord;
+import org.apache.helix.model.InstanceConfig;
+import org.apache.helix.store.HelixPropertyStore;
+import org.apache.pinot.common.config.OfflineTagConfig;
+import org.apache.pinot.common.config.RealtimeTagConfig;
+import org.apache.pinot.common.config.TableConfig;
+import org.apache.pinot.common.metadata.ZKMetadataProvider;
+import org.apache.pinot.common.utils.CommonConstants;
+import org.apache.pinot.common.utils.helix.HelixHelper;
+
+
+/**
+ * Utility class for instance partitions.
+ */
+public class InstancePartitionsUtils {
+  private InstancePartitionsUtils() {
+  }
+
+  /**
+   * Fetches the instance partitions from Helix property store if exists, or computes it for backward compatibility.
+   */
+  public static InstancePartitions fetchOrComputeInstancePartitions(HelixManager helixManager,
+      TableConfig tableConfig) {
+    String tableNameWithType = tableConfig.getTableName();
+
+    // Fetch the instance partitions from property store if exists
+    String path = ZKMetadataProvider.constructPropertyStorePathForInstancePartitions(tableNameWithType);
+    ZNRecord znRecord = helixManager.getHelixPropertyStore().get(path, null, AccessOption.PERSISTENT);
+    if (znRecord != null) {
+      return InstancePartitions.fromZNRecord(znRecord);
+    }
+
+    // Compute the instance partitions (for backward compatible)
+    // Sort all enabled instances with the server tag, rotate the list based on the table name to prevent creating
+    // hotspot servers
+    InstancePartitions instancePartitions = new InstancePartitions(tableNameWithType);
+    List<InstanceConfig> instanceConfigs = HelixHelper.getInstanceConfigs(helixManager);
+    String serverTag =
+        tableConfig.getTableType() == CommonConstants.Helix.TableType.OFFLINE ? new OfflineTagConfig(tableConfig)
+            .getOfflineServerTag() : new RealtimeTagConfig(tableConfig).getConsumingServerTag();
+    List<String> instances = HelixHelper.getEnabledInstancesWithTag(instanceConfigs, serverTag);
+    instances.sort(null);
+    int numInstances = instances.size();
+    Collections.rotate(instances, -(Math.abs(tableNameWithType.hashCode()) % numInstances));
 
 Review comment:
   Yes, backward compatible with the current realtime behavior (UniformStreamPartitionAssignmentStrategy.class).

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