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From Keith Turner <ke...@deenlo.com>
Subject Re: Fix "Table x has a hole" [SEC=UNOFFICIAL]
Date Wed, 01 Mar 2017 16:32:06 GMT
On Wed, Mar 1, 2017 at 12:23 AM, Dickson, Matt MR
<matt.dickson@defence.gov.au> wrote:
> UNOFFICIAL
>
> Thanks for that Keith,
>
> That's got it working again.  As for the cause, I had an error in the logs stating a
tablet was hosted and assigned.  I've always removed the referenced tablet in the metadata
table to fix this and had no issues in the past.  It looks like I fat fingered the deletion
which removed the wrong entry so not an issue with Accumulo.

Hosted and assigned, that's not good. What version of Accumulo are you
running?  Do you have any ideas on what may cause this? How often do
you see this?  Is there any event that usually precedes this?
>
> Thanks.
>
> -----Original Message-----
> From: Keith Turner [mailto:keith@deenlo.com]
> Sent: Wednesday, 1 March 2017 03:36
> To: user@accumulo.apache.org
> Subject: Re: Fix "Table x has a hole" [SEC=UNOFFICIAL]
>
> Below are some commands that show how to recreate this problem and how
> to fix it.   Each table in the metadata table has a pointer to the
> previous tablets.  Adding and removing splits to a table changes this.
>
>   root@uno> createtable test
>
> Get the tables ID below we will need it later.
>
>   root@uno test> tables -l
>   accumulo.metadata    =>        !0
>   accumulo.replication =>      +rep
>   accumulo.root        =>        +r
>   test                 =>         3
>   trace                =>         1
>
> Add some splits and then scan the metadata table.  The pointers to the previous tablet
are in the ~tab:~pr column.  The scan below uses the table id above.
>
>   root@uno test> addsplits 11111111 3333333
>   root@uno test> scan -t accumulo.metadata -c ~tab:~pr -b 3; -e 3<
>   3;11111111 ~tab:~pr []    \x00
>   3;3333333 ~tab:~pr []    \x0111111111
>   3< ~tab:~pr []    \x013333333
>
> Add another split and rescan the metadata table.
>
>   root@uno test> addsplits 2222222
>   root@uno test> scan -t accumulo.metadata -c ~tab:~pr -b 3; -e 3<
>   3;11111111 ~tab:~pr []    \x00
>   3;2222222 ~tab:~pr []    \x0111111111
>   3;3333333 ~tab:~pr []    \x012222222
>   3< ~tab:~pr []    \x013333333
>
> Grant permission to write to the metadata table and then recreate the problem you have.
>
>   root@uno test> grant Table.WRITE -u root -t accumulo.metadata
>   root@uno test> table accumulo.metadata
>   root@uno accumulo.metadata> insert 3;3333333 ~tab ~pr \x0111111111
>   root@uno accumulo.metadata> scan -t accumulo.metadata -c ~tab:~pr -b 3; -e 3<
>   3;11111111 ~tab:~pr []    \x00
>   3;2222222 ~tab:~pr []    \x0111111111
>   3;3333333 ~tab:~pr []    \x0111111111
>   3< ~tab:~pr []    \x013333333
>
> If you ran check for metadata problems here, should see the error message you saw.  Below,
the pointer is fixed and write permission is revoked (to prevent accidental writes in the
future).
>
>   root@uno accumulo.metadata> insert 3;3333333 ~tab ~pr \x012222222
>   root@uno accumulo.metadata> revoke Table.WRITE -u root -t accumulo.metadata
>   root@uno accumulo.metadata>
>
> After running the command above to fix the potiner, check for metadata problems should
be happy.
>
> It would be nice to try to track down the cause of this.  Spliting a tablet involves
three metadata operations.  For fault tolerance, the columns ~tab:oldprevrow and ~tab:splitRatio
are temporarily written.
> If a tablet server dies in the middle of splitting a tablet, then Accumulo will see these
temporary columns and attempt to continue the split.  So I am curious if you see these columns?
>
> On Sun, Feb 26, 2017 at 6:49 PM, Dickson, Matt MR <matt.dickson@defence.gov.au>
wrote:
>> UNOFFICIAL
>>
>> Running the CheckForMetadataProblems on Accumulo is listing
>>
>> Table xxx has a hole 11111111 != 2222222
>>
>> Is there a correct way to repair this?
>>
>> Thanks in advance.

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