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.commons.lang3.builder.ToStringBuilder;
021import org.apache.commons.lang3.builder.ToStringStyle;
022import org.apache.yetus.audience.InterfaceAudience;
023
024/**
025 * Interface to get status of a Lock without getting access to acquire/release lock. Currently used
026 * in MasterProcedureScheduler where we want to give Queues access to lock's status for scheduling
027 * purposes, but not the ability to acquire/release it.
028 */
029@InterfaceAudience.Private
030public interface LockStatus {
031
032  /**
033   * Return whether this lock has already been held,
034   * <p/>
035   * Notice that, holding the exclusive lock or shared lock are both considered as locked, i.e, this
036   * method usually equals to {@code hasExclusiveLock() || getSharedLockCount() > 0}.
037   */
038  default boolean isLocked() {
039    return hasExclusiveLock() || getSharedLockCount() > 0;
040  }
041
042  /**
043   * Whether the exclusive lock has been held.
044   */
045  boolean hasExclusiveLock();
046
047  /**
048   * Return true if the procedure itself holds the exclusive lock, or any ancestors of the give
049   * procedure hold the exclusive lock.
050   */
051  boolean hasLockAccess(Procedure<?> proc);
052
053  /**
054   * Get the procedure which holds the exclusive lock.
055   */
056  Procedure<?> getExclusiveLockOwnerProcedure();
057
058  /**
059   * Return the id of the procedure which holds the exclusive lock, if exists. Or a negative value
060   * which means no one holds the exclusive lock.
061   * <p/>
062   * Notice that, in HBase, we assume that the procedure id is positive, or at least non-negative.
063   */
064  default long getExclusiveLockProcIdOwner() {
065    Procedure<?> proc = getExclusiveLockOwnerProcedure();
066    return proc != null ? proc.getProcId() : -1L;
067  }
068
069  /**
070   * Get the number of procedures which hold the shared lock.
071   */
072  int getSharedLockCount();
073
074  default String describeLockStatus() {
075    ToStringBuilder builder = new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
076      .append("exclusiveLock", hasExclusiveLock());
077    if (hasExclusiveLock()) {
078      builder.append("exclusiveLockProcIdOwner", getExclusiveLockProcIdOwner());
079    }
080    builder.append("sharedLockCount", getSharedLockCount());
081    return builder.build();
082  }
083}