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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.charset.Charset;
23  import java.util.Arrays;
24  import java.util.Collections;
25  import java.util.List;
26  import java.util.UUID;
27  import java.util.regex.Pattern;
28  
29  import org.apache.commons.lang.ArrayUtils;
30  import org.apache.hadoop.hbase.classification.InterfaceAudience;
31  import org.apache.hadoop.hbase.classification.InterfaceStability;
32  import org.apache.hadoop.hbase.util.Bytes;
33  
34  /**
35   * HConstants holds a bunch of HBase-related constants
36   */
37  @InterfaceAudience.Public
38  @InterfaceStability.Stable
39  public final class HConstants {
40    // NOTICE!!!! Please do not add a constants here, unless they are referenced by a lot of classes.
41  
42    //Bytes.UTF8_ENCODING should be updated if this changed
43    /** When we encode strings, we always specify UTF8 encoding */
44    public static final String UTF8_ENCODING = "UTF-8";
45  
46    //Bytes.UTF8_CHARSET should be updated if this changed
47    /** When we encode strings, we always specify UTF8 encoding */
48    public static final Charset UTF8_CHARSET = Charset.forName(UTF8_ENCODING);
49    /**
50     * Default block size for an HFile.
51     */
52    public final static int DEFAULT_BLOCKSIZE = 64 * 1024;
53  
54    /** Used as a magic return value while optimized index key feature enabled(HBASE-7845) */
55    public final static int INDEX_KEY_MAGIC = -2;
56    /*
57       * Name of directory that holds recovered edits written by the wal log
58       * splitting code, one per region
59       */
60    public static final String RECOVERED_EDITS_DIR = "recovered.edits";
61    /**
62     * The first four bytes of Hadoop RPC connections
63     */
64    public static final byte[] RPC_HEADER = new byte[] { 'H', 'B', 'a', 's' };
65    public static final byte RPC_CURRENT_VERSION = 0;
66  
67    // HFileBlock constants.
68  
69    /** The size data structures with minor version is 0 */
70    public static final int HFILEBLOCK_HEADER_SIZE_NO_CHECKSUM = MAGIC_LENGTH + 2 * Bytes.SIZEOF_INT
71        + Bytes.SIZEOF_LONG;
72    /** The size of a version 2 HFile block header, minor version 1.
73     * There is a 1 byte checksum type, followed by a 4 byte bytesPerChecksum
74     * followed by another 4 byte value to store sizeofDataOnDisk.
75     */
76    public static final int HFILEBLOCK_HEADER_SIZE = HFILEBLOCK_HEADER_SIZE_NO_CHECKSUM +
77      Bytes.SIZEOF_BYTE + 2 * Bytes.SIZEOF_INT;
78    /** Just an array of bytes of the right size. */
79    public static final byte[] HFILEBLOCK_DUMMY_HEADER = new byte[HFILEBLOCK_HEADER_SIZE];
80  
81    //End HFileBlockConstants.
82  
83    /**
84     * Status codes used for return values of bulk operations.
85     */
86    @InterfaceAudience.Private
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 = 16000;
143 
144   /** default port for master web api */
145   public static final int DEFAULT_MASTER_INFOPORT = 16010;
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   /**
154    * by default every master is a possible primary master unless the conf explicitly overrides it
155    */
156   public static final boolean DEFAULT_MASTER_TYPE_BACKUP = false;
157 
158   /** Name of ZooKeeper quorum configuration parameter. */
159   public static final String ZOOKEEPER_QUORUM = "hbase.zookeeper.quorum";
160 
161   /** Name of ZooKeeper config file in conf/ directory. */
162   public static final String ZOOKEEPER_CONFIG_NAME = "zoo.cfg";
163 
164   /** Common prefix of ZooKeeper configuration properties */
165   public static final String ZK_CFG_PROPERTY_PREFIX =
166       "hbase.zookeeper.property.";
167 
168   public static final int ZK_CFG_PROPERTY_PREFIX_LEN =
169       ZK_CFG_PROPERTY_PREFIX.length();
170 
171   /**
172    * The ZK client port key in the ZK properties map. The name reflects the
173    * fact that this is not an HBase configuration key.
174    */
175   public static final String CLIENT_PORT_STR = "clientPort";
176 
177   /** Parameter name for the client port that the zookeeper listens on */
178   public static final String ZOOKEEPER_CLIENT_PORT =
179       ZK_CFG_PROPERTY_PREFIX + CLIENT_PORT_STR;
180 
181   /** Default client port that the zookeeper listens on */
182   public static final int DEFAULT_ZOOKEPER_CLIENT_PORT = 2181;
183 
184   /**
185    * Parameter name for the wait time for the recoverable zookeeper
186    */
187   public static final String ZOOKEEPER_RECOVERABLE_WAITTIME =
188       "hbase.zookeeper.recoverable.waittime";
189 
190   /** Default wait time for the recoverable zookeeper */
191   public static final long DEFAULT_ZOOKEPER_RECOVERABLE_WAITIME = 10000;
192 
193   /** Parameter name for the root dir in ZK for this cluster */
194   public static final String ZOOKEEPER_ZNODE_PARENT = "zookeeper.znode.parent";
195 
196   public static final String DEFAULT_ZOOKEEPER_ZNODE_PARENT = "/hbase";
197 
198   /**
199    * Parameter name for the limit on concurrent client-side zookeeper
200    * connections
201    */
202   public static final String ZOOKEEPER_MAX_CLIENT_CNXNS =
203       ZK_CFG_PROPERTY_PREFIX + "maxClientCnxns";
204 
205   /** Parameter name for the ZK data directory */
206   public static final String ZOOKEEPER_DATA_DIR =
207       ZK_CFG_PROPERTY_PREFIX + "dataDir";
208 
209   /** Default limit on concurrent client-side zookeeper connections */
210   public static final int DEFAULT_ZOOKEPER_MAX_CLIENT_CNXNS = 300;
211 
212   /** Configuration key for ZooKeeper session timeout */
213   public static final String ZK_SESSION_TIMEOUT = "zookeeper.session.timeout";
214 
215   /** Default value for ZooKeeper session timeout */
216   public static final int DEFAULT_ZK_SESSION_TIMEOUT = 180 * 1000;
217 
218   /** Configuration key for whether to use ZK.multi */
219   public static final String ZOOKEEPER_USEMULTI = "hbase.zookeeper.useMulti";
220 
221   /** Parameter name for port region server listens on. */
222   public static final String REGIONSERVER_PORT = "hbase.regionserver.port";
223 
224   /** Default port region server listens on. */
225   public static final int DEFAULT_REGIONSERVER_PORT = 16020;
226 
227   /** default port for region server web api */
228   public static final int DEFAULT_REGIONSERVER_INFOPORT = 16030;
229 
230   /** A configuration key for regionserver info port */
231   public static final String REGIONSERVER_INFO_PORT =
232     "hbase.regionserver.info.port";
233 
234   /** A flag that enables automatic selection of regionserver info port */
235   public static final String REGIONSERVER_INFO_PORT_AUTO =
236       REGIONSERVER_INFO_PORT + ".auto";
237 
238   /** Parameter name for what region server implementation to use. */
239   public static final String REGION_SERVER_IMPL= "hbase.regionserver.impl";
240 
241   /** Parameter name for what master implementation to use. */
242   public static final String MASTER_IMPL= "hbase.master.impl";
243 
244   /** Parameter name for what hbase client implementation to use. */
245   public static final String HBASECLIENT_IMPL= "hbase.hbaseclient.impl";
246 
247   /** Parameter name for how often threads should wake up */
248   public static final String THREAD_WAKE_FREQUENCY = "hbase.server.thread.wakefrequency";
249 
250   /** Default value for thread wake frequency */
251   public static final int DEFAULT_THREAD_WAKE_FREQUENCY = 10 * 1000;
252 
253   /** Parameter name for how often we should try to write a version file, before failing */
254   public static final String VERSION_FILE_WRITE_ATTEMPTS = "hbase.server.versionfile.writeattempts";
255 
256   /** Parameter name for how often we should try to write a version file, before failing */
257   public static final int DEFAULT_VERSION_FILE_WRITE_ATTEMPTS = 3;
258 
259   /** Parameter name for how often a region should should perform a major compaction */
260   public static final String MAJOR_COMPACTION_PERIOD = "hbase.hregion.majorcompaction";
261 
262   /** Parameter name for the maximum batch of KVs to be used in flushes and compactions */
263   public static final String COMPACTION_KV_MAX = "hbase.hstore.compaction.kv.max";
264   public static final int COMPACTION_KV_MAX_DEFAULT = 10;
265 
266   /** Parameter name for HBase instance root directory */
267   public static final String HBASE_DIR = "hbase.rootdir";
268 
269   /** Parameter name for HBase client IPC pool type */
270   public static final String HBASE_CLIENT_IPC_POOL_TYPE = "hbase.client.ipc.pool.type";
271 
272   /** Parameter name for HBase client IPC pool size */
273   public static final String HBASE_CLIENT_IPC_POOL_SIZE = "hbase.client.ipc.pool.size";
274 
275   /** Parameter name for HBase client operation timeout, which overrides RPC timeout */
276   public static final String HBASE_CLIENT_OPERATION_TIMEOUT = "hbase.client.operation.timeout";
277 
278   /** Parameter name for HBase client operation timeout, which overrides RPC timeout */
279   public static final String HBASE_CLIENT_META_OPERATION_TIMEOUT =
280     "hbase.client.meta.operation.timeout";
281 
282   /** Default HBase client operation timeout, which is tantamount to a blocking call */
283   public static final int DEFAULT_HBASE_CLIENT_OPERATION_TIMEOUT = Integer.MAX_VALUE;
284 
285   /** Used to construct the name of the log directory for a region server */
286   public static final String HREGION_LOGDIR_NAME = "WALs";
287 
288   /** Used to construct the name of the splitlog directory for a region server */
289   public static final String SPLIT_LOGDIR_NAME = "splitWAL";
290 
291   /** Like the previous, but for old logs that are about to be deleted */
292   public static final String HREGION_OLDLOGDIR_NAME = "oldWALs";
293 
294   public static final String CORRUPT_DIR_NAME = "corrupt";
295 
296   /** Used by HBCK to sideline backup data */
297   public static final String HBCK_SIDELINEDIR_NAME = ".hbck";
298 
299   /** Any artifacts left from migration can be moved here */
300   public static final String MIGRATION_NAME = ".migration";
301 
302   /**
303    * The directory from which co-processor/custom filter jars can be loaded
304    * dynamically by the region servers. This value can be overridden by the
305    * hbase.dynamic.jars.dir config.
306    */
307   public static final String LIB_DIR = "lib";
308 
309   /** Used to construct the name of the compaction directory during compaction */
310   public static final String HREGION_COMPACTIONDIR_NAME = "compaction.dir";
311 
312   /** Conf key for the max file size after which we split the region */
313   public static final String HREGION_MAX_FILESIZE =
314       "hbase.hregion.max.filesize";
315 
316   /** Default maximum file size */
317   public static final long DEFAULT_MAX_FILE_SIZE = 10 * 1024 * 1024 * 1024L;
318 
319   /**
320    * Max size of single row for Get's or Scan's without in-row scanning flag set.
321    */
322   public static final String TABLE_MAX_ROWSIZE_KEY = "hbase.table.max.rowsize";
323 
324   /**
325    * Default max row size (1 Gb).
326    */
327   public static final long TABLE_MAX_ROWSIZE_DEFAULT = 1024 * 1024 * 1024L;
328 
329   /**
330    * The max number of threads used for opening and closing stores or store
331    * files in parallel
332    */
333   public static final String HSTORE_OPEN_AND_CLOSE_THREADS_MAX =
334     "hbase.hstore.open.and.close.threads.max";
335 
336   /**
337    * The default number for the max number of threads used for opening and
338    * closing stores or store files in parallel
339    */
340   public static final int DEFAULT_HSTORE_OPEN_AND_CLOSE_THREADS_MAX = 1;
341 
342 
343   /** Conf key for the memstore size at which we flush the memstore */
344   public static final String HREGION_MEMSTORE_FLUSH_SIZE =
345       "hbase.hregion.memstore.flush.size";
346 
347   public static final String HREGION_EDITS_REPLAY_SKIP_ERRORS =
348       "hbase.hregion.edits.replay.skip.errors";
349 
350   public static final boolean DEFAULT_HREGION_EDITS_REPLAY_SKIP_ERRORS =
351       false;
352 
353   /** Maximum value length, enforced on KeyValue construction */
354   public static final int MAXIMUM_VALUE_LENGTH = Integer.MAX_VALUE - 1;
355 
356   /** name of the file for unique cluster ID */
357   public static final String CLUSTER_ID_FILE_NAME = "hbase.id";
358 
359   /** Default value for cluster ID */
360   public static final String CLUSTER_ID_DEFAULT = "default-cluster";
361 
362   /** Parameter name for # days to keep MVCC values during a major compaction */
363   public static final String KEEP_SEQID_PERIOD = "hbase.hstore.compaction.keep.seqId.period";
364   /** At least to keep MVCC values in hfiles for 5 days */
365   public static final int MIN_KEEP_SEQID_PERIOD = 5;
366 
367   // Always store the location of the root table's HRegion.
368   // This HRegion is never split.
369 
370   // region name = table + startkey + regionid. This is the row key.
371   // each row in the root and meta tables describes exactly 1 region
372   // Do we ever need to know all the information that we are storing?
373 
374   // Note that the name of the root table starts with "-" and the name of the
375   // meta table starts with "." Why? it's a trick. It turns out that when we
376   // store region names in memory, we use a SortedMap. Since "-" sorts before
377   // "." (and since no other table name can start with either of these
378   // characters, the root region will always be the first entry in such a Map,
379   // followed by all the meta regions (which will be ordered by their starting
380   // row key as well), followed by all user tables. So when the Master is
381   // choosing regions to assign, it will always choose the root region first,
382   // followed by the meta regions, followed by user regions. Since the root
383   // and meta regions always need to be on-line, this ensures that they will
384   // be the first to be reassigned if the server(s) they are being served by
385   // should go down.
386 
387 
388   /**
389    * The hbase:meta table's name.
390    * 
391    */
392   @Deprecated  // for compat from 0.94 -> 0.96.
393   public static final byte[] META_TABLE_NAME = TableName.META_TABLE_NAME.getName();
394 
395   public static final String BASE_NAMESPACE_DIR = "data";
396 
397   /** delimiter used between portions of a region name */
398   public static final int META_ROW_DELIMITER = ',';
399 
400   /** The catalog family as a string*/
401   public static final String CATALOG_FAMILY_STR = "info";
402 
403   /** The catalog family */
404   public static final byte [] CATALOG_FAMILY = Bytes.toBytes(CATALOG_FAMILY_STR);
405 
406   /** The RegionInfo qualifier as a string */
407   public static final String REGIONINFO_QUALIFIER_STR = "regioninfo";
408 
409   /** The regioninfo column qualifier */
410   public static final byte [] REGIONINFO_QUALIFIER = Bytes.toBytes(REGIONINFO_QUALIFIER_STR);
411 
412   /** The server column qualifier */
413   public static final String SERVER_QUALIFIER_STR = "server";
414   /** The server column qualifier */
415   public static final byte [] SERVER_QUALIFIER = Bytes.toBytes(SERVER_QUALIFIER_STR);
416 
417   /** The startcode column qualifier */
418   public static final String STARTCODE_QUALIFIER_STR = "serverstartcode";
419   /** The startcode column qualifier */
420   public static final byte [] STARTCODE_QUALIFIER = Bytes.toBytes(STARTCODE_QUALIFIER_STR);
421 
422   /** The open seqnum column qualifier */
423   public static final String SEQNUM_QUALIFIER_STR = "seqnumDuringOpen";
424   /** The open seqnum column qualifier */
425   public static final byte [] SEQNUM_QUALIFIER = Bytes.toBytes(SEQNUM_QUALIFIER_STR);
426 
427   /** The state column qualifier */
428   public static final String STATE_QUALIFIER_STR = "state";
429 
430   public static final byte [] STATE_QUALIFIER = Bytes.toBytes(STATE_QUALIFIER_STR);
431 
432   /**
433    * The serverName column qualifier. Its the server where the region is
434    * transitioning on, while column server is the server where the region is
435    * opened on. They are the same when the region is in state OPEN.
436    */
437   public static final String SERVERNAME_QUALIFIER_STR = "sn";
438 
439   public static final byte [] SERVERNAME_QUALIFIER = Bytes.toBytes(SERVERNAME_QUALIFIER_STR);
440 
441   /** The lower-half split region column qualifier */
442   public static final byte [] SPLITA_QUALIFIER = Bytes.toBytes("splitA");
443 
444   /** The upper-half split region column qualifier */
445   public static final byte [] SPLITB_QUALIFIER = Bytes.toBytes("splitB");
446 
447   /** The lower-half merge region column qualifier */
448   public static final byte[] MERGEA_QUALIFIER = Bytes.toBytes("mergeA");
449 
450   /** The upper-half merge region column qualifier */
451   public static final byte[] MERGEB_QUALIFIER = Bytes.toBytes("mergeB");
452 
453   /** The catalog family as a string*/
454   public static final String TABLE_FAMILY_STR = "table";
455 
456   /** The catalog family */
457   public static final byte [] TABLE_FAMILY = Bytes.toBytes(TABLE_FAMILY_STR);
458 
459   /** The serialized table state qualifier */
460   public static final byte[] TABLE_STATE_QUALIFIER = Bytes.toBytes("state");
461 
462 
463   /**
464    * The meta table version column qualifier.
465    * We keep current version of the meta table in this column in <code>-ROOT-</code>
466    * table: i.e. in the 'info:v' column.
467    */
468   public static final byte [] META_VERSION_QUALIFIER = Bytes.toBytes("v");
469 
470   /**
471    * The current version of the meta table.
472    * - pre-hbase 0.92.  There is no META_VERSION column in the root table
473    * in this case. The meta has HTableDescriptor serialized into the HRegionInfo;
474    * - version 0 is 0.92 and 0.94. Meta data has serialized HRegionInfo's using
475    * Writable serialization, and HRegionInfo's does not contain HTableDescriptors.
476    * - version 1 for 0.96+ keeps HRegionInfo data structures, but changes the
477    * byte[] serialization from Writables to Protobuf.
478    * See HRegionInfo.VERSION
479    */
480   public static final short META_VERSION = 1;
481 
482   // Other constants
483 
484   /**
485    * An empty instance.
486    */
487   public static final byte [] EMPTY_BYTE_ARRAY = new byte [0];
488 
489   /**
490    * Used by scanners, etc when they want to start at the beginning of a region
491    */
492   public static final byte [] EMPTY_START_ROW = EMPTY_BYTE_ARRAY;
493 
494   /**
495    * Last row in a table.
496    */
497   public static final byte [] EMPTY_END_ROW = EMPTY_START_ROW;
498 
499   /**
500     * Used by scanners and others when they're trying to detect the end of a
501     * table
502     */
503   public static final byte [] LAST_ROW = EMPTY_BYTE_ARRAY;
504 
505   /**
506    * Max length a row can have because of the limitation in TFile.
507    */
508   public static final int MAX_ROW_LENGTH = Short.MAX_VALUE;
509 
510   /**
511    * Timestamp to use when we want to refer to the latest cell.
512    * This is the timestamp sent by clients when no timestamp is specified on
513    * commit.
514    */
515   public static final long LATEST_TIMESTAMP = Long.MAX_VALUE;
516 
517   /**
518    * Timestamp to use when we want to refer to the oldest cell.
519    */
520   public static final long OLDEST_TIMESTAMP = Long.MIN_VALUE;
521 
522   /**
523    * LATEST_TIMESTAMP in bytes form
524    */
525   public static final byte [] LATEST_TIMESTAMP_BYTES = {
526     // big-endian
527     (byte) (LATEST_TIMESTAMP >>> 56),
528     (byte) (LATEST_TIMESTAMP >>> 48),
529     (byte) (LATEST_TIMESTAMP >>> 40),
530     (byte) (LATEST_TIMESTAMP >>> 32),
531     (byte) (LATEST_TIMESTAMP >>> 24),
532     (byte) (LATEST_TIMESTAMP >>> 16),
533     (byte) (LATEST_TIMESTAMP >>> 8),
534     (byte) LATEST_TIMESTAMP,
535   };
536 
537   /**
538    * Define for 'return-all-versions'.
539    */
540   public static final int ALL_VERSIONS = Integer.MAX_VALUE;
541 
542   /**
543    * Unlimited time-to-live.
544    */
545 //  public static final int FOREVER = -1;
546   public static final int FOREVER = Integer.MAX_VALUE;
547 
548   /**
549    * Seconds in a week
550    */
551   public static final int WEEK_IN_SECONDS = 7 * 24 * 3600;
552 
553   /**
554    * Seconds in a day, hour and minute
555    */
556   public static final int DAY_IN_SECONDS = 24 * 60 * 60;
557   public static final int HOUR_IN_SECONDS = 60 * 60;
558   public static final int MINUTE_IN_SECONDS = 60;
559 
560   //TODO: although the following are referenced widely to format strings for
561   //      the shell. They really aren't a part of the public API. It would be
562   //      nice if we could put them somewhere where they did not need to be
563   //      public. They could have package visibility
564   public static final String NAME = "NAME";
565   public static final String VERSIONS = "VERSIONS";
566   public static final String IN_MEMORY = "IN_MEMORY";
567   public static final String METADATA = "METADATA";
568   public static final String CONFIGURATION = "CONFIGURATION";
569 
570   /**
571    * Retrying we multiply hbase.client.pause setting by what we have in this array until we
572    * run out of array items.  Retries beyond this use the last number in the array.  So, for
573    * example, if hbase.client.pause is 1 second, and maximum retries count
574    * hbase.client.retries.number is 10, we will retry at the following intervals:
575    * 1, 2, 3, 5, 10, 20, 40, 100, 100, 100.
576    * With 100ms, a back-off of 200 means 20s
577    */
578   public static final int RETRY_BACKOFF[] = {1, 2, 3, 5, 10, 20, 40, 100, 100, 100, 100, 200, 200};
579 
580   public static final String REGION_IMPL = "hbase.hregion.impl";
581 
582   /** modifyTable op for replacing the table descriptor */
583   @InterfaceAudience.Private
584   public static enum Modify {
585     CLOSE_REGION,
586     TABLE_COMPACT,
587     TABLE_FLUSH,
588     TABLE_MAJOR_COMPACT,
589     TABLE_SET_HTD,
590     TABLE_SPLIT
591   }
592 
593   /**
594    * Scope tag for locally scoped data.
595    * This data will not be replicated.
596    */
597   public static final int REPLICATION_SCOPE_LOCAL = 0;
598 
599   /**
600    * Scope tag for globally scoped data.
601    * This data will be replicated to all peers.
602    */
603   public static final int REPLICATION_SCOPE_GLOBAL = 1;
604 
605   /**
606    * Default cluster ID, cannot be used to identify a cluster so a key with
607    * this value means it wasn't meant for replication.
608    */
609   public static final UUID DEFAULT_CLUSTER_ID = new UUID(0L,0L);
610 
611     /**
612      * Parameter name for maximum number of bytes returned when calling a
613      * scanner's next method.
614      */
615   public static final String HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE_KEY =
616       "hbase.client.scanner.max.result.size";
617 
618   /**
619    * Maximum number of bytes returned when calling a scanner's next method.
620    * Note that when a single row is larger than this limit the row is still
621    * returned completely.
622    *
623    * The default value is 2MB.
624    */
625   public static final long DEFAULT_HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE = 2 * 1024 * 1024;
626 
627   /**
628    * Parameter name for client pause value, used mostly as value to wait
629    * before running a retry of a failed get, region lookup, etc.
630    */
631   public static final String HBASE_CLIENT_PAUSE = "hbase.client.pause";
632 
633   /**
634    * Default value of {@link #HBASE_CLIENT_PAUSE}.
635    */
636   public static final long DEFAULT_HBASE_CLIENT_PAUSE = 100;
637 
638   /**
639    * The maximum number of concurrent connections the client will maintain.
640    */
641   public static final String HBASE_CLIENT_MAX_TOTAL_TASKS = "hbase.client.max.total.tasks";
642 
643   /**
644    * Default value of {@link #HBASE_CLIENT_MAX_TOTAL_TASKS}.
645    */
646   public static final int DEFAULT_HBASE_CLIENT_MAX_TOTAL_TASKS = 100;
647 
648   /**
649    * The maximum number of concurrent connections the client will maintain to a single
650    * RegionServer.
651    */
652   public static final String HBASE_CLIENT_MAX_PERSERVER_TASKS = "hbase.client.max.perserver.tasks";
653 
654   /**
655    * Default value of {@link #HBASE_CLIENT_MAX_PERSERVER_TASKS}.
656    */
657   public static final int DEFAULT_HBASE_CLIENT_MAX_PERSERVER_TASKS = 2;
658 
659   /**
660    * The maximum number of concurrent connections the client will maintain to a single
661    * Region.
662    */
663   public static final String HBASE_CLIENT_MAX_PERREGION_TASKS = "hbase.client.max.perregion.tasks";
664 
665   /**
666    * Default value of {@link #HBASE_CLIENT_MAX_PERREGION_TASKS}.
667    */
668   public static final int DEFAULT_HBASE_CLIENT_MAX_PERREGION_TASKS = 1;
669 
670   /**
671    * Parameter name for server pause value, used mostly as value to wait before
672    * running a retry of a failed operation.
673    */
674   public static final String HBASE_SERVER_PAUSE = "hbase.server.pause";
675 
676   /**
677    * Default value of {@link #HBASE_SERVER_PAUSE}.
678    */
679   public static final int DEFAULT_HBASE_SERVER_PAUSE = 1000;
680 
681   /**
682    * Parameter name for maximum retries, used as maximum for all retryable
683    * operations such as fetching of the root region from root region server,
684    * getting a cell's value, starting a row update, etc.
685    */
686   public static final String HBASE_CLIENT_RETRIES_NUMBER = "hbase.client.retries.number";
687 
688   /**
689    * Default value of {@link #HBASE_CLIENT_RETRIES_NUMBER}.
690    */
691   public static final int DEFAULT_HBASE_CLIENT_RETRIES_NUMBER = 31;
692 
693   /**
694    * Parameter name to set the default scanner caching for all clients.
695    */
696   public static final String HBASE_CLIENT_SCANNER_CACHING = "hbase.client.scanner.caching";
697 
698   /**
699    * Default value for {@link #HBASE_CLIENT_SCANNER_CACHING}
700    */
701   public static final int DEFAULT_HBASE_CLIENT_SCANNER_CACHING = 100;
702 
703   /**
704    * Parameter name for number of rows that will be fetched when calling next on
705    * a scanner if it is not served from memory. Higher caching values will
706    * enable faster scanners but will eat up more memory and some calls of next
707    * may take longer and longer times when the cache is empty.
708    */
709   public static final String HBASE_META_SCANNER_CACHING = "hbase.meta.scanner.caching";
710 
711   /**
712    * Default value of {@link #HBASE_META_SCANNER_CACHING}.
713    */
714   public static final int DEFAULT_HBASE_META_SCANNER_CACHING = 100;
715 
716   /**
717    * Parameter name for number of versions, kept by meta table.
718    */
719   public static final String HBASE_META_VERSIONS = "hbase.meta.versions";
720 
721   /**
722    * Default value of {@link #HBASE_META_VERSIONS}.
723    */
724   public static final int DEFAULT_HBASE_META_VERSIONS = 3;
725 
726   /**
727    * Parameter name for number of versions, kept by meta table.
728    */
729   public static final String HBASE_META_BLOCK_SIZE = "hbase.meta.blocksize";
730 
731   /**
732    * Default value of {@link #HBASE_META_BLOCK_SIZE}.
733    */
734   public static final int DEFAULT_HBASE_META_BLOCK_SIZE = 8 * 1024;
735 
736   /**
737    * Parameter name for unique identifier for this {@link org.apache.hadoop.conf.Configuration}
738    * instance. If there are two or more {@link org.apache.hadoop.conf.Configuration} instances that,
739    * for all intents and purposes, are the same except for their instance ids, then they will not be
740    * able to share the same org.apache.hadoop.hbase.client.HConnection instance. On the other hand,
741    * even if the instance ids are the same, it could result in non-shared
742    * org.apache.hadoop.hbase.client.HConnection instances if some of the other connection parameters
743    * differ.
744    */
745   public static final String HBASE_CLIENT_INSTANCE_ID = "hbase.client.instance.id";
746 
747   /**
748    * The client scanner timeout period in milliseconds.
749    */
750   public static final String HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD =
751       "hbase.client.scanner.timeout.period";
752 
753   /**
754    * Use {@link #HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD} instead.
755    * @deprecated This config option is deprecated. Will be removed at later releases after 0.96.
756    */
757   @Deprecated
758   public static final String HBASE_REGIONSERVER_LEASE_PERIOD_KEY =
759       "hbase.regionserver.lease.period";
760 
761   /**
762    * Default value of {@link #HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD}.
763    */
764   public static final int DEFAULT_HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD = 60000;
765 
766   /**
767    * timeout for each RPC
768    */
769   public static final String HBASE_RPC_TIMEOUT_KEY = "hbase.rpc.timeout";
770 
771   /**
772    * Default value of {@link #HBASE_RPC_TIMEOUT_KEY}
773    */
774   public static final int DEFAULT_HBASE_RPC_TIMEOUT = 60000;
775 
776   /**
777    * timeout for short operation RPC
778    */
779   public static final String HBASE_RPC_SHORTOPERATION_TIMEOUT_KEY = "hbase.rpc.shortoperation.timeout";
780 
781   /**
782    * Default value of {@link #HBASE_RPC_SHORTOPERATION_TIMEOUT_KEY}
783    */
784   public static final int DEFAULT_HBASE_RPC_SHORTOPERATION_TIMEOUT = 10000;
785 
786   /**
787    * Value indicating the server name was saved with no sequence number.
788    */
789   public static final long NO_SEQNUM = -1;
790 
791 
792   /*
793    * cluster replication constants.
794    */
795   public static final String
796       REPLICATION_ENABLE_KEY = "hbase.replication";
797   public static final boolean
798       REPLICATION_ENABLE_DEFAULT = true;
799   public static final String
800       REPLICATION_SOURCE_SERVICE_CLASSNAME = "hbase.replication.source.service";
801   public static final String
802       REPLICATION_SINK_SERVICE_CLASSNAME = "hbase.replication.sink.service";
803   public static final String REPLICATION_SERVICE_CLASSNAME_DEFAULT =
804     "org.apache.hadoop.hbase.replication.regionserver.Replication";
805 
806   /** HBCK special code name used as server name when manipulating ZK nodes */
807   public static final String HBCK_CODE_NAME = "HBCKServerName";
808 
809   public static final String KEY_FOR_HOSTNAME_SEEN_BY_MASTER =
810     "hbase.regionserver.hostname.seen.by.master";
811 
812   public static final String HBASE_MASTER_LOGCLEANER_PLUGINS =
813       "hbase.master.logcleaner.plugins";
814 
815   public static final String HBASE_REGION_SPLIT_POLICY_KEY =
816     "hbase.regionserver.region.split.policy";
817 
818   /** Whether nonces are enabled; default is true. */
819   public static final String HBASE_RS_NONCES_ENABLED = "hbase.regionserver.nonces.enabled";
820 
821   /**
822    * Configuration key for the size of the block cache
823    */
824   public static final String HFILE_BLOCK_CACHE_SIZE_KEY =
825     "hfile.block.cache.size";
826 
827   public static final float HFILE_BLOCK_CACHE_SIZE_DEFAULT = 0.4f;
828 
829   /*
830     * Minimum percentage of free heap necessary for a successful cluster startup.
831     */
832   public static final float HBASE_CLUSTER_MINIMUM_MEMORY_THRESHOLD = 0.2f;
833 
834   public static final Pattern CP_HTD_ATTR_KEY_PATTERN = Pattern.compile
835       ("^coprocessor\\$([0-9]+)$", Pattern.CASE_INSENSITIVE);
836   public static final Pattern CP_HTD_ATTR_VALUE_PATTERN =
837       Pattern.compile("(^[^\\|]*)\\|([^\\|]+)\\|[\\s]*([\\d]*)[\\s]*(\\|.*)?$");
838 
839   public static final String CP_HTD_ATTR_VALUE_PARAM_KEY_PATTERN = "[^=,]+";
840   public static final String CP_HTD_ATTR_VALUE_PARAM_VALUE_PATTERN = "[^,]+";
841   public static final Pattern CP_HTD_ATTR_VALUE_PARAM_PATTERN = Pattern.compile(
842       "(" + CP_HTD_ATTR_VALUE_PARAM_KEY_PATTERN + ")=(" +
843       CP_HTD_ATTR_VALUE_PARAM_VALUE_PATTERN + "),?");
844 
845   /** The delay when re-trying a socket operation in a loop (HBASE-4712) */
846   public static final int SOCKET_RETRY_WAIT_MS = 200;
847 
848   /** Host name of the local machine */
849   public static final String LOCALHOST = "localhost";
850 
851   /**
852    * If this parameter is set to true, then hbase will read
853    * data and then verify checksums. Checksum verification
854    * inside hdfs will be switched off.  However, if the hbase-checksum
855    * verification fails, then it will switch back to using
856    * hdfs checksums for verifiying data that is being read from storage.
857    *
858    * If this parameter is set to false, then hbase will not
859    * verify any checksums, instead it will depend on checksum verification
860    * being done in the hdfs client.
861    */
862   public static final String HBASE_CHECKSUM_VERIFICATION =
863       "hbase.regionserver.checksum.verify";
864 
865   public static final String LOCALHOST_IP = "127.0.0.1";
866 
867   /** Conf key that enables unflushed WAL edits directly being replayed to region servers */
868   public static final String DISTRIBUTED_LOG_REPLAY_KEY = "hbase.master.distributed.log.replay";
869   /**
870    * Default 'distributed log replay' as true since hbase 0.99.0
871    */
872   public static final boolean DEFAULT_DISTRIBUTED_LOG_REPLAY_CONFIG = true;
873   public static final String DISALLOW_WRITES_IN_RECOVERING =
874       "hbase.regionserver.disallow.writes.when.recovering";
875   public static final boolean DEFAULT_DISALLOW_WRITES_IN_RECOVERING_CONFIG = false;
876 
877   public static final String REGION_SERVER_HANDLER_COUNT = "hbase.regionserver.handler.count";
878   public static final int DEFAULT_REGION_SERVER_HANDLER_COUNT = 30;
879 
880   /*
881    * REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT:
882    * -1  => Disable aborting
883    * 0   => Abort if even a single handler has died
884    * 0.x => Abort only when this percent of handlers have died
885    * 1   => Abort only all of the handers have died
886    */
887   public static final String REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT =
888 		  "hbase.regionserver.handler.abort.on.error.percent";
889   public static final double DEFAULT_REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT = 0.5;
890 
891   //High priority handlers to deal with admin requests and system table operation requests
892   public static final String REGION_SERVER_HIGH_PRIORITY_HANDLER_COUNT =
893       "hbase.regionserver.metahandler.count";
894   public static final int DEFAULT_REGION_SERVER_HIGH_PRIORITY_HANDLER_COUNT = 10;
895 
896   public static final String REGION_SERVER_REPLICATION_HANDLER_COUNT =
897       "hbase.regionserver.replication.handler.count";
898   public static final int DEFAULT_REGION_SERVER_REPLICATION_HANDLER_COUNT = 3;
899 
900   public static final String MASTER_HANDLER_COUNT = "hbase.master.handler.count";
901   public static final int DEFAULT_MASTER_HANLDER_COUNT = 25;
902 
903   /** Conf key that specifies timeout value to wait for a region ready */
904   public static final String LOG_REPLAY_WAIT_REGION_TIMEOUT =
905       "hbase.master.log.replay.wait.region.timeout";
906 
907   /** Conf key for enabling meta replication */
908   public static final String USE_META_REPLICAS = "hbase.meta.replicas.use";
909   public static final boolean DEFAULT_USE_META_REPLICAS = false;
910   public static final String META_REPLICAS_NUM = "hbase.meta.replica.count";
911   public static final int DEFAULT_META_REPLICA_NUM = 1;
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 WAL Compression */
934   public static final String ENABLE_WAL_COMPRESSION =
935     "hbase.regionserver.wal.enablecompression";
936 
937   /** Configuration name of WAL storage policy
938    * Valid values are:
939    *  NONE: no preference in destination of replicas
940    *  ONE_SSD: place only one replica in SSD and the remaining in default storage
941    *  and ALL_SSD: place all replica on SSD
942    *  
943    * See http://hadoop.apache.org/docs/r2.6.0/hadoop-project-dist/hadoop-hdfs/ArchivalStorage.html*/
944   public static final String WAL_STORAGE_POLICY = "hbase.wal.storage.policy";
945   public static final String DEFAULT_WAL_STORAGE_POLICY = "NONE";
946 
947   /** Region in Transition metrics threshold time */
948   public static final String METRICS_RIT_STUCK_WARNING_THRESHOLD="hbase.metrics.rit.stuck.warning.threshold";
949 
950   public static final String LOAD_BALANCER_SLOP_KEY = "hbase.regions.slop";
951 
952   /**
953    * The byte array represents for NO_NEXT_INDEXED_KEY;
954    * The actual value is irrelevant because this is always compared by reference.
955    */
956   public static final byte [] NO_NEXT_INDEXED_KEY = Bytes.toBytes("NO_NEXT_INDEXED_KEY");
957   /** delimiter used between portions of a region name */
958   public static final int DELIMITER = ',';
959   public static final String HBASE_CONFIG_READ_ZOOKEEPER_CONFIG =
960       "hbase.config.read.zookeeper.config";
961   public static final boolean DEFAULT_HBASE_CONFIG_READ_ZOOKEEPER_CONFIG =
962       false;
963 
964   /**
965    * QOS attributes: these attributes are used to demarcate RPC call processing
966    * by different set of handlers. For example, HIGH_QOS tagged methods are
967    * handled by high priority handlers.
968    */
969   public static final int NORMAL_QOS = 0;
970   public static final int QOS_THRESHOLD = 10;
971   public static final int HIGH_QOS = 200;
972   public static final int REPLICATION_QOS = 5; // normal_QOS < replication_QOS < high_QOS
973   public static final int REPLAY_QOS = 6; // REPLICATION_QOS < REPLAY_QOS < high_QOS
974   public static final int ADMIN_QOS = 100; // QOS_THRESHOLD < ADMIN_QOS < high_QOS
975   public static final int SYSTEMTABLE_QOS = HIGH_QOS;
976 
977   /** Directory under /hbase where archived hfiles are stored */
978   public static final String HFILE_ARCHIVE_DIRECTORY = "archive";
979 
980   /**
981    * Name of the directory to store all snapshots. See SnapshotDescriptionUtils for
982    * remaining snapshot constants; this is here to keep HConstants dependencies at a minimum and
983    * uni-directional.
984    */
985   public static final String SNAPSHOT_DIR_NAME = ".hbase-snapshot";
986 
987   /* Name of old snapshot directory. See HBASE-8352 for details on why it needs to be renamed */
988   public static final String OLD_SNAPSHOT_DIR_NAME = ".snapshot";
989 
990   /** Temporary directory used for table creation and deletion */
991   public static final String HBASE_TEMP_DIRECTORY = ".tmp";
992   /**
993    * The period (in milliseconds) between computing region server point in time metrics
994    */
995   public static final String REGIONSERVER_METRICS_PERIOD = "hbase.regionserver.metrics.period";
996   public static final long DEFAULT_REGIONSERVER_METRICS_PERIOD = 5000;
997   /** Directories that are not HBase table directories */
998   public static final List<String> HBASE_NON_TABLE_DIRS =
999     Collections.unmodifiableList(Arrays.asList(new String[] {
1000       HBCK_SIDELINEDIR_NAME, HBASE_TEMP_DIRECTORY, MIGRATION_NAME
1001     }));
1002 
1003   /** Directories that are not HBase user table directories */
1004   public static final List<String> HBASE_NON_USER_TABLE_DIRS =
1005     Collections.unmodifiableList(Arrays.asList((String[])ArrayUtils.addAll(
1006       new String[] { TableName.META_TABLE_NAME.getNameAsString() },
1007       HBASE_NON_TABLE_DIRS.toArray())));
1008 
1009   /** Health script related settings. */
1010   public static final String HEALTH_SCRIPT_LOC = "hbase.node.health.script.location";
1011   public static final String HEALTH_SCRIPT_TIMEOUT = "hbase.node.health.script.timeout";
1012   public static final String HEALTH_CHORE_WAKE_FREQ =
1013       "hbase.node.health.script.frequency";
1014   public static final long DEFAULT_HEALTH_SCRIPT_TIMEOUT = 60000;
1015   /**
1016    * The maximum number of health check failures a server can encounter consecutively.
1017    */
1018   public static final String HEALTH_FAILURE_THRESHOLD =
1019       "hbase.node.health.failure.threshold";
1020   public static final int DEFAULT_HEALTH_FAILURE_THRESHOLD = 3;
1021 
1022 
1023   /**
1024    * Setting to activate, or not, the publication of the status by the master. Default
1025    *  notification is by a multicast message.
1026    */
1027   public static final String STATUS_PUBLISHED = "hbase.status.published";
1028   public static final boolean STATUS_PUBLISHED_DEFAULT = false;
1029 
1030   /**
1031    * IP to use for the multicast status messages between the master and the clients.
1032    * The default address is chosen as one among others within the ones suitable for multicast
1033    * messages.
1034    */
1035   public static final String STATUS_MULTICAST_ADDRESS = "hbase.status.multicast.address.ip";
1036   public static final String DEFAULT_STATUS_MULTICAST_ADDRESS = "226.1.1.3";
1037 
1038   /**
1039    * The address to use for binding the local socket for receiving multicast. Defaults to
1040    * 0.0.0.0.
1041    * @see <a href="https://issues.apache.org/jira/browse/HBASE-9961">HBASE-9961</a>
1042    */
1043   public static final String STATUS_MULTICAST_BIND_ADDRESS = "hbase.status.multicast.bind.address.ip";
1044   public static final String DEFAULT_STATUS_MULTICAST_BIND_ADDRESS = "0.0.0.0";
1045 
1046   /**
1047    * The port to use for the multicast messages.
1048    */
1049   public static final String STATUS_MULTICAST_PORT = "hbase.status.multicast.address.port";
1050   public static final int DEFAULT_STATUS_MULTICAST_PORT = 16100;
1051 
1052   public static final long NO_NONCE = 0;
1053 
1054   /** Configuration key for the crypto algorithm provider, a class name */
1055   public static final String CRYPTO_CIPHERPROVIDER_CONF_KEY = "hbase.crypto.cipherprovider";
1056 
1057   /** Configuration key for the crypto key provider, a class name */
1058   public static final String CRYPTO_KEYPROVIDER_CONF_KEY = "hbase.crypto.keyprovider";
1059 
1060   /** Configuration key for the crypto key provider parameters */
1061   public static final String CRYPTO_KEYPROVIDER_PARAMETERS_KEY =
1062       "hbase.crypto.keyprovider.parameters";
1063 
1064   /** Configuration key for the name of the master key for the cluster, a string */
1065   public static final String CRYPTO_MASTERKEY_NAME_CONF_KEY = "hbase.crypto.master.key.name";
1066 
1067   /** Configuration key for the name of the alternate master key for the cluster, a string */
1068   public static final String CRYPTO_MASTERKEY_ALTERNATE_NAME_CONF_KEY =
1069     "hbase.crypto.master.alternate.key.name";
1070 
1071   /** Configuration key for the algorithm to use when encrypting the WAL, a string */
1072   public static final String CRYPTO_WAL_ALGORITHM_CONF_KEY = "hbase.crypto.wal.algorithm";
1073 
1074   /** Configuration key for the name of the master WAL encryption key for the cluster, a string */
1075   public static final String CRYPTO_WAL_KEY_NAME_CONF_KEY = "hbase.crypto.wal.key.name";
1076 
1077   /** Configuration key for enabling WAL encryption, a boolean */
1078   public static final String ENABLE_WAL_ENCRYPTION = "hbase.regionserver.wal.encryption";
1079 
1080   /** Configuration key for setting RPC codec class name */
1081   public static final String RPC_CODEC_CONF_KEY = "hbase.client.rpc.codec";
1082 
1083   /** Configuration key for setting replication codec class name */
1084   public static final String REPLICATION_CODEC_CONF_KEY = "hbase.replication.rpc.codec";
1085 
1086   /** Config for pluggable consensus provider */
1087   public static final String HBASE_COORDINATED_STATE_MANAGER_CLASS =
1088     "hbase.coordinated.state.manager.class";
1089 
1090   /** Configuration key for SplitLog manager timeout */
1091   public static final String HBASE_SPLITLOG_MANAGER_TIMEOUT = "hbase.splitlog.manager.timeout";
1092 
1093   /**
1094    * Configuration keys for Bucket cache
1095    */
1096   // TODO moving these bucket cache implementation specific configs to this level is violation of
1097   // encapsulation. But as these has to be referred from hbase-common and bucket cache
1098   // sits in hbase-server, there were no other go! Can we move the cache implementation to
1099   // hbase-common?
1100 
1101   /**
1102    * Current ioengine options in include: heap, offheap and file:PATH (where PATH is the path
1103    * to the file that will host the file-based cache.  See BucketCache#getIOEngineFromName() for
1104    * list of supported ioengine options.
1105    * <p>Set this option and a non-zero {@link #BUCKET_CACHE_SIZE_KEY} to enable bucket cache.
1106    */
1107   public static final String BUCKET_CACHE_IOENGINE_KEY = "hbase.bucketcache.ioengine";
1108 
1109   /**
1110    * When using bucket cache, this is a float that EITHER represents a percentage of total heap
1111    * memory size to give to the cache (if < 1.0) OR, it is the capacity in megabytes of the cache.
1112    */
1113   public static final String BUCKET_CACHE_SIZE_KEY = "hbase.bucketcache.size";
1114 
1115   /**
1116    * HConstants for fast fail on the client side follow
1117    */
1118   /**
1119    * Config for enabling/disabling the fast fail mode.
1120    */
1121   public static final String HBASE_CLIENT_FAST_FAIL_MODE_ENABLED =
1122       "hbase.client.fast.fail.mode.enabled";
1123 
1124   public static final boolean HBASE_CLIENT_ENABLE_FAST_FAIL_MODE_DEFAULT =
1125       false;
1126 
1127   public static final String HBASE_CLIENT_FAST_FAIL_THREASHOLD_MS =
1128       "hbase.client.fastfail.threshold";
1129   
1130   public static final long HBASE_CLIENT_FAST_FAIL_THREASHOLD_MS_DEFAULT =
1131       60000;
1132 
1133   public static final String HBASE_CLIENT_FAST_FAIL_CLEANUP_MS_DURATION_MS =
1134       "hbase.client.fast.fail.cleanup.duration";
1135 
1136   public static final long HBASE_CLIENT_FAST_FAIL_CLEANUP_DURATION_MS_DEFAULT =
1137       600000;
1138 
1139   public static final String HBASE_CLIENT_FAST_FAIL_INTERCEPTOR_IMPL =
1140       "hbase.client.fast.fail.interceptor.impl"; 
1141 
1142   /** Config key for if the server should send backpressure and if the client should listen to
1143    * that backpressure from the server */
1144   public static final String ENABLE_CLIENT_BACKPRESSURE = "hbase.client.backpressure.enabled";
1145   public static final boolean DEFAULT_ENABLE_CLIENT_BACKPRESSURE = false;
1146 
1147   public static final String HEAP_OCCUPANCY_LOW_WATERMARK_KEY =
1148       "hbase.heap.occupancy.low_water_mark";
1149   public static final float DEFAULT_HEAP_OCCUPANCY_LOW_WATERMARK = 0.95f;
1150   public static final String HEAP_OCCUPANCY_HIGH_WATERMARK_KEY =
1151       "hbase.heap.occupancy.high_water_mark";
1152   public static final float DEFAULT_HEAP_OCCUPANCY_HIGH_WATERMARK = 0.98f;
1153 
1154   private HConstants() {
1155     // Can't be instantiated with this ctor.
1156   }
1157 }