[
https://issues.apache.org/jira/browse/HBASE-16894?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15677428#comment-15677428
]
Yi Liang commented on HBASE-16894:
----------------------------------
I have not seen any activity on this jira, so I will work on this one.
[~enis], from your description, if I understand correctly for you intention,
then I have some proposal for this jira
(1) To split large regions and maybe merge too small regions:
(2) It is better for customer to specify desired split size for each split
(2) Algorithm to extend the algorithm in HBase-12590
If (region size > split size + threshold) : cut the region into
(regionsize/splitsize) MR input splits
If (split size - threshold <= region size <= split size + threshold)
: one region as one MR input split
If (sum of several continuous regions size < split size -
threshold): combine these continuous regions into one MR input split.
The threshold may be based on the input split size.
Is there any other suggestion? Thanks
> Create more than 1 split per region, generalize HBASE-12590
> -----------------------------------------------------------
>
> Key: HBASE-16894
> URL: https://issues.apache.org/jira/browse/HBASE-16894
> Project: HBase
> Issue Type: Improvement
> Reporter: Enis Soztutar
> Labels: beginner, beginners
>
> A common request from users is to be able to better control how many map
> tasks are created per region. Right now, it is always 1 region = 1 input
> split = 1 map task. Same goes for Spark since it uses the TIF. With region
> sizes as large as 50 GBs, it is desirable to be able to create more than 1
> split per region.
> HBASE-12590 adds a config property for MR jobs to be able to handle skew in
> region sizes. The algorithm is roughly:
> {code}
> If (region size >= average size*ratio) : cut the region into two MR input
> splits
> If (average size <= region size < average size*ratio) : one region as one MR
> input split
> If (sum of several continuous regions size < average size * ratio): combine
> these regions into one MR input split.
> {code}
> Although we can set data skew ratio to be 0.5 or something to abuse
> HBASE-12590 into creating more than 1 split task per region, it is not ideal.
> But there is no way to create more with the patch as it is. For example we
> cannot create more than 2 tasks per region.
> If we want to fix this properly, we should extend the approach in
> HBASE-12590, and make it so that the client can specify the desired num of
> mappers, or desired split size, and the TIF generates the splits based on the
> current region sizes very similar to the algorithm in HBASE-12590, but a more
> generic way. This also would eliminate the hand tuning of data skew ratio.
> We also can think about the guidepost approach that Phoenix has in the stats
> table which is used for exactly this purpose. Right now, the region can be
> split into powers of two assuming uniform distribution within the region.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
