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From Keith Turner <ke...@deenlo.com>
Subject Re: question on data block cache
Date Tue, 26 Jan 2016 17:18:25 GMT
On Fri, Jan 22, 2016 at 2:22 PM, z11373 <z11373@outlook.com> wrote:

> Another observation which I really want to know why.
>
> I see 1 tablet server consistently shows high number of waiting scans, i.e.
> '16 (435)' or '14 (476)' on Running Scans column, while the other 19 tablet
> servers all showing '0 (0)' or sometimes showing single digit number. The
> thing I don't understand is what I've seen from the Monitor UI for a table
> at one snapshot for example, and this is more or less consistent from time
> to time (when the test clients are still running).
>
> Server | Query | Running Scans
> ====================
> TServer1 | 24 | 0 (0)
> TServer2 | 37 | 0 (0)
> TServer3 | 40 | 0 (0)
> TServer4 | 1 | 0 (0)
> TServer5 | 0 | 0 (0)
> TServer6 | 57 | 0 (0)
> TServer7 | 5 | 0 (0)
> TServer8 | 4 | 0 (0)
> TServer9 | 7 | 0 (0)
> TServer10 | 0 | 0 (0)
> TServer11 | 56 | 0 (0)
> TServer12 | 124 | 0 (0)
> TServer13 | 25 | 0 (0)
> TServer14 | 121 | 16 (435)
> TServer15 | 36 | 0 (0)
> TServer16 | 21 | 0 (0)
> TServer17 | 3 | 0 (0)
> TServer18 | 107 | 0 (0)
> TServer19 | 21 | 0 (0)
> TServer20 | 92 | 0 (0)
>
> I'd really appreciate if someone could explain what may have happened, or
> can point me to the right direction for starting the investigation. For the
> record, there are 50 test clients, each may create multiple scanners to
> query different data from that table.
>

One starting point is to see what tablets are on that tablet server.  One
way to do this a grep like the following in the accumulo shell (note this
command is from memory so it may have mistakes)

  grep -t accumulo.metadata -c loc <TServer14 addr as it would appear in
metadata table>


In the output of this, rows will contain <table id>:<tablet end row>.
Maybe the tablet end rows can give you  a clue.

You can narrow the grep by restricting the row range using the table id.

  grep -t accumulo.metadata -b <table id>   -e <table id>~ -c loc
<TServer14 addr as it would appear in metadata table>


There is a command in the shell to get table ids.



> Thanks,
> Z
>
>
>
> --
> View this message in context:
> http://apache-accumulo.1065345.n5.nabble.com/question-on-data-block-cache-tp15906p15934.html
> Sent from the Developers mailing list archive at Nabble.com.
>

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