[jira] [Comment Edited] (HBASE-14918) In-Memory MemStore Flush and Compaction

["stack (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-14918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15169406#comment-15169406 ] 

stack edited comment on HBASE-14918 at 2/26/16 8:32 PM:
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Move ByteRange into the prefix-tree module? If prefix-tree is enabled, just warn that offheaping will not work at same time and that we'll be making copies everywhere. Add a warning?

We'd do this because the handling in Prefix-tree is involved and exotic, hard to get right. Prefix-tree is also not widely used (topic of another discussion). Meantime it should not slow down general improvement. We might consider moving this module out of core.


was (Author: stack):
Move ByteRange into the prefix-tree module? If prefix-tree is enabled, offheaping will not work? Add warnings?

> In-Memory MemStore Flush and Compaction
> ---------------------------------------
>
>                 Key: HBASE-14918
>                 URL: https://issues.apache.org/jira/browse/HBASE-14918
>             Project: HBase
>          Issue Type: Umbrella
>    Affects Versions: 2.0.0
>            Reporter: Eshcar Hillel
>            Assignee: Eshcar Hillel
>             Fix For: 0.98.18
>
>         Attachments: CellBlocksSegmentDesign.pdf, MSLABMove.patch
>
>
> A memstore serves as the in-memory component of a store unit, absorbing all updates to the store. From time to time these updates are flushed to a file on disk, where they are compacted (by eliminating redundancies) and compressed (i.e., written in a compressed format to reduce their storage size).
> We aim to speed up data access, and therefore suggest to apply in-memory memstore flush. That is to flush the active in-memory segment into an intermediate buffer where it can be accessed by the application. Data in the buffer is subject to compaction and can be stored in any format that allows it to take up smaller space in RAM. The less space the buffer consumes the longer it can reside in memory before data is flushed to disk, resulting in better performance.
> Specifically, the optimization is beneficial for workloads with medium-to-high key churn which incur many redundant cells, like persistent messaging. 
> We suggest to structure the solution as 4 subtasks (respectively, patches). 
> (1) Infrastructure - refactoring of the MemStore hierarchy, introducing segment (StoreSegment) as first-class citizen, and decoupling memstore scanner from the memstore implementation;
> (2) Adding StoreServices facility at the region level to allow memstores update region counters and access region level synchronization mechanism;
> (3) Implementation of a new memstore (CompactingMemstore) with non-optimized immutable segment representation, and 
> (4) Memory optimization including compressed format representation and off heap allocations.
> This Jira continues the discussion in HBASE-13408.
> Design documents, evaluation results and previous patches can be found in HBASE-13408. 



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