/**
 * 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;

import static org.apache.hadoop.hbase.io.hfile.BlockType.MAGIC_LENGTH;

import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.UUID;
import java.util.regex.Pattern;

import org.apache.commons.lang.ArrayUtils;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hbase.util.Bytes;

/**
 * HConstants holds a bunch of HBase-related constants
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public final class HConstants {
  // NOTICE!!!! Please do not add a constants here, unless they are referenced by a lot of classes.

  //Bytes.UTF8_ENCODING should be updated if this changed
  /** When we encode strings, we always specify UTF8 encoding */
  public static final String UTF8_ENCODING = "UTF-8";

  //Bytes.UTF8_CHARSET should be updated if this changed
  /** When we encode strings, we always specify UTF8 encoding */
  public static final Charset UTF8_CHARSET = Charset.forName(UTF8_ENCODING);
  /**
   * Default block size for an HFile.
   */
  public final static int DEFAULT_BLOCKSIZE = 64 * 1024;

  /** Used as a magic return value while optimized index key feature enabled(HBASE-7845) */
  public final static int INDEX_KEY_MAGIC = -2;
  /*
     * Name of directory that holds recovered edits written by the wal log
     * splitting code, one per region
     */
  public static final String RECOVERED_EDITS_DIR = "recovered.edits";
  /**
   * The first four bytes of Hadoop RPC connections
   */
  public static final ByteBuffer RPC_HEADER = ByteBuffer.wrap("HBas".getBytes());
  public static final byte RPC_CURRENT_VERSION = 0;

  // HFileBlock constants.

  /** The size data structures with minor version is 0 */
  public static final int HFILEBLOCK_HEADER_SIZE_NO_CHECKSUM = MAGIC_LENGTH + 2 * Bytes.SIZEOF_INT
      + Bytes.SIZEOF_LONG;
  /** The size of a version 2 HFile block header, minor version 1.
   * There is a 1 byte checksum type, followed by a 4 byte bytesPerChecksum
   * followed by another 4 byte value to store sizeofDataOnDisk.
   */
  public static final int HFILEBLOCK_HEADER_SIZE = HFILEBLOCK_HEADER_SIZE_NO_CHECKSUM +
    Bytes.SIZEOF_BYTE + 2 * Bytes.SIZEOF_INT;
  /** Just an array of bytes of the right size. */
  public static final byte[] HFILEBLOCK_DUMMY_HEADER = new byte[HFILEBLOCK_HEADER_SIZE];

  //End HFileBlockConstants.

  /**
   * Status codes used for return values of bulk operations.
   */
  public enum OperationStatusCode {
    NOT_RUN,
    SUCCESS,
    BAD_FAMILY,
    SANITY_CHECK_FAILURE,
    FAILURE;
  }

  /** long constant for zero */
  public static final Long ZERO_L = Long.valueOf(0L);
  public static final String NINES = "99999999999999";
  public static final String ZEROES = "00000000000000";

  // For migration

  /** name of version file */
  public static final String VERSION_FILE_NAME = "hbase.version";

  /**
   * Current version of file system.
   * Version 4 supports only one kind of bloom filter.
   * Version 5 changes versions in catalog table regions.
   * Version 6 enables blockcaching on catalog tables.
   * Version 7 introduces hfile -- hbase 0.19 to 0.20..
   * Version 8 introduces namespace
   */
  // public static final String FILE_SYSTEM_VERSION = "6";
  public static final String FILE_SYSTEM_VERSION = "8";

  // Configuration parameters

  //TODO: Is having HBase homed on port 60k OK?

  /** Cluster is in distributed mode or not */
  public static final String CLUSTER_DISTRIBUTED = "hbase.cluster.distributed";

  /** Config for pluggable load balancers */
  public static final String HBASE_MASTER_LOADBALANCER_CLASS = "hbase.master.loadbalancer.class";

  /** Cluster is standalone or pseudo-distributed */
  public static final boolean CLUSTER_IS_LOCAL = false;

  /** Cluster is fully-distributed */
  public static final boolean CLUSTER_IS_DISTRIBUTED = true;

  /** Default value for cluster distributed mode */
  public static final boolean DEFAULT_CLUSTER_DISTRIBUTED = CLUSTER_IS_LOCAL;

  /** default host address */
  public static final String DEFAULT_HOST = "0.0.0.0";

  /** Parameter name for port master listens on. */
  public static final String MASTER_PORT = "hbase.master.port";

  /** default port that the master listens on */
  public static final int DEFAULT_MASTER_PORT = 60000;

  /** default port for master web api */
  public static final int DEFAULT_MASTER_INFOPORT = 60010;

  /** Configuration key for master web API port */
  public static final String MASTER_INFO_PORT = "hbase.master.info.port";

  /** Parameter name for the master type being backup (waits for primary to go inactive). */
  public static final String MASTER_TYPE_BACKUP = "hbase.master.backup";

  /** by default every master is a possible primary master unless the conf explicitly overrides it */
  public static final boolean DEFAULT_MASTER_TYPE_BACKUP = false;

  /** Name of ZooKeeper quorum configuration parameter. */
  public static final String ZOOKEEPER_QUORUM = "hbase.zookeeper.quorum";

  /** Name of ZooKeeper config file in conf/ directory. */
  public static final String ZOOKEEPER_CONFIG_NAME = "zoo.cfg";

  /** Common prefix of ZooKeeper configuration properties */
  public static final String ZK_CFG_PROPERTY_PREFIX =
      "hbase.zookeeper.property.";

  public static final int ZK_CFG_PROPERTY_PREFIX_LEN =
      ZK_CFG_PROPERTY_PREFIX.length();

  /**
   * The ZK client port key in the ZK properties map. The name reflects the
   * fact that this is not an HBase configuration key.
   */
  public static final String CLIENT_PORT_STR = "clientPort";

  /** Parameter name for the client port that the zookeeper listens on */
  public static final String ZOOKEEPER_CLIENT_PORT =
      ZK_CFG_PROPERTY_PREFIX + CLIENT_PORT_STR;

  /** Default client port that the zookeeper listens on */
  public static final int DEFAULT_ZOOKEPER_CLIENT_PORT = 2181;

  /** Parameter name for the wait time for the recoverable zookeeper */
  public static final String ZOOKEEPER_RECOVERABLE_WAITTIME = "hbase.zookeeper.recoverable.waittime";

  /** Default wait time for the recoverable zookeeper */
  public static final long DEFAULT_ZOOKEPER_RECOVERABLE_WAITIME = 10000;

  /** Parameter name for the root dir in ZK for this cluster */
  public static final String ZOOKEEPER_ZNODE_PARENT = "zookeeper.znode.parent";

  public static final String DEFAULT_ZOOKEEPER_ZNODE_PARENT = "/hbase";

  /**
   * Parameter name for the limit on concurrent client-side zookeeper
   * connections
   */
  public static final String ZOOKEEPER_MAX_CLIENT_CNXNS =
      ZK_CFG_PROPERTY_PREFIX + "maxClientCnxns";

  /** Parameter name for the ZK data directory */
  public static final String ZOOKEEPER_DATA_DIR =
      ZK_CFG_PROPERTY_PREFIX + "dataDir";

  /** Default limit on concurrent client-side zookeeper connections */
  public static final int DEFAULT_ZOOKEPER_MAX_CLIENT_CNXNS = 300;

  /** Configuration key for ZooKeeper session timeout */
  public static final String ZK_SESSION_TIMEOUT = "zookeeper.session.timeout";

  /** Default value for ZooKeeper session timeout */
  public static final int DEFAULT_ZK_SESSION_TIMEOUT = 180 * 1000;

  /** Configuration key for whether to use ZK.multi */
  public static final String ZOOKEEPER_USEMULTI = "hbase.zookeeper.useMulti";

  /** Parameter name for port region server listens on. */
  public static final String REGIONSERVER_PORT = "hbase.regionserver.port";

  /** Default port region server listens on. */
  public static final int DEFAULT_REGIONSERVER_PORT = 60020;

  /** default port for region server web api */
  public static final int DEFAULT_REGIONSERVER_INFOPORT = 60030;

  /** A configuration key for regionserver info port */
  public static final String REGIONSERVER_INFO_PORT =
    "hbase.regionserver.info.port";

  /** A flag that enables automatic selection of regionserver info port */
  public static final String REGIONSERVER_INFO_PORT_AUTO =
      REGIONSERVER_INFO_PORT + ".auto";

  /** Parameter name for what region server implementation to use. */
  public static final String REGION_SERVER_IMPL= "hbase.regionserver.impl";

  /** Parameter name for what master implementation to use. */
  public static final String MASTER_IMPL= "hbase.master.impl";

  /** Parameter name for what hbase client implementation to use. */
  public static final String HBASECLIENT_IMPL= "hbase.hbaseclient.impl";

  /** Parameter name for how often threads should wake up */
  public static final String THREAD_WAKE_FREQUENCY = "hbase.server.thread.wakefrequency";

  /** Default value for thread wake frequency */
  public static final int DEFAULT_THREAD_WAKE_FREQUENCY = 10 * 1000;

  /** Parameter name for how often we should try to write a version file, before failing */
  public static final String VERSION_FILE_WRITE_ATTEMPTS = "hbase.server.versionfile.writeattempts";

  /** Parameter name for how often we should try to write a version file, before failing */
  public static final int DEFAULT_VERSION_FILE_WRITE_ATTEMPTS = 3;

  /** Parameter name for how often a region should should perform a major compaction */
  public static final String MAJOR_COMPACTION_PERIOD = "hbase.hregion.majorcompaction";

  /** Parameter name for the maximum batch of KVs to be used in flushes and compactions */
  public static final String COMPACTION_KV_MAX = "hbase.hstore.compaction.kv.max";
  public static final int COMPACTION_KV_MAX_DEFAULT = 10;

  /** Parameter name for HBase instance root directory */
  public static final String HBASE_DIR = "hbase.rootdir";

  /** Parameter name for HBase client IPC pool type */
  public static final String HBASE_CLIENT_IPC_POOL_TYPE = "hbase.client.ipc.pool.type";

  /** Parameter name for HBase client IPC pool size */
  public static final String HBASE_CLIENT_IPC_POOL_SIZE = "hbase.client.ipc.pool.size";

  /** Parameter name for HBase client operation timeout, which overrides RPC timeout */
  public static final String HBASE_CLIENT_OPERATION_TIMEOUT = "hbase.client.operation.timeout";

  /** Parameter name for HBase client operation timeout, which overrides RPC timeout */
  public static final String HBASE_CLIENT_META_OPERATION_TIMEOUT =
    "hbase.client.meta.operation.timeout";

  /** Default HBase client operation timeout, which is tantamount to a blocking call */
  public static final int DEFAULT_HBASE_CLIENT_OPERATION_TIMEOUT = Integer.MAX_VALUE;

  /** Used to construct the name of the log directory for a region server */
  public static final String HREGION_LOGDIR_NAME = "WALs";

  /** Used to construct the name of the splitlog directory for a region server */
  public static final String SPLIT_LOGDIR_NAME = "splitWAL";

  /** Like the previous, but for old logs that are about to be deleted */
  public static final String HREGION_OLDLOGDIR_NAME = "oldWALs";

  public static final String CORRUPT_DIR_NAME = "corrupt";

  /** Used by HBCK to sideline backup data */
  public static final String HBCK_SIDELINEDIR_NAME = ".hbck";

  /** Any artifacts left from migration can be moved here */
  public static final String MIGRATION_NAME = ".migration";

  /**
   * The directory from which co-processor/custom filter jars can be loaded
   * dynamically by the region servers. This value can be overridden by the
   * hbase.dynamic.jars.dir config.
   */
  public static final String LIB_DIR = "lib";

  /** Used to construct the name of the compaction directory during compaction */
  public static final String HREGION_COMPACTIONDIR_NAME = "compaction.dir";

  /** Conf key for the max file size after which we split the region */
  public static final String HREGION_MAX_FILESIZE =
      "hbase.hregion.max.filesize";

  /** Default maximum file size */
  public static final long DEFAULT_MAX_FILE_SIZE = 10 * 1024 * 1024 * 1024L;

  /**
   * The max number of threads used for opening and closing stores or store
   * files in parallel
   */
  public static final String HSTORE_OPEN_AND_CLOSE_THREADS_MAX =
    "hbase.hstore.open.and.close.threads.max";

  /**
   * The default number for the max number of threads used for opening and
   * closing stores or store files in parallel
   */
  public static final int DEFAULT_HSTORE_OPEN_AND_CLOSE_THREADS_MAX = 1;


  /** Conf key for the memstore size at which we flush the memstore */
  public static final String HREGION_MEMSTORE_FLUSH_SIZE =
      "hbase.hregion.memstore.flush.size";

  public static final String HREGION_EDITS_REPLAY_SKIP_ERRORS =
      "hbase.hregion.edits.replay.skip.errors";

  public static final boolean DEFAULT_HREGION_EDITS_REPLAY_SKIP_ERRORS =
      false;

  /** Maximum value length, enforced on KeyValue construction */
  public static final int MAXIMUM_VALUE_LENGTH = Integer.MAX_VALUE - 1;

  /** name of the file for unique cluster ID */
  public static final String CLUSTER_ID_FILE_NAME = "hbase.id";

  /** Default value for cluster ID */
  public static final String CLUSTER_ID_DEFAULT = "default-cluster";

  // Always store the location of the root table's HRegion.
  // This HRegion is never split.

  // region name = table + startkey + regionid. This is the row key.
  // each row in the root and meta tables describes exactly 1 region
  // Do we ever need to know all the information that we are storing?

  // Note that the name of the root table starts with "-" and the name of the
  // meta table starts with "." Why? it's a trick. It turns out that when we
  // store region names in memory, we use a SortedMap. Since "-" sorts before
  // "." (and since no other table name can start with either of these
  // characters, the root region will always be the first entry in such a Map,
  // followed by all the meta regions (which will be ordered by their starting
  // row key as well), followed by all user tables. So when the Master is
  // choosing regions to assign, it will always choose the root region first,
  // followed by the meta regions, followed by user regions. Since the root
  // and meta regions always need to be on-line, this ensures that they will
  // be the first to be reassigned if the server(s) they are being served by
  // should go down.


  /** The hbase:meta table's name. */
  @Deprecated  // for compat from 0.94 -> 0.96.
  public static final byte[] META_TABLE_NAME = TableName.META_TABLE_NAME.getName();

  public static final String BASE_NAMESPACE_DIR = "data";

  /** delimiter used between portions of a region name */
  public static final int META_ROW_DELIMITER = ',';

  /** The catalog family as a string*/
  public static final String CATALOG_FAMILY_STR = "info";

  /** The catalog family */
  public static final byte [] CATALOG_FAMILY = Bytes.toBytes(CATALOG_FAMILY_STR);

  /** The RegionInfo qualifier as a string */
  public static final String REGIONINFO_QUALIFIER_STR = "regioninfo";

  /** The regioninfo column qualifier */
  public static final byte [] REGIONINFO_QUALIFIER = Bytes.toBytes(REGIONINFO_QUALIFIER_STR);

  /** The server column qualifier */
  public static final byte [] SERVER_QUALIFIER = Bytes.toBytes("server");

  /** The startcode column qualifier */
  public static final byte [] STARTCODE_QUALIFIER = Bytes.toBytes("serverstartcode");

  /** The open seqnum column qualifier */
  public static final byte [] SEQNUM_QUALIFIER = Bytes.toBytes("seqnumDuringOpen");

  /** The lower-half split region column qualifier */
  public static final byte [] SPLITA_QUALIFIER = Bytes.toBytes("splitA");

  /** The upper-half split region column qualifier */
  public static final byte [] SPLITB_QUALIFIER = Bytes.toBytes("splitB");

  /** The lower-half merge region column qualifier */
  public static final byte[] MERGEA_QUALIFIER = Bytes.toBytes("mergeA");

  /** The upper-half merge region column qualifier */
  public static final byte[] MERGEB_QUALIFIER = Bytes.toBytes("mergeB");

  /**
   * The meta table version column qualifier.
   * We keep current version of the meta table in this column in <code>-ROOT-</code>
   * table: i.e. in the 'info:v' column.
   */
  public static final byte [] META_VERSION_QUALIFIER = Bytes.toBytes("v");

  /**
   * The current version of the meta table.
   * - pre-hbase 0.92.  There is no META_VERSION column in the root table
   * in this case. The meta has HTableDescriptor serialized into the HRegionInfo;
   * - version 0 is 0.92 and 0.94. Meta data has serialized HRegionInfo's using
   * Writable serialization, and HRegionInfo's does not contain HTableDescriptors.
   * - version 1 for 0.96+ keeps HRegionInfo data structures, but changes the
   * byte[] serialization from Writables to Protobuf.
   * See HRegionInfo.VERSION
   */
  public static final short META_VERSION = 1;

  // Other constants

  /**
   * An empty instance.
   */
  public static final byte [] EMPTY_BYTE_ARRAY = new byte [0];

  /**
   * Used by scanners, etc when they want to start at the beginning of a region
   */
  public static final byte [] EMPTY_START_ROW = EMPTY_BYTE_ARRAY;

  /**
   * Last row in a table.
   */
  public static final byte [] EMPTY_END_ROW = EMPTY_START_ROW;

  /**
    * Used by scanners and others when they're trying to detect the end of a
    * table
    */
  public static final byte [] LAST_ROW = EMPTY_BYTE_ARRAY;

  /**
   * Max length a row can have because of the limitation in TFile.
   */
  public static final int MAX_ROW_LENGTH = Short.MAX_VALUE;

  /**
   * Timestamp to use when we want to refer to the latest cell.
   * This is the timestamp sent by clients when no timestamp is specified on
   * commit.
   */
  public static final long LATEST_TIMESTAMP = Long.MAX_VALUE;

  /**
   * Timestamp to use when we want to refer to the oldest cell.
   */
  public static final long OLDEST_TIMESTAMP = Long.MIN_VALUE;

  /**
   * LATEST_TIMESTAMP in bytes form
   */
  public static final byte [] LATEST_TIMESTAMP_BYTES = {
    // big-endian
    (byte) (LATEST_TIMESTAMP >>> 56),
    (byte) (LATEST_TIMESTAMP >>> 48),
    (byte) (LATEST_TIMESTAMP >>> 40),
    (byte) (LATEST_TIMESTAMP >>> 32),
    (byte) (LATEST_TIMESTAMP >>> 24),
    (byte) (LATEST_TIMESTAMP >>> 16),
    (byte) (LATEST_TIMESTAMP >>> 8),
    (byte) LATEST_TIMESTAMP,
  };

  /**
   * Define for 'return-all-versions'.
   */
  public static final int ALL_VERSIONS = Integer.MAX_VALUE;

  /**
   * Unlimited time-to-live.
   */
//  public static final int FOREVER = -1;
  public static final int FOREVER = Integer.MAX_VALUE;

  /**
   * Seconds in a week
   */
  public static final int WEEK_IN_SECONDS = 7 * 24 * 3600;

  //TODO: although the following are referenced widely to format strings for
  //      the shell. They really aren't a part of the public API. It would be
  //      nice if we could put them somewhere where they did not need to be
  //      public. They could have package visibility
  public static final String NAME = "NAME";
  public static final String VERSIONS = "VERSIONS";
  public static final String IN_MEMORY = "IN_MEMORY";
  public static final String METADATA = "METADATA";
  public static final String CONFIGURATION = "CONFIGURATION";

  /**
   * Retrying we multiply hbase.client.pause setting by what we have in this array until we
   * run out of array items.  Retries beyond this use the last number in the array.  So, for
   * example, if hbase.client.pause is 1 second, and maximum retries count
   * hbase.client.retries.number is 10, we will retry at the following intervals:
   * 1, 2, 3, 5, 10, 20, 40, 100, 100, 100.
   * With 100ms, a back-off of 200 means 20s
   */
  public static int RETRY_BACKOFF[] = { 1, 2, 3, 5, 10, 20, 40, 100, 100, 100, 100, 200, 200 };

  public static final String REGION_IMPL = "hbase.hregion.impl";

  /** modifyTable op for replacing the table descriptor */
  public static enum Modify {
    CLOSE_REGION,
    TABLE_COMPACT,
    TABLE_FLUSH,
    TABLE_MAJOR_COMPACT,
    TABLE_SET_HTD,
    TABLE_SPLIT
  }

  /**
   * Scope tag for locally scoped data.
   * This data will not be replicated.
   */
  public static final int REPLICATION_SCOPE_LOCAL = 0;

  /**
   * Scope tag for globally scoped data.
   * This data will be replicated to all peers.
   */
  public static final int REPLICATION_SCOPE_GLOBAL = 1;

  /**
   * Default cluster ID, cannot be used to identify a cluster so a key with
   * this value means it wasn't meant for replication.
   */
  public static final UUID DEFAULT_CLUSTER_ID = new UUID(0L,0L);

    /**
     * Parameter name for maximum number of bytes returned when calling a
     * scanner's next method.
     */
  public static String HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE_KEY = "hbase.client.scanner.max.result.size";

  /**
   * Maximum number of bytes returned when calling a scanner's next method.
   * Note that when a single row is larger than this limit the row is still
   * returned completely.
   *
   * The default value is unlimited.
   */
  public static long DEFAULT_HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE = Long.MAX_VALUE;

  /**
   * Parameter name for client pause value, used mostly as value to wait
   * before running a retry of a failed get, region lookup, etc.
   */
  public static String HBASE_CLIENT_PAUSE = "hbase.client.pause";

  /**
   * Default value of {@link #HBASE_CLIENT_PAUSE}.
   */
  public static long DEFAULT_HBASE_CLIENT_PAUSE = 100;

  /**
   * The maximum number of concurrent connections the client will maintain.
   */
  public static final String HBASE_CLIENT_MAX_TOTAL_TASKS = "hbase.client.max.total.tasks";

  /**
   * Default value of {@link #HBASE_CLIENT_MAX_TOTAL_TASKS}.
   */
  public static final int DEFAULT_HBASE_CLIENT_MAX_TOTAL_TASKS = 100;

  /**
   * The maximum number of concurrent connections the client will maintain to a single
   * RegionServer.
   */
  public static final String HBASE_CLIENT_MAX_PERSERVER_TASKS = "hbase.client.max.perserver.tasks";

  /**
   * Default value of {@link #HBASE_CLIENT_MAX_PERSERVER_TASKS}.
   */
  public static final int DEFAULT_HBASE_CLIENT_MAX_PERSERVER_TASKS = 2;

  /**
   * The maximum number of concurrent connections the client will maintain to a single
   * Region.
   */
  public static final String HBASE_CLIENT_MAX_PERREGION_TASKS = "hbase.client.max.perregion.tasks";

  /**
   * Default value of {@link #HBASE_CLIENT_MAX_PERREGION_TASKS}.
   */
  public static final int DEFAULT_HBASE_CLIENT_MAX_PERREGION_TASKS = 1;

  /**
   * Parameter name for server pause value, used mostly as value to wait before
   * running a retry of a failed operation.
   */
  public static String HBASE_SERVER_PAUSE = "hbase.server.pause";

  /**
   * Default value of {@link #HBASE_SERVER_PAUSE}.
   */
  public static int DEFAULT_HBASE_SERVER_PAUSE = 1000;

  /**
   * Parameter name for maximum retries, used as maximum for all retryable
   * operations such as fetching of the root region from root region server,
   * getting a cell's value, starting a row update, etc.
   */
  public static String HBASE_CLIENT_RETRIES_NUMBER = "hbase.client.retries.number";

  /**
   * Default value of {@link #HBASE_CLIENT_RETRIES_NUMBER}.
   */
  public static int DEFAULT_HBASE_CLIENT_RETRIES_NUMBER = 31;

  /**
   * Parameter name for client prefetch limit, used as the maximum number of regions
   * info that will be prefetched.
   */
  public static String HBASE_CLIENT_PREFETCH_LIMIT = "hbase.client.prefetch.limit";

  /**
   * Default value of {@link #HBASE_CLIENT_PREFETCH_LIMIT}.
   */
  public static int DEFAULT_HBASE_CLIENT_PREFETCH_LIMIT = 10;

  /**
   * Parameter name to set the default scanner caching for all clients.
   */
  public static String HBASE_CLIENT_SCANNER_CACHING = "hbase.client.scanner.caching";

  /**
   * Default value for {@link #HBASE_CLIENT_SCANNER_CACHING}
   */
  public static int DEFAULT_HBASE_CLIENT_SCANNER_CACHING = 100;

  /**
   * Parameter name for number of rows that will be fetched when calling next on
   * a scanner if it is not served from memory. Higher caching values will
   * enable faster scanners but will eat up more memory and some calls of next
   * may take longer and longer times when the cache is empty.
   */
  public static String HBASE_META_SCANNER_CACHING = "hbase.meta.scanner.caching";

  /**
   * Default value of {@link #HBASE_META_SCANNER_CACHING}.
   */
  public static int DEFAULT_HBASE_META_SCANNER_CACHING = 100;

  /**
   * Parameter name for unique identifier for this {@link org.apache.hadoop.conf.Configuration}
   * instance. If there are two or more {@link org.apache.hadoop.conf.Configuration} instances that,
   * for all intents and purposes, are the same except for their instance ids, then they will not be
   * able to share the same org.apache.hadoop.hbase.client.HConnection instance. On the other hand,
   * even if the instance ids are the same, it could result in non-shared
   * org.apache.hadoop.hbase.client.HConnection instances if some of the other connection parameters
   * differ.
   */
  public static String HBASE_CLIENT_INSTANCE_ID = "hbase.client.instance.id";

  /**
   * The client scanner timeout period in milliseconds.
   */
  public static String HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD = "hbase.client.scanner.timeout.period";

  /**
   * Use {@link #HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD} instead.
   * @deprecated This config option is deprecated. Will be removed at later releases after 0.96.
   */
  @Deprecated
  public static String HBASE_REGIONSERVER_LEASE_PERIOD_KEY =
      "hbase.regionserver.lease.period";

  /**
   * Default value of {@link #HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD}.
   */
  public static int DEFAULT_HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD = 60000;

  /**
   * timeout for each RPC
   */
  public static String HBASE_RPC_TIMEOUT_KEY = "hbase.rpc.timeout";

  /**
   * Default value of {@link #HBASE_RPC_TIMEOUT_KEY}
   */
  public static int DEFAULT_HBASE_RPC_TIMEOUT = 60000;

  /**
   * timeout for short operation RPC
   */
  public static String HBASE_RPC_SHORTOPERATION_TIMEOUT_KEY = "hbase.rpc.shortoperation.timeout";

  /**
   * Default value of {@link #HBASE_RPC_SHORTOPERATION_TIMEOUT_KEY}
   */
  public static int DEFAULT_HBASE_RPC_SHORTOPERATION_TIMEOUT = 10000;

  /**
   * Value indicating the server name was saved with no sequence number.
   */
  public static final long NO_SEQNUM = -1;


  /*
   * cluster replication constants.
   */
  public static final String
      REPLICATION_ENABLE_KEY = "hbase.replication";
  public static final boolean
      REPLICATION_ENABLE_DEFAULT = true;
  public static final String
      REPLICATION_SOURCE_SERVICE_CLASSNAME = "hbase.replication.source.service";
  public static final String
      REPLICATION_SINK_SERVICE_CLASSNAME = "hbase.replication.sink.service";
  public static final String REPLICATION_SERVICE_CLASSNAME_DEFAULT =
    "org.apache.hadoop.hbase.replication.regionserver.Replication";

  /** HBCK special code name used as server name when manipulating ZK nodes */
  public static final String HBCK_CODE_NAME = "HBCKServerName";

  public static final String KEY_FOR_HOSTNAME_SEEN_BY_MASTER =
    "hbase.regionserver.hostname.seen.by.master";

  public static final String HBASE_MASTER_LOGCLEANER_PLUGINS =
      "hbase.master.logcleaner.plugins";

  public static final String HBASE_REGION_SPLIT_POLICY_KEY =
    "hbase.regionserver.region.split.policy";

  /** Whether nonces are enabled; default is true. */
  public static String HBASE_RS_NONCES_ENABLED = "hbase.regionserver.nonces.enabled";

  /**
   * Configuration key for the size of the block cache
   */
  public static final String HFILE_BLOCK_CACHE_SIZE_KEY =
    "hfile.block.cache.size";

  public static final float HFILE_BLOCK_CACHE_SIZE_DEFAULT = 0.25f;

  /*
    * Minimum percentage of free heap necessary for a successful cluster startup.
    */
  public static final float HBASE_CLUSTER_MINIMUM_MEMORY_THRESHOLD = 0.2f;

  public static final Pattern CP_HTD_ATTR_KEY_PATTERN = Pattern.compile
      ("^coprocessor\\$([0-9]+)$", Pattern.CASE_INSENSITIVE);
  public static final Pattern CP_HTD_ATTR_VALUE_PATTERN =
      Pattern.compile("(^[^\\|]*)\\|([^\\|]+)\\|[\\s]*([\\d]*)[\\s]*(\\|.*)?$");

  public static final String CP_HTD_ATTR_VALUE_PARAM_KEY_PATTERN = "[^=,]+";
  public static final String CP_HTD_ATTR_VALUE_PARAM_VALUE_PATTERN = "[^,]+";
  public static final Pattern CP_HTD_ATTR_VALUE_PARAM_PATTERN = Pattern.compile(
      "(" + CP_HTD_ATTR_VALUE_PARAM_KEY_PATTERN + ")=(" +
      CP_HTD_ATTR_VALUE_PARAM_VALUE_PATTERN + "),?");

  /** The delay when re-trying a socket operation in a loop (HBASE-4712) */
  public static final int SOCKET_RETRY_WAIT_MS = 200;

  /** Host name of the local machine */
  public static final String LOCALHOST = "localhost";

  /**
   * If this parameter is set to true, then hbase will read
   * data and then verify checksums. Checksum verification
   * inside hdfs will be switched off.  However, if the hbase-checksum
   * verification fails, then it will switch back to using
   * hdfs checksums for verifiying data that is being read from storage.
   *
   * If this parameter is set to false, then hbase will not
   * verify any checksums, instead it will depend on checksum verification
   * being done in the hdfs client.
   */
  public static final String HBASE_CHECKSUM_VERIFICATION =
      "hbase.regionserver.checksum.verify";

  public static final String LOCALHOST_IP = "127.0.0.1";

  /** Conf key that enables unflushed WAL edits directly being replayed to region servers */
  public static final String DISTRIBUTED_LOG_REPLAY_KEY = "hbase.master.distributed.log.replay";
  public static final boolean DEFAULT_DISTRIBUTED_LOG_REPLAY_CONFIG = false;
  public static final String DISALLOW_WRITES_IN_RECOVERING =
      "hbase.regionserver.disallow.writes.when.recovering";
  public static final boolean DEFAULT_DISALLOW_WRITES_IN_RECOVERING_CONFIG = false;

  public static final String REGION_SERVER_HANDLER_COUNT = "hbase.regionserver.handler.count";
  public static final int DEFAULT_REGION_SERVER_HANDLER_COUNT = 30;

  public static final String REGION_SERVER_META_HANDLER_COUNT =
      "hbase.regionserver.metahandler.count";
  public static final int DEFAULT_REGION_SERVER_META_HANDLER_COUNT = 10;

  public static final String REGION_SERVER_REPLICATION_HANDLER_COUNT =
      "hbase.regionserver.replication.handler.count";
  public static final int DEFAULT_REGION_SERVER_REPLICATION_HANDLER_COUNT = 3;

  public static final String MASTER_HANDLER_COUNT = "hbase.master.handler.count";
  public static final int DEFAULT_MASTER_HANLDER_COUNT = 25;

  /** Conf key that specifies timeout value to wait for a region ready */
  public static final String LOG_REPLAY_WAIT_REGION_TIMEOUT =
      "hbase.master.log.replay.wait.region.timeout";

  /**
   * The name of the configuration parameter that specifies
   * the number of bytes in a newly created checksum chunk.
   */
  public static final String BYTES_PER_CHECKSUM =
      "hbase.hstore.bytes.per.checksum";

  /**
   * The name of the configuration parameter that specifies
   * the name of an algorithm that is used to compute checksums
   * for newly created blocks.
   */
  public static final String CHECKSUM_TYPE_NAME =
      "hbase.hstore.checksum.algorithm";

  /** Enable file permission modification from standard hbase */
  public static final String ENABLE_DATA_FILE_UMASK = "hbase.data.umask.enable";
  /** File permission umask to use when creating hbase data files */
  public static final String DATA_FILE_UMASK_KEY = "hbase.data.umask";

  /** Configuration name of HLog Compression */
  public static final String ENABLE_WAL_COMPRESSION =
    "hbase.regionserver.wal.enablecompression";

  /** Region in Transition metrics threshold time */
  public static final String METRICS_RIT_STUCK_WARNING_THRESHOLD="hbase.metrics.rit.stuck.warning.threshold";

  public static final String LOAD_BALANCER_SLOP_KEY = "hbase.regions.slop";

  /**
   * The byte array represents for NO_NEXT_INDEXED_KEY;
   * The actual value is irrelevant because this is always compared by reference.
   */
  public static final byte [] NO_NEXT_INDEXED_KEY = Bytes.toBytes("NO_NEXT_INDEXED_KEY");
  /** delimiter used between portions of a region name */
  public static final int DELIMITER = ',';
  public static final String HBASE_CONFIG_READ_ZOOKEEPER_CONFIG =
      "hbase.config.read.zookeeper.config";
  public static final boolean DEFAULT_HBASE_CONFIG_READ_ZOOKEEPER_CONFIG =
      false;

  /**
   * QOS attributes: these attributes are used to demarcate RPC call processing
   * by different set of handlers. For example, HIGH_QOS tagged methods are
   * handled by high priority handlers.
   */
  public static final int NORMAL_QOS = 0;
  public static final int QOS_THRESHOLD = 10;
  public static final int HIGH_QOS = 100;
  public static final int REPLICATION_QOS = 5; // normal_QOS < replication_QOS < high_QOS
  public static final int REPLAY_QOS = 6; // REPLICATION_QOS < REPLAY_QOS < high_QOS

  /** Directory under /hbase where archived hfiles are stored */
  public static final String HFILE_ARCHIVE_DIRECTORY = "archive";

  /**
   * Name of the directory to store all snapshots. See SnapshotDescriptionUtils for
   * remaining snapshot constants; this is here to keep HConstants dependencies at a minimum and
   * uni-directional.
   */
  public static final String SNAPSHOT_DIR_NAME = ".hbase-snapshot";

  /* Name of old snapshot directory. See HBASE-8352 for details on why it needs to be renamed */
  public static final String OLD_SNAPSHOT_DIR_NAME = ".snapshot";

  /** Temporary directory used for table creation and deletion */
  public static final String HBASE_TEMP_DIRECTORY = ".tmp";
  /**
   * The period (in milliseconds) between computing region server point in time metrics
   */
  public static final String REGIONSERVER_METRICS_PERIOD = "hbase.regionserver.metrics.period";
  public static final long DEFAULT_REGIONSERVER_METRICS_PERIOD = 5000;
  /** Directories that are not HBase table directories */
  public static final List<String> HBASE_NON_TABLE_DIRS =
    Collections.unmodifiableList(Arrays.asList(new String[] { HREGION_LOGDIR_NAME,
      HREGION_OLDLOGDIR_NAME, CORRUPT_DIR_NAME, SPLIT_LOGDIR_NAME,
      HBCK_SIDELINEDIR_NAME, HFILE_ARCHIVE_DIRECTORY, SNAPSHOT_DIR_NAME, HBASE_TEMP_DIRECTORY,
      OLD_SNAPSHOT_DIR_NAME, BASE_NAMESPACE_DIR, MIGRATION_NAME, LIB_DIR}));

  /** Directories that are not HBase user table directories */
  public static final List<String> HBASE_NON_USER_TABLE_DIRS =
    Collections.unmodifiableList(Arrays.asList((String[])ArrayUtils.addAll(
      new String[] { TableName.META_TABLE_NAME.getNameAsString() },
      HBASE_NON_TABLE_DIRS.toArray())));

  /** Health script related settings. */
  public static final String HEALTH_SCRIPT_LOC = "hbase.node.health.script.location";
  public static final String HEALTH_SCRIPT_TIMEOUT = "hbase.node.health.script.timeout";
  public static final String HEALTH_CHORE_WAKE_FREQ =
      "hbase.node.health.script.frequency";
  public static final long DEFAULT_HEALTH_SCRIPT_TIMEOUT = 60000;
  /**
   * The maximum number of health check failures a server can encounter consecutively.
   */
  public static final String HEALTH_FAILURE_THRESHOLD =
      "hbase.node.health.failure.threshold";
  public static final int DEFAULT_HEALTH_FAILURE_THRESHOLD = 3;


  /**
   * Setting to activate, or not, the publication of the status by the master. Default
   *  notification is by a multicast message.
   */
  public static final String STATUS_PUBLISHED = "hbase.status.published";
  public static final boolean STATUS_PUBLISHED_DEFAULT = false;

  /**
   * IP to use for the multicast status messages between the master and the clients.
   * The default address is chosen as one among others within the ones suitable for multicast
   * messages.
   */
  public static final String STATUS_MULTICAST_ADDRESS = "hbase.status.multicast.address.ip";
  public static final String DEFAULT_STATUS_MULTICAST_ADDRESS = "226.1.1.3";

  /**
   * The address to use for binding the local socket for receiving multicast. Defaults to
   * 0.0.0.0.
   * @see <a href="https://issues.apache.org/jira/browse/HBASE-9961">HBASE-9961</a>
   */
  public static final String STATUS_MULTICAST_BIND_ADDRESS = "hbase.status.multicast.bind.address.ip";
  public static final String DEFAULT_STATUS_MULTICAST_BIND_ADDRESS = "0.0.0.0";

  /**
   * The port to use for the multicast messages.
   */
  public static final String STATUS_MULTICAST_PORT = "hbase.status.multicast.address.port";
  public static final int DEFAULT_STATUS_MULTICAST_PORT = 60100;

  public static final long NO_NONCE = 0;

  /** Configuration key for the crypto algorithm provider, a class name */
  public static final String CRYPTO_CIPHERPROVIDER_CONF_KEY = "hbase.crypto.cipherprovider";

  /** Configuration key for the crypto key provider, a class name */
  public static final String CRYPTO_KEYPROVIDER_CONF_KEY = "hbase.crypto.keyprovider";

  /** Configuration key for the crypto key provider parameters */
  public static final String CRYPTO_KEYPROVIDER_PARAMETERS_KEY =
      "hbase.crypto.keyprovider.parameters";

  /** Configuration key for the name of the master key for the cluster, a string */
  public static final String CRYPTO_MASTERKEY_NAME_CONF_KEY = "hbase.crypto.master.key.name";

  /** Configuration key for the name of the alternate master key for the cluster, a string */
  public static final String CRYPTO_MASTERKEY_ALTERNATE_NAME_CONF_KEY =
    "hbase.crypto.master.alternate.key.name";

  /** Configuration key for the algorithm to use when encrypting the WAL, a string */
  public static final String CRYPTO_WAL_ALGORITHM_CONF_KEY = "hbase.crypto.wal.algorithm";

  /** Configuration key for the name of the master WAL encryption key for the cluster, a string */
  public static final String CRYPTO_WAL_KEY_NAME_CONF_KEY = "hbase.crypto.wal.key.name";

  /** Configuration key for enabling HLog encryption, a boolean */
  public static final String ENABLE_WAL_ENCRYPTION = "hbase.regionserver.wal.encryption";

  /** Configuration key for setting RPC codec class name */
  public static final String RPC_CODEC_CONF_KEY = "hbase.client.rpc.codec";

  /** Configuration key for setting replication codec class name */
  public static final String REPLICATION_CODEC_CONF_KEY = "hbase.replication.rpc.codec";

  private HConstants() {
    // Can't be instantiated with this ctor.
  }
}
