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https://issues.apache.org/jira/browse/HBASE-13408?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eshcar Hillel updated HBASE-13408:
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Attachment: HBaseIn-MemoryMemstoreCompactionDesignDocument-ver03.pdf
Hi All,
We compiled a new design document (attached) capturing all changes (we noticed
there are many changes since the original design suggestion).
In this new design document the behavior of the compacted memstore is confined
mainly to the scope of the memstore, however some minimal changes are done at
the scope of the region level, in order to give compacted memstore some slack
to manage the in-memory flushes and in-memory compaction.
Next we plan to prepare the patch; main changes with respect to current patch
would be to remove most of the code changes at the region level, and allow
compacted memstore have access to the region lock to apply in-memory flushes.
> HBase In-Memory Memstore Compaction
> -----------------------------------
>
> Key: HBASE-13408
> URL: https://issues.apache.org/jira/browse/HBASE-13408
> Project: HBase
> Issue Type: New Feature
> Reporter: Eshcar Hillel
> Assignee: Eshcar Hillel
> Fix For: 2.0.0
>
> Attachments: HBASE-13408-trunk-v01.patch,
> HBASE-13408-trunk-v02.patch, HBASE-13408-trunk-v03.patch,
> HBASE-13408-trunk-v04.patch, HBASE-13408-trunk-v05.patch,
> HBASE-13408-trunk-v06.patch, HBASE-13408-trunk-v07.patch,
> HBASE-13408-trunk-v08.patch,
> HBaseIn-MemoryMemstoreCompactionDesignDocument-ver02.pdf,
> HBaseIn-MemoryMemstoreCompactionDesignDocument-ver03.pdf,
> HBaseIn-MemoryMemstoreCompactionDesignDocument.pdf,
> InMemoryMemstoreCompactionEvaluationResults.pdf,
> InMemoryMemstoreCompactionMasterEvaluationResults.pdf,
> InMemoryMemstoreCompactionScansEvaluationResults.pdf,
> StoreSegmentandStoreSegmentScannerClassHierarchies.pdf
>
>
> A store unit holds a column family in a region, where the memstore is its
> in-memory component. The memstore absorbs all updates to the store; from time
> to time these updates are flushed to a file on disk, where they are
> compacted. Unlike disk components, the memstore is not compacted until it is
> written to the filesystem and optionally to block-cache. This may result in
> underutilization of the memory due to duplicate entries per row, for example,
> when hot data is continuously updated.
> Generally, the faster the data is accumulated in memory, more flushes are
> triggered, the data sinks to disk more frequently, slowing down retrieval of
> data, even if very recent.
> In high-churn workloads, compacting the memstore can help maintain the data
> in memory, and thereby speed up data retrieval.
> We suggest a new compacted memstore with the following principles:
> 1. The data is kept in memory for as long as possible
> 2. Memstore data is either compacted or in process of being compacted
> 3. Allow a panic mode, which may interrupt an in-progress compaction and
> force a flush of part of the memstore.
> We suggest applying this optimization only to in-memory column families.
> A design document is attached.
> This feature was previously discussed in HBASE-5311.
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