content: /*
   * 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.ambari.server.logging;
  
  import java.util.Set;
  import java.util.concurrent.CopyOnWriteArraySet;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReadWriteLock;
  import java.util.concurrent.locks.ReentrantLock;
  import java.util.concurrent.locks.ReentrantReadWriteLock;
  
  import org.apache.ambari.server.configuration.Configuration;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.google.common.base.Ticker;
  import com.google.inject.Inject;
  import com.google.inject.Singleton;
  
  /**
   * Factory to create locks depending on configuration.  If lock profiling is enabled,
   * it creates instrumented locks that collect statistics and log requests.  If profiling is
   * disabled, it creates regular reentrant locks.
   *
   * @see Configuration#isServerLocksProfilingEnabled()
   */
  @Singleton
  public class LockFactory {
  
    private static final Logger LOG = LoggerFactory.getLogger(LockFactory.class);
  
    private final boolean profiling;
    private final Set<ProfiledLock> profiledLocks;
  
    @Inject
    public LockFactory(Configuration config) {
      profiling = config.isServerLocksProfilingEnabled();
      profiledLocks = profiling ? new CopyOnWriteArraySet<>() : null;
      LOG.info("Lock profiling is {}", profiling ? "enabled" : "disabled");
    }
  
    /**
     * @return a new Lock instance (implementation depends on configuration setting) without any special label to identify it in log messages
     */
    public Lock newLock() {
      return newLock(getDefaultPrefix());
    }
  
    /**
     * @return a new Lock instance (implementation depends on configuration setting) with <code>label</code> to identify it in log messages
     */
    public Lock newLock(String label) {
      ReentrantLock baseLock = new ReentrantLock();
      if (profiling) {
        ProfiledReentrantLock profiledLock = new ProfiledReentrantLock(baseLock, Ticker.systemTicker(), label);
        profiledLocks.add(profiledLock);
        return profiledLock;
      }
      return baseLock;
    }
  
    /**
     * @return a new ReadWriteLock instance (implementation depends on configuration setting) without any special label to identify it in log messages
     */
    public ReadWriteLock newReadWriteLock() {
      return newReadWriteLock(getDefaultPrefix());
    }
  
    /**
     * @return a new ReadWriteLock instance (implementation depends on configuration setting) with <code>label</code> to identify it in log messages
     */
    public ReadWriteLock newReadWriteLock(String label) {
      ReentrantReadWriteLock baseLock = new ReentrantReadWriteLock();
      if (profiling) {
        ProfiledReentrantReadWriteLock profiledLock = new ProfiledReentrantReadWriteLock(baseLock, Ticker.systemTicker(), label);
        profiledLocks.add(profiledLock.readLock());
        profiledLocks.add(profiledLock.writeLock());
        return profiledLock;
      }
      return baseLock;
    }
  
    /**
     * If lock profiling is enabled, append summary statistics about lock usage to <code>sb</code>
     * @param sb the buffer to append the statistics to
     */
    public void debugDump(StringBuilder sb) {
      if (profiling) {
        sb.append("\n\t\tLocks: [");
        for (ProfiledLock lock : profiledLocks) {
          sb.append("\n\t\t\t").append(lock.getLabel())
            .append(lock)
            .append(" waited: ").append(lock.getTimeSpentWaitingForLock())
            .append(" held: ").append(lock.getTimeSpentLocked())
            .append(" times locked: ").append(lock.getLockCount());
        }
        if (!profiledLocks.isEmpty()) {
          sb.append("\n");
        }
        sb.append("]");
      }
    }
  
    private static String getDefaultPrefix() {
      StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
      // 0: getStackTrace()
      // 1: getDefaultPrefix()
      // 2: newLock()
      // 3: caller of newLock()
      return stackTrace.length > 3
        ? stackTrace[3].getFileName() + ":" + stackTrace[3].getLineNumber()
        : "";
    }
  }
  