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1   /**
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  package org.apache.hadoop.hbase;
19  
20  import static org.apache.hadoop.hbase.io.hfile.BlockType.MAGIC_LENGTH;
21  
22  import java.nio.ByteBuffer;
23  import java.nio.charset.Charset;
24  import java.util.Arrays;
25  import java.util.Collections;
26  import java.util.List;
27  import java.util.UUID;
28  import java.util.regex.Pattern;
29  
30  import org.apache.commons.lang.ArrayUtils;
31  import org.apache.hadoop.hbase.classification.InterfaceAudience;
32  import org.apache.hadoop.hbase.classification.InterfaceStability;
33  import org.apache.hadoop.hbase.util.Bytes;
34  
35  /**
36   * HConstants holds a bunch of HBase-related constants
37   */
38  @InterfaceAudience.Public
39  @InterfaceStability.Stable
40  public final class HConstants {
41    // NOTICE!!!! Please do not add a constants here, unless they are referenced by a lot of classes.
42  
43    //Bytes.UTF8_ENCODING should be updated if this changed
44    /** When we encode strings, we always specify UTF8 encoding */
45    public static final String UTF8_ENCODING = "UTF-8";
46  
47    //Bytes.UTF8_CHARSET should be updated if this changed
48    /** When we encode strings, we always specify UTF8 encoding */
49    public static final Charset UTF8_CHARSET = Charset.forName(UTF8_ENCODING);
50    /**
51     * Default block size for an HFile.
52     */
53    public final static int DEFAULT_BLOCKSIZE = 64 * 1024;
54  
55    /** Used as a magic return value while optimized index key feature enabled(HBASE-7845) */
56    public final static int INDEX_KEY_MAGIC = -2;
57    /*
58       * Name of directory that holds recovered edits written by the wal log
59       * splitting code, one per region
60       */
61    public static final String RECOVERED_EDITS_DIR = "recovered.edits";
62    /**
63     * The first four bytes of Hadoop RPC connections
64     */
65    public static final ByteBuffer RPC_HEADER = ByteBuffer.wrap("HBas".getBytes());
66    public static final byte RPC_CURRENT_VERSION = 0;
67  
68    // HFileBlock constants.
69  
70    /** The size data structures with minor version is 0 */
71    public static final int HFILEBLOCK_HEADER_SIZE_NO_CHECKSUM = MAGIC_LENGTH + 2 * Bytes.SIZEOF_INT
72        + Bytes.SIZEOF_LONG;
73    /** The size of a version 2 HFile block header, minor version 1.
74     * There is a 1 byte checksum type, followed by a 4 byte bytesPerChecksum
75     * followed by another 4 byte value to store sizeofDataOnDisk.
76     */
77    public static final int HFILEBLOCK_HEADER_SIZE = HFILEBLOCK_HEADER_SIZE_NO_CHECKSUM +
78      Bytes.SIZEOF_BYTE + 2 * Bytes.SIZEOF_INT;
79    /** Just an array of bytes of the right size. */
80    public static final byte[] HFILEBLOCK_DUMMY_HEADER = new byte[HFILEBLOCK_HEADER_SIZE];
81  
82    //End HFileBlockConstants.
83  
84    /**
85     * Status codes used for return values of bulk operations.
86     */
87    public enum OperationStatusCode {
88      NOT_RUN,
89      SUCCESS,
90      BAD_FAMILY,
91      SANITY_CHECK_FAILURE,
92      FAILURE;
93    }
94  
95    /** long constant for zero */
96    public static final Long ZERO_L = Long.valueOf(0L);
97    public static final String NINES = "99999999999999";
98    public static final String ZEROES = "00000000000000";
99  
100   // For migration
101 
102   /** name of version file */
103   public static final String VERSION_FILE_NAME = "hbase.version";
104 
105   /**
106    * Current version of file system.
107    * Version 4 supports only one kind of bloom filter.
108    * Version 5 changes versions in catalog table regions.
109    * Version 6 enables blockcaching on catalog tables.
110    * Version 7 introduces hfile -- hbase 0.19 to 0.20..
111    * Version 8 introduces namespace
112    */
113   // public static final String FILE_SYSTEM_VERSION = "6";
114   public static final String FILE_SYSTEM_VERSION = "8";
115 
116   // Configuration parameters
117 
118   //TODO: Is having HBase homed on port 60k OK?
119 
120   /** Cluster is in distributed mode or not */
121   public static final String CLUSTER_DISTRIBUTED = "hbase.cluster.distributed";
122 
123   /** Config for pluggable load balancers */
124   public static final String HBASE_MASTER_LOADBALANCER_CLASS = "hbase.master.loadbalancer.class";
125 
126   /** Cluster is standalone or pseudo-distributed */
127   public static final boolean CLUSTER_IS_LOCAL = false;
128 
129   /** Cluster is fully-distributed */
130   public static final boolean CLUSTER_IS_DISTRIBUTED = true;
131 
132   /** Default value for cluster distributed mode */
133   public static final boolean DEFAULT_CLUSTER_DISTRIBUTED = CLUSTER_IS_LOCAL;
134 
135   /** default host address */
136   public static final String DEFAULT_HOST = "0.0.0.0";
137 
138   /** Parameter name for port master listens on. */
139   public static final String MASTER_PORT = "hbase.master.port";
140 
141   /** default port that the master listens on */
142   public static final int DEFAULT_MASTER_PORT = 60000;
143 
144   /** default port for master web api */
145   public static final int DEFAULT_MASTER_INFOPORT = 60010;
146 
147   /** Configuration key for master web API port */
148   public static final String MASTER_INFO_PORT = "hbase.master.info.port";
149 
150   /** Parameter name for the master type being backup (waits for primary to go inactive). */
151   public static final String MASTER_TYPE_BACKUP = "hbase.master.backup";
152 
153   /** by default every master is a possible primary master unless the conf explicitly overrides it */
154   public static final boolean DEFAULT_MASTER_TYPE_BACKUP = false;
155 
156   /** Name of ZooKeeper quorum configuration parameter. */
157   public static final String ZOOKEEPER_QUORUM = "hbase.zookeeper.quorum";
158 
159   /** Name of ZooKeeper config file in conf/ directory. */
160   public static final String ZOOKEEPER_CONFIG_NAME = "zoo.cfg";
161 
162   /** Common prefix of ZooKeeper configuration properties */
163   public static final String ZK_CFG_PROPERTY_PREFIX =
164       "hbase.zookeeper.property.";
165 
166   public static final int ZK_CFG_PROPERTY_PREFIX_LEN =
167       ZK_CFG_PROPERTY_PREFIX.length();
168 
169   /**
170    * The ZK client port key in the ZK properties map. The name reflects the
171    * fact that this is not an HBase configuration key.
172    */
173   public static final String CLIENT_PORT_STR = "clientPort";
174 
175   /** Parameter name for the client port that the zookeeper listens on */
176   public static final String ZOOKEEPER_CLIENT_PORT =
177       ZK_CFG_PROPERTY_PREFIX + CLIENT_PORT_STR;
178 
179   /** Default client port that the zookeeper listens on */
180   public static final int DEFAULT_ZOOKEPER_CLIENT_PORT = 2181;
181 
182   /** Parameter name for the wait time for the recoverable zookeeper */
183   public static final String ZOOKEEPER_RECOVERABLE_WAITTIME = "hbase.zookeeper.recoverable.waittime";
184 
185   /** Default wait time for the recoverable zookeeper */
186   public static final long DEFAULT_ZOOKEPER_RECOVERABLE_WAITIME = 10000;
187 
188   /** Parameter name for the root dir in ZK for this cluster */
189   public static final String ZOOKEEPER_ZNODE_PARENT = "zookeeper.znode.parent";
190 
191   public static final String DEFAULT_ZOOKEEPER_ZNODE_PARENT = "/hbase";
192 
193   /**
194    * Parameter name for the limit on concurrent client-side zookeeper
195    * connections
196    */
197   public static final String ZOOKEEPER_MAX_CLIENT_CNXNS =
198       ZK_CFG_PROPERTY_PREFIX + "maxClientCnxns";
199 
200   /** Parameter name for the ZK data directory */
201   public static final String ZOOKEEPER_DATA_DIR =
202       ZK_CFG_PROPERTY_PREFIX + "dataDir";
203 
204   /** Parameter name for the ZK tick time */
205   public static final String ZOOKEEPER_TICK_TIME =
206       ZK_CFG_PROPERTY_PREFIX + "tickTime";
207 
208   /** Default limit on concurrent client-side zookeeper connections */
209   public static final int DEFAULT_ZOOKEPER_MAX_CLIENT_CNXNS = 300;
210 
211   /** Configuration key for ZooKeeper session timeout */
212   public static final String ZK_SESSION_TIMEOUT = "zookeeper.session.timeout";
213 
214   /** Default value for ZooKeeper session timeout */
215   public static final int DEFAULT_ZK_SESSION_TIMEOUT = 180 * 1000;
216 
217   /** Configuration key for whether to use ZK.multi */
218   public static final String ZOOKEEPER_USEMULTI = "hbase.zookeeper.useMulti";
219 
220   /** Parameter name for port region server listens on. */
221   public static final String REGIONSERVER_PORT = "hbase.regionserver.port";
222 
223   /** Default port region server listens on. */
224   public static final int DEFAULT_REGIONSERVER_PORT = 60020;
225 
226   /** default port for region server web api */
227   public static final int DEFAULT_REGIONSERVER_INFOPORT = 60030;
228 
229   /** A configuration key for regionserver info port */
230   public static final String REGIONSERVER_INFO_PORT =
231     "hbase.regionserver.info.port";
232 
233   /** A flag that enables automatic selection of regionserver info port */
234   public static final String REGIONSERVER_INFO_PORT_AUTO =
235       REGIONSERVER_INFO_PORT + ".auto";
236 
237   /** Parameter name for what region server implementation to use. */
238   public static final String REGION_SERVER_IMPL= "hbase.regionserver.impl";
239 
240   /** Parameter name for what master implementation to use. */
241   public static final String MASTER_IMPL= "hbase.master.impl";
242 
243   /** Parameter name for what hbase client implementation to use. */
244   public static final String HBASECLIENT_IMPL= "hbase.hbaseclient.impl";
245 
246   /** Parameter name for how often threads should wake up */
247   public static final String THREAD_WAKE_FREQUENCY = "hbase.server.thread.wakefrequency";
248 
249   /** Default value for thread wake frequency */
250   public static final int DEFAULT_THREAD_WAKE_FREQUENCY = 10 * 1000;
251 
252   /** Parameter name for how often we should try to write a version file, before failing */
253   public static final String VERSION_FILE_WRITE_ATTEMPTS = "hbase.server.versionfile.writeattempts";
254 
255   /** Parameter name for how often we should try to write a version file, before failing */
256   public static final int DEFAULT_VERSION_FILE_WRITE_ATTEMPTS = 3;
257 
258   /** Parameter name for how often a region should should perform a major compaction */
259   public static final String MAJOR_COMPACTION_PERIOD = "hbase.hregion.majorcompaction";
260 
261   /** Parameter name for the maximum batch of KVs to be used in flushes and compactions */
262   public static final String COMPACTION_KV_MAX = "hbase.hstore.compaction.kv.max";
263   public static final int COMPACTION_KV_MAX_DEFAULT = 10;
264 
265   /** Parameter name for HBase instance root directory */
266   public static final String HBASE_DIR = "hbase.rootdir";
267 
268   /** Parameter name for HBase client IPC pool type */
269   public static final String HBASE_CLIENT_IPC_POOL_TYPE = "hbase.client.ipc.pool.type";
270 
271   /** Parameter name for HBase client IPC pool size */
272   public static final String HBASE_CLIENT_IPC_POOL_SIZE = "hbase.client.ipc.pool.size";
273 
274   /** Parameter name for HBase client operation timeout, which overrides RPC timeout */
275   public static final String HBASE_CLIENT_OPERATION_TIMEOUT = "hbase.client.operation.timeout";
276 
277   /** Parameter name for HBase client operation timeout, which overrides RPC timeout */
278   public static final String HBASE_CLIENT_META_OPERATION_TIMEOUT =
279     "hbase.client.meta.operation.timeout";
280 
281   /** Default HBase client operation timeout, which is tantamount to a blocking call */
282   public static final int DEFAULT_HBASE_CLIENT_OPERATION_TIMEOUT = 1200000;
283 
284   /** Used to construct the name of the log directory for a region server */
285   public static final String HREGION_LOGDIR_NAME = "WALs";
286 
287   /** Used to construct the name of the splitlog directory for a region server */
288   public static final String SPLIT_LOGDIR_NAME = "splitWAL";
289 
290   /** Like the previous, but for old logs that are about to be deleted */
291   public static final String HREGION_OLDLOGDIR_NAME = "oldWALs";
292 
293   public static final String CORRUPT_DIR_NAME = "corrupt";
294 
295   /** Used by HBCK to sideline backup data */
296   public static final String HBCK_SIDELINEDIR_NAME = ".hbck";
297 
298   /** Any artifacts left from migration can be moved here */
299   public static final String MIGRATION_NAME = ".migration";
300 
301   /**
302    * The directory from which co-processor/custom filter jars can be loaded
303    * dynamically by the region servers. This value can be overridden by the
304    * hbase.dynamic.jars.dir config.
305    */
306   public static final String LIB_DIR = "lib";
307 
308   /** Used to construct the name of the compaction directory during compaction */
309   public static final String HREGION_COMPACTIONDIR_NAME = "compaction.dir";
310 
311   /** Conf key for the max file size after which we split the region */
312   public static final String HREGION_MAX_FILESIZE =
313       "hbase.hregion.max.filesize";
314 
315   /** Default maximum file size */
316   public static final long DEFAULT_MAX_FILE_SIZE = 10 * 1024 * 1024 * 1024L;
317 
318   /**
319    * The max number of threads used for opening and closing stores or store
320    * files in parallel
321    */
322   public static final String HSTORE_OPEN_AND_CLOSE_THREADS_MAX =
323     "hbase.hstore.open.and.close.threads.max";
324 
325   /**
326    * The default number for the max number of threads used for opening and
327    * closing stores or store files in parallel
328    */
329   public static final int DEFAULT_HSTORE_OPEN_AND_CLOSE_THREADS_MAX = 1;
330 
331   /**
332    * Block updates if memstore has hbase.hregion.memstore.block.multiplier
333    * times hbase.hregion.memstore.flush.size bytes.  Useful preventing
334    * runaway memstore during spikes in update traffic.
335    */
336   public static final String HREGION_MEMSTORE_BLOCK_MULTIPLIER =
337           "hbase.hregion.memstore.block.multiplier";
338 
339   /**
340    * Default value for hbase.hregion.memstore.block.multiplier
341    */
342   public static final int DEFAULT_HREGION_MEMSTORE_BLOCK_MULTIPLIER = 4;
343 
344   /** Conf key for the memstore size at which we flush the memstore */
345   public static final String HREGION_MEMSTORE_FLUSH_SIZE =
346       "hbase.hregion.memstore.flush.size";
347 
348   public static final String HREGION_EDITS_REPLAY_SKIP_ERRORS =
349       "hbase.hregion.edits.replay.skip.errors";
350 
351   public static final boolean DEFAULT_HREGION_EDITS_REPLAY_SKIP_ERRORS =
352       false;
353 
354   /** Maximum value length, enforced on KeyValue construction */
355   public static final int MAXIMUM_VALUE_LENGTH = Integer.MAX_VALUE - 1;
356 
357   /** name of the file for unique cluster ID */
358   public static final String CLUSTER_ID_FILE_NAME = "hbase.id";
359 
360   /** Default value for cluster ID */
361   public static final String CLUSTER_ID_DEFAULT = "default-cluster";
362 
363   // Always store the location of the root table's HRegion.
364   // This HRegion is never split.
365 
366   // region name = table + startkey + regionid. This is the row key.
367   // each row in the root and meta tables describes exactly 1 region
368   // Do we ever need to know all the information that we are storing?
369 
370   // Note that the name of the root table starts with "-" and the name of the
371   // meta table starts with "." Why? it's a trick. It turns out that when we
372   // store region names in memory, we use a SortedMap. Since "-" sorts before
373   // "." (and since no other table name can start with either of these
374   // characters, the root region will always be the first entry in such a Map,
375   // followed by all the meta regions (which will be ordered by their starting
376   // row key as well), followed by all user tables. So when the Master is
377   // choosing regions to assign, it will always choose the root region first,
378   // followed by the meta regions, followed by user regions. Since the root
379   // and meta regions always need to be on-line, this ensures that they will
380   // be the first to be reassigned if the server(s) they are being served by
381   // should go down.
382 
383 
384   /** The hbase:meta table's name. */
385   @Deprecated  // for compat from 0.94 -> 0.96.
386   public static final byte[] META_TABLE_NAME = TableName.META_TABLE_NAME.getName();
387 
388   public static final String BASE_NAMESPACE_DIR = "data";
389 
390   /** delimiter used between portions of a region name */
391   public static final int META_ROW_DELIMITER = ',';
392 
393   /** The catalog family as a string*/
394   public static final String CATALOG_FAMILY_STR = "info";
395 
396   /** The catalog family */
397   public static final byte [] CATALOG_FAMILY = Bytes.toBytes(CATALOG_FAMILY_STR);
398 
399   /** The RegionInfo qualifier as a string */
400   public static final String REGIONINFO_QUALIFIER_STR = "regioninfo";
401 
402   /** The regioninfo column qualifier */
403   public static final byte [] REGIONINFO_QUALIFIER = Bytes.toBytes(REGIONINFO_QUALIFIER_STR);
404 
405   /** The server column qualifier */
406   public static final byte [] SERVER_QUALIFIER = Bytes.toBytes("server");
407 
408   /** The startcode column qualifier */
409   public static final byte [] STARTCODE_QUALIFIER = Bytes.toBytes("serverstartcode");
410 
411   /** The open seqnum column qualifier */
412   public static final byte [] SEQNUM_QUALIFIER = Bytes.toBytes("seqnumDuringOpen");
413 
414   /** The state column qualifier */
415   public static final byte [] STATE_QUALIFIER = Bytes.toBytes("state");
416 
417   /**
418    * The serverName column qualifier. Its the server where the region is
419    * transitioning on, while column server is the server where the region is
420    * opened on. They are the same when the region is in state OPEN.
421    */
422   public static final byte [] SERVERNAME_QUALIFIER = Bytes.toBytes("sn");
423 
424   /** The lower-half split region column qualifier */
425   public static final byte [] SPLITA_QUALIFIER = Bytes.toBytes("splitA");
426 
427   /** The upper-half split region column qualifier */
428   public static final byte [] SPLITB_QUALIFIER = Bytes.toBytes("splitB");
429 
430   /** The lower-half merge region column qualifier */
431   public static final byte[] MERGEA_QUALIFIER = Bytes.toBytes("mergeA");
432 
433   /** The upper-half merge region column qualifier */
434   public static final byte[] MERGEB_QUALIFIER = Bytes.toBytes("mergeB");
435 
436   /**
437    * The meta table version column qualifier.
438    * We keep current version of the meta table in this column in <code>-ROOT-</code>
439    * table: i.e. in the 'info:v' column.
440    */
441   public static final byte [] META_VERSION_QUALIFIER = Bytes.toBytes("v");
442 
443   /**
444    * The current version of the meta table.
445    * - pre-hbase 0.92.  There is no META_VERSION column in the root table
446    * in this case. The meta has HTableDescriptor serialized into the HRegionInfo;
447    * - version 0 is 0.92 and 0.94. Meta data has serialized HRegionInfo's using
448    * Writable serialization, and HRegionInfo's does not contain HTableDescriptors.
449    * - version 1 for 0.96+ keeps HRegionInfo data structures, but changes the
450    * byte[] serialization from Writables to Protobuf.
451    * See HRegionInfo.VERSION
452    */
453   public static final short META_VERSION = 1;
454 
455   // Other constants
456 
457   /**
458    * An empty instance.
459    */
460   public static final byte [] EMPTY_BYTE_ARRAY = new byte [0];
461 
462   /**
463    * Used by scanners, etc when they want to start at the beginning of a region
464    */
465   public static final byte [] EMPTY_START_ROW = EMPTY_BYTE_ARRAY;
466 
467   /**
468    * Last row in a table.
469    */
470   public static final byte [] EMPTY_END_ROW = EMPTY_START_ROW;
471 
472   /**
473     * Used by scanners and others when they're trying to detect the end of a
474     * table
475     */
476   public static final byte [] LAST_ROW = EMPTY_BYTE_ARRAY;
477 
478   /**
479    * Max length a row can have because of the limitation in TFile.
480    */
481   public static final int MAX_ROW_LENGTH = Short.MAX_VALUE;
482 
483   /**
484    * Timestamp to use when we want to refer to the latest cell.
485    * This is the timestamp sent by clients when no timestamp is specified on
486    * commit.
487    */
488   public static final long LATEST_TIMESTAMP = Long.MAX_VALUE;
489 
490   /**
491    * Timestamp to use when we want to refer to the oldest cell.
492    */
493   public static final long OLDEST_TIMESTAMP = Long.MIN_VALUE;
494 
495   /**
496    * LATEST_TIMESTAMP in bytes form
497    */
498   public static final byte [] LATEST_TIMESTAMP_BYTES = {
499     // big-endian
500     (byte) (LATEST_TIMESTAMP >>> 56),
501     (byte) (LATEST_TIMESTAMP >>> 48),
502     (byte) (LATEST_TIMESTAMP >>> 40),
503     (byte) (LATEST_TIMESTAMP >>> 32),
504     (byte) (LATEST_TIMESTAMP >>> 24),
505     (byte) (LATEST_TIMESTAMP >>> 16),
506     (byte) (LATEST_TIMESTAMP >>> 8),
507     (byte) LATEST_TIMESTAMP,
508   };
509 
510   /**
511    * Define for 'return-all-versions'.
512    */
513   public static final int ALL_VERSIONS = Integer.MAX_VALUE;
514 
515   /**
516    * Unlimited time-to-live.
517    */
518 //  public static final int FOREVER = -1;
519   public static final int FOREVER = Integer.MAX_VALUE;
520 
521   /**
522    * Seconds in a week
523    */
524   public static final int WEEK_IN_SECONDS = 7 * 24 * 3600;
525 
526   /**
527    * Seconds in a day, hour and minute
528    */
529   public static final int DAY_IN_SECONDS = 24 * 60 * 60;
530   public static final int HOUR_IN_SECONDS = 60 * 60;
531   public static final int MINUTE_IN_SECONDS = 60;
532 
533   //TODO: although the following are referenced widely to format strings for
534   //      the shell. They really aren't a part of the public API. It would be
535   //      nice if we could put them somewhere where they did not need to be
536   //      public. They could have package visibility
537   public static final String NAME = "NAME";
538   public static final String VERSIONS = "VERSIONS";
539   public static final String IN_MEMORY = "IN_MEMORY";
540   public static final String METADATA = "METADATA";
541   public static final String CONFIGURATION = "CONFIGURATION";
542 
543   /**
544    * Retrying we multiply hbase.client.pause setting by what we have in this array until we
545    * run out of array items.  Retries beyond this use the last number in the array.  So, for
546    * example, if hbase.client.pause is 1 second, and maximum retries count
547    * hbase.client.retries.number is 10, we will retry at the following intervals:
548    * 1, 2, 3, 5, 10, 20, 40, 100, 100, 100.
549    * With 100ms, a back-off of 200 means 20s
550    */
551   public static final int RETRY_BACKOFF[] = {1, 2, 3, 5, 10, 20, 40, 100, 100, 100, 100, 200, 200};
552 
553   public static final String REGION_IMPL = "hbase.hregion.impl";
554 
555   /** modifyTable op for replacing the table descriptor */
556   public static enum Modify {
557     CLOSE_REGION,
558     TABLE_COMPACT,
559     TABLE_FLUSH,
560     TABLE_MAJOR_COMPACT,
561     TABLE_SET_HTD,
562     TABLE_SPLIT
563   }
564 
565   /**
566    * Scope tag for locally scoped data.
567    * This data will not be replicated.
568    */
569   public static final int REPLICATION_SCOPE_LOCAL = 0;
570 
571   /**
572    * Scope tag for globally scoped data.
573    * This data will be replicated to all peers.
574    */
575   public static final int REPLICATION_SCOPE_GLOBAL = 1;
576 
577   /**
578    * Default cluster ID, cannot be used to identify a cluster so a key with
579    * this value means it wasn't meant for replication.
580    */
581   public static final UUID DEFAULT_CLUSTER_ID = new UUID(0L,0L);
582 
583     /**
584      * Parameter name for maximum number of bytes returned when calling a
585      * scanner's next method.
586      */
587   public static final String HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE_KEY =
588       "hbase.client.scanner.max.result.size";
589 
590   /**
591    * Parameter name for maximum number of bytes returned when calling a scanner's next method.
592    * Controlled by the server.
593    */
594   public static final String HBASE_SERVER_SCANNER_MAX_RESULT_SIZE_KEY =
595       "hbase.server.scanner.max.result.size";
596 
597   /**
598    * Maximum number of bytes returned when calling a scanner's next method.
599    * Note that when a single row is larger than this limit the row is still
600    * returned completely.
601    *
602    * The default value is 2MB.
603    */
604   public static final long DEFAULT_HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE = 2 * 1024 * 1024;
605 
606   /**
607    * Maximum number of bytes returned when calling a scanner's next method.
608    * Note that when a single row is larger than this limit the row is still
609    * returned completely.
610    * Safety setting to protect the region server.
611    *
612    * The default value unlimited for backwards compatibility
613    */
614   public static final long DEFAULT_HBASE_SERVER_SCANNER_MAX_RESULT_SIZE = Long.MAX_VALUE;
615 
616   /**
617    * Parameter name for client pause value, used mostly as value to wait
618    * before running a retry of a failed get, region lookup, etc.
619    */
620   public static final String HBASE_CLIENT_PAUSE = "hbase.client.pause";
621 
622   /**
623    * Default value of {@link #HBASE_CLIENT_PAUSE}.
624    */
625   public static final long DEFAULT_HBASE_CLIENT_PAUSE = 100;
626 
627   /**
628    * The maximum number of concurrent connections the client will maintain.
629    */
630   public static final String HBASE_CLIENT_MAX_TOTAL_TASKS = "hbase.client.max.total.tasks";
631 
632   /**
633    * Default value of {@link #HBASE_CLIENT_MAX_TOTAL_TASKS}.
634    */
635   public static final int DEFAULT_HBASE_CLIENT_MAX_TOTAL_TASKS = 100;
636 
637   /**
638    * The maximum number of concurrent connections the client will maintain to a single
639    * RegionServer.
640    */
641   public static final String HBASE_CLIENT_MAX_PERSERVER_TASKS = "hbase.client.max.perserver.tasks";
642 
643   /**
644    * Default value of {@link #HBASE_CLIENT_MAX_PERSERVER_TASKS}.
645    */
646   public static final int DEFAULT_HBASE_CLIENT_MAX_PERSERVER_TASKS = 2;
647 
648   /**
649    * The maximum number of concurrent connections the client will maintain to a single
650    * Region.
651    */
652   public static final String HBASE_CLIENT_MAX_PERREGION_TASKS = "hbase.client.max.perregion.tasks";
653 
654   /**
655    * Default value of {@link #HBASE_CLIENT_MAX_PERREGION_TASKS}.
656    */
657   public static final int DEFAULT_HBASE_CLIENT_MAX_PERREGION_TASKS = 1;
658 
659   /**
660    * Parameter name for server pause value, used mostly as value to wait before
661    * running a retry of a failed operation.
662    */
663   public static final String HBASE_SERVER_PAUSE = "hbase.server.pause";
664 
665   /**
666    * Default value of {@link #HBASE_SERVER_PAUSE}.
667    */
668   public static final int DEFAULT_HBASE_SERVER_PAUSE = 1000;
669 
670   /**
671    * Parameter name for maximum retries, used as maximum for all retryable
672    * operations such as fetching of the root region from root region server,
673    * getting a cell's value, starting a row update, etc.
674    */
675   public static final String HBASE_CLIENT_RETRIES_NUMBER = "hbase.client.retries.number";
676 
677   /**
678    * Default value of {@link #HBASE_CLIENT_RETRIES_NUMBER}.
679    */
680   public static final int DEFAULT_HBASE_CLIENT_RETRIES_NUMBER = 31;
681 
682   /**
683    * Parameter name for client region location prefetch toggle.
684    */
685   public static String HBASE_CLIENT_PREFETCH = "hbase.client.prefetch";
686 
687   /**
688    * Default value of {@link #HBASE_CLIENT_PREFETCH}.
689    */
690   public static boolean DEFAULT_HBASE_CLIENT_PREFETCH = true;
691 
692   /**
693    * Parameter name for client prefetch limit, used as the maximum number of regions
694    * info that will be prefetched.
695    */
696   public static String HBASE_CLIENT_PREFETCH_LIMIT = "hbase.client.prefetch.limit";
697 
698   /**
699    * Default value of {@link #HBASE_CLIENT_PREFETCH_LIMIT}.
700    */
701   public static int DEFAULT_HBASE_CLIENT_PREFETCH_LIMIT = 10;
702 
703   /**
704    * Parameter name to set the default scanner caching for all clients.
705    */
706   public static final String HBASE_CLIENT_SCANNER_CACHING = "hbase.client.scanner.caching";
707 
708   /**
709    * Default value for {@link #HBASE_CLIENT_SCANNER_CACHING}
710    */
711   public static final int DEFAULT_HBASE_CLIENT_SCANNER_CACHING = 100;
712 
713   /**
714    * Parameter name for number of versions, kept by meta table.
715    */
716   public static String HBASE_META_VERSIONS = "hbase.meta.versions";
717 
718   /**
719    * Default value of {@link #HBASE_META_VERSIONS}.
720    */
721   public static int DEFAULT_HBASE_META_VERSIONS = 10;
722 
723   /**
724    * Parameter name for number of versions, kept by meta table.
725    */
726   public static String HBASE_META_BLOCK_SIZE = "hbase.meta.blocksize";
727 
728   /**
729    * Default value of {@link #HBASE_META_BLOCK_SIZE}.
730    */
731   public static int DEFAULT_HBASE_META_BLOCK_SIZE = 8 * 1024;
732 
733   /**
734    * Parameter name for number of rows that will be fetched when calling next on
735    * a scanner if it is not served from memory. Higher caching values will
736    * enable faster scanners but will eat up more memory and some calls of next
737    * may take longer and longer times when the cache is empty.
738    */
739   public static final String HBASE_META_SCANNER_CACHING = "hbase.meta.scanner.caching";
740 
741   /**
742    * Default value of {@link #HBASE_META_SCANNER_CACHING}.
743    */
744   public static final int DEFAULT_HBASE_META_SCANNER_CACHING = 100;
745 
746   /**
747    * Parameter name for unique identifier for this {@link org.apache.hadoop.conf.Configuration}
748    * instance. If there are two or more {@link org.apache.hadoop.conf.Configuration} instances that,
749    * for all intents and purposes, are the same except for their instance ids, then they will not be
750    * able to share the same org.apache.hadoop.hbase.client.HConnection instance. On the other hand,
751    * even if the instance ids are the same, it could result in non-shared
752    * org.apache.hadoop.hbase.client.HConnection instances if some of the other connection parameters
753    * differ.
754    */
755   public static final String HBASE_CLIENT_INSTANCE_ID = "hbase.client.instance.id";
756 
757   /**
758    * The client scanner timeout period in milliseconds.
759    */
760   public static final String HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD = "hbase.client.scanner.timeout.period";
761 
762   /**
763    * Use {@link #HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD} instead.
764    * @deprecated This config option is deprecated. Will be removed at later releases after 0.96.
765    */
766   @Deprecated
767   public static final String HBASE_REGIONSERVER_LEASE_PERIOD_KEY =
768       "hbase.regionserver.lease.period";
769 
770   /**
771    * Default value of {@link #HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD}.
772    */
773   public static final int DEFAULT_HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD = 60000;
774 
775   /**
776    * timeout for each RPC
777    */
778   public static final String HBASE_RPC_TIMEOUT_KEY = "hbase.rpc.timeout";
779 
780   /**
781    * Default value of {@link #HBASE_RPC_TIMEOUT_KEY}
782    */
783   public static final int DEFAULT_HBASE_RPC_TIMEOUT = 60000;
784 
785   /**
786    * timeout for short operation RPC
787    */
788   public static final String HBASE_RPC_SHORTOPERATION_TIMEOUT_KEY =
789       "hbase.rpc.shortoperation.timeout";
790 
791   /**
792    * Default value of {@link #HBASE_RPC_SHORTOPERATION_TIMEOUT_KEY}
793    */
794   public static final int DEFAULT_HBASE_RPC_SHORTOPERATION_TIMEOUT = 10000;
795 
796   /**
797    * Value indicating the server name was saved with no sequence number.
798    */
799   public static final long NO_SEQNUM = -1;
800 
801 
802   /*
803    * cluster replication constants.
804    */
805   public static final String
806       REPLICATION_ENABLE_KEY = "hbase.replication";
807   public static final boolean
808       REPLICATION_ENABLE_DEFAULT = true;
809   public static final String
810       REPLICATION_SOURCE_SERVICE_CLASSNAME = "hbase.replication.source.service";
811   public static final String
812       REPLICATION_SINK_SERVICE_CLASSNAME = "hbase.replication.sink.service";
813   public static final String REPLICATION_SERVICE_CLASSNAME_DEFAULT =
814     "org.apache.hadoop.hbase.replication.regionserver.Replication";
815 
816   /** HBCK special code name used as server name when manipulating ZK nodes */
817   public static final String HBCK_CODE_NAME = "HBCKServerName";
818 
819   public static final String KEY_FOR_HOSTNAME_SEEN_BY_MASTER =
820     "hbase.regionserver.hostname.seen.by.master";
821 
822   public static final String HBASE_MASTER_LOGCLEANER_PLUGINS =
823       "hbase.master.logcleaner.plugins";
824 
825   public static final String HBASE_REGION_SPLIT_POLICY_KEY =
826     "hbase.regionserver.region.split.policy";
827 
828   /** Whether nonces are enabled; default is true. */
829   public static final String HBASE_RS_NONCES_ENABLED = "hbase.regionserver.nonces.enabled";
830 
831   /**
832    * Configuration key for the size of the block cache
833    */
834   public static final String HFILE_BLOCK_CACHE_SIZE_KEY =
835     "hfile.block.cache.size";
836 
837   public static final float HFILE_BLOCK_CACHE_SIZE_DEFAULT = 0.25f;
838 
839   /*
840     * Minimum percentage of free heap necessary for a successful cluster startup.
841     */
842   public static final float HBASE_CLUSTER_MINIMUM_MEMORY_THRESHOLD = 0.2f;
843 
844   public static final Pattern CP_HTD_ATTR_KEY_PATTERN =
845       Pattern.compile("^coprocessor\\$([0-9]+)$", Pattern.CASE_INSENSITIVE);
846   public static final Pattern CP_HTD_ATTR_VALUE_PATTERN =
847       Pattern.compile("(^[^\\|]*)\\|([^\\|]+)\\|[\\s]*([\\d]*)[\\s]*(\\|.*)?$");
848 
849   public static final String CP_HTD_ATTR_VALUE_PARAM_KEY_PATTERN = "[^=,]+";
850   public static final String CP_HTD_ATTR_VALUE_PARAM_VALUE_PATTERN = "[^,]+";
851   public static final Pattern CP_HTD_ATTR_VALUE_PARAM_PATTERN = Pattern.compile(
852       "(" + CP_HTD_ATTR_VALUE_PARAM_KEY_PATTERN + ")=(" +
853       CP_HTD_ATTR_VALUE_PARAM_VALUE_PATTERN + "),?");
854 
855   /** The delay when re-trying a socket operation in a loop (HBASE-4712) */
856   public static final int SOCKET_RETRY_WAIT_MS = 200;
857 
858   /** Host name of the local machine */
859   public static final String LOCALHOST = "localhost";
860 
861   /**
862    * If this parameter is set to true, then hbase will read
863    * data and then verify checksums. Checksum verification
864    * inside hdfs will be switched off.  However, if the hbase-checksum
865    * verification fails, then it will switch back to using
866    * hdfs checksums for verifiying data that is being read from storage.
867    *
868    * If this parameter is set to false, then hbase will not
869    * verify any checksums, instead it will depend on checksum verification
870    * being done in the hdfs client.
871    */
872   public static final String HBASE_CHECKSUM_VERIFICATION =
873       "hbase.regionserver.checksum.verify";
874 
875   public static final String LOCALHOST_IP = "127.0.0.1";
876 
877   /** Conf key that enables unflushed WAL edits directly being replayed to region servers */
878   public static final String DISTRIBUTED_LOG_REPLAY_KEY = "hbase.master.distributed.log.replay";
879   public static final boolean DEFAULT_DISTRIBUTED_LOG_REPLAY_CONFIG = false;
880   public static final String DISALLOW_WRITES_IN_RECOVERING =
881       "hbase.regionserver.disallow.writes.when.recovering";
882   public static final boolean DEFAULT_DISALLOW_WRITES_IN_RECOVERING_CONFIG = false;
883 
884   public static final String REGION_SERVER_HANDLER_COUNT = "hbase.regionserver.handler.count";
885   public static final int DEFAULT_REGION_SERVER_HANDLER_COUNT = 30;
886 
887   /*
888    * REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT:
889    * -1  => Disable aborting
890    * 0   => Abort if even a single handler has died
891    * 0.x => Abort only when this percent of handlers have died
892    * 1   => Abort only all of the handers have died
893    */
894   public static final String REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT =
895       "hbase.regionserver.handler.abort.on.error.percent";
896   public static final float DEFAULT_REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT = -1;
897   
898   public static final String REGION_SERVER_META_HANDLER_COUNT =
899       "hbase.regionserver.metahandler.count";
900   public static final int DEFAULT_REGION_SERVER_META_HANDLER_COUNT = 10;
901 
902   public static final String REGION_SERVER_REPLICATION_HANDLER_COUNT =
903       "hbase.regionserver.replication.handler.count";
904   public static final int DEFAULT_REGION_SERVER_REPLICATION_HANDLER_COUNT = 3;
905 
906   public static final String MASTER_HANDLER_COUNT = "hbase.master.handler.count";
907   public static final int DEFAULT_MASTER_HANLDER_COUNT = 25;
908 
909   /** Conf key that specifies timeout value to wait for a region ready */
910   public static final String LOG_REPLAY_WAIT_REGION_TIMEOUT =
911       "hbase.master.log.replay.wait.region.timeout";
912 
913   /**
914    * The name of the configuration parameter that specifies
915    * the number of bytes in a newly created checksum chunk.
916    */
917   public static final String BYTES_PER_CHECKSUM =
918       "hbase.hstore.bytes.per.checksum";
919 
920   /**
921    * The name of the configuration parameter that specifies
922    * the name of an algorithm that is used to compute checksums
923    * for newly created blocks.
924    */
925   public static final String CHECKSUM_TYPE_NAME =
926       "hbase.hstore.checksum.algorithm";
927 
928   /** Enable file permission modification from standard hbase */
929   public static final String ENABLE_DATA_FILE_UMASK = "hbase.data.umask.enable";
930   /** File permission umask to use when creating hbase data files */
931   public static final String DATA_FILE_UMASK_KEY = "hbase.data.umask";
932 
933   /** Configuration name of HLog Compression */
934   public static final String ENABLE_WAL_COMPRESSION =
935     "hbase.regionserver.wal.enablecompression";
936 
937   /** Region in Transition metrics threshold time */
938   public static final String METRICS_RIT_STUCK_WARNING_THRESHOLD =
939       "hbase.metrics.rit.stuck.warning.threshold";
940 
941   public static final String LOAD_BALANCER_SLOP_KEY = "hbase.regions.slop";
942 
943   /**
944    * The byte array represents for NO_NEXT_INDEXED_KEY;
945    * The actual value is irrelevant because this is always compared by reference.
946    */
947   public static final byte [] NO_NEXT_INDEXED_KEY = Bytes.toBytes("NO_NEXT_INDEXED_KEY");
948   /** delimiter used between portions of a region name */
949   public static final int DELIMITER = ',';
950   public static final String HBASE_CONFIG_READ_ZOOKEEPER_CONFIG =
951       "hbase.config.read.zookeeper.config";
952   public static final boolean DEFAULT_HBASE_CONFIG_READ_ZOOKEEPER_CONFIG =
953       false;
954 
955   /**
956    * QOS attributes: these attributes are used to demarcate RPC call processing
957    * by different set of handlers. For example, HIGH_QOS tagged methods are
958    * handled by high priority handlers.
959    */
960   public static final int NORMAL_QOS = 0;
961   public static final int QOS_THRESHOLD = 10;
962   public static final int HIGH_QOS = 100;
963   public static final int REPLICATION_QOS = 5; // normal_QOS < replication_QOS < high_QOS
964   public static final int REPLAY_QOS = 6; // REPLICATION_QOS < REPLAY_QOS < high_QOS
965 
966   /** Directory under /hbase where archived hfiles are stored */
967   public static final String HFILE_ARCHIVE_DIRECTORY = "archive";
968 
969   /**
970    * Name of the directory to store all snapshots. See SnapshotDescriptionUtils for
971    * remaining snapshot constants; this is here to keep HConstants dependencies at a minimum and
972    * uni-directional.
973    */
974   public static final String SNAPSHOT_DIR_NAME = ".hbase-snapshot";
975 
976   /* Name of old snapshot directory. See HBASE-8352 for details on why it needs to be renamed */
977   public static final String OLD_SNAPSHOT_DIR_NAME = ".snapshot";
978 
979   /** Temporary directory used for table creation and deletion */
980   public static final String HBASE_TEMP_DIRECTORY = ".tmp";
981   /**
982    * The period (in milliseconds) between computing region server point in time metrics
983    */
984   public static final String REGIONSERVER_METRICS_PERIOD = "hbase.regionserver.metrics.period";
985   public static final long DEFAULT_REGIONSERVER_METRICS_PERIOD = 5000;
986   /** Directories that are not HBase table directories */
987   public static final List<String> HBASE_NON_TABLE_DIRS =
988     Collections.unmodifiableList(Arrays.asList(new String[] {
989       HBCK_SIDELINEDIR_NAME, HBASE_TEMP_DIRECTORY, MIGRATION_NAME
990     }));
991 
992   /** Directories that are not HBase user table directories */
993   public static final List<String> HBASE_NON_USER_TABLE_DIRS =
994     Collections.unmodifiableList(Arrays.asList((String[])ArrayUtils.addAll(
995       new String[] { TableName.META_TABLE_NAME.getNameAsString() },
996       HBASE_NON_TABLE_DIRS.toArray())));
997 
998   /** Health script related settings. */
999   public static final String HEALTH_SCRIPT_LOC = "hbase.node.health.script.location";
1000   public static final String HEALTH_SCRIPT_TIMEOUT = "hbase.node.health.script.timeout";
1001   public static final String HEALTH_CHORE_WAKE_FREQ =
1002       "hbase.node.health.script.frequency";
1003   public static final long DEFAULT_HEALTH_SCRIPT_TIMEOUT = 60000;
1004   /**
1005    * The maximum number of health check failures a server can encounter consecutively.
1006    */
1007   public static final String HEALTH_FAILURE_THRESHOLD =
1008       "hbase.node.health.failure.threshold";
1009   public static final int DEFAULT_HEALTH_FAILURE_THRESHOLD = 3;
1010 
1011 
1012   /**
1013    * Setting to activate, or not, the publication of the status by the master. Default
1014    *  notification is by a multicast message.
1015    */
1016   public static final String STATUS_PUBLISHED = "hbase.status.published";
1017   public static final boolean STATUS_PUBLISHED_DEFAULT = false;
1018 
1019   /**
1020    * IP to use for the multicast status messages between the master and the clients.
1021    * The default address is chosen as one among others within the ones suitable for multicast
1022    * messages.
1023    */
1024   public static final String STATUS_MULTICAST_ADDRESS = "hbase.status.multicast.address.ip";
1025   public static final String DEFAULT_STATUS_MULTICAST_ADDRESS = "226.1.1.3";
1026 
1027   /**
1028    * The address to use for binding the local socket for receiving multicast. Defaults to
1029    * 0.0.0.0.
1030    * @see <a href="https://issues.apache.org/jira/browse/HBASE-9961">HBASE-9961</a>
1031    */
1032   public static final String STATUS_MULTICAST_BIND_ADDRESS =
1033       "hbase.status.multicast.bind.address.ip";
1034   public static final String DEFAULT_STATUS_MULTICAST_BIND_ADDRESS = "0.0.0.0";
1035 
1036   /**
1037    * The port to use for the multicast messages.
1038    */
1039   public static final String STATUS_MULTICAST_PORT = "hbase.status.multicast.address.port";
1040   public static final int DEFAULT_STATUS_MULTICAST_PORT = 60100;
1041 
1042   public static final long NO_NONCE = 0;
1043 
1044   /** Default cipher for encryption */
1045   public static final String CIPHER_AES = "AES";
1046 
1047   /** Configuration key for the crypto algorithm provider, a class name */
1048   @InterfaceStability.Unstable
1049   public static final String CRYPTO_CIPHERPROVIDER_CONF_KEY = "hbase.crypto.cipherprovider";
1050 
1051   /** Configuration key for the crypto key provider, a class name */
1052   @InterfaceStability.Unstable
1053   public static final String CRYPTO_KEYPROVIDER_CONF_KEY = "hbase.crypto.keyprovider";
1054 
1055   /** Configuration key for the crypto key provider parameters */
1056   @InterfaceStability.Unstable
1057   public static final String CRYPTO_KEYPROVIDER_PARAMETERS_KEY =
1058       "hbase.crypto.keyprovider.parameters";
1059 
1060   /** Configuration key for the name of the master key for the cluster, a string */
1061   @InterfaceStability.Unstable
1062   public static final String CRYPTO_MASTERKEY_NAME_CONF_KEY = "hbase.crypto.master.key.name";
1063 
1064   /** Configuration key for the name of the alternate master key for the cluster, a string */
1065   @InterfaceStability.Unstable
1066   public static final String CRYPTO_MASTERKEY_ALTERNATE_NAME_CONF_KEY =
1067     "hbase.crypto.master.alternate.key.name";
1068 
1069   /** Configuration key for the algorithm to use when encrypting the WAL, a string */
1070   @InterfaceStability.Unstable
1071   public static final String CRYPTO_WAL_ALGORITHM_CONF_KEY = "hbase.crypto.wal.algorithm";
1072 
1073   /** Configuration key for the name of the master WAL encryption key for the cluster, a string */
1074   @InterfaceStability.Unstable
1075   public static final String CRYPTO_WAL_KEY_NAME_CONF_KEY = "hbase.crypto.wal.key.name";
1076 
1077   /** Configuration key for the algorithm used for creating jks key, a string */
1078   public static final String CRYPTO_KEY_ALGORITHM_CONF_KEY = "hbase.crypto.key.algorithm";
1079 
1080   /** Configuration key for the name of the alternate cipher algorithm for the cluster, a string */
1081   public static final String CRYPTO_ALTERNATE_KEY_ALGORITHM_CONF_KEY =
1082       "hbase.crypto.alternate.key.algorithm";
1083 
1084   /** Configuration key for enabling WAL encryption, a boolean */
1085   public static final String ENABLE_WAL_ENCRYPTION = "hbase.regionserver.wal.encryption";
1086 
1087   /** Configuration key for setting RPC codec class name */
1088   public static final String RPC_CODEC_CONF_KEY = "hbase.client.rpc.codec";
1089 
1090   /** Configuration key for setting replication codec class name */
1091   public static final String REPLICATION_CODEC_CONF_KEY = "hbase.replication.rpc.codec";
1092 
1093   /** Config key for if the server should send backpressure and if the client should listen to
1094    * that backpressure from the server */
1095   public static final String ENABLE_CLIENT_BACKPRESSURE = "hbase.client.backpressure.enabled";
1096   public static final boolean DEFAULT_ENABLE_CLIENT_BACKPRESSURE = false;
1097 
1098   public static final String HEAP_OCCUPANCY_LOW_WATERMARK_KEY =
1099       "hbase.heap.occupancy.low_water_mark";
1100   public static final float DEFAULT_HEAP_OCCUPANCY_LOW_WATERMARK = 0.95f;
1101   public static final String HEAP_OCCUPANCY_HIGH_WATERMARK_KEY =
1102       "hbase.heap.occupancy.high_water_mark";
1103   public static final float DEFAULT_HEAP_OCCUPANCY_HIGH_WATERMARK = 0.98f;
1104 
1105   /**
1106    * The max number of threads used for splitting storefiles in parallel during
1107    * the region split process.
1108    */
1109   public static final String REGION_SPLIT_THREADS_MAX =
1110     "hbase.regionserver.region.split.threads.max";
1111 
1112   /** Canary config keys */
1113   public static final String HBASE_CANARY_WRITE_DATA_TTL_KEY = "hbase.canary.write.data.ttl";
1114 
1115   public static final String HBASE_CANARY_WRITE_PERSERVER_REGIONS_LOWERLIMIT_KEY =
1116       "hbase.canary.write.perserver.regions.lowerLimit";
1117 
1118   public static final String HBASE_CANARY_WRITE_PERSERVER_REGIONS_UPPERLIMIT_KEY =
1119       "hbase.canary.write.perserver.regions.upperLimit";
1120 
1121   public static final String HBASE_CANARY_WRITE_VALUE_SIZE_KEY = "hbase.canary.write.value.size";
1122 
1123   public static final String HBASE_CANARY_WRITE_TABLE_CHECK_PERIOD_KEY =
1124       "hbase.canary.write.table.check.period";
1125 
1126   private HConstants() {
1127     // Can't be instantiated with this ctor.
1128   }
1129 }