/*
 * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
 * (the "License"). You may not use this work except in compliance with the License, which is
 * available at www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied, as more fully set forth in the License.
 *
 * See the NOTICE file distributed with this work for information regarding copyright ownership.
 */

package alluxio.master.metastore.rocks;

import alluxio.conf.PropertyKey;
import alluxio.conf.ServerConfiguration;
import alluxio.master.metastore.BlockStore;
import alluxio.proto.meta.Block.BlockLocation;
import alluxio.proto.meta.Block.BlockMeta;
import alluxio.util.io.FileUtils;
import alluxio.util.io.PathUtils;

import com.google.common.primitives.Longs;
import org.rocksdb.ColumnFamilyDescriptor;
import org.rocksdb.ColumnFamilyHandle;
import org.rocksdb.ColumnFamilyOptions;
import org.rocksdb.CompressionType;
import org.rocksdb.DBOptions;
import org.rocksdb.HashLinkedListMemTableConfig;
import org.rocksdb.ReadOptions;
import org.rocksdb.RocksDB;
import org.rocksdb.RocksDBException;
import org.rocksdb.RocksIterator;
import org.rocksdb.Slice;
import org.rocksdb.WriteOptions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicReference;

import javax.annotation.concurrent.ThreadSafe;

/**
 * Block store backed by RocksDB.
 */
@ThreadSafe
public class RocksBlockStore implements BlockStore {
  private static final Logger LOG = LoggerFactory.getLogger(RocksBlockStore.class);
  private static final String BLOCKS_DB_NAME = "blocks";
  private static final String BLOCK_META_COLUMN = "block-meta";
  private static final String BLOCK_LOCATIONS_COLUMN = "block-locations";

  // This is a field instead of a constant because it depends on the call to RocksDB.loadLibrary().
  private final WriteOptions mDisableWAL;
  private final ReadOptions mIteratorOption;

  private final RocksStore mRocksStore;
  private final AtomicReference<ColumnFamilyHandle> mBlockMetaColumn = new AtomicReference<>();
  private final AtomicReference<ColumnFamilyHandle> mBlockLocationsColumn = new AtomicReference<>();

  /**
   * Creates and initializes a rocks block store.
   *
   * @param baseDir the base directory in which to store block store metadata
   */
  public RocksBlockStore(String baseDir) {
    RocksDB.loadLibrary();
    mDisableWAL = new WriteOptions().setDisableWAL(true);
    mIteratorOption = new ReadOptions().setReadaheadSize(
        ServerConfiguration.getBytes(PropertyKey.MASTER_METASTORE_ITERATOR_READAHEAD_SIZE));
    ColumnFamilyOptions cfOpts = new ColumnFamilyOptions()
        .setMemTableConfig(new HashLinkedListMemTableConfig())
        .setCompressionType(CompressionType.NO_COMPRESSION);
    List<ColumnFamilyDescriptor> columns =
        Arrays.asList(new ColumnFamilyDescriptor(BLOCK_META_COLUMN.getBytes(), cfOpts),
            new ColumnFamilyDescriptor(BLOCK_LOCATIONS_COLUMN.getBytes(), cfOpts));
    DBOptions dbOpts = new DBOptions()
        // Concurrent memtable write is not supported for hash linked list memtable
        .setAllowConcurrentMemtableWrite(false)
        .setMaxOpenFiles(-1)
        .setCreateIfMissing(true)
        .setCreateMissingColumnFamilies(true);
    String dbPath = PathUtils.concatPath(baseDir, BLOCKS_DB_NAME);
    String backupPath = PathUtils.concatPath(baseDir, BLOCKS_DB_NAME + "-backups");
    // Create block store db path if it does not exist.
    if (!FileUtils.exists(dbPath)) {
      try {
        FileUtils.createDir(dbPath);
      } catch (IOException e) {
        LOG.warn("Failed to create nonexistent db path at: {}. Error:{}", dbPath, e);
      }
    }
    mRocksStore = new RocksStore(dbPath, backupPath, columns, dbOpts,
        Arrays.asList(mBlockMetaColumn, mBlockLocationsColumn));
  }

  @Override
  public Optional<BlockMeta> getBlock(long id) {
    byte[] meta;
    try {
      meta = db().get(mBlockMetaColumn.get(), Longs.toByteArray(id));
    } catch (RocksDBException e) {
      throw new RuntimeException(e);
    }
    if (meta == null) {
      return Optional.empty();
    }
    try {
      return Optional.of(BlockMeta.parseFrom(meta));
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public void putBlock(long id, BlockMeta meta) {
    try {
      // Overwrites the key if it already exists.
      db().put(mBlockMetaColumn.get(), mDisableWAL, Longs.toByteArray(id), meta.toByteArray());
    } catch (RocksDBException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public void removeBlock(long id) {
    try {
      db().delete(mBlockMetaColumn.get(), mDisableWAL, Longs.toByteArray(id));
    } catch (RocksDBException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public void clear() {
    mRocksStore.clear();
  }

  @Override
  public void close() {
    mRocksStore.close();
  }

  @Override
  public List<BlockLocation> getLocations(long id) {
    byte[] startKey = RocksUtils.toByteArray(id, 0);
    byte[] endKey = RocksUtils.toByteArray(id, Long.MAX_VALUE);

    final ReadOptions readOptions = new ReadOptions().setIterateUpperBound(new Slice(endKey));
    try (RocksIterator iter = db().newIterator(mBlockLocationsColumn.get(), readOptions)) {
      iter.seek(startKey);
      List<BlockLocation> locations = new ArrayList<>();
      for (; iter.isValid(); iter.next()) {
        try {
          locations.add(BlockLocation.parseFrom(iter.value()));
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
      }
      return locations;
    }
  }

  @Override
  public void addLocation(long id, BlockLocation location) {
    byte[] key = RocksUtils.toByteArray(id, location.getWorkerId());
    try {
      db().put(mBlockLocationsColumn.get(), mDisableWAL, key, location.toByteArray());
    } catch (RocksDBException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public void removeLocation(long blockId, long workerId) {
    byte[] key = RocksUtils.toByteArray(blockId, workerId);
    try {
      db().delete(mBlockLocationsColumn.get(), mDisableWAL, key);
    } catch (RocksDBException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public Iterator<Block> iterator() {
    return RocksUtils.createIterator(db().newIterator(mBlockMetaColumn.get(), mIteratorOption),
        (iter) -> new Block(Longs.fromByteArray(iter.key()), BlockMeta.parseFrom(iter.value())));
  }

  private RocksDB db() {
    return mRocksStore.getDb();
  }
}

@@ -5366,16 +5366,172 @@
 ALUE);%0A%0A
+    // Explicitly hold a reference to the ReadOptions object from the discussion in%0A    // https://groups.google.com/g/rocksdb/c/PwapmWwyBbc/m/ecl7oW3AAgAJ%0A
     fina

Document odd rocksdb code