Chapter 3. Configuration

Table of Contents

3.1. hbase-site.xml and hbase-default.xml
3.1.1. HBase Default Configuration
3.2. hbase-env.sh
3.3. log4j.properties
3.4. The Important Configurations
3.4.1. Required Configurations
3.4.2. Recommended Configuations
3.5. Client configuration and dependencies connecting to an HBase cluster
3.5.1. Java client configuration

HBase uses the same configuration system as Hadoop. To configure a deploy, edit a file of environment variables in conf/hbase-env.sh -- this configuration is used mostly by the launcher shell scripts getting the cluster off the ground -- and then add configuration to an XML file to do things like override HBase defaults, tell HBase what Filesystem to use, and the location of the ZooKeeper ensemble [10] .

When running in distributed mode, after you make an edit to an HBase configuration, make sure you copy the content of the conf directory to all nodes of the cluster. HBase will not do this for you. Use rsync.

3.1. hbase-site.xml and hbase-default.xml

Just as in Hadoop where you add site-specific HDFS configuration to the hdfs-site.xml file, for HBase, site specific customizations go into the file conf/hbase-site.xml. For the list of configurable properties, see Section 3.1.1, “HBase Default Configuration” below or view the raw hbase-default.xml source file in the HBase source code at src/main/resources.

Not all configuration options make it out to hbase-default.xml. Configuration that it is thought rare anyone would change can exist only in code; the only way to turn up such configurations is via a reading of the source code itself.

Currently, changes here will require a cluster restart for HBase to notice the change.

3.1.1. HBase Default Configuration

HBase Default Configuration

This documentation is generated using the default hbase configuration file, hbase-default.xml, as source.

hbase.rootdir

The directory shared by region servers and into which HBase persists. The URL should be 'fully-qualified' to include the filesystem scheme. For example, to specify the HDFS directory '/hbase' where the HDFS instance's namenode is running at namenode.example.org on port 9000, set this value to: hdfs://namenode.example.org:9000/hbase. By default HBase writes into /tmp. Change this configuration else all data will be lost on machine restart.

Default: file:///tmp/hbase-${user.name}/hbase

hbase.master.port

The port the HBase Master should bind to.

Default: 60000

hbase.cluster.distributed

The mode the cluster will be in. Possible values are false for standalone mode and true for distributed mode. If false, startup will run all HBase and ZooKeeper daemons together in the one JVM.

Default: false

hbase.tmp.dir

Temporary directory on the local filesystem. Change this setting to point to a location more permanent than '/tmp' (The '/tmp' directory is often cleared on machine restart).

Default: /tmp/hbase-${user.name}

hbase.master.info.port

The port for the HBase Master web UI. Set to -1 if you do not want a UI instance run.

Default: 60010

hbase.master.info.bindAddress

The bind address for the HBase Master web UI

Default: 0.0.0.0

hbase.client.write.buffer

Default size of the HTable clien write buffer in bytes. A bigger buffer takes more memory -- on both the client and server side since server instantiates the passed write buffer to process it -- but a larger buffer size reduces the number of RPCs made. For an estimate of server-side memory-used, evaluate hbase.client.write.buffer * hbase.regionserver.handler.count

Default: 2097152

hbase.regionserver.port

The port the HBase RegionServer binds to.

Default: 60020

hbase.regionserver.info.port

The port for the HBase RegionServer web UI Set to -1 if you do not want the RegionServer UI to run.

Default: 60030

hbase.regionserver.info.port.auto

Whether or not the Master or RegionServer UI should search for a port to bind to. Enables automatic port search if hbase.regionserver.info.port is already in use. Useful for testing, turned off by default.

Default: false

hbase.regionserver.info.bindAddress

The address for the HBase RegionServer web UI

Default: 0.0.0.0

hbase.regionserver.class

The RegionServer interface to use. Used by the client opening proxy to remote region server.

Default: org.apache.hadoop.hbase.ipc.HRegionInterface

hbase.client.pause

General client pause value. Used mostly as value to wait before running a retry of a failed get, region lookup, etc.

Default: 1000

hbase.client.retries.number

Maximum retries. Used as maximum for all retryable operations such as fetching of the root region from root region server, getting a cell's value, starting a row update, etc. Default: 10.

Default: 10

hbase.client.scanner.caching

Number of rows that will be fetched when calling next on a scanner if it is not served from (local, client) memory. Higher caching values will enable faster scanners but will eat up more memory and some calls of next may take longer and longer times when the cache is empty. Do not set this value such that the time between invocations is greater than the scanner timeout; i.e. hbase.regionserver.lease.period

Default: 1

hbase.client.keyvalue.maxsize

Specifies the combined maximum allowed size of a KeyValue instance. This is to set an upper boundary for a single entry saved in a storage file. Since they cannot be split it helps avoiding that a region cannot be split any further because the data is too large. It seems wise to set this to a fraction of the maximum region size. Setting it to zero or less disables the check.

Default: 10485760

hbase.regionserver.lease.period

HRegion server lease period in milliseconds. Default is 60 seconds. Clients must report in within this period else they are considered dead.

Default: 60000

hbase.regionserver.handler.count

Count of RPC Server instances spun up on RegionServers Same property is used by the Master for count of master handlers. Default is 10.

Default: 10

hbase.regionserver.msginterval

Interval between messages from the RegionServer to Master in milliseconds.

Default: 3000

hbase.regionserver.optionallogflushinterval

Sync the HLog to the HDFS after this interval if it has not accumulated enough entries to trigger a sync. Default 1 second. Units: milliseconds.

Default: 1000

hbase.regionserver.regionSplitLimit

Limit for the number of regions after which no more region splitting should take place. This is not a hard limit for the number of regions but acts as a guideline for the regionserver to stop splitting after a certain limit. Default is set to MAX_INT; i.e. do not block splitting.

Default: 2147483647

hbase.regionserver.logroll.period

Period at which we will roll the commit log regardless of how many edits it has.

Default: 3600000

hbase.regionserver.hlog.reader.impl

The HLog file reader implementation.

Default: org.apache.hadoop.hbase.regionserver.wal.SequenceFileLogReader

hbase.regionserver.hlog.writer.impl

The HLog file writer implementation.

Default: org.apache.hadoop.hbase.regionserver.wal.SequenceFileLogWriter

hbase.regionserver.thread.splitcompactcheckfrequency

How often a region server runs the split/compaction check.

Default: 20000

hbase.regionserver.nbreservationblocks

The number of resevoir blocks of memory release on OOME so we can cleanup properly before server shutdown.

Default: 4

hbase.zookeeper.dns.interface

The name of the Network Interface from which a ZooKeeper server should report its IP address.

Default: default

hbase.zookeeper.dns.nameserver

The host name or IP address of the name server (DNS) which a ZooKeeper server should use to determine the host name used by the master for communication and display purposes.

Default: default

hbase.regionserver.dns.interface

The name of the Network Interface from which a region server should report its IP address.

Default: default

hbase.regionserver.dns.nameserver

The host name or IP address of the name server (DNS) which a region server should use to determine the host name used by the master for communication and display purposes.

Default: default

hbase.master.dns.interface

The name of the Network Interface from which a master should report its IP address.

Default: default

hbase.master.dns.nameserver

The host name or IP address of the name server (DNS) which a master should use to determine the host name used for communication and display purposes.

Default: default

hbase.balancer.period

Period at which the region balancer runs in the Master.

Default: 300000

hbase.regions.slop

Rebalance if any regionserver has average + (average * slop) regions. Default is 0% slop.

Default: 0

hbase.master.logcleaner.ttl

Maximum time a HLog can stay in the .oldlogdir directory, after which it will be cleaned by a Master thread.

Default: 600000

hbase.master.logcleaner.plugins

A comma-separated list of LogCleanerDelegate invoked by the LogsCleaner service. These WAL/HLog cleaners are called in order, so put the HLog cleaner that prunes the most HLog files in front. To implement your own LogCleanerDelegate, just put it in HBase's classpath and add the fully qualified class name here. Always add the above default log cleaners in the list.

Default: org.apache.hadoop.hbase.master.TimeToLiveLogCleaner

hbase.regionserver.global.memstore.upperLimit

Maximum size of all memstores in a region server before new updates are blocked and flushes are forced. Defaults to 40% of heap

Default: 0.4

hbase.regionserver.global.memstore.lowerLimit

When memstores are being forced to flush to make room in memory, keep flushing until we hit this mark. Defaults to 35% of heap. This value equal to hbase.regionserver.global.memstore.upperLimit causes the minimum possible flushing to occur when updates are blocked due to memstore limiting.

Default: 0.35

hbase.server.thread.wakefrequency

Time to sleep in between searches for work (in milliseconds). Used as sleep interval by service threads such as log roller.

Default: 10000

hbase.hregion.memstore.flush.size

Memstore will be flushed to disk if size of the memstore exceeds this number of bytes. Value is checked by a thread that runs every hbase.server.thread.wakefrequency.

Default: 67108864

hbase.hregion.preclose.flush.size

If the memstores in a region are this size or larger when we go to close, run a "pre-flush" to clear out memstores before we put up the region closed flag and take the region offline. On close, a flush is run under the close flag to empty memory. During this time the region is offline and we are not taking on any writes. If the memstore content is large, this flush could take a long time to complete. The preflush is meant to clean out the bulk of the memstore before putting up the close flag and taking the region offline so the flush that runs under the close flag has little to do.

Default: 5242880

hbase.hregion.memstore.block.multiplier

Block updates if memstore has hbase.hregion.block.memstore time hbase.hregion.flush.size bytes. Useful preventing runaway memstore during spikes in update traffic. Without an upper-bound, memstore fills such that when it flushes the resultant flush files take a long time to compact or split, or worse, we OOME.

Default: 2

hbase.hregion.memstore.mslab.enabled

Experimental: Enables the MemStore-Local Allocation Buffer, a feature which works to prevent heap fragmentation under heavy write loads. This can reduce the frequency of stop-the-world GC pauses on large heaps.

Default: false

hbase.hregion.max.filesize

Maximum HStoreFile size. If any one of a column families' HStoreFiles has grown to exceed this value, the hosting HRegion is split in two. Default: 256M.

Default: 268435456

hbase.hstore.compactionThreshold

If more than this number of HStoreFiles in any one HStore (one HStoreFile is written per flush of memstore) then a compaction is run to rewrite all HStoreFiles files as one. Larger numbers put off compaction but when it runs, it takes longer to complete.

Default: 3

hbase.hstore.blockingStoreFiles

If more than this number of StoreFiles in any one Store (one StoreFile is written per flush of MemStore) then updates are blocked for this HRegion until a compaction is completed, or until hbase.hstore.blockingWaitTime has been exceeded.

Default: 7

hbase.hstore.blockingWaitTime

The time an HRegion will block updates for after hitting the StoreFile limit defined by hbase.hstore.blockingStoreFiles. After this time has elapsed, the HRegion will stop blocking updates even if a compaction has not been completed. Default: 90 seconds.

Default: 90000

hbase.hstore.compaction.max

Max number of HStoreFiles to compact per 'minor' compaction.

Default: 10

hbase.hregion.majorcompaction

The time (in miliseconds) between 'major' compactions of all HStoreFiles in a region. Default: 1 day. Set to 0 to disable automated major compactions.

Default: 86400000

hbase.mapreduce.hfileoutputformat.blocksize

The mapreduce HFileOutputFormat writes storefiles/hfiles. This is the minimum hfile blocksize to emit. Usually in hbase, writing hfiles, the blocksize is gotten from the table schema (HColumnDescriptor) but in the mapreduce outputformat context, we don't have access to the schema so get blocksize from Configuation. The smaller you make the blocksize, the bigger your index and the less you fetch on a random-access. Set the blocksize down if you have small cells and want faster random-access of individual cells.

Default: 65536

hfile.block.cache.size

Percentage of maximum heap (-Xmx setting) to allocate to block cache used by HFile/StoreFile. Default of 0.2 means allocate 20%. Set to 0 to disable.

Default: 0.2

hbase.hash.type

The hashing algorithm for use in HashFunction. Two values are supported now: murmur (MurmurHash) and jenkins (JenkinsHash). Used by bloom filters.

Default: murmur

hbase.master.keytab.file

Full path to the kerberos keytab file to use for logging in the configured HMaster server principal.

Default:

hbase.master.kerberos.principal

Ex. "hbase/_HOST@EXAMPLE.COM". The kerberos principal name that should be used to run the HMaster process. The principal name should be in the form: user/hostname@DOMAIN. If "_HOST" is used as the hostname portion, it will be replaced with the actual hostname of the running instance.

Default:

hbase.regionserver.keytab.file

Full path to the kerberos keytab file to use for logging in the configured HRegionServer server principal.

Default:

hbase.regionserver.kerberos.principal

Ex. "hbase/_HOST@EXAMPLE.COM". The kerberos principal name that should be used to run the HRegionServer process. The principal name should be in the form: user/hostname@DOMAIN. If "_HOST" is used as the hostname portion, it will be replaced with the actual hostname of the running instance. An entry for this principal must exist in the file specified in hbase.regionserver.keytab.file

Default:

zookeeper.session.timeout

ZooKeeper session timeout. HBase passes this to the zk quorum as suggested maximum time for a session. See http://hadoop.apache.org/zookeeper/docs/current/zookeeperProgrammers.html#ch_zkSessions "The client sends a requested timeout, the server responds with the timeout that it can give the client. " In milliseconds.

Default: 180000

zookeeper.znode.parent

Root ZNode for HBase in ZooKeeper. All of HBase's ZooKeeper files that are configured with a relative path will go under this node. By default, all of HBase's ZooKeeper file path are configured with a relative path, so they will all go under this directory unless changed.

Default: /hbase

zookeeper.znode.rootserver

Path to ZNode holding root region location. This is written by the master and read by clients and region servers. If a relative path is given, the parent folder will be ${zookeeper.znode.parent}. By default, this means the root location is stored at /hbase/root-region-server.

Default: root-region-server

hbase.zookeeper.quorum

Comma separated list of servers in the ZooKeeper Quorum. For example, "host1.mydomain.com,host2.mydomain.com,host3.mydomain.com". By default this is set to localhost for local and pseudo-distributed modes of operation. For a fully-distributed setup, this should be set to a full list of ZooKeeper quorum servers. If HBASE_MANAGES_ZK is set in hbase-env.sh this is the list of servers which we will start/stop ZooKeeper on.

Default: localhost

hbase.zookeeper.peerport

Port used by ZooKeeper peers to talk to each other. See http://hadoop.apache.org/zookeeper/docs/r3.1.1/zookeeperStarted.html#sc_RunningReplicatedZooKeeper for more information.

Default: 2888

hbase.zookeeper.leaderport

Port used by ZooKeeper for leader election. See http://hadoop.apache.org/zookeeper/docs/r3.1.1/zookeeperStarted.html#sc_RunningReplicatedZooKeeper for more information.

Default: 3888

hbase.zookeeper.property.initLimit

Property from ZooKeeper's config zoo.cfg. The number of ticks that the initial synchronization phase can take.

Default: 10

hbase.zookeeper.property.syncLimit

Property from ZooKeeper's config zoo.cfg. The number of ticks that can pass between sending a request and getting an acknowledgment.

Default: 5

hbase.zookeeper.property.dataDir

Property from ZooKeeper's config zoo.cfg. The directory where the snapshot is stored.

Default: ${hbase.tmp.dir}/zookeeper

hbase.zookeeper.property.clientPort

Property from ZooKeeper's config zoo.cfg. The port at which the clients will connect.

Default: 2181

hbase.zookeeper.property.maxClientCnxns

Property from ZooKeeper's config zoo.cfg. Limit on number of concurrent connections (at the socket level) that a single client, identified by IP address, may make to a single member of the ZooKeeper ensemble. Set high to avoid zk connection issues running standalone and pseudo-distributed.

Default: 2000

hbase.rest.port

The port for the HBase REST server.

Default: 8080

hbase.rest.readonly

Defines the mode the REST server will be started in. Possible values are: false: All HTTP methods are permitted - GET/PUT/POST/DELETE. true: Only the GET method is permitted.

Default: false



[10] Be careful editing XML. Make sure you close all elements. Run your file through xmllint or similar to ensure well-formedness of your document after an edit session.