001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.procedure2;
019
020import org.apache.yetus.audience.InterfaceAudience;
021
022/**
023 * Interface to get status of a Lock without getting access to acquire/release lock. Currently used
024 * in MasterProcedureScheduler where we want to give Queues access to lock's status for scheduling
025 * purposes, but not the ability to acquire/release it.
026 */
027@InterfaceAudience.Private
028public interface LockStatus {
029
030  /**
031   * Return whether this lock has already been held,
032   * <p/>
033   * Notice that, holding the exclusive lock or shared lock are both considered as locked, i.e, this
034   * method usually equals to {@code hasExclusiveLock() || getSharedLockCount() > 0}.
035   */
036  default boolean isLocked() {
037    return hasExclusiveLock() || getSharedLockCount() > 0;
038  }
039
040  /**
041   * Whether the exclusive lock has been held.
042   */
043  boolean hasExclusiveLock();
044
045  /**
046   * Return true if the procedure itself holds the exclusive lock, or any ancestors of the give
047   * procedure hold the exclusive lock.
048   */
049  boolean hasLockAccess(Procedure<?> proc);
050
051  /**
052   * Get the procedure which holds the exclusive lock.
053   */
054  Procedure<?> getExclusiveLockOwnerProcedure();
055
056  /**
057   * Return the id of the procedure which holds the exclusive lock, if exists. Or a negative value
058   * which means no one holds the exclusive lock.
059   * <p/>
060   * Notice that, in HBase, we assume that the procedure id is positive, or at least non-negative.
061   */
062  default long getExclusiveLockProcIdOwner() {
063    Procedure<?> proc = getExclusiveLockOwnerProcedure();
064    return proc != null ? proc.getProcId() : -1L;
065  }
066
067  /**
068   * Get the number of procedures which hold the shared lock.
069   */
070  int getSharedLockCount();
071}