somandal commented on code in PR #16857: URL: https://github.com/apache/pinot/pull/16857#discussion_r2414466805
########## pinot-controller/src/main/java/org/apache/pinot/controller/helix/core/minion/DistributedTaskLockManager.java: ########## @@ -0,0 +1,288 @@ +/** + * 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.minion; + +import com.google.common.annotations.VisibleForTesting; +import java.util.concurrent.TimeUnit; +import javax.annotation.Nullable; +import org.apache.helix.AccessOption; +import org.apache.helix.store.zk.ZkHelixPropertyStore; +import org.apache.helix.zookeeper.datamodel.ZNRecord; +import org.apache.pinot.common.metadata.ZKMetadataProvider; +import org.apache.pinot.common.metrics.ControllerMetrics; +import org.apache.pinot.common.metrics.ControllerTimer; +import org.apache.zookeeper.data.Stat; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + + +/** + * Manages distributed locks for minion task generation using ZooKeeper ephemeral nodes that automatically disappear + * when the controller session ends or when the lock is explicitly released. This approach provides automatic cleanup + * and is suitable for long-running task generation. + * Locks are at the table level, to ensure that only one type of task can be generated per table at any given time. + * This is to prevent task types which shouldn't run in parallel from being generated at the same time. + * <p> + * ZK EPHEMERAL Lock Node: + * <ul> + * <li>Every lock is created at the table level with the name: {tableName}-Lock, under the base path + * MINION_TASK_METADATA within the PROPERTYSTORE. + * <li>If the propertyStore::create() call returns true, that means the lock node was successfully created and the + * lock belongs to the current controller, otherwise it was not. If the lock node already exists, this will return + * false. No clean-up of the lock node is needed if the propertyStore::create() call returns false. + * <li>The locks are EPHEMERAL in nature, meaning that once the session with ZK is lost, the lock is automatically + * cleaned up. Scenarios when the ZK session can be lost: a) controller shutdown, b) controller crash, c) ZK session + * expiry (e.g. long GC pauses can cause this). This property helps ensure that the lock is released under + * controller failure. + * </ul> + * <p> + */ +public class DistributedTaskLockManager { + private static final Logger LOGGER = LoggerFactory.getLogger(DistributedTaskLockManager.class); + + // Lock paths are constructed using ZKMetadataProvider + private static final String LOCK_OWNER_KEY = "lockOwner"; + private static final String LOCK_CREATION_TIME_MS = "lockCreationTimeMs"; + + private final ZkHelixPropertyStore<ZNRecord> _propertyStore; + private final String _controllerInstanceId; + private final ControllerMetrics _controllerMetrics; + + public DistributedTaskLockManager(ZkHelixPropertyStore<ZNRecord> propertyStore, String controllerInstanceId) { + _propertyStore = propertyStore; + _controllerInstanceId = controllerInstanceId; + _controllerMetrics = ControllerMetrics.get(); + } + + /** + * Attempts to acquire a distributed lock at the table level for task generation using session-based locking. + * The lock is at the table level instead of the task level to ensure that only a single task can be generated for + * a given table at any time. Certain tasks depend on other tasks not being generated at the same time + * The lock is held until explicitly released or the controller session ends. + * + * @param tableNameWithType the table name with type + * @return TaskLock object if successful, null if lock could not be acquired + */ + @Nullable + public TaskLock acquireLock(String tableNameWithType) { + LOGGER.info("Attempting to acquire task generation lock for table: {} by controller: {}", tableNameWithType, + _controllerInstanceId); + + try { + // Check if task generation is already in progress + if (isTaskGenerationInProgress(tableNameWithType)) { + LOGGER.info("Task generation already in progress for: {} by this or another controller", tableNameWithType); + return null; + } + + // Try to acquire the lock using ephemeral node + TaskLock lock = tryAcquireSessionBasedLock(tableNameWithType); + if (lock != null) { + LOGGER.info("Successfully acquired task generation lock for table: {} by controller: {}", tableNameWithType, + _controllerInstanceId); + return lock; + } else { + LOGGER.warn("Could not acquire lock for table: {} - another controller must hold it", tableNameWithType); + } + } catch (Exception e) { + LOGGER.error("Error while trying to acquire task lock for table: {}", tableNameWithType, e); + } + return null; + } + + private String getLockPath(String tableNameForPath) { + return ZKMetadataProvider.constructPropertyStorePathForMinionTaskGenerationLock(tableNameForPath); + } + + /** + * Releases a previously acquired session-based lock and marks task generation as completed. + * + * @param lock the lock to release + * @return true if successfully released, false otherwise + */ + public boolean releaseLock(TaskLock lock) { + if (lock == null) { + return true; + } + + String tableNameWithType = lock.getTableNameWithType(); + String lockNode = lock.getLockZNodePath(); + + // Remove the ephemeral lock node + boolean status = true; + if (lockNode != null) { + try { + if (_propertyStore.exists(lockNode, AccessOption.EPHEMERAL)) { + status = _propertyStore.remove(lockNode, AccessOption.EPHEMERAL); Review Comment: done -- This is an automated message from the Apache Git Service. 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