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From Gen Liu <ge...@zynga.com>
Subject Re: Is there a way to replicate root and meta table in HBase?
Date Tue, 04 Sep 2012 22:20:02 GMT


On 9/4/12 3:07 PM, "Stack" <stack@duboce.net> wrote:

>On Tue, Sep 4, 2012 at 2:52 PM, Gen Liu <geliu@zynga.com> wrote:
>> We are running into a case that if the region server that serves meta
>>table is down, all request will timeouts because region lookup is not
>>available.
>
>Only requests to .META. fail (and most of the time, .META. info is
>cached so should be relatively rare to do .META. lookups).  It should
>not be all requests.

We get a lot of region lookup error in the client side:
(zlive-hbase-08.int.zynga.com is not dead, we killed another server)
2012-09-04 14:28:11,829 DEBUG
org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation
: locateRegionInMeta parentTable=-ROOT-,
metaLocation={region=-ROOT-,,0.70236052,
hostname=zlive-hbase-08.int.zynga.com, port=60020}, attempt=8 of 10
failed; retrying after sleep of 16000 because: Connection refused

>
>> It seems that regions that serve root and meta are the single point of
>>failure in HBase.
>
>They can be offline if a server crashes but they should be back on
>line soon enough; is this not your experience?

We set hbase.regionserver.maxlogs=256 to enable big memstore flush to
lower compaction stress, so the log split takes about 5-10 minutes. I
think META will come back after the log split.
Is there a way to specify where should HBase put root and meta table?

>
>> Is there a way to get rid of it? Does HBase give a higher recover
>>priority to meta and root table?
>>
>
>HBase gets .META. and -ROOT- back on line ahead of all other regions, yes.
>
>St.Ack


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