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From Alexey Serbin <aser...@cloudera.com>
Subject Re: What does RowSet Compaction Duration means?
Date Tue, 14 Mar 2017 18:48:05 GMT
Hi Jason,

As I understand, that 'milliseconds / second' cryptic unit means 'number of
units / for sampling (or averaging) interval'.

I.e., they capture that metric reading (expressed in milliseconds) every
second, subtract previous value from the current value, and declare the
result as the result measurement at current time.  If not capturing every
second, then it's about measuring every X seconds, do the subtraction of
the previous from the current measurement, and then divide by X.

For a single tablet, the 'compact_rs_duration' metric stands for 'Time
spent compacting RowSets'.  As I understand, that
'total_kudu_compact_rs_duration_sum_rate_across_kudu_replicas' is
sum/accumulation of those measurements for all existing replicas of the
specified tablet across Kudu cluster.

I suspect you have the replication factor of 5 for that tablet, and at some
point all replicas become busy with rowset compaction all the time.

Compactions on tables are run in the background.  Compactions on different
tables run independently.  So, if you have some other activity doing
inserts/updates on tableB, then it's natural to see compaction happen on
tabletB as well.


Best regards,

Alexey

On Tue, Mar 14, 2017 at 12:50 AM, Jason Heo <jason.heo.sde@gmail.com> wrote:

> Hi.
>
> I'm stuck with performance degradation on compaction happens.
>
> My Duration is "4956.71 milliseconds / second" What does this mean? I
> can't figure it out.
>
> Here is the captured image: http://imgur.com/WU9sRRq
>
> When I'm doing bulk indexing on tableA, sometimes compaction happens over
> tableB. Is this situation is natural?
>
> Thanks.
>

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