accumulo-notifications mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-3602) BatchScanner optimization for AccumuloInputFormat
Date Tue, 07 Apr 2015 21:22:12 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14484080#comment-14484080
] 

ASF GitHub Bot commented on ACCUMULO-3602:
------------------------------------------

Github user keith-turner commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/25#discussion_r27921845
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/mapreduce/lib/impl/InputConfigurator.java
---
    @@ -517,6 +517,74 @@ public static Boolean isOfflineScan(Class<?> implementingClass,
Configuration co
       }
     
       /**
    +   * Controls the use of the {@link BatchScanner} in this job.
    +   * Using this feature will group ranges by their source tablet per InputSplit and use
BatchScanner to read them.
    +   *
    +   * <p>
    +   * By default, this feature is <b>disabled</b>.
    +   *
    +   * @param implementingClass
    +   *          the class whose name will be used as a prefix for the property configuration
key
    +   * @param conf
    +   *          the Hadoop configuration object to configure
    +   * @param enableFeature
    +   *          the feature is enabled if true, disabled otherwise
    +   * @since 1.7.0
    +   */
    +  public static void setBatchScan(Class<?> implementingClass, Configuration conf,
boolean enableFeature) {
    +    conf.setBoolean(enumToConfKey(implementingClass, Features.BATCH_SCANNER), enableFeature);
    +  }
    +
    +  /**
    +   * Determines whether a configuration has the BatchScanner feature enabled.
    +   *
    +   * @param implementingClass
    +   *          the class whose name will be used as a prefix for the property configuration
key
    +   * @param conf
    +   *          the Hadoop configuration object to configure
    +   * @return true if the feature is enabled, false otherwise
    +   * @since 1.7.0
    +   * @see #setBatchScan(Class, Configuration, boolean)
    +   */
    +  public static Boolean isBatchScan(Class<?> implementingClass, Configuration conf)
{
    +    return conf.getBoolean(enumToConfKey(implementingClass, Features.BATCH_SCANNER),
false);
    +  }
    +
    +  /**
    +   * Controls the use of the {@link BatchScanner} in this job.
    +   * Using this feature will group ranges by their source tablet per InputSplit and use
BatchScanner to read them.
    +   *
    +   * <p>
    +   * By default, this feature is <b>disabled</b>.
    +   *
    +   * @param implementingClass
    +   *          the class whose name will be used as a prefix for the property configuration
key
    +   * @param conf
    +   *          the Hadoop configuration object to configure
    +   * @param count
    +   *          number of threads to use with BatchScanner
    +   * @since 1.7.0
    +   */
    +  public static void setBatchScanThreads(Class<?> implementingClass, Configuration
conf, int count) {
    --- End diff --
    
    The batch scanner will not use more than one thread per tablet.  If each mapper is using
a batch scanner to read multiple ranges from a single tablet, then the batch scanner will
only use a single thread to do this even if it has more threads it could use.


> BatchScanner optimization for AccumuloInputFormat
> -------------------------------------------------
>
>                 Key: ACCUMULO-3602
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3602
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client
>    Affects Versions: 1.6.1, 1.6.2
>            Reporter: Eugene Cheipesh
>            Assignee: Eugene Cheipesh
>              Labels: performance
>             Fix For: 1.7.0
>
>
> Currently {{AccumuloInputFormat}} produces a split for reach {{Range}} specified in the
configuration. Some table indexing schemes, for instance z-order geospacial index, produce
large number of small ranges resulting in large number of splits. This is specifically a concern
when using {{AccumuloInputFormat}} as a source for Spark RDD where each Split is mapped to
an RDD partition.
> Large number of small RDD partitions leads to poor parallism on read and high overhead
on processing. A desirable alternative is to group ranges by tablet into a single split and
use {{BatchScanner}} to produce the records. Grouping by tablets is useful because it represents
Accumulos attempt to distributed stored records and can be influance by the user through table
splits.
> The grouping functionality already exists in the internal {{TabletLocator}} class. 
> Current proposal is to modify {{AbstractInputFormat}} such that it generates either {{RangeInputSplit}}
or {{MultiRangeInputSplit}} based on a new setting in {{InputConfigurator}}.  {{AccumuloInputFormat}}
would then be able to inspect the type of the split and instantiate an appropriate reader.
> The functinality of {{TabletLocator}} should be exposed as a public API in 1.7 as it
is useful for optimizations.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message