info:sn and info:server in hbase:meta table

[Stephen Jiang]

I scanned the hbase:meta table in a fresh-build master branch and get the
following results.  Seems to me that info:sn and info:server are some kind
of duplicate (well, info:sn has the timestamp of RS, we could store this in
info:server too if we want).  Searching the code in master branch, I saw
some comment on "info:server", but could not find any information on
"info:sn".  Is this "info:sn" legacy information?  If so, for a new 2.0
cluster, should we not create the value in meta?

hbase(main):002:0> scan 'hbase:meta'
ROW
                 COLUMN+CELL
 hbase:meta
                 column=table:state, timestamp=1473185666041, value=\x08\x00
 hbase:namespace
                  column=table:state, timestamp=1473185667442,
value=\x08\x00
 hbase:namespace,,1473185666375.4c7fc12f243854e0af6c9e30ce7d6d90.
                 column=info:regioninfo, timestamp=1473185667273,
value={ENCODED => 4c7fc12f243854e0af6c9e30ce7d6d90, NAME =>
'hbase:namespace,,1473185666375.4c7fc12f243854e0af6c9e30ce7d6d90.',
STARTKEY => '', ENDKEY => ''}
 hbase:namespace,,1473185666375.4c7fc12f243854e0af6c9e30ce7d6d90.
                 column=info:seqnumDuringOpen, timestamp=1473185667603,
value=\x00\x00\x00\x00\x00\x00\x00\x02
 hbase:namespace,,1473185666375.4c7fc12f243854e0af6c9e30ce7d6d90.
                 column=info:server, timestamp=1473185667603, value=
10.22.2.122:58498
 hbase:namespace,,1473185666375.4c7fc12f243854e0af6c9e30ce7d6d90.
                 column=info:serverstartcode, timestamp=1473185667603,
value=1473185651426
 hbase:namespace,,1473185666375.4c7fc12f243854e0af6c9e30ce7d6d90.
                 column=info:sn, timestamp=1473185667421,
value=10.22.2.122,58498,1473185651426
 hbase:namespace,,1473185666375.4c7fc12f243854e0af6c9e30ce7d6d90.
                 column=info:state, timestamp=1473185667610, value=OPEN
3 row(s)