/*
 * 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 org.apache.commons.lang3.ArrayUtils;
import org.apache.hadoop.hbase.conf.ConfigKey;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * HConstants holds a bunch of HBase-related constants
 */
@InterfaceAudience.Public
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";

  /*
   * Name of directory that holds recovered hfiles written by the wal log splitting code, one per
   * region
   */
  public static final String RECOVERED_HFILES_DIR = "recovered.hfiles";

  /**
   * Date Tiered Compaction tmp dir prefix name if use storage policy
   */
  public static final String STORAGE_POLICY_PREFIX = "storage_policy_";

  /**
   * The first four bytes of Hadoop RPC connections
   */
  public static final byte[] RPC_HEADER = new byte[] { 'H', 'B', 'a', 's' };
  public static final byte RPC_CURRENT_VERSION = 0;

  // HFileBlock constants. TODO!!!! THESE DEFINES BELONG IN HFILEBLOCK, NOT UP HERE.
  // Needed down in hbase-common though by encoders but these encoders should not be dealing
  // in the internals of hfileblocks. Fix encapsulation.

  /** 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.
   */
  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
  public enum OperationStatusCode {
    NOT_RUN,
    SUCCESS,
    BAD_FAMILY,
    STORE_TOO_BUSY,
    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";

  /** Config for balancing the cluster by table */
  public static final String HBASE_MASTER_LOADBALANCE_BYTABLE = "hbase.master.loadbalance.bytable";

  /** Config for the max percent of regions in transition */
  public static final String HBASE_MASTER_BALANCER_MAX_RIT_PERCENT =
    "hbase.master.balancer.maxRitPercent";

  /** Default value for the max percent of regions in transition */
  public static final double DEFAULT_HBASE_MASTER_BALANCER_MAX_RIT_PERCENT = 1.0;

  /** Config for the max balancing time */
  public static final String HBASE_BALANCER_MAX_BALANCING = "hbase.balancer.max.balancing";

  /** Config for the balancer period */
  public static final String HBASE_BALANCER_PERIOD = "hbase.balancer.period";

  /** Default value for the balancer period */
  public static final int DEFAULT_HBASE_BALANCER_PERIOD = 300000;

  /** Config for the oldWALs directory size updater period */
  public static final String HBASE_OLDWAL_DIR_SIZE_UPDATER_PERIOD =
    "hbase.master.oldwals.dir.updater.period";

  /** Default value for the oldWALs directory size updater period */
  public static final int DEFAULT_HBASE_OLDWAL_DIR_SIZE_UPDATER_PERIOD = 300000;

  /**
   * Config key for enable/disable automatically separate child regions to different region servers
   * in the procedure of split regions. One child will be kept to the server where parent region is
   * on, and the other child will be assigned to a random server. See HBASE-25518.
   */
  public static final String HBASE_ENABLE_SEPARATE_CHILD_REGIONS =
    "hbase.master.auto.separate.child.regions.after.split.enabled";

  /**
   * Default value for automatically separate child regions to different region servers (set to
   * "false" to keep all child regions to the server where parent region is on)
   */
  public static final boolean DEFAULT_HBASE_ENABLE_SEPARATE_CHILD_REGIONS = false;

  /** The name of the ensemble table */
  public static final TableName ENSEMBLE_TABLE_NAME = TableName.valueOf("hbase:ensemble");

  /** Config for pluggable region normalizer */
  public static final String HBASE_MASTER_NORMALIZER_CLASS = "hbase.master.normalizer.class";

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

  /** 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 = 16000;

  /** default port for master web api */
  public static final int DEFAULT_MASTER_INFOPORT = 16010;

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

  /** Configuration key for the list of master host:ports **/
  public static final String MASTER_ADDRS_KEY = "hbase.masters";

  /** Full class name of the Zookeeper based connection registry implementation */
  public static final String ZK_CONNECTION_REGISTRY_CLASS =
    "org.apache.hadoop.hbase.client.ZKConnectionRegistry";

  /** 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 quorum configuration parameter for client to locate meta. */
  public static final String CLIENT_ZOOKEEPER_QUORUM = "hbase.client.zookeeper.quorum";

  /** Client port of ZooKeeper for client to locate meta */
  public static final String CLIENT_ZOOKEEPER_CLIENT_PORT =
    "hbase.client.zookeeper.property.clientPort";

  /** Indicate whether the client ZK are observer nodes of the server ZK */
  public static final String CLIENT_ZOOKEEPER_OBSERVER_MODE =
    "hbase.client.zookeeper.observer.mode";
  /** Assuming client zk not in observer mode and master need to synchronize information */
  public static final boolean DEFAULT_CLIENT_ZOOKEEPER_OBSERVER_MODE = false;

  /** 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_ZOOKEEPER_CLIENT_PORT = 2181;

  /** 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";

  /** Parameter name for the ZK tick time */
  public static final String ZOOKEEPER_TICK_TIME = ZK_CFG_PROPERTY_PREFIX + "tickTime";

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

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

  /** Timeout for the ZK sync() call */
  public static final String ZK_SYNC_BLOCKING_TIMEOUT_MS = "hbase.zookeeper.sync.timeout.millis";
  // Choice of the default value is based on the following ZK recommendation (from docs). Keeping it
  // lower lets the callers fail fast in case of any issues.
  // "The clients view of the system is guaranteed to be up-to-date within a certain time bound.
  // (On the order of tens of seconds.) Either system changes will be seen by a client within this
  // bound, or the client will detect a service outage."
  public static final long ZK_SYNC_BLOCKING_TIMEOUT_DEFAULT_MS = 30 * 1000;

  /** Default value for ZooKeeper session timeout */
  public static final int DEFAULT_ZK_SESSION_TIMEOUT = 90 * 1000;

  /** 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 = 16020;

  /** default port for region server web api */
  public static final int DEFAULT_REGIONSERVER_INFOPORT = 16030;

  /** 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 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 and default value for how often a region should perform a major compaction */
  public static final String MAJOR_COMPACTION_PERIOD =
    ConfigKey.LONG("hbase.hregion.majorcompaction");
  public static final long DEFAULT_MAJOR_COMPACTION_PERIOD = 1000 * 60 * 60 * 24 * 7; // 7 days

  /**
   * Parameter name and default value for major compaction jitter. Used as a multiplier applied to
   * {@link HConstants#MAJOR_COMPACTION_PERIOD} to cause compaction to occur a given amount of time
   * either side of {@link HConstants#MAJOR_COMPACTION_PERIOD}. Default to 0.5 so jitter has us fall
   * evenly either side of when the compaction should run.
   */
  public static final String MAJOR_COMPACTION_JITTER =
    ConfigKey.FLOAT("hbase.hregion.majorcompaction.jitter");
  public static final float DEFAULT_MAJOR_COMPACTION_JITTER = 0.50F;

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

  /** Parameter name for the scanner size limit to be used in compactions */
  public static final String COMPACTION_SCANNER_SIZE_MAX =
    ConfigKey.LONG("hbase.hstore.compaction.scanner.size.limit");
  public static final long COMPACTION_SCANNER_SIZE_MAX_DEFAULT = 10 * 1024 * 1024L; // 10MB

  /** 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. */
  public static final String HBASE_CLIENT_OPERATION_TIMEOUT = "hbase.client.operation.timeout";

  /** Parameter name for HBase client meta operation 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 = 1200000;

  /** Parameter name for HBase client meta replica scan call timeout. */
  public static final String HBASE_CLIENT_META_REPLICA_SCAN_TIMEOUT =
    "hbase.client.meta.replica.scan.timeout";

  /** Default HBase client meta replica scan call timeout, 1 second */
  public static final int HBASE_CLIENT_META_REPLICA_SCAN_TIMEOUT_DEFAULT = 1000000;

  /** 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";

  /** Staging dir used by bulk load */
  public static final String BULKLOAD_STAGING_DIR_NAME = "staging";

  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";

  /** 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 = ConfigKey.LONG("hbase.hregion.max.filesize");

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

  /** Conf key for if we should sum overall region files size when check to split */
  public static final String OVERALL_HREGION_FILES = "hbase.hregion.split.overallfiles";

  /** Default overall region files */
  public static final boolean DEFAULT_OVERALL_HREGION_FILES = true;

  /**
   * Max size of single row for Get's or Scan's without in-row scanning flag set.
   */
  public static final String TABLE_MAX_ROWSIZE_KEY = "hbase.table.max.rowsize";

  /**
   * Default max row size (1 Gb).
   */
  public static final long TABLE_MAX_ROWSIZE_DEFAULT = 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 =
    ConfigKey.INT("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;

  /**
   * Block updates if memstore has hbase.hregion.memstore.block.multiplier times
   * hbase.hregion.memstore.flush.size bytes. Useful preventing runaway memstore during spikes in
   * update traffic.
   */
  public static final String HREGION_MEMSTORE_BLOCK_MULTIPLIER =
    ConfigKey.INT("hbase.hregion.memstore.block.multiplier", v -> v > 0);

  /**
   * Default value for hbase.hregion.memstore.block.multiplier
   */
  public static final int DEFAULT_HREGION_MEMSTORE_BLOCK_MULTIPLIER = 4;

  /** Conf key for the memstore size at which we flush the memstore */
  public static final String HREGION_MEMSTORE_FLUSH_SIZE =
    ConfigKey.LONG("hbase.hregion.memstore.flush.size", v -> v > 0);

  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";

  /** Parameter name for # days to keep MVCC values during a major compaction */
  public static final String KEEP_SEQID_PERIOD =
    ConfigKey.INT("hbase.hstore.compaction.keep.seqId.period");
  /** At least to keep MVCC values in hfiles for 5 days */
  public static final int MIN_KEEP_SEQID_PERIOD = 5;

  // 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.

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

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

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

  /** The state column qualifier */
  public static final String STATE_QUALIFIER_STR = "state";

  public static final byte[] STATE_QUALIFIER = Bytes.toBytes(STATE_QUALIFIER_STR);

  /**
   * The serverName column qualifier. Its the server where the region is transitioning on, while
   * column server is the server where the region is opened on. They are the same when the region is
   * in state OPEN.
   */
  public static final String SERVERNAME_QUALIFIER_STR = "sn";

  public static final byte[] SERVERNAME_QUALIFIER = Bytes.toBytes(SERVERNAME_QUALIFIER_STR);

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

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

  /**
   * Merge qualifier prefix. We used to only allow two regions merge; mergeA and mergeB. Now we
   * allow many to merge. Each region to merge will be referenced in a column whose qualifier starts
   * with this define.
   */
  public static final String MERGE_QUALIFIER_PREFIX_STR = "merge";
  public static final byte[] MERGE_QUALIFIER_PREFIX = Bytes.toBytes(MERGE_QUALIFIER_PREFIX_STR);

  /**
   * The lower-half merge region column qualifier
   * @deprecated Since 2.3.0 and 2.2.1. Not used anymore. Instead we look for the
   *             {@link #MERGE_QUALIFIER_PREFIX_STR} prefix.
   */
  @Deprecated
  public static final byte[] MERGEA_QUALIFIER = Bytes.toBytes(MERGE_QUALIFIER_PREFIX_STR + "A");

  /**
   * The upper-half merge region column qualifier
   * @deprecated Since 2.3.0 and 2.2.1. Not used anymore. Instead we look for the
   *             {@link #MERGE_QUALIFIER_PREFIX_STR} prefix.
   */
  @Deprecated
  public static final byte[] MERGEB_QUALIFIER = Bytes.toBytes(MERGE_QUALIFIER_PREFIX_STR + "B");

  /** The catalog family as a string */
  public static final String TABLE_FAMILY_STR = "table";

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

  /** The serialized table state qualifier */
  public static final byte[] TABLE_STATE_QUALIFIER = Bytes.toBytes("state");

  /** The replication barrier family as a string */
  public static final String REPLICATION_BARRIER_FAMILY_STR = "rep_barrier";

  /** The replication barrier family */
  public static final byte[] REPLICATION_BARRIER_FAMILY =
    Bytes.toBytes(REPLICATION_BARRIER_FAMILY_STR);

  /** The namespace family as a string */
  public static final String NAMESPACE_FAMILY_STR = "ns";

  /** The namespace family */
  public static final byte[] NAMESPACE_FAMILY = Bytes.toBytes(NAMESPACE_FAMILY_STR);

  public static final byte[] NAMESPACE_COL_DESC_QUALIFIER = Bytes.toBytes("d");
  /**
   * 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 family str as a key in map */
  public static final String FAMILY_KEY_STR = "family";

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

  /**
   * An empty string instance.
   */
  public static final String EMPTY_STRING = "";

  public static final ByteBuffer EMPTY_BYTE_BUFFER = ByteBuffer.wrap(EMPTY_BYTE_ARRAY);

  /**
   * 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_BYTE_ARRAY;

  /**
   * 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. On client side, this is the
   * timestamp set by default when no timestamp is specified, to refer to the latest. On server
   * side, this acts as a notation. (1) For a cell of Put, which has this notation, its timestamp
   * will be replaced with server's current time. (2) For a cell of Delete, which has this notation,
   * A. If the cell is of {@link KeyValue.Type#Delete}, HBase issues a Get operation firstly. a.
   * When the count of cell it gets is less than the count of cell to delete, the timestamp of
   * Delete cell will be replaced with server's current time. b. When the count of cell it gets is
   * equal to the count of cell to delete, the timestamp of Delete cell will be replaced with the
   * latest timestamp of cell it gets. (c. It is invalid and an exception will be thrown, if the
   * count of cell it gets is greater than the count of cell to delete, as the max version of Get is
   * set to the count of cell to delete.) B. If the cell is of other Delete types, like
   * {@link KeyValue.Type#DeleteFamilyVersion}, {@link KeyValue.Type#DeleteColumn}, or
   * {@link KeyValue.Type#DeleteFamily}, the timestamp of Delete cell will be replaced with server's
   * current time. So that is why it is named as "latest" but assigned as the max value of Long.
   */
  public static final long LATEST_TIMESTAMP = Long.MAX_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 day, hour and minute
   */
  public static final int DAY_IN_SECONDS = 24 * 60 * 60;
  public static final int HOUR_IN_SECONDS = 60 * 60;
  public static final int MINUTE_IN_SECONDS = 60;

  /**
   * KB, MB, GB, TB equivalent to how many bytes
   */
  public static final long KB_IN_BYTES = 1024;
  public static final long MB_IN_BYTES = 1024 * KB_IN_BYTES;
  public static final long GB_IN_BYTES = 1024 * MB_IN_BYTES;
  public static final long TB_IN_BYTES = 1024 * GB_IN_BYTES;

  // 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 final 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";

  /**
   * 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.
   * Controlled by the client.
   */
  public static final String HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE_KEY =
    "hbase.client.scanner.max.result.size";

  /**
   * Parameter name for maximum number of bytes returned when calling a scanner's next method.
   * Controlled by the server.
   */
  public static final String HBASE_SERVER_SCANNER_MAX_RESULT_SIZE_KEY =
    "hbase.server.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 2MB.
   */
  public static final long DEFAULT_HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE = 2 * 1024 * 1024;

  /**
   * 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. Safety setting to protect
   * the region server. The default value is 100MB. (a client would rarely request larger chunks on
   * purpose)
   */
  public static final long DEFAULT_HBASE_SERVER_SCANNER_MAX_RESULT_SIZE = 100 * 1024 * 1024;

  /**
   * 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 final String HBASE_CLIENT_PAUSE = "hbase.client.pause";

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

  /**
   * Parameter name for client pause value for special case such as call queue too big, etc.
   * @deprecated Since 2.5.0, will be removed in 4.0.0. Please use
   *             hbase.client.pause.server.overloaded instead.
   */
  @Deprecated
  public static final String HBASE_CLIENT_PAUSE_FOR_CQTBE = "hbase.client.pause.cqtbe";

  /**
   * 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;

  /**
   * The maximum number of concurrent pending RPC requests for one server in process level.
   */
  public static final String HBASE_CLIENT_PERSERVER_REQUESTS_THRESHOLD =
    "hbase.client.perserver.requests.threshold";

  /**
   * Default value of {@link #HBASE_CLIENT_PERSERVER_REQUESTS_THRESHOLD}.
   */
  public static final int DEFAULT_HBASE_CLIENT_PERSERVER_REQUESTS_THRESHOLD = Integer.MAX_VALUE;

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

  /**
   * Default value of {@link #HBASE_SERVER_PAUSE}.
   */
  public static final 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 final String HBASE_CLIENT_RETRIES_NUMBER = "hbase.client.retries.number";

  /**
   * Default value of {@link #HBASE_CLIENT_RETRIES_NUMBER}.
   */
  public static final int DEFAULT_HBASE_CLIENT_RETRIES_NUMBER = 15;

  public static final String HBASE_CLIENT_SERVERSIDE_RETRIES_MULTIPLIER =
    "hbase.client.serverside.retries.multiplier";

  public static final int DEFAULT_HBASE_CLIENT_SERVERSIDE_RETRIES_MULTIPLIER = 3;

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

  /**
   * Default value for {@link #HBASE_CLIENT_SCANNER_CACHING}
   */
  public static final int DEFAULT_HBASE_CLIENT_SCANNER_CACHING = Integer.MAX_VALUE;

  /**
   * 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 final String HBASE_META_SCANNER_CACHING = "hbase.meta.scanner.caching";

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

  /**
   * Parameter name for number of versions, kept by meta table.
   */
  public static final String HBASE_META_VERSIONS = "hbase.meta.versions";

  /**
   * Default value of {@link #HBASE_META_VERSIONS}.
   */
  public static final int DEFAULT_HBASE_META_VERSIONS = 3;

  /**
   * Parameter name for number of versions, kept by meta table.
   */
  public static final String HBASE_META_BLOCK_SIZE = "hbase.meta.blocksize";

  /**
   * Default value of {@link #HBASE_META_BLOCK_SIZE}.
   */
  public static final int DEFAULT_HBASE_META_BLOCK_SIZE = 8 * 1024;

  /**
   * 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 final String HBASE_CLIENT_INSTANCE_ID = "hbase.client.instance.id";

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

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

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

  /**
   * timeout for each read RPC
   */
  public static final String HBASE_RPC_READ_TIMEOUT_KEY = "hbase.rpc.read.timeout";

  /**
   * timeout for each write RPC
   */
  public static final String HBASE_RPC_WRITE_TIMEOUT_KEY = "hbase.rpc.write.timeout";

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

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

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

  /**
   * Retry pause time for short operation RPC
   */
  public static final String HBASE_RPC_SHORTOPERATION_RETRY_PAUSE_TIME =
    "hbase.rpc.shortoperation.retry.pause.time";

  /**
   * Default value of {@link #HBASE_RPC_SHORTOPERATION_RETRY_PAUSE_TIME}
   */
  public static final long DEFAULT_HBASE_RPC_SHORTOPERATION_RETRY_PAUSE_TIME = 1000;

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

  /**
   * Registry implementation to be used on the client side.
   */
  public static final String CLIENT_CONNECTION_REGISTRY_IMPL_CONF_KEY =
    "hbase.client.registry.impl";

  /*
   * cluster replication constants.
   */
  public static final String REPLICATION_SOURCE_SERVICE_CLASSNAME =
    "hbase.replication.source.service";
  public static final String REPLICATION_SERVICE_CLASSNAME_DEFAULT =
    "org.apache.hadoop.hbase.replication.regionserver.Replication";
  public static final String REPLICATION_SINK_SERVICE_CLASSNAME = "hbase.replication.sink.service";
  public static final String REPLICATION_SINK_SERVICE_CLASSNAME_DEFAULT =
    "org.apache.hadoop.hbase.replication.ReplicationSinkServiceImpl";
  public static final String REPLICATION_BULKLOAD_ENABLE_KEY = "hbase.replication.bulkload.enabled";
  public static final boolean REPLICATION_BULKLOAD_ENABLE_DEFAULT = false;
  /** Replication cluster id of source cluster which uniquely identifies itself with peer cluster */
  public static final String REPLICATION_CLUSTER_ID = "hbase.replication.cluster.id";
  /**
   * Max total size of buffered entries in all replication peers. It will prevent server getting OOM
   * if there are many peers. Default value is 256MB which is four times to default
   * replication.source.size.capacity.
   */
  public static final String REPLICATION_SOURCE_TOTAL_BUFFER_KEY = "replication.total.buffer.quota";

  public static final int REPLICATION_SOURCE_TOTAL_BUFFER_DFAULT = 256 * 1024 * 1024;

  /** Configuration key for ReplicationSource shipeEdits timeout */
  public static final String REPLICATION_SOURCE_SHIPEDITS_TIMEOUT =
    "replication.source.shipedits.timeout";
  public static final int REPLICATION_SOURCE_SHIPEDITS_TIMEOUT_DFAULT = 60000;

  /**
   * Directory where the source cluster file system client configuration are placed which is used by
   * sink cluster to copy HFiles from source cluster file system
   */
  public static final String REPLICATION_CONF_DIR = "hbase.replication.conf.dir";

  /** Maximum time to retry for a failed bulk load request */
  public static final String BULKLOAD_MAX_RETRIES_NUMBER = "hbase.bulkload.retries.number";

  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 final 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 = 0.4f;

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

  /**
   * Configuration key for setting the fix size of the block size, default do nothing and it should
   * be explicitly set by user or only used within ClientSideRegionScanner. if it's set less than
   * current max on heap size, it overrides the max size of block cache
   */
  public static final String HFILE_ONHEAP_BLOCK_CACHE_FIXED_SIZE_KEY =
    "hfile.onheap.block.cache.fixed.size";
  public static final long HFILE_ONHEAP_BLOCK_CACHE_FIXED_SIZE_DEFAULT = 0L;
  public static final long HBASE_CLIENT_SCANNER_ONHEAP_BLOCK_CACHE_FIXED_SIZE_DEFAULT =
    32 * 1024 * 1024L;

  /**
   * Configuration key for setting pread must read both necessaryLen and extraLen, default is
   * disabled. This is an optimized flag for reading HFile from blob storage.
   */
  public static final String HFILE_PREAD_ALL_BYTES_ENABLED_KEY = "hfile.pread.all.bytes.enabled";
  public static final boolean HFILE_PREAD_ALL_BYTES_ENABLED_DEFAULT = false;

  /*
   * 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 String CP_HTD_ATTR_INCLUSION_KEY =
    "hbase.coprocessor.classloader.included.classes";

  /** 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";

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

  /*
   * REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT: -1 => Disable aborting 0 => Abort if even a
   * single handler has died 0.x => Abort only when this percent of handlers have died 1 => Abort
   * only all of the handers have died
   */
  public static final String REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT =
    "hbase.regionserver.handler.abort.on.error.percent";
  public static final double DEFAULT_REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT = 0.5;

  // High priority handlers to deal with admin requests and system table operation requests
  public static final String REGION_SERVER_HIGH_PRIORITY_HANDLER_COUNT =
    "hbase.regionserver.metahandler.count";
  public static final int DEFAULT_REGION_SERVER_HIGH_PRIORITY_HANDLER_COUNT = 20;

  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 REGION_SERVER_BULKLOAD_HANDLER_COUNT =
    "hbase.regionserver.bulkload.handler.count";
  public static final int DEFAULT_REGION_SERVER_BULKLOAD_HANDLER_COUNT = 0;
  // Meta Transition handlers to deal with meta ReportRegionStateTransitionRequest. Meta transition
  // should be dealt with in a separate handler in case blocking other region's transition.
  public static final String MASTER_META_TRANSITION_HANDLER_COUNT =
    "hbase.master.meta.transition.handler.count";
  public static final int MASTER__META_TRANSITION_HANDLER_COUNT_DEFAULT = 1;

  /** Conf key for enabling meta replication */
  public static final String USE_META_REPLICAS = "hbase.meta.replicas.use";
  public static final boolean DEFAULT_USE_META_REPLICAS = false;

  /**
   * @deprecated Since 2.4.0, will be removed in 4.0.0. Please change the meta replicas number by
   *             altering meta table, i.e, set a new 'region replication' number and call
   *             modifyTable.
   */
  @Deprecated
  public static final String META_REPLICAS_NUM = "hbase.meta.replica.count";
  /**
   * @deprecated Since 2.4.0, will be removed in 4.0.0. Please change the meta replicas number by
   *             altering meta table, i.e, set a new 'region replication' number and call
   *             modifyTable.
   */
  @Deprecated
  public static final int DEFAULT_META_REPLICA_NUM = 1;

  /**
   * 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 WAL Compression */
  public static final String ENABLE_WAL_COMPRESSION = "hbase.regionserver.wal.enablecompression";

  /**
   * Configuration name of WAL storage policy Valid values are: HOT, COLD, WARM, ALL_SSD, ONE_SSD,
   * LAZY_PERSIST See
   * http://hadoop.apache.org/docs/r2.7.3/hadoop-project-dist/hadoop-hdfs/ArchivalStorage.html
   */
  public static final String WAL_STORAGE_POLICY = "hbase.wal.storage.policy";
  /**
   * "NONE" is not a valid storage policy and means we defer the policy to HDFS. @see
   * <a href="https://issues.apache.org/jira/browse/HBASE-20691">HBASE-20691</a>
   */
  public static final String DEFER_TO_HDFS_STORAGE_POLICY = "NONE";
  /** By default we defer the WAL storage policy to HDFS */
  public static final String DEFAULT_WAL_STORAGE_POLICY = DEFER_TO_HDFS_STORAGE_POLICY;

  /** 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";

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

  /**
   * 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.
   */
  // normal_QOS < replication_QOS < replay_QOS < QOS_threshold < admin_QOS < high_QOS < meta_QOS
  public static final int PRIORITY_UNSET = -1;
  public static final int NORMAL_QOS = 0;
  public static final int REPLICATION_QOS = 5;
  public static final int BULKLOAD_QOS = 4;
  /**
   * @deprecated since 3.0.0, will be removed in 4.0.0. DLR has been purged for a long time and
   *             region replication has its own 'replay' method.
   */
  @Deprecated
  public static final int REPLAY_QOS = 6;
  public static final int REGION_REPLICATION_QOS = REPLAY_QOS;
  public static final int QOS_THRESHOLD = 10;
  public static final int ADMIN_QOS = 100;
  public static final int HIGH_QOS = 200;
  public static final int SYSTEMTABLE_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[] { HBCK_SIDELINEDIR_NAME, HBASE_TEMP_DIRECTORY, MIGRATION_NAME }));

  /**
   * Directories that are not HBase user table directories.
   * @deprecated Since hbase-2.3.0; no replacement as not used any more (internally at least)
   */
  @Deprecated
  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;

  public static final String EXECUTOR_STATUS_COLLECT_ENABLED =
    "hbase.executors.status.collect.enabled";
  public static final boolean DEFAULT_EXECUTOR_STATUS_COLLECT_ENABLED = true;

  /**
   * 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 = 16100;

  /**
   * The network interface name to use for the multicast messages.
   */
  public static final String STATUS_MULTICAST_NI_NAME = "hbase.status.multicast.ni.name";

  /**
   * The address to use for binding the local socket for sending multicast. Defaults to 0.0.0.0.
   */
  public static final String STATUS_MULTICAST_PUBLISHER_BIND_ADDRESS =
    "hbase.status.multicast.publisher.bind.address.ip";
  public static final String DEFAULT_STATUS_MULTICAST_PUBLISHER_BIND_ADDRESS = "0.0.0.0";

  public static final long NO_NONCE = 0;

  /** Default cipher for encryption */
  public static final String CIPHER_AES = "AES";

  /** 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 the algorithm used for creating jks key, a string */
  public static final String CRYPTO_KEY_ALGORITHM_CONF_KEY = "hbase.crypto.key.algorithm";

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

  /** Configuration key for enabling WAL 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";

  /** Maximum number of threads used by the replication source for shipping edits to the sinks */
  public static final String REPLICATION_SOURCE_MAXTHREADS_KEY =
    "hbase.replication.source.maxthreads";

  /**
   * Drop edits for tables that been deleted from the replication source and target
   * @deprecated since 3.0.0. Will be removed in 4.0.0. Moved it into
   *             HBaseInterClusterReplicationEndpoint.
   * @see <a href="https://issues.apache.org/jira/browse/HBASE-24359">HBASE-24359</a>
   */
  @Deprecated
  public static final String REPLICATION_DROP_ON_DELETED_TABLE_KEY =
    "hbase.replication.drop.on.deleted.table";

  /** Maximum number of threads used by the replication source for shipping edits to the sinks */
  public static final int REPLICATION_SOURCE_MAXTHREADS_DEFAULT = 10;

  /** Configuration key for SplitLog manager timeout */
  public static final String HBASE_SPLITLOG_MANAGER_TIMEOUT = "hbase.splitlog.manager.timeout";

  /**
   * Configuration keys for Bucket cache
   */
  // TODO moving these bucket cache implementation specific configs to this level is violation of
  // encapsulation. But as these has to be referred from hbase-common and bucket cache
  // sits in hbase-server, there were no other go! Can we move the cache implementation to
  // hbase-common?

  /**
   * Current ioengine options in include: heap, offheap and file:PATH (where PATH is the path to the
   * file that will host the file-based cache. See BucketCache#getIOEngineFromName() for list of
   * supported ioengine options.
   * <p>
   * Set this option and a non-zero {@link #BUCKET_CACHE_SIZE_KEY} to enable bucket cache.
   */
  public static final String BUCKET_CACHE_IOENGINE_KEY = "hbase.bucketcache.ioengine";

  /**
   * When using bucket cache, it is the capacity in megabytes of the cache.
   */
  public static final String BUCKET_CACHE_SIZE_KEY = "hbase.bucketcache.size";

  /**
   * If the chosen ioengine can persist its state across restarts, the path to the file to persist
   * to. This file is NOT the data file. It is a file into which we will serialize the map of what
   * is in the data file. For example, if you pass the following argument as
   * BUCKET_CACHE_IOENGINE_KEY ("hbase.bucketcache.ioengine"),
   * <code>file:/tmp/bucketcache.data </code>, then we will write the bucketcache data to the file
   * <code>/tmp/bucketcache.data</code> but the metadata on where the data is in the supplied file
   * is an in-memory map that needs to be persisted across restarts. Where to store this in-memory
   * state is what you supply here: e.g. <code>/tmp/bucketcache.map</code>.
   */
  public static final String BUCKET_CACHE_PERSISTENT_PATH_KEY = "hbase.bucketcache.persistent.path";

  /**
   * HConstants for fast fail on the client side follow
   */
  /**
   * Config for enabling/disabling the fast fail mode.
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final String HBASE_CLIENT_FAST_FAIL_MODE_ENABLED =
    "hbase.client.fast.fail.mode.enabled";

  /**
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final boolean HBASE_CLIENT_ENABLE_FAST_FAIL_MODE_DEFAULT = false;

  /**
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final String HBASE_CLIENT_FAST_FAIL_THREASHOLD_MS =
    "hbase.client.fastfail.threshold";

  /**
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final long HBASE_CLIENT_FAST_FAIL_THREASHOLD_MS_DEFAULT = 60000;

  /**
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final String HBASE_CLIENT_FAILURE_MAP_CLEANUP_INTERVAL_MS =
    "hbase.client.failure.map.cleanup.interval";

  /**
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final long HBASE_CLIENT_FAILURE_MAP_CLEANUP_INTERVAL_MS_DEFAULT = 600000;

  /**
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final String HBASE_CLIENT_FAST_FAIL_CLEANUP_MS_DURATION_MS =
    "hbase.client.fast.fail.cleanup.duration";

  /**
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final long HBASE_CLIENT_FAST_FAIL_CLEANUP_DURATION_MS_DEFAULT = 600000;

  /**
   * @deprecated since 2.3.0, and in 3.0.0 the actually implementation will be removed so config
   *             this value will have no effect. The constants itself will be removed in 4.0.0.
   */
  @Deprecated
  public static final String HBASE_CLIENT_FAST_FAIL_INTERCEPTOR_IMPL =
    "hbase.client.fast.fail.interceptor.impl";

  /**
   * @deprecated since 2.4.0 and in 3.0.0, to be removed in 4.0.0, replaced by procedure-based
   *             distributed WAL splitter; see SplitWALManager.
   */
  @Deprecated
  public static final String HBASE_SPLIT_WAL_COORDINATED_BY_ZK = "hbase.split.wal.zk.coordinated";

  /**
   * @deprecated since 2.4.0 and in 3.0.0, to be removed in 4.0.0.
   */
  @Deprecated
  public static final boolean DEFAULT_HBASE_SPLIT_COORDINATED_BY_ZK = false;

  public static final String HBASE_SPLIT_WAL_MAX_SPLITTER = "hbase.regionserver.wal.max.splitters";

  public static final int DEFAULT_HBASE_SPLIT_WAL_MAX_SPLITTER = 2;

  /**
   * Config key for if the server should send backpressure and if the client should listen to that
   * backpressure from the server
   */
  public static final String ENABLE_CLIENT_BACKPRESSURE = "hbase.client.backpressure.enabled";
  public static final boolean DEFAULT_ENABLE_CLIENT_BACKPRESSURE = false;

  public static final String HEAP_OCCUPANCY_LOW_WATERMARK_KEY =
    "hbase.heap.occupancy.low_water_mark";
  public static final float DEFAULT_HEAP_OCCUPANCY_LOW_WATERMARK = 0.95f;
  public static final String HEAP_OCCUPANCY_HIGH_WATERMARK_KEY =
    "hbase.heap.occupancy.high_water_mark";
  public static final float DEFAULT_HEAP_OCCUPANCY_HIGH_WATERMARK = 0.98f;

  /**
   * The max number of threads used for splitting storefiles in parallel during the region split
   * process.
   */
  public static final String REGION_SPLIT_THREADS_MAX =
    "hbase.regionserver.region.split.threads.max";

  /** Canary config keys */
  // TODO: Move these defines to Canary Class
  public static final String HBASE_CANARY_WRITE_DATA_TTL_KEY = "hbase.canary.write.data.ttl";

  public static final String HBASE_CANARY_WRITE_PERSERVER_REGIONS_LOWERLIMIT_KEY =
    "hbase.canary.write.perserver.regions.lowerLimit";

  public static final String HBASE_CANARY_WRITE_PERSERVER_REGIONS_UPPERLIMIT_KEY =
    "hbase.canary.write.perserver.regions.upperLimit";

  public static final String HBASE_CANARY_WRITE_VALUE_SIZE_KEY = "hbase.canary.write.value.size";

  public static final String HBASE_CANARY_WRITE_TABLE_CHECK_PERIOD_KEY =
    "hbase.canary.write.table.check.period";

  public static final String HBASE_CANARY_READ_RAW_SCAN_KEY = "hbase.canary.read.raw.enabled";

  public static final String HBASE_CANARY_READ_ALL_CF = "hbase.canary.read.all.column.famliy";
  /**
   * Configuration keys for programmatic JAAS configuration for secured ZK interaction
   */
  public static final String ZK_CLIENT_KEYTAB_FILE = "hbase.zookeeper.client.keytab.file";
  public static final String ZK_CLIENT_KERBEROS_PRINCIPAL =
    "hbase.zookeeper.client.kerberos.principal";
  public static final String ZK_SERVER_KEYTAB_FILE = "hbase.zookeeper.server.keytab.file";
  public static final String ZK_SERVER_KERBEROS_PRINCIPAL =
    "hbase.zookeeper.server.kerberos.principal";

  /** Config key for hbase temporary directory in hdfs */
  public static final String TEMPORARY_FS_DIRECTORY_KEY = "hbase.fs.tmp.dir";

  /**
   * Don't use it! This'll get you the wrong path in a secure cluster. Use
   * FileSystem.getHomeDirectory() or "/user/" +
   * UserGroupInformation.getCurrentUser().getShortUserName()
   */
  public static final String DEFAULT_TEMPORARY_HDFS_DIRECTORY =
    "/user/" + System.getProperty("user.name") + "/hbase-staging";

  public static final String SNAPSHOT_RESTORE_TAKE_FAILSAFE_SNAPSHOT =
    "hbase.snapshot.restore.take.failsafe.snapshot";
  public static final boolean DEFAULT_SNAPSHOT_RESTORE_TAKE_FAILSAFE_SNAPSHOT = true;

  public static final String SNAPSHOT_RESTORE_FAILSAFE_NAME =
    "hbase.snapshot.restore.failsafe.name";
  public static final String DEFAULT_SNAPSHOT_RESTORE_FAILSAFE_NAME =
    "hbase-failsafe-{snapshot.name}-{restore.timestamp}";

  public static final String DEFAULT_LOSSY_COUNTING_ERROR_RATE =
    "hbase.util.default.lossycounting.errorrate";
  public static final String NOT_IMPLEMENTED = "Not implemented";

  // Default TTL - FOREVER
  public static final long DEFAULT_SNAPSHOT_TTL = 0;

  // User defined Default TTL config key
  public static final String DEFAULT_SNAPSHOT_TTL_CONFIG_KEY = "hbase.master.snapshot.ttl";

  // Regions Recovery based on high storeFileRefCount threshold value
  public static final String STORE_FILE_REF_COUNT_THRESHOLD =
    "hbase.regions.recovery.store.file.ref.count";

  // default -1 indicates there is no threshold on high storeRefCount
  public static final int DEFAULT_STORE_FILE_REF_COUNT_THRESHOLD = -1;

  public static final String REGIONS_RECOVERY_INTERVAL =
    "hbase.master.regions.recovery.check.interval";

  public static final int DEFAULT_REGIONS_RECOVERY_INTERVAL = 1200 * 1000; // Default 20 min

  /**
   * Configurations for master executor services.
   */
  public static final String MASTER_OPEN_REGION_THREADS =
    "hbase.master.executor.openregion.threads";
  public static final int MASTER_OPEN_REGION_THREADS_DEFAULT = 5;

  public static final String MASTER_CLOSE_REGION_THREADS =
    "hbase.master.executor.closeregion.threads";
  public static final int MASTER_CLOSE_REGION_THREADS_DEFAULT = 5;

  public static final String MASTER_SERVER_OPERATIONS_THREADS =
    "hbase.master.executor.serverops.threads";
  public static final int MASTER_SERVER_OPERATIONS_THREADS_DEFAULT = 5;

  /**
   * Number of threads used to dispatch merge operations to the regionservers.
   */
  public static final String MASTER_MERGE_DISPATCH_THREADS =
    "hbase.master.executor.merge.dispatch.threads";
  public static final int MASTER_MERGE_DISPATCH_THREADS_DEFAULT = 2;

  public static final String MASTER_META_SERVER_OPERATIONS_THREADS =
    "hbase.master.executor.meta.serverops.threads";
  public static final int MASTER_META_SERVER_OPERATIONS_THREADS_DEFAULT = 5;

  public static final String MASTER_LOG_REPLAY_OPS_THREADS =
    "hbase.master.executor.logreplayops.threads";
  public static final int MASTER_LOG_REPLAY_OPS_THREADS_DEFAULT = 10;

  public static final int DEFAULT_SLOW_LOG_RING_BUFFER_SIZE = 256;

  public static final String SLOW_LOG_BUFFER_ENABLED_KEY =
    "hbase.regionserver.slowlog.buffer.enabled";
  public static final boolean DEFAULT_ONLINE_LOG_PROVIDER_ENABLED = false;

  /** The slowlog info family as a string */
  private static final String SLOWLOG_INFO_FAMILY_STR = "info";

  /** The slowlog info family */
  public static final byte[] SLOWLOG_INFO_FAMILY = Bytes.toBytes(SLOWLOG_INFO_FAMILY_STR);

  public static final String SLOW_LOG_SYS_TABLE_ENABLED_KEY =
    "hbase.regionserver.slowlog.systable.enabled";
  public static final boolean DEFAULT_SLOW_LOG_SYS_TABLE_ENABLED_KEY = false;

  @Deprecated
  // since <need to know the version number> and will be removed in <version number>
  // Instead use hbase.regionserver.named.queue.chore.duration config property
  public static final String SLOW_LOG_SYS_TABLE_CHORE_DURATION_KEY =
    "hbase.slowlog.systable.chore.duration";
  // Default 10 mins.
  public static final int DEFAULT_SLOW_LOG_SYS_TABLE_CHORE_DURATION = 10 * 60 * 1000;

  public static final String SLOW_LOG_SCAN_PAYLOAD_ENABLED = "hbase.slowlog.scan.payload.enabled";
  public static final boolean SLOW_LOG_SCAN_PAYLOAD_ENABLED_DEFAULT = false;

  public static final String SHELL_TIMESTAMP_FORMAT_EPOCH_KEY =
    "hbase.shell.timestamp.format.epoch";

  public static final boolean DEFAULT_SHELL_TIMESTAMP_FORMAT_EPOCH = false;

  /**
   * Number of rows in a batch operation above which a warning will be logged.
   */
  public static final String BATCH_ROWS_THRESHOLD_NAME = "hbase.rpc.rows.warning.threshold";

  /**
   * Default value of {@link #BATCH_ROWS_THRESHOLD_NAME}
   */
  public static final int BATCH_ROWS_THRESHOLD_DEFAULT = 5000;

  /**
   * In some scenarios, such as the elastic scaling scenario on the cloud, the HBase client may not
   * be able to resolve the hostname of the newly added node. If the network is interconnected, the
   * client can actually access the HBase cluster nodes through ip. However, since the HBase client
   * obtains the Master/RS address info from or the ZK or the meta table, so the Master/RS of the
   * HBase cluster needs to expose the service with ip instead of the hostname. Therefore, We can
   * use hostname by default, but at the same time, we can also provide a config to support whether
   * to use ip for Master/RS service. See HBASE-27304 for details.
   */
  public final static String HBASE_SERVER_USEIP_ENABLED_KEY = "hbase.server.useip.enabled";

  /**
   * Default value of {@link #HBASE_SERVER_USEIP_ENABLED_KEY}
   */
  public final static boolean HBASE_SERVER_USEIP_ENABLED_DEFAULT = false;

  /**
   * Should the HMaster reject hosts of decommissioned RegionServers, bypass matching their port and
   * startcode parts of their ServerName or not? When True, the HMaster will reject a RegionServer's
   * request to `reportForDuty` if it's hostname exists in the list of decommissioned RegionServers
   * it maintains internally. Added in HBASE-28342.
   */
  public final static String REJECT_DECOMMISSIONED_HOSTS_KEY =
    "hbase.master.reject.decommissioned.hosts";

  /**
   * Default value of {@link #REJECT_DECOMMISSIONED_HOSTS_KEY}
   */
  public final static boolean REJECT_DECOMMISSIONED_HOSTS_DEFAULT = false;

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