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https://issues.apache.org/jira/browse/HBASE-18294?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16351674#comment-16351674
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Eshcar Hillel commented on HBASE-18294:
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Here is my response from RB regarding the change in HCD
In the new implementation we compare on-heap size against on-heap threshold and
off-heap size against off-heap threshold. Exceeding one of these two thresholds
triggers a flush. If we only consider one unified threshold for on- and
off-heap data we can get OOME.
For example, consider an off-heap cluster with 96GB memory machines, and assume
in each machine 90GB are allocated to off-heap data and 6GB are allocated to
on-heap objects. Assume we manage 700 regions per RS, and the flush size is
128MB. It only requires 46 regions to get to 128MB on-heap or for all regions
to exceed 8.5MB(!) on-heap to get an OOME.
Therefore I think giving the user an optional(!) control on the flush size both
for on-heap and off-heap sizes is essential. And they both fall back on default
value so they are both optional and may not be an unnecessary burden on the
user.
I also see I need to re-base my patch. Waiting for review comments to create my
next patch.
> Reduce global heap pressure: flush based on heap occupancy
> ----------------------------------------------------------
>
> Key: HBASE-18294
> URL: https://issues.apache.org/jira/browse/HBASE-18294
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 3.0.0
> Reporter: Eshcar Hillel
> Assignee: Eshcar Hillel
> Priority: Major
> Fix For: 2.0.0-beta-2
>
> Attachments: HBASE-18294.01.patch, HBASE-18294.01.patch,
> HBASE-18294.01.patch, HBASE-18294.01.patch, HBASE-18294.02.patch,
> HBASE-18294.03.patch, HBASE-18294.04.patch, HBASE-18294.05.patch,
> HBASE-18294.06.patch, HBASE-18294.07.patch, HBASE-18294.07.patch,
> HBASE-18294.08.patch, HBASE-18294.09.patch, HBASE-18294.10.patch,
> HBASE-18294.11.patch, HBASE-18294.11.patch, HBASE-18294.12.patch,
> HBASE-18294.13.patch, HBASE-18294.15.patch, HBASE-18294.16.patch,
> HBASE-18294.master.01.patch
>
>
> A region is flushed if its memory component exceed a threshold (default size
> is 128MB).
> A flush policy decides whether to flush a store by comparing the size of the
> store to another threshold (that can be configured with
> hbase.hregion.percolumnfamilyflush.size.lower.bound).
> Currently the implementation (in both cases) compares the data size
> (key-value only) to the threshold where it should compare the heap size
> (which includes index size, and metadata).
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