Re: Multiple start regions in a table

stack Wed, 12 Nov 2008 12:15:52 -0800

Arthur van Hoff wrote:

We are using hbase 0.18.1. The count seems happy to count the first
100,000 rows...
I was able to merge the two regions.


However, I noticed that there are many overlapping regions in this
table. Is that expected?

No. Only time you should see overlap is if the first region in list ofregions out of .META. is offline and parent of the next two regions thatfollow.

Here are some of the start/end keys:

                    -0000010225 (newly merged)
0000003046-0000005771 (overlaps with the previous section)
0000005771-0000008992
0000008992-0000012909
0000010225-0000020097 (overlaps with the previous section)
0000012909-0000015835 (overlaps with the previous section)


Do your MR jobs work now?

...

How can this happen?


Should never happen.

Could happen if edits to .META. were dropped. Have seen rare case ofthis split events but the gaping holes should be closed at least in theversion you are running.

If you can't have your MR run to completion, and if overlapping regionis not offlined, may have to do more repairs. Then, run with DEBUGenabled and if it happens again, should be able to see by examination oflogs how it came about.


St.Ack

On Wed, Nov 12, 2008 at 11:05 AM, stack <[EMAIL PROTECTED]> wrote:

Arthur van Hoff wrote:

Below are the two regions in the .META. scan. I don't think either of
them is disabled.

Right.  One should be offlined.  Which version of hbase is this?

The table is too large to count, and I am not sure how to enable DEBUG.

Well, looks like problem is in first region so you could start the count and
looks like issue should pop up quick.

To enable DEBUG, http://wiki.apache.org/hadoop/Hbase/FAQ#5.

To 'repair', your table, shut it down and then run:

$ ./bin/hbase org.apache.hadoop.hbase.util.Merge
Usage: bin/hbase merge <table-name> <region-1> <region-2>

Supply table name, and two regions to merge.

Let us know how it goes.

St.Ack

 wikipedia,,1226039865543    column=historian:assignment,
timestamp=1226471612375, value=Region assigned to server
192.168.33.31:60020
 wikipedia,,1226039865543    column=historian:open,
timestamp=1226471627434, value=Region opened on server :
gore.int.ellerdale.com
 wikipedia,,1226039865543    column=historian:split,
timestamp=1226039870630, value=Region split from  :
wikipedia,,1226039822665
 wikipedia,,1226039865543    column=info:regioninfo,
timestamp=1226039870633, value=REGION => {NAME =>
'wikipedia,,1226039865543', STARTKEY => '', ENDKEY => '0000020097',
ENCODED => 1423314116, TABLE => {{NAME => 'wikipedia', IS_ROOT =>
'false', IS_META => 'false', FAMILIES => [{NAME => 'data', BLOOMFILTER
=> 'false', VERSIONS => '3', COMPRESSION => 'NONE', LENGTH =>
'2147483647', TTL => '-1', IN_MEMORY => 'false', BLOCKCACHE =>
'false'}]}}
 wikipedia,,1226039865543    column=info:server,
timestamp=1226471627433, value=192.168.33.31:60020
 wikipedia,,1226039865543    column=info:serverstartcode,
timestamp=1226471627433, value=1226471577772
 wikipedia,,1226469112210    column=historian:assignment,
timestamp=1226471612379, value=Region assigned to server
192.168.33.31:60020
 wikipedia,,1226469112210    column=historian:open,
timestamp=1226471630431, value=Region opened on server :
gore.int.ellerdale.com
 wikipedia,,1226469112210    column=historian:split,
timestamp=1226469113121, value=Region split from  :
wikipedia,,1226356665025
 wikipedia,,1226469112210    column=info:regioninfo,
timestamp=1226469113125, value=REGION => {NAME =>
'wikipedia,,1226469112210', STARTKEY => '', ENDKEY => '0000003046',
ENCODED => 566585206, TABLE => {{NAME => 'wikipedia', IS_ROOT =>
'false', IS_META => 'false', FAMILIES => [{NAME => 'data', BLOOMFILTER
=> 'false', VERSIONS => '3', COMPRESSION => 'NONE', LENGTH =>
'2147483647', TTL => '-1', IN_MEMORY => 'false', BLOCKCACHE =>
'false'}]}}
 wikipedia,,1226469112210    column=info:server,
timestamp=1226471630430, value=192.168.33.31:60020
 wikipedia,,1226469112210    column=info:serverstartcode,
timestamp=1226471630430, value=1226471577772


On Wed, Nov 12, 2008 at 10:09 AM, stack <[EMAIL PROTECTED]> wrote:

Are they both enabled?

You can see by doing "scan '.META.'" in the shell and then look at the
particular regions in the output.  Disabled regions will have a disabled
attribute.

What error are you seeing when in your job?

You could enable DEBUG and then in shell try running "count 'TABLENAME'".
 With DEBUG enabled, you'll see the regions loading and you'll be able to
pinpoint the problematic one.  Or, if your table is large, run a "scan
'TABLENAME', ['NONEXISTANT_COLUMNNAME']".  That'll cause the scanner to spin
through all regions quickly -- there'll be no values found as it scans --
and again with DEBUG you can see the regions loading and figure the bad one.

When you've found the bad region, look at its listing in the '.META.'
output.  Or paste it in here and we'll take a look for you.

Thanks Arthur,
St.Ack


Arthur van Hoff wrote:

Hi,

I have a table which appears to have two regions without a start key.
Is that expected? My job is getting stuck scanning these two regions.

Any suggestions?

Thanks.


--
Arthur van Hoff - Grand Master of Alphabetical Order
The Ellerdale Project, Menlo Park, CA
[EMAIL PROTECTED], 650-283-0842

Re: Multiple start regions in a table

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