/**
    * 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.master.snapshot;
  
  import java.io.IOException;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  import org.apache.hadoop.hbase.master.HMaster;
  import org.apache.hadoop.hbase.master.MasterServices;
  import org.apache.hadoop.hbase.master.cleaner.BaseHFileCleanerDelegate;
  import org.apache.hadoop.hbase.snapshot.CorruptedSnapshotException;
  import org.apache.hadoop.hbase.snapshot.SnapshotReferenceUtil;
  import org.apache.hadoop.hbase.util.FSUtils;
  
  /**
   * Implementation of a file cleaner that checks if a hfile is still used by snapshots of HBase
   * tables.
   */
  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
  @InterfaceStability.Evolving
  public class SnapshotHFileCleaner extends BaseHFileCleanerDelegate {
    private static final Log LOG = LogFactory.getLog(SnapshotHFileCleaner.class);
  
    /**
     * Conf key for the frequency to attempt to refresh the cache of hfiles currently used in
     * snapshots (ms)
     */
    public static final String HFILE_CACHE_REFRESH_PERIOD_CONF_KEY =
        "hbase.master.hfilecleaner.plugins.snapshot.period";
  
    /** Refresh cache, by default, every 5 minutes */
    private static final long DEFAULT_HFILE_CACHE_REFRESH_PERIOD = 300000;
  
    /** File cache for HFiles in the completed and currently running snapshots */
    private SnapshotFileCache cache;
  
    private MasterServices master;
  
    @Override
    public synchronized Iterable<FileStatus> getDeletableFiles(Iterable<FileStatus> files) {
      try {
        return cache.getUnreferencedFiles(files, master.getSnapshotManager());
      } catch (CorruptedSnapshotException cse) {
        LOG.debug("Corrupted in-progress snapshot file exception, ignored ", cse);
      } catch (IOException e) {
        LOG.error("Exception while checking if files were valid, keeping them just in case.", e);
      }
      return Collections.emptyList();
    }
  
    @Override
    public void init(Map<String, Object> params) {
      if (params.containsKey(HMaster.MASTER)) {
        this.master = (MasterServices) params.get(HMaster.MASTER);
      }
    }
  
    @Override
    protected boolean isFileDeletable(FileStatus fStat) {
      return false;
    }
  
    public void setConf(final Configuration conf) {
      super.setConf(conf);
      try {
        long cacheRefreshPeriod = conf.getLong(HFILE_CACHE_REFRESH_PERIOD_CONF_KEY,
          DEFAULT_HFILE_CACHE_REFRESH_PERIOD);
        final FileSystem fs = FSUtils.getCurrentFileSystem(conf);
        Path rootDir = FSUtils.getRootDir(conf);
        cache = new SnapshotFileCache(fs, rootDir, cacheRefreshPeriod, cacheRefreshPeriod,
            "snapshot-hfile-cleaner-cache-refresher", new SnapshotFileCache.SnapshotFileInspector() {
              public Collection<String> filesUnderSnapshot(final Path snapshotDir)
                  throws IOException {
               return SnapshotReferenceUtil.getHFileNames(conf, fs, snapshotDir);
             }
           });
     } catch (IOException e) {
       LOG.error("Failed to create cleaner util", e);
     }
   }
 
 
   @Override
   public void stop(String why) {
     this.cache.stop(why);
   }
 
   @Override
   public boolean isStopped() {
     return this.cache.isStopped();
   }
 
   /**
    * Exposed for Testing!
    * @return the cache of all hfiles
    */
   public SnapshotFileCache getFileCacheForTesting() {
     return this.cache;
   }
 }