/*
    * 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.hadoop.hbase.replication.regionserver;
  
  import java.util.Map;
  import java.util.Queue;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.PriorityBlockingQueue;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /*
    Class that does enqueueing/dequeuing of wal at one place so that we can update the metrics
    just at one place.
   */
  @InterfaceAudience.Private
  @InterfaceStability.Evolving
  public class ReplicationSourceLogQueue {
    private static final Logger LOG = LoggerFactory.getLogger(ReplicationSource.class);
    // Queues of logs to process, entry in format of walGroupId->queue,
    // each presents a queue for one wal group
    private Map<String, PriorityBlockingQueue<Path>> queues = new ConcurrentHashMap<>();
    private MetricsSource metrics;
    private Configuration conf;
    // per group queue size, keep no more than this number of logs in each wal group
    private int queueSizePerGroup;
    // WARN threshold for the number of queued logs, defaults to 2
    private int logQueueWarnThreshold;
  
    public ReplicationSourceLogQueue(Configuration conf, MetricsSource metrics) {
      this.conf = conf;
      this.metrics = metrics;
      this.queueSizePerGroup = this.conf.getInt("hbase.regionserver.maxlogs", 32);
      this.logQueueWarnThreshold = this.conf.getInt("replication.source.log.queue.warn", 2);
    }
  
    /**
     * Enqueue the wal
     * @param wal wal to be enqueued
     * @param walGroupId Key for the wal in @queues map
     * @return boolean whether this is the first time we are seeing this walGroupId.
     */
    public boolean enqueueLog(Path wal, String walGroupId) {
      boolean exists = false;
      PriorityBlockingQueue<Path> queue = queues.get(walGroupId);
      if (queue == null) {
        queue = new PriorityBlockingQueue<>(queueSizePerGroup,
          new ReplicationSource.LogsComparator());
        // make sure that we do not use an empty queue when setting up a ReplicationSource, otherwise
        // the shipper may quit immediately
        queue.put(wal);
        queues.put(walGroupId, queue);
      } else {
        exists = true;
        queue.put(wal);
      }
      // Increment size of logQueue
      this.metrics.incrSizeOfLogQueue();
      // Compute oldest wal age
      this.metrics.setOldestWalAge(getOldestWalAge());
      // This will wal a warning for each new wal that gets created above the warn threshold
      int queueSize = queue.size();
      if (queueSize > this.logQueueWarnThreshold) {
        LOG.warn("WAL group " + walGroupId + " queue size: " + queueSize
          + " exceeds value of replication.source.log.queue.warn: " + logQueueWarnThreshold);
      }
      return exists;
    }
  
    /**
     * Get the queue size for the given walGroupId.
     * @param walGroupId walGroupId
     */
    public int getQueueSize(String walGroupId) {
      Queue queue = queues.get(walGroupId);
      if (queue == null) {
        return 0;
      }
      return queue.size();
   }
 
   /**
    * Returns number of queues.
    */
   public int getNumQueues() {
     return queues.size();
   }
 
   public Map<String, PriorityBlockingQueue<Path>> getQueues() {
     return queues;
   }
 
   /**
    * Return queue for the given walGroupId
    * Please don't add or remove elements from the returned queue.
    * Use @enqueueLog and @remove methods respectively.
    * @param walGroupId walGroupId
    */
   public PriorityBlockingQueue<Path> getQueue(String walGroupId) {
     return queues.get(walGroupId);
   }
 
   /**
    * Remove head from the queue corresponding to given walGroupId.
    * @param walGroupId walGroupId
    */
   public void remove(String walGroupId) {
     PriorityBlockingQueue<Path> queue = getQueue(walGroupId);
     if (queue == null || queue.isEmpty()) {
       return;
     }
     queue.remove();
     // Decrease size logQueue.
     this.metrics.decrSizeOfLogQueue();
     // Re-compute age of oldest wal metric.
     this.metrics.setOldestWalAge(getOldestWalAge());
   }
 
   /**
    * Remove all the elements from the queue corresponding to walGroupId
    * @param walGroupId walGroupId
    */
   public void clear(String walGroupId) {
     PriorityBlockingQueue<Path> queue = getQueue(walGroupId);
     while (!queue.isEmpty()) {
       // Need to iterate since metrics#decrSizeOfLogQueue decrements just by 1.
       queue.remove();
       metrics.decrSizeOfLogQueue();
     }
     this.metrics.setOldestWalAge(getOldestWalAge());
   }
 
   /*
     Returns the age of oldest wal.
    */
   long getOldestWalAge() {
     long now = EnvironmentEdgeManager.currentTime();
     long timestamp = getOldestWalTimestamp();
     if (timestamp == Long.MAX_VALUE) {
       // If there are no wals in the queue then set the oldest wal timestamp to current time
       // so that the oldest wal age will be 0.
       timestamp = now;
     }
     long age = now - timestamp;
     return age;
   }
 
   /*
   Get the oldest wal timestamp from all the queues.
   */
   private long getOldestWalTimestamp() {
     long oldestWalTimestamp = Long.MAX_VALUE;
     for (Map.Entry<String, PriorityBlockingQueue<Path>> entry : queues.entrySet()) {
       PriorityBlockingQueue<Path> queue = entry.getValue();
       Path path = queue.peek();
       // Can path ever be null ?
       if (path != null) {
         oldestWalTimestamp = Math.min(oldestWalTimestamp,
           ReplicationSource.LogsComparator.getTS(path));
       }
     }
     return oldestWalTimestamp;
   }
 
   public MetricsSource getMetrics() {
     return metrics;
   }
 }