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| //// | ||
| /** | ||
| * | ||
| * 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. | ||
| */ | ||
| //// | ||
| [[hbase_mob]] | ||
| == Storing Medium-sized Objects (MOB) | ||
| :doctype: book | ||
| :numbered: | ||
| :toc: left | ||
| :icons: font | ||
| :experimental: | ||
| :toc: left | ||
| :source-language: java | ||
| Data comes in many sizes, and saving all of your data in HBase, including binary | ||
| data such as images and documents, is ideal. While HBase can technically handle | ||
| binary objects with cells that are larger than 100 KB in size, HBase's normal | ||
| read and write paths are optimized for values smaller than 100KB in size. When | ||
| HBase deals with large numbers of objects over this threshold, referred to here | ||
| as medium objects, or MOBs, performance is degraded due to write amplification | ||
| caused by splits and compactions. When using MOBs, ideally your objects will be between | ||
| 100KB and 10MB. HBase ***FIX_VERSION_NUMBER*** adds support | ||
| for better managing large numbers of MOBs while maintaining performance, | ||
| consistency, and low operational overhead. MOB support is provided by the work | ||
| done in link:https://issues.apache.org/jira/browse/HBASE-11339[HBASE-11339]. To | ||
| take advantage of MOB, you need to use <<hfilev3,HFile version 3>>. Optionally, | ||
| configure the MOB file reader's cache settings for each RegionServer (see | ||
| <<mob.cache.configure>>), then configure specific columns to hold MOB data. | ||
| Client code does not need to change to take advantage of HBase MOB support. The | ||
| feature is transparent to the client. | ||
|
|
||
| === Configuring Columns for MOB | ||
|
|
||
| You can configure columns to support MOB during table creation or alteration, | ||
| either in HBase Shell or via the Java API. The two relevant properties are the | ||
| boolean `IS_MOB` and the `MOB_THRESHOLD`, which is the number of bytes at which | ||
| an object is considered to be a MOB. Only `IS_MOB` is required. If you do not | ||
| specify the `MOB_THRESHOLD`, the default threshold value of 100 KB is used. | ||
|
|
||
| .Configure a Column for MOB Using HBase Shell | ||
| ==== | ||
| ---- | ||
| hbase> create 't1', {NAME => 'f1', IS_MOB => true, MOB_THRESHOLD => 102400} | ||
| hbase> alter 't1', {NAME => 'f1', IS_MOB => true, MOB_THRESHOLD => 102400} | ||
| ---- | ||
| ==== | ||
|
|
||
| .Configure a Column for MOB Using the Java API | ||
| ==== | ||
| [source,java] | ||
| ---- | ||
| ... | ||
| HColumnDescriptor hcd = new HColumnDescriptor(“f”); | ||
| hcd.setMobEnabled(true); | ||
| ... | ||
| hcd.setMobThreshold(102400L); | ||
| ... | ||
| ---- | ||
| ==== | ||
|
|
||
|
|
||
| === Testing MOB | ||
|
|
||
| The utility `org.apache.hadoop.hbase.IntegrationTestIngestMOB` is provided to assist with testing | ||
| the MOB feature. The utility is run as follows: | ||
| [source,bash] | ||
| ---- | ||
| $ sudo -u hbase hbase org.apache.hadoop.hbase.IntegrationTestIngestMOB \ | ||
| -threshold 102400 \ | ||
| -minMobDataSize 512 \ | ||
| -maxMobDataSize 5120 | ||
| ---- | ||
|
|
||
| * `*threshold*` is the threshold at which cells are considered to be MOBs. | ||
| The default is 1 kB, expressed in bytes. | ||
| * `*minMobDataSize*` is the minimum value for the size of MOB data. | ||
| The default is 512 B, expressed in bytes. | ||
| * `*maxMobDataSize*` is the maximum value for the size of MOB data. | ||
| The default is 5 kB, expressed in bytes. | ||
|
|
||
|
|
||
| [[mob.cache.configure]] | ||
| === Configuring the MOB Cache | ||
|
|
||
|
|
||
| Because there can be a large number of MOB files at any time, as compared to the number of HFiles, | ||
| MOB files are not always kept open. The MOB file reader cache is a LRU cache which keeps the most | ||
| recently used MOB files open. To configure the MOB file reader's cache on each RegionServer, add | ||
| the following properties to the RegionServer's `hbase-site.xml`, customize the configuration to | ||
| suit your environment, and restart or rolling restart the RegionServer. | ||
|
|
||
| .Example MOB Cache Configuration | ||
| ==== | ||
| [source,xml] | ||
| ---- | ||
| <property> | ||
| <name>hbase.mob.file.cache.size</name> | ||
| <value>1000</value> | ||
| <description> | ||
| Number of opened file handlers to cache. | ||
| A larger value will benefit reads by provinding more file handlers per mob | ||
| file cache and would reduce frequent file opening and closing. | ||
| However, if this is set too high, this could lead to a "too many opened file handers" | ||
| The default value is 1000. | ||
| </description> | ||
| </property> | ||
| <property> | ||
| <name>hbase.mob.cache.evict.period</name> | ||
| <value>3600</value> | ||
| <description> | ||
| The amount of time in seconds after which an unused file is evicted from the | ||
| MOB cache. The default value is 3600 seconds. | ||
| </description> | ||
| </property> | ||
| <property> | ||
| <name>hbase.mob.cache.evict.remain.ratio</name> | ||
| <value>0.5f</value> | ||
| <description> | ||
| A multiplier (between 0.0 and 1.0), which determines how many files remain cached | ||
| after the threshold of files that remains cached after a cache eviction occurs | ||
| which is triggered by reaching the `hbase.mob.file.cache.size` threshold. | ||
| The default value is 0.5f, which means that half the files (the least-recently-used | ||
| ones) are evicted. | ||
| </description> | ||
| </property> | ||
| ---- | ||
| ==== | ||
|
|
||
| === MOB Optimization Tasks | ||
|
|
||
| ==== Manually Compacting MOB Files | ||
|
|
||
| To manually compact MOB files, rather than waiting for the | ||
| <<mob.cache.configure,configuration>> to trigger compaction, use the | ||
| `compact_mob` or `major_compact_mob` HBase shell commands. These commands | ||
| require the first argument to be the table name, and take an optional column | ||
| family as the second argument. If the column family is omitted, all MOB-enabled | ||
| column families are compacted. | ||
|
|
||
| ---- | ||
| hbase> compact_mob 't1', 'c1' | ||
| hbase> compact_mob 't1' | ||
| hbase> major_compact_mob 't1', 'c1' | ||
| hbase> major_compact_mob 't1' | ||
| ---- | ||
|
|
||
| These commands are also available via `Admin.compactMob` and | ||
| `Admin.majorCompactMob` methods. | ||
|
|
||
| ==== MOB Sweeper | ||
|
|
||
| HBase MOB a MapReduce job called the Sweeper tool for | ||
| optimization. The Sweeper tool oalesces small MOB files or MOB files with many | ||
| deletions or updates. The Sweeper tool is not required if you use native MOB compaction, which | ||
| does not rely on MapReduce. | ||
|
|
||
| To configure the Sweeper tool, set the following options: | ||
|
|
||
| [source,xml] | ||
| ---- | ||
| <property> | ||
| <name>hbase.mob.sweep.tool.compaction.ratio</name> | ||
| <value>0.5f</value> | ||
| <description> | ||
| If there are too many cells deleted in a mob file, it's regarded | ||
| as an invalid file and needs to be merged. | ||
| If existingCellsSize/mobFileSize is less than ratio, it's regarded | ||
| as an invalid file. The default value is 0.5f. | ||
| </description> | ||
| </property> | ||
| <property> | ||
| <name>hbase.mob.sweep.tool.compaction.mergeable.size</name> | ||
| <value>134217728</value> | ||
| <description> | ||
| If the size of a mob file is less than this value, it's regarded as a small | ||
| file and needs to be merged. The default value is 128MB. | ||
| </description> | ||
| </property> | ||
| <property> | ||
| <name>hbase.mob.sweep.tool.compaction.memstore.flush.size</name> | ||
| <value>134217728</value> | ||
| <description> | ||
| The flush size for the memstore used by sweep job. Each sweep reducer owns such a memstore. | ||
| The default value is 128MB. | ||
| </description> | ||
| </property> | ||
| <property> | ||
| <name>hbase.master.mob.ttl.cleaner.period</name> | ||
| <value>86400</value> | ||
| <description> | ||
| The period that ExpiredMobFileCleanerChore runs. The unit is second. | ||
| The default value is one day. | ||
| </description> | ||
| </property> | ||
| ---- | ||
|
|
||
| Next, add the HBase install directory, _`$HBASE_HOME`/*_, and HBase library directory to | ||
| _yarn-site.xml_ Adjust this example to suit your environment. | ||
| [source,xml] | ||
| ---- | ||
| <property> | ||
| <description>Classpath for typical applications.</description> | ||
| <name>yarn.application.classpath</name> | ||
| <value> | ||
| $HADOOP_CONF_DIR, | ||
| $HADOOP_COMMON_HOME/*,$HADOOP_COMMON_HOME/lib/*, | ||
| $HADOOP_HDFS_HOME/*,$HADOOP_HDFS_HOME/lib/*, | ||
| $HADOOP_MAPRED_HOME/*,$HADOOP_MAPRED_HOME/lib/*, | ||
| $HADOOP_YARN_HOME/*,$HADOOP_YARN_HOME/lib/*, | ||
| $HBASE_HOME/*, $HBASE_HOME/lib/* | ||
| </value> | ||
| </property> | ||
| ---- | ||
|
|
||
| Finally, run the `sweeper` tool for each column which is configured for MOB. | ||
| [source,bash] | ||
| ---- | ||
| $ org.apache.hadoop.hbase.mob.compactions.Sweeper _tableName_ _familyName_ | ||
| ---- |
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