saintstack commented on a change in pull request #2454: URL: https://github.com/apache/hbase/pull/2454#discussion_r501329639
########## File path: hbase-server/src/main/java/org/apache/hadoop/hbase/master/normalizer/package-info.java ########## @@ -0,0 +1,100 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +/** + * 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. + * </p> + * The public interface to the Region Normalizer subsystem is limited to the following classes: + * <ul> + * <li> + * The {@link org.apache.hadoop.hbase.master.normalizer.RegionNormalizerFactory} provides an + * entry point for creating an instance of the + * {@link org.apache.hadoop.hbase.master.normalizer.RegionNormalizerManager}. + * </li> + * <li> + * The {@link org.apache.hadoop.hbase.master.normalizer.RegionNormalizerManager} encapsulates + * the whole Region Normalizer subsystem. You'll find one of these hanging off of the + * {@link org.apache.hadoop.hbase.master.HMaster}, which uses it to delegate API calls. There + * is usually only a single instance of this class. + * </li> + * <li> + * Various configuration points that share the common prefix of {@code hbase.normalizer}. + * <ul> + * <li>Whether to split a region as part of normalization. Configuration: + * {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#SPLIT_ENABLED_KEY}, + * default: {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#DEFAULT_SPLIT_ENABLED}. + * </li> + * <li>Whether to merge a region as part of normalization. Configuration: + * {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#MERGE_ENABLED_KEY}, + * default: {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#DEFAULT_MERGE_ENABLED}. + * </li> + * <li>The minimum number of regions in a table to consider it for merge normalization. + * Configuration: {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#MIN_REGION_COUNT_KEY}, + * default: {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#DEFAULT_MIN_REGION_COUNT}. + * </li> + * <li>The minimum age for a region to be considered for a merge, in days. Configuration: + * {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#MERGE_MIN_REGION_AGE_DAYS_KEY}, + * default: {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#DEFAULT_MERGE_MIN_REGION_AGE_DAYS}. + * </li> + * <li>The minimum size for a region to be considered for a merge, in whole MBs. Configuration: + * {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#MERGE_MIN_REGION_SIZE_MB_KEY}, + * default: {@value org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer#DEFAULT_MERGE_MIN_REGION_SIZE_MB}. + * </li> + * <li>The limit on total throughput of the Region Normalizer's actions, in whole MBs. Configuration: + * {@value org.apache.hadoop.hbase.master.normalizer.RegionNormalizerWorker#RATE_LIMIT_BYTES_PER_SEC_KEY}, + * default: unlimited. + * </li> + * </ul> + * <p> + * To see detailed logging of the application of these configuration values, set the log + * level for this package to `TRACE`. + * </p> + * </li> + * </ul> + * The Region Normalizer subsystem is composed of a handful of related classes: + * <ul> + * <li> + * The {@link org.apache.hadoop.hbase.zookeeper.RegionNormalizerTracker} provides a system by + * which the Normalizer can be disabled at runtime. It currently does this by managing a znode, + * but this is an implementation detail. + * </li> + * <li> + * The {@link org.apache.hadoop.hbase.master.normalizer.RegionNormalizerWorkQueue} is a + * {@link java.util.Set}-like {@link java.util.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. + * </li> + * <li> + * The {@link org.apache.hadoop.hbase.master.normalizer.RegionNormalizerChore} wakes up + * periodically and schedules new normalization work, adding targets to the queue. + * </li> + * <li> + * The {@link org.apache.hadoop.hbase.master.normalizer.RegionNormalizerWorker} runs in a + * daemon thread, grabbing work off the queue as is it becomes available. + * </li> + * <li> + * The {@link org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer} implements the + * logic for calculating target region sizes and emitting a list of corresponding + * {@link org.apache.hadoop.hbase.master.normalizer.NormalizationPlan} objects. + * </li> + * </ul> + */ +package org.apache.hadoop.hbase.master.normalizer; Review comment: nice ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected]
