Package org.apache.hadoop.hbase.master.normalizer

package org.apache.hadoop.hbase.master.normalizer

The Region Normalizer subsystem is responsible for coaxing all the regions in a table toward a "normal" size, according to their storefile size. It does this by splitting regions that are significantly larger than the norm, and merging regions that are significantly smaller than the norm.

The public interface to the Region Normalizer subsystem is limited to the following classes:

• The RegionNormalizerFactory provides an entry point for creating an instance of the RegionNormalizerManager.
• The RegionNormalizerManager encapsulates the whole Region Normalizer subsystem. You'll find one of these hanging off of the HMaster, which uses it to delegate API calls. There is usually only a single instance of this class.
• Various configuration points that share the common prefix of hbase.normalizer.
  • Whether to split a region as part of normalization. Configuration: "hbase.normalizer.split.enabled", default: true.
  • Whether to merge a region as part of normalization. Configuration: "hbase.normalizer.merge.enabled", default: true.
  • The minimum number of regions in a table to consider it for merge normalization. Configuration: "hbase.normalizer.merge.min.region.count", default: 3.
  • The minimum age for a region to be considered for a merge, in days. Configuration: "hbase.normalizer.merge.min_region_age.days", default: 3.
  • The minimum size for a region to be considered for a merge, in whole MBs. Configuration: "hbase.normalizer.merge.min_region_size.mb", default: 0.
  • The limit on total throughput of the Region Normalizer's actions, in whole MBs. Configuration: "hbase.normalizer.throughput.max_bytes_per_sec", default: unlimited.

  To see detailed logging of the application of these configuration values, set the log level for this package to TRACE.

The Region Normalizer subsystem is composed of a handful of related classes:

• The RegionNormalizerStateStore provides a system by which the Normalizer can be disabled at runtime. It currently does this by storing the state in master local region, but this is an implementation detail.
• The RegionNormalizerWorkQueue is a Set-like Queue that permits a single copy of a given work item to exist in the queue at one time. It also provides a facility for a producer to add an item to the front of the line. Consumers are blocked waiting for new work.
• The RegionNormalizerChore wakes up periodically and schedules new normalization work, adding targets to the queue.
• The RegionNormalizerWorker runs in a daemon thread, grabbing work off the queue as is it becomes available.
• The SimpleRegionNormalizer implements the logic for calculating target region sizes and emitting a list of corresponding NormalizationPlan objects.

Related Packages

Package	Description
org.apache.hadoop.hbase.master

Class	Description
MergeNormalizationPlan	Normalization plan to merge adjacent regions.
MergeNormalizationPlan.Builder	A helper for constructing instances of MergeNormalizationPlan.
NormalizationPlan	A NormalizationPlan describes some modification to region split points as identified by an instance of RegionNormalizer.
NormalizationPlan.PlanType
NormalizationTarget	A POJO that caries details about a region selected for normalization through the pipeline.
RegionNormalizer	Performs "normalization" of regions of a table, making sure that suboptimal choice of split keys doesn't leave cluster in a situation when some regions are substantially larger than others for considerable amount of time.
RegionNormalizerChore	Chore that will periodically call HMaster.normalizeRegions(NormalizeTableFilterParams, boolean).
RegionNormalizerFactory	Factory to create instance of RegionNormalizer as configured.
RegionNormalizerManager	This class encapsulates the details of the RegionNormalizer subsystem.
RegionNormalizerStateStore	Store region normalizer state.
RegionNormalizerWorker	Consumes normalization request targets (TableNames) off the RegionNormalizerWorkQueue, dispatches them to the RegionNormalizer, and executes the resulting NormalizationPlans.
RegionNormalizerWorkQueue<E>	A specialized collection that holds pending work for the RegionNormalizerWorker.
SimpleRegionNormalizer	Simple implementation of region normalizer.
SimpleRegionNormalizer.NormalizerConfiguration	Holds the configuration values read from Configuration.
SplitNormalizationPlan	Normalization plan to split a region.