View Javadoc

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    @InterfaceAudience.Private
88    public enum OperationStatusCode {
89      NOT_RUN,
90      SUCCESS,
91      BAD_FAMILY,
92      SANITY_CHECK_FAILURE,
93      FAILURE;
94    }
95  
96    /** long constant for zero */
97    public static final Long ZERO_L = Long.valueOf(0L);
98    public static final String NINES = "99999999999999";
99    public static final String ZEROES = "00000000000000";
100 
101   // For migration
102 
103   /** name of version file */
104   public static final String VERSION_FILE_NAME = "hbase.version";
105 
106   /**
107    * Current version of file system.
108    * Version 4 supports only one kind of bloom filter.
109    * Version 5 changes versions in catalog table regions.
110    * Version 6 enables blockcaching on catalog tables.
111    * Version 7 introduces hfile -- hbase 0.19 to 0.20..
112    * Version 8 introduces namespace
113    */
114   // public static final String FILE_SYSTEM_VERSION = "6";
115   public static final String FILE_SYSTEM_VERSION = "8";
116 
117   // Configuration parameters
118 
119   //TODO: Is having HBase homed on port 60k OK?
120 
121   /** Cluster is in distributed mode or not */
122   public static final String CLUSTER_DISTRIBUTED = "hbase.cluster.distributed";
123 
124   /** Config for pluggable load balancers */
125   public static final String HBASE_MASTER_LOADBALANCER_CLASS = "hbase.master.loadbalancer.class";
126 
127   /** Cluster is standalone or pseudo-distributed */
128   public static final boolean CLUSTER_IS_LOCAL = false;
129 
130   /** Cluster is fully-distributed */
131   public static final boolean CLUSTER_IS_DISTRIBUTED = true;
132 
133   /** Default value for cluster distributed mode */
134   public static final boolean DEFAULT_CLUSTER_DISTRIBUTED = CLUSTER_IS_LOCAL;
135 
136   /** default host address */
137   public static final String DEFAULT_HOST = "0.0.0.0";
138 
139   /** Parameter name for port master listens on. */
140   public static final String MASTER_PORT = "hbase.master.port";
141 
142   /** default port that the master listens on */
143   public static final int DEFAULT_MASTER_PORT = 60000;
144 
145   /** default port for master web api */
146   public static final int DEFAULT_MASTER_INFOPORT = 60010;
147 
148   /** Configuration key for master web API port */
149   public static final String MASTER_INFO_PORT = "hbase.master.info.port";
150 
151   /** Parameter name for the master type being backup (waits for primary to go inactive). */
152   public static final String MASTER_TYPE_BACKUP = "hbase.master.backup";
153 
154   /** by default every master is a possible primary master unless the conf explicitly overrides it */
155   public static final boolean DEFAULT_MASTER_TYPE_BACKUP = false;
156 
157   /** Name of ZooKeeper quorum configuration parameter. */
158   public static final String ZOOKEEPER_QUORUM = "hbase.zookeeper.quorum";
159 
160   /** Name of ZooKeeper config file in conf/ directory. */
161   public static final String ZOOKEEPER_CONFIG_NAME = "zoo.cfg";
162 
163   /** Common prefix of ZooKeeper configuration properties */
164   public static final String ZK_CFG_PROPERTY_PREFIX =
165       "hbase.zookeeper.property.";
166 
167   public static final int ZK_CFG_PROPERTY_PREFIX_LEN =
168       ZK_CFG_PROPERTY_PREFIX.length();
169 
170   /**
171    * The ZK client port key in the ZK properties map. The name reflects the
172    * fact that this is not an HBase configuration key.
173    */
174   public static final String CLIENT_PORT_STR = "clientPort";
175 
176   /** Parameter name for the client port that the zookeeper listens on */
177   public static final String ZOOKEEPER_CLIENT_PORT =
178       ZK_CFG_PROPERTY_PREFIX + CLIENT_PORT_STR;
179 
180   /** Default client port that the zookeeper listens on */
181   public static final int DEFAULT_ZOOKEPER_CLIENT_PORT = 2181;
182 
183   /** Parameter name for the wait time for the recoverable zookeeper */
184   public static final String ZOOKEEPER_RECOVERABLE_WAITTIME = "hbase.zookeeper.recoverable.waittime";
185 
186   /** Default wait time for the recoverable zookeeper */
187   public static final long DEFAULT_ZOOKEPER_RECOVERABLE_WAITIME = 10000;
188 
189   /** Parameter name for the root dir in ZK for this cluster */
190   public static final String ZOOKEEPER_ZNODE_PARENT = "zookeeper.znode.parent";
191 
192   public static final String DEFAULT_ZOOKEEPER_ZNODE_PARENT = "/hbase";
193 
194   /**
195    * Parameter name for the limit on concurrent client-side zookeeper
196    * connections
197    */
198   public static final String ZOOKEEPER_MAX_CLIENT_CNXNS =
199       ZK_CFG_PROPERTY_PREFIX + "maxClientCnxns";
200 
201   /** Parameter name for the ZK data directory */
202   public static final String ZOOKEEPER_DATA_DIR =
203       ZK_CFG_PROPERTY_PREFIX + "dataDir";
204 
205   /** Parameter name for the ZK tick time */
206   public static final String ZOOKEEPER_TICK_TIME =
207       ZK_CFG_PROPERTY_PREFIX + "tickTime";
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 = 60020;
226 
227   /** default port for region server web api */
228   public static final int DEFAULT_REGIONSERVER_INFOPORT = 60030;
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 = 1200000;
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    * The max number of threads used for opening and closing stores or store
321    * files in parallel
322    */
323   public static final String HSTORE_OPEN_AND_CLOSE_THREADS_MAX =
324     "hbase.hstore.open.and.close.threads.max";
325 
326   /**
327    * The default number for the max number of threads used for opening and
328    * closing stores or store files in parallel
329    */
330   public static final int DEFAULT_HSTORE_OPEN_AND_CLOSE_THREADS_MAX = 1;
331 
332   /**
333    * Block updates if memstore has hbase.hregion.memstore.block.multiplier
334    * times hbase.hregion.memstore.flush.size bytes.  Useful preventing
335    * runaway memstore during spikes in update traffic.
336    */
337   public static final String HREGION_MEMSTORE_BLOCK_MULTIPLIER =
338           "hbase.hregion.memstore.block.multiplier";
339 
340   /**
341    * Default value for hbase.hregion.memstore.block.multiplier
342    */
343   public static final int DEFAULT_HREGION_MEMSTORE_BLOCK_MULTIPLIER = 4;
344 
345   /** Conf key for the memstore size at which we flush the memstore */
346   public static final String HREGION_MEMSTORE_FLUSH_SIZE =
347       "hbase.hregion.memstore.flush.size";
348 
349   public static final String HREGION_EDITS_REPLAY_SKIP_ERRORS =
350       "hbase.hregion.edits.replay.skip.errors";
351 
352   public static final boolean DEFAULT_HREGION_EDITS_REPLAY_SKIP_ERRORS =
353       false;
354 
355   /** Maximum value length, enforced on KeyValue construction */
356   public static final int MAXIMUM_VALUE_LENGTH = Integer.MAX_VALUE - 1;
357 
358   /** name of the file for unique cluster ID */
359   public static final String CLUSTER_ID_FILE_NAME = "hbase.id";
360 
361   /** Default value for cluster ID */
362   public static final String CLUSTER_ID_DEFAULT = "default-cluster";
363 
364   // Always store the location of the root table's HRegion.
365   // This HRegion is never split.
366 
367   // region name = table + startkey + regionid. This is the row key.
368   // each row in the root and meta tables describes exactly 1 region
369   // Do we ever need to know all the information that we are storing?
370 
371   // Note that the name of the root table starts with "-" and the name of the
372   // meta table starts with "." Why? it's a trick. It turns out that when we
373   // store region names in memory, we use a SortedMap. Since "-" sorts before
374   // "." (and since no other table name can start with either of these
375   // characters, the root region will always be the first entry in such a Map,
376   // followed by all the meta regions (which will be ordered by their starting
377   // row key as well), followed by all user tables. So when the Master is
378   // choosing regions to assign, it will always choose the root region first,
379   // followed by the meta regions, followed by user regions. Since the root
380   // and meta regions always need to be on-line, this ensures that they will
381   // be the first to be reassigned if the server(s) they are being served by
382   // should go down.
383 
384 
385   /** The hbase:meta table's name. */
386   @Deprecated  // for compat from 0.94 -> 0.96.
387   public static final byte[] META_TABLE_NAME = TableName.META_TABLE_NAME.getName();
388 
389   public static final String BASE_NAMESPACE_DIR = "data";
390 
391   /** delimiter used between portions of a region name */
392   public static final int META_ROW_DELIMITER = ',';
393 
394   /** The catalog family as a string*/
395   public static final String CATALOG_FAMILY_STR = "info";
396 
397   /** The catalog family */
398   public static final byte [] CATALOG_FAMILY = Bytes.toBytes(CATALOG_FAMILY_STR);
399 
400   /** The RegionInfo qualifier as a string */
401   public static final String REGIONINFO_QUALIFIER_STR = "regioninfo";
402 
403   /** The regioninfo column qualifier */
404   public static final byte [] REGIONINFO_QUALIFIER = Bytes.toBytes(REGIONINFO_QUALIFIER_STR);
405 
406   /** The server column qualifier */
407   public static final byte [] SERVER_QUALIFIER = Bytes.toBytes("server");
408 
409   /** The startcode column qualifier */
410   public static final byte [] STARTCODE_QUALIFIER = Bytes.toBytes("serverstartcode");
411 
412   /** The open seqnum column qualifier */
413   public static final byte [] SEQNUM_QUALIFIER = Bytes.toBytes("seqnumDuringOpen");
414 
415   /** The state column qualifier */
416   public static final byte [] STATE_QUALIFIER = Bytes.toBytes("state");
417 
418   /**
419    * The serverName column qualifier. Its the server where the region is
420    * transitioning on, while column server is the server where the region is
421    * opened on. They are the same when the region is in state OPEN.
422    */
423   public static final byte [] SERVERNAME_QUALIFIER = Bytes.toBytes("sn");
424 
425   /** The lower-half split region column qualifier */
426   public static final byte [] SPLITA_QUALIFIER = Bytes.toBytes("splitA");
427 
428   /** The upper-half split region column qualifier */
429   public static final byte [] SPLITB_QUALIFIER = Bytes.toBytes("splitB");
430 
431   /** The lower-half merge region column qualifier */
432   public static final byte[] MERGEA_QUALIFIER = Bytes.toBytes("mergeA");
433 
434   /** The upper-half merge region column qualifier */
435   public static final byte[] MERGEB_QUALIFIER = Bytes.toBytes("mergeB");
436 
437   /**
438    * The meta table version column qualifier.
439    * We keep current version of the meta table in this column in <code>-ROOT-</code>
440    * table: i.e. in the 'info:v' column.
441    */
442   public static final byte [] META_VERSION_QUALIFIER = Bytes.toBytes("v");
443 
444   /**
445    * The current version of the meta table.
446    * - pre-hbase 0.92.  There is no META_VERSION column in the root table
447    * in this case. The meta has HTableDescriptor serialized into the HRegionInfo;
448    * - version 0 is 0.92 and 0.94. Meta data has serialized HRegionInfo's using
449    * Writable serialization, and HRegionInfo's does not contain HTableDescriptors.
450    * - version 1 for 0.96+ keeps HRegionInfo data structures, but changes the
451    * byte[] serialization from Writables to Protobuf.
452    * See HRegionInfo.VERSION
453    */
454   public static final short META_VERSION = 1;
455 
456   // Other constants
457 
458   /**
459    * An empty instance.
460    */
461   public static final byte [] EMPTY_BYTE_ARRAY = new byte [0];
462 
463   /**
464    * Used by scanners, etc when they want to start at the beginning of a region
465    */
466   public static final byte [] EMPTY_START_ROW = EMPTY_BYTE_ARRAY;
467 
468   /**
469    * Last row in a table.
470    */
471   public static final byte [] EMPTY_END_ROW = EMPTY_START_ROW;
472 
473   /**
474     * Used by scanners and others when they're trying to detect the end of a
475     * table
476     */
477   public static final byte [] LAST_ROW = EMPTY_BYTE_ARRAY;
478 
479   /**
480    * Max length a row can have because of the limitation in TFile.
481    */
482   public static final int MAX_ROW_LENGTH = Short.MAX_VALUE;
483 
484   /**
485    * Timestamp to use when we want to refer to the latest cell.
486    * This is the timestamp sent by clients when no timestamp is specified on
487    * commit.
488    */
489   public static final long LATEST_TIMESTAMP = Long.MAX_VALUE;
490 
491   /**
492    * Timestamp to use when we want to refer to the oldest cell.
493    */
494   public static final long OLDEST_TIMESTAMP = Long.MIN_VALUE;
495 
496   /**
497    * LATEST_TIMESTAMP in bytes form
498    */
499   public static final byte [] LATEST_TIMESTAMP_BYTES = {
500     // big-endian
501     (byte) (LATEST_TIMESTAMP >>> 56),
502     (byte) (LATEST_TIMESTAMP >>> 48),
503     (byte) (LATEST_TIMESTAMP >>> 40),
504     (byte) (LATEST_TIMESTAMP >>> 32),
505     (byte) (LATEST_TIMESTAMP >>> 24),
506     (byte) (LATEST_TIMESTAMP >>> 16),
507     (byte) (LATEST_TIMESTAMP >>> 8),
508     (byte) LATEST_TIMESTAMP,
509   };
510 
511   /**
512    * Define for 'return-all-versions'.
513    */
514   public static final int ALL_VERSIONS = Integer.MAX_VALUE;
515 
516   /**
517    * Unlimited time-to-live.
518    */
519 //  public static final int FOREVER = -1;
520   public static final int FOREVER = Integer.MAX_VALUE;
521 
522   /**
523    * Seconds in a week
524    */
525   public static final int WEEK_IN_SECONDS = 7 * 24 * 3600;
526 
527   /**
528    * Seconds in a day, hour and minute
529    */
530   public static final int DAY_IN_SECONDS = 24 * 60 * 60;
531   public static final int HOUR_IN_SECONDS = 60 * 60;
532   public static final int MINUTE_IN_SECONDS = 60;
533 
534   //TODO: although the following are referenced widely to format strings for
535   //      the shell. They really aren't a part of the public API. It would be
536   //      nice if we could put them somewhere where they did not need to be
537   //      public. They could have package visibility
538   public static final String NAME = "NAME";
539   public static final String VERSIONS = "VERSIONS";
540   public static final String IN_MEMORY = "IN_MEMORY";
541   public static final String METADATA = "METADATA";
542   public static final String CONFIGURATION = "CONFIGURATION";
543 
544   /**
545    * Retrying we multiply hbase.client.pause setting by what we have in this array until we
546    * run out of array items.  Retries beyond this use the last number in the array.  So, for
547    * example, if hbase.client.pause is 1 second, and maximum retries count
548    * hbase.client.retries.number is 10, we will retry at the following intervals:
549    * 1, 2, 3, 5, 10, 20, 40, 100, 100, 100.
550    * With 100ms, a back-off of 200 means 20s
551    */
552   public static final int RETRY_BACKOFF[] = {1, 2, 3, 5, 10, 20, 40, 100, 100, 100, 100, 200, 200};
553 
554   public static final String REGION_IMPL = "hbase.hregion.impl";
555 
556   /** modifyTable op for replacing the table descriptor */
557   @InterfaceAudience.Private
558   public static enum Modify {
559     CLOSE_REGION,
560     TABLE_COMPACT,
561     TABLE_FLUSH,
562     TABLE_MAJOR_COMPACT,
563     TABLE_SET_HTD,
564     TABLE_SPLIT
565   }
566 
567   /**
568    * Scope tag for locally scoped data.
569    * This data will not be replicated.
570    */
571   public static final int REPLICATION_SCOPE_LOCAL = 0;
572 
573   /**
574    * Scope tag for globally scoped data.
575    * This data will be replicated to all peers.
576    */
577   public static final int REPLICATION_SCOPE_GLOBAL = 1;
578 
579   /**
580    * Default cluster ID, cannot be used to identify a cluster so a key with
581    * this value means it wasn't meant for replication.
582    */
583   public static final UUID DEFAULT_CLUSTER_ID = new UUID(0L,0L);
584 
585     /**
586      * Parameter name for maximum number of bytes returned when calling a
587      * scanner's next method.
588      */
589   public static final String HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE_KEY =
590       "hbase.client.scanner.max.result.size";
591 
592   /**
593    * Parameter name for maximum number of bytes returned when calling a scanner's next method.
594    * Controlled by the server.
595    */
596   public static final String HBASE_SERVER_SCANNER_MAX_RESULT_SIZE_KEY =
597       "hbase.server.scanner.max.result.size";
598 
599   /**
600    * Maximum number of bytes returned when calling a scanner's next method.
601    * Note that when a single row is larger than this limit the row is still
602    * returned completely.
603    *
604    * The default value is 2MB.
605    */
606   public static final long DEFAULT_HBASE_CLIENT_SCANNER_MAX_RESULT_SIZE = 2 * 1024 * 1024;
607 
608   /**
609    * Maximum number of bytes returned when calling a scanner's next method.
610    * Note that when a single row is larger than this limit the row is still
611    * returned completely.
612    * Safety setting to protect the region server.
613    *
614    * The default value unlimited for backwards compatibility
615    */
616   public static final long DEFAULT_HBASE_SERVER_SCANNER_MAX_RESULT_SIZE = Long.MAX_VALUE;
617 
618   /**
619    * Parameter name for client pause value, used mostly as value to wait
620    * before running a retry of a failed get, region lookup, etc.
621    */
622   public static final String HBASE_CLIENT_PAUSE = "hbase.client.pause";
623 
624   /**
625    * Default value of {@link #HBASE_CLIENT_PAUSE}.
626    */
627   public static final long DEFAULT_HBASE_CLIENT_PAUSE = 100;
628 
629   /**
630    * The maximum number of concurrent connections the client will maintain.
631    */
632   public static final String HBASE_CLIENT_MAX_TOTAL_TASKS = "hbase.client.max.total.tasks";
633 
634   /**
635    * Default value of {@link #HBASE_CLIENT_MAX_TOTAL_TASKS}.
636    */
637   public static final int DEFAULT_HBASE_CLIENT_MAX_TOTAL_TASKS = 100;
638 
639   /**
640    * The maximum number of concurrent connections the client will maintain to a single
641    * RegionServer.
642    */
643   public static final String HBASE_CLIENT_MAX_PERSERVER_TASKS = "hbase.client.max.perserver.tasks";
644 
645   /**
646    * Default value of {@link #HBASE_CLIENT_MAX_PERSERVER_TASKS}.
647    */
648   public static final int DEFAULT_HBASE_CLIENT_MAX_PERSERVER_TASKS = 2;
649 
650   /**
651    * The maximum number of concurrent connections the client will maintain to a single
652    * Region.
653    */
654   public static final String HBASE_CLIENT_MAX_PERREGION_TASKS = "hbase.client.max.perregion.tasks";
655 
656   /**
657    * Default value of {@link #HBASE_CLIENT_MAX_PERREGION_TASKS}.
658    */
659   public static final int DEFAULT_HBASE_CLIENT_MAX_PERREGION_TASKS = 1;
660 
661   /**
662    * Parameter name for server pause value, used mostly as value to wait before
663    * running a retry of a failed operation.
664    */
665   public static final String HBASE_SERVER_PAUSE = "hbase.server.pause";
666 
667   /**
668    * Default value of {@link #HBASE_SERVER_PAUSE}.
669    */
670   public static final int DEFAULT_HBASE_SERVER_PAUSE = 1000;
671 
672   /**
673    * Parameter name for maximum retries, used as maximum for all retryable
674    * operations such as fetching of the root region from root region server,
675    * getting a cell's value, starting a row update, etc.
676    */
677   public static final String HBASE_CLIENT_RETRIES_NUMBER = "hbase.client.retries.number";
678 
679   /**
680    * Default value of {@link #HBASE_CLIENT_RETRIES_NUMBER}.
681    */
682   public static final int DEFAULT_HBASE_CLIENT_RETRIES_NUMBER = 31;
683 
684   /**
685    * Parameter name for client region location prefetch toggle.
686    */
687   public static String HBASE_CLIENT_PREFETCH = "hbase.client.prefetch";
688 
689   /**
690    * Default value of {@link #HBASE_CLIENT_PREFETCH}.
691    */
692   public static boolean DEFAULT_HBASE_CLIENT_PREFETCH = true;
693 
694   /**
695    * Parameter name for client prefetch limit, used as the maximum number of regions
696    * info that will be prefetched.
697    */
698   public static String HBASE_CLIENT_PREFETCH_LIMIT = "hbase.client.prefetch.limit";
699 
700   /**
701    * Default value of {@link #HBASE_CLIENT_PREFETCH_LIMIT}.
702    */
703   public static int DEFAULT_HBASE_CLIENT_PREFETCH_LIMIT = 10;
704 
705   /**
706    * Parameter name to set the default scanner caching for all clients.
707    */
708   public static final String HBASE_CLIENT_SCANNER_CACHING = "hbase.client.scanner.caching";
709 
710   /**
711    * Default value for {@link #HBASE_CLIENT_SCANNER_CACHING}
712    */
713   public static final int DEFAULT_HBASE_CLIENT_SCANNER_CACHING = 100;
714 
715   /**
716    * Parameter name for number of versions, kept by meta table.
717    */
718   public static String HBASE_META_VERSIONS = "hbase.meta.versions";
719 
720   /**
721    * Default value of {@link #HBASE_META_VERSIONS}.
722    */
723   public static int DEFAULT_HBASE_META_VERSIONS = 10;
724 
725   /**
726    * Parameter name for number of versions, kept by meta table.
727    */
728   public static String HBASE_META_BLOCK_SIZE = "hbase.meta.blocksize";
729 
730   /**
731    * Default value of {@link #HBASE_META_BLOCK_SIZE}.
732    */
733   public static int DEFAULT_HBASE_META_BLOCK_SIZE = 8 * 1024;
734 
735   /**
736    * Parameter name for number of rows that will be fetched when calling next on
737    * a scanner if it is not served from memory. Higher caching values will
738    * enable faster scanners but will eat up more memory and some calls of next
739    * may take longer and longer times when the cache is empty.
740    */
741   public static final String HBASE_META_SCANNER_CACHING = "hbase.meta.scanner.caching";
742 
743   /**
744    * Default value of {@link #HBASE_META_SCANNER_CACHING}.
745    */
746   public static final int DEFAULT_HBASE_META_SCANNER_CACHING = 100;
747 
748   /**
749    * Parameter name for unique identifier for this {@link org.apache.hadoop.conf.Configuration}
750    * instance. If there are two or more {@link org.apache.hadoop.conf.Configuration} instances that,
751    * for all intents and purposes, are the same except for their instance ids, then they will not be
752    * able to share the same org.apache.hadoop.hbase.client.HConnection instance. On the other hand,
753    * even if the instance ids are the same, it could result in non-shared
754    * org.apache.hadoop.hbase.client.HConnection instances if some of the other connection parameters
755    * differ.
756    */
757   public static final String HBASE_CLIENT_INSTANCE_ID = "hbase.client.instance.id";
758 
759   /**
760    * The client scanner timeout period in milliseconds.
761    */
762   public static final String HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD = "hbase.client.scanner.timeout.period";
763 
764   /**
765    * Use {@link #HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD} instead.
766    * @deprecated This config option is deprecated. Will be removed at later releases after 0.96.
767    */
768   @Deprecated
769   public static final String HBASE_REGIONSERVER_LEASE_PERIOD_KEY =
770       "hbase.regionserver.lease.period";
771 
772   /**
773    * Default value of {@link #HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD}.
774    */
775   public static final int DEFAULT_HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD = 60000;
776 
777   /**
778    * timeout for each RPC
779    */
780   public static final String HBASE_RPC_TIMEOUT_KEY = "hbase.rpc.timeout";
781 
782   /**
783    * Default value of {@link #HBASE_RPC_TIMEOUT_KEY}
784    */
785   public static final int DEFAULT_HBASE_RPC_TIMEOUT = 60000;
786 
787   /**
788    * timeout for short operation RPC
789    */
790   public static final String HBASE_RPC_SHORTOPERATION_TIMEOUT_KEY =
791       "hbase.rpc.shortoperation.timeout";
792 
793   /**
794    * Default value of {@link #HBASE_RPC_SHORTOPERATION_TIMEOUT_KEY}
795    */
796   public static final int DEFAULT_HBASE_RPC_SHORTOPERATION_TIMEOUT = 10000;
797 
798   /**
799    * Value indicating the server name was saved with no sequence number.
800    */
801   public static final long NO_SEQNUM = -1;
802 
803 
804   /*
805    * cluster replication constants.
806    */
807   public static final String
808       REPLICATION_ENABLE_KEY = "hbase.replication";
809   public static final boolean
810       REPLICATION_ENABLE_DEFAULT = true;
811   public static final String
812       REPLICATION_SOURCE_SERVICE_CLASSNAME = "hbase.replication.source.service";
813   public static final String
814       REPLICATION_SINK_SERVICE_CLASSNAME = "hbase.replication.sink.service";
815   public static final String REPLICATION_SERVICE_CLASSNAME_DEFAULT =
816     "org.apache.hadoop.hbase.replication.regionserver.Replication";
817 
818   /** HBCK special code name used as server name when manipulating ZK nodes */
819   public static final String HBCK_CODE_NAME = "HBCKServerName";
820 
821   public static final String KEY_FOR_HOSTNAME_SEEN_BY_MASTER =
822     "hbase.regionserver.hostname.seen.by.master";
823 
824   public static final String HBASE_MASTER_LOGCLEANER_PLUGINS =
825       "hbase.master.logcleaner.plugins";
826 
827   public static final String HBASE_REGION_SPLIT_POLICY_KEY =
828     "hbase.regionserver.region.split.policy";
829 
830   /** Whether nonces are enabled; default is true. */
831   public static final String HBASE_RS_NONCES_ENABLED = "hbase.regionserver.nonces.enabled";
832 
833   /**
834    * Configuration key for the size of the block cache
835    */
836   public static final String HFILE_BLOCK_CACHE_SIZE_KEY =
837     "hfile.block.cache.size";
838 
839   public static final float HFILE_BLOCK_CACHE_SIZE_DEFAULT = 0.25f;
840 
841   /*
842     * Minimum percentage of free heap necessary for a successful cluster startup.
843     */
844   public static final float HBASE_CLUSTER_MINIMUM_MEMORY_THRESHOLD = 0.2f;
845 
846   public static final Pattern CP_HTD_ATTR_KEY_PATTERN =
847       Pattern.compile("^coprocessor\\$([0-9]+)$", Pattern.CASE_INSENSITIVE);
848 
849   /**
850    * Pattern that matches a coprocessor specification. Form is:
851    * <code>
852    *&lt;coprocessor jar file location> '|' &lt<class name> ['|' &lt;priority> ['|' &lt;arguments>]]
853    * </code>
854    * ...where arguments are <code>&lt;KEY> '=' &lt;VALUE> [,...]</code>
855    * <p>For example: <code>hdfs:///foo.jar|com.foo.FooRegionObserver|1001|arg1=1,arg2=2</code>
856    */
857   public static final Pattern CP_HTD_ATTR_VALUE_PATTERN =
858       Pattern.compile("(^[^\\|]*)\\|([^\\|]+)\\|[\\s]*([\\d]*)[\\s]*(\\|.*)?$");
859 
860   public static final String CP_HTD_ATTR_VALUE_PARAM_KEY_PATTERN = "[^=,]+";
861   public static final String CP_HTD_ATTR_VALUE_PARAM_VALUE_PATTERN = "[^,]+";
862   public static final Pattern CP_HTD_ATTR_VALUE_PARAM_PATTERN = Pattern.compile(
863       "(" + CP_HTD_ATTR_VALUE_PARAM_KEY_PATTERN + ")=(" +
864       CP_HTD_ATTR_VALUE_PARAM_VALUE_PATTERN + "),?");
865 
866   /** The delay when re-trying a socket operation in a loop (HBASE-4712) */
867   public static final int SOCKET_RETRY_WAIT_MS = 200;
868 
869   /** Host name of the local machine */
870   public static final String LOCALHOST = "localhost";
871 
872   /**
873    * If this parameter is set to true, then hbase will read
874    * data and then verify checksums. Checksum verification
875    * inside hdfs will be switched off.  However, if the hbase-checksum
876    * verification fails, then it will switch back to using
877    * hdfs checksums for verifiying data that is being read from storage.
878    *
879    * If this parameter is set to false, then hbase will not
880    * verify any checksums, instead it will depend on checksum verification
881    * being done in the hdfs client.
882    */
883   public static final String HBASE_CHECKSUM_VERIFICATION =
884       "hbase.regionserver.checksum.verify";
885 
886   public static final String LOCALHOST_IP = "127.0.0.1";
887 
888   /** Conf key that enables unflushed WAL edits directly being replayed to region servers */
889   public static final String DISTRIBUTED_LOG_REPLAY_KEY = "hbase.master.distributed.log.replay";
890   public static final boolean DEFAULT_DISTRIBUTED_LOG_REPLAY_CONFIG = false;
891   public static final String DISALLOW_WRITES_IN_RECOVERING =
892       "hbase.regionserver.disallow.writes.when.recovering";
893   public static final boolean DEFAULT_DISALLOW_WRITES_IN_RECOVERING_CONFIG = false;
894 
895   public static final String REGION_SERVER_HANDLER_COUNT = "hbase.regionserver.handler.count";
896   public static final int DEFAULT_REGION_SERVER_HANDLER_COUNT = 30;
897 
898   /*
899    * REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT:
900    * -1  => Disable aborting
901    * 0   => Abort if even a single handler has died
902    * 0.x => Abort only when this percent of handlers have died
903    * 1   => Abort only all of the handers have died
904    */
905   public static final String REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT =
906       "hbase.regionserver.handler.abort.on.error.percent";
907   public static final float DEFAULT_REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT = -1;
908   
909   public static final String REGION_SERVER_META_HANDLER_COUNT =
910       "hbase.regionserver.metahandler.count";
911   public static final int DEFAULT_REGION_SERVER_META_HANDLER_COUNT = 10;
912 
913   public static final String REGION_SERVER_REPLICATION_HANDLER_COUNT =
914       "hbase.regionserver.replication.handler.count";
915   public static final int DEFAULT_REGION_SERVER_REPLICATION_HANDLER_COUNT = 3;
916 
917   public static final String MASTER_HANDLER_COUNT = "hbase.master.handler.count";
918   public static final int DEFAULT_MASTER_HANLDER_COUNT = 25;
919 
920   /** Conf key that specifies timeout value to wait for a region ready */
921   public static final String LOG_REPLAY_WAIT_REGION_TIMEOUT =
922       "hbase.master.log.replay.wait.region.timeout";
923 
924   /**
925    * The name of the configuration parameter that specifies
926    * the number of bytes in a newly created checksum chunk.
927    */
928   public static final String BYTES_PER_CHECKSUM =
929       "hbase.hstore.bytes.per.checksum";
930 
931   /**
932    * The name of the configuration parameter that specifies
933    * the name of an algorithm that is used to compute checksums
934    * for newly created blocks.
935    */
936   public static final String CHECKSUM_TYPE_NAME =
937       "hbase.hstore.checksum.algorithm";
938 
939   /** Enable file permission modification from standard hbase */
940   public static final String ENABLE_DATA_FILE_UMASK = "hbase.data.umask.enable";
941   /** File permission umask to use when creating hbase data files */
942   public static final String DATA_FILE_UMASK_KEY = "hbase.data.umask";
943 
944   /** Configuration name of HLog Compression */
945   public static final String ENABLE_WAL_COMPRESSION =
946     "hbase.regionserver.wal.enablecompression";
947 
948   /** Region in Transition metrics threshold time */
949   public static final String METRICS_RIT_STUCK_WARNING_THRESHOLD =
950       "hbase.metrics.rit.stuck.warning.threshold";
951 
952   public static final String LOAD_BALANCER_SLOP_KEY = "hbase.regions.slop";
953 
954   /**
955    * The byte array represents for NO_NEXT_INDEXED_KEY;
956    * The actual value is irrelevant because this is always compared by reference.
957    */
958   public static final byte [] NO_NEXT_INDEXED_KEY = Bytes.toBytes("NO_NEXT_INDEXED_KEY");
959   /** delimiter used between portions of a region name */
960   public static final int DELIMITER = ',';
961   public static final String HBASE_CONFIG_READ_ZOOKEEPER_CONFIG =
962       "hbase.config.read.zookeeper.config";
963   public static final boolean DEFAULT_HBASE_CONFIG_READ_ZOOKEEPER_CONFIG =
964       false;
965 
966   /**
967    * QOS attributes: these attributes are used to demarcate RPC call processing
968    * by different set of handlers. For example, HIGH_QOS tagged methods are
969    * handled by high priority handlers.
970    */
971   public static final int NORMAL_QOS = 0;
972   public static final int QOS_THRESHOLD = 10;
973   public static final int HIGH_QOS = 100;
974   public static final int REPLICATION_QOS = 5; // normal_QOS < replication_QOS < high_QOS
975   public static final int REPLAY_QOS = 6; // REPLICATION_QOS < REPLAY_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 =
1044       "hbase.status.multicast.bind.address.ip";
1045   public static final String DEFAULT_STATUS_MULTICAST_BIND_ADDRESS = "0.0.0.0";
1046 
1047   /**
1048    * The port to use for the multicast messages.
1049    */
1050   public static final String STATUS_MULTICAST_PORT = "hbase.status.multicast.address.port";
1051   public static final int DEFAULT_STATUS_MULTICAST_PORT = 60100;
1052 
1053   public static final long NO_NONCE = 0;
1054 
1055   /** Default cipher for encryption */
1056   public static final String CIPHER_AES = "AES";
1057 
1058   /** Configuration key for the crypto algorithm provider, a class name */
1059   @InterfaceStability.Unstable
1060   public static final String CRYPTO_CIPHERPROVIDER_CONF_KEY = "hbase.crypto.cipherprovider";
1061 
1062   /** Configuration key for the crypto key provider, a class name */
1063   @InterfaceStability.Unstable
1064   public static final String CRYPTO_KEYPROVIDER_CONF_KEY = "hbase.crypto.keyprovider";
1065 
1066   /** Configuration key for the crypto key provider parameters */
1067   @InterfaceStability.Unstable
1068   public static final String CRYPTO_KEYPROVIDER_PARAMETERS_KEY =
1069       "hbase.crypto.keyprovider.parameters";
1070 
1071   /** Configuration key for the name of the master key for the cluster, a string */
1072   @InterfaceStability.Unstable
1073   public static final String CRYPTO_MASTERKEY_NAME_CONF_KEY = "hbase.crypto.master.key.name";
1074 
1075   /** Configuration key for the name of the alternate master key for the cluster, a string */
1076   @InterfaceStability.Unstable
1077   public static final String CRYPTO_MASTERKEY_ALTERNATE_NAME_CONF_KEY =
1078     "hbase.crypto.master.alternate.key.name";
1079 
1080   /** Configuration key for the algorithm to use when encrypting the WAL, a string */
1081   @InterfaceStability.Unstable
1082   public static final String CRYPTO_WAL_ALGORITHM_CONF_KEY = "hbase.crypto.wal.algorithm";
1083 
1084   /** Configuration key for the name of the master WAL encryption key for the cluster, a string */
1085   @InterfaceStability.Unstable
1086   public static final String CRYPTO_WAL_KEY_NAME_CONF_KEY = "hbase.crypto.wal.key.name";
1087 
1088   /** Configuration key for the algorithm used for creating jks key, a string */
1089   public static final String CRYPTO_KEY_ALGORITHM_CONF_KEY = "hbase.crypto.key.algorithm";
1090 
1091   /** Configuration key for the name of the alternate cipher algorithm for the cluster, a string */
1092   public static final String CRYPTO_ALTERNATE_KEY_ALGORITHM_CONF_KEY =
1093       "hbase.crypto.alternate.key.algorithm";
1094 
1095   /** Configuration key for enabling WAL encryption, a boolean */
1096   public static final String ENABLE_WAL_ENCRYPTION = "hbase.regionserver.wal.encryption";
1097 
1098   /** Configuration key for setting RPC codec class name */
1099   public static final String RPC_CODEC_CONF_KEY = "hbase.client.rpc.codec";
1100 
1101   /** Configuration key for setting replication codec class name */
1102   public static final String REPLICATION_CODEC_CONF_KEY = "hbase.replication.rpc.codec";
1103 
1104   /** Config key for if the server should send backpressure and if the client should listen to
1105    * that backpressure from the server */
1106   public static final String ENABLE_CLIENT_BACKPRESSURE = "hbase.client.backpressure.enabled";
1107   public static final boolean DEFAULT_ENABLE_CLIENT_BACKPRESSURE = false;
1108 
1109   public static final String HEAP_OCCUPANCY_LOW_WATERMARK_KEY =
1110       "hbase.heap.occupancy.low_water_mark";
1111   public static final float DEFAULT_HEAP_OCCUPANCY_LOW_WATERMARK = 0.95f;
1112   public static final String HEAP_OCCUPANCY_HIGH_WATERMARK_KEY =
1113       "hbase.heap.occupancy.high_water_mark";
1114   public static final float DEFAULT_HEAP_OCCUPANCY_HIGH_WATERMARK = 0.98f;
1115 
1116   /**
1117    * The max number of threads used for splitting storefiles in parallel during
1118    * the region split process.
1119    */
1120   public static final String REGION_SPLIT_THREADS_MAX =
1121     "hbase.regionserver.region.split.threads.max";
1122 
1123   /** Canary config keys */
1124   public static final String HBASE_CANARY_WRITE_DATA_TTL_KEY = "hbase.canary.write.data.ttl";
1125 
1126   public static final String HBASE_CANARY_WRITE_PERSERVER_REGIONS_LOWERLIMIT_KEY =
1127       "hbase.canary.write.perserver.regions.lowerLimit";
1128 
1129   public static final String HBASE_CANARY_WRITE_PERSERVER_REGIONS_UPPERLIMIT_KEY =
1130       "hbase.canary.write.perserver.regions.upperLimit";
1131 
1132   public static final String HBASE_CANARY_WRITE_VALUE_SIZE_KEY = "hbase.canary.write.value.size";
1133 
1134   public static final String HBASE_CANARY_WRITE_TABLE_CHECK_PERIOD_KEY =
1135       "hbase.canary.write.table.check.period";
1136   
1137   /**
1138    * Config keys for programmatic JAAS config for secured ZK interaction
1139    */
1140   public static final String ZK_CLIENT_KEYTAB_FILE = "hbase.zookeeper.client.keytab.file";
1141   public static final String ZK_CLIENT_KERBEROS_PRINCIPAL =
1142       "hbase.zookeeper.client.kerberos.principal";
1143   public static final String ZK_SERVER_KEYTAB_FILE = "hbase.zookeeper.server.keytab.file";
1144   public static final String ZK_SERVER_KERBEROS_PRINCIPAL =
1145       "hbase.zookeeper.server.kerberos.principal";
1146 
1147   /**
1148    * Allow legacy object serialization. Disabled by default because it is a security risk */
1149   public static final String ALLOW_LEGACY_OBJECT_SERIALIZATION_KEY =
1150       "hbase.allow.legacy.object.serialization";
1151 
1152   /** Config key for hbase temporary directory in hdfs */
1153   public static final String TEMPORARY_FS_DIRECTORY_KEY = "hbase.fs.tmp.dir";
1154   public static final String DEFAULT_TEMPORARY_HDFS_DIRECTORY = "/user/"
1155       + System.getProperty("user.name") + "/hbase-staging";
1156 
1157   private HConstants() {
1158     // Can't be instantiated with this ctor.
1159   }
1160 }