Hi,
I am using HBase 0.98.6.
I learned from this maillist before, that the recommended method to 'connect'
to HBase from client is to use HConnectionManager like this:
HConnection
con=HConnectionManager.createConnection(configuration);
HTableInterfacetable =
con.getTable("hbase_table1");
Instead of
HTableInterface table = new
HTable(configuration, "hbase_table1");
I don't quite understand the reason. I was thinking that each time I initialize
a HTable instance, it needs to create a new HConnection. And that is expensive.
But using the first method, multiple HTable instances can share the same
HConnection. That is quite reasonable to me.
However, I was reading from some articles on internet that , even if I use the
'new HTable(conf, tbl)' method, if the 'conf' object is the same one, all the
HTable instances will still share the same HConnection. I was recently read yet
another article and said when using 'new HTable(conf, tbl)', one don't need to
use the exactly same 'conf' object (same one in memory). if two 'conf' objects,
two different objects are all the same, I mean all attributes of these two are
same (for example, created from the same hbase-site.xml and never change) then
HTable objects can still share the same HConnection. I also try to read the
HTable src code, it is very hard, but it seems to me the last statement is
correct: 'HTable will share HConnection, if configuration is all the same'.
Sorry for so verbose. My question:
If two 'configuration' objects are same, then two HTable object instantiated
with them respectively can still share the same HConnection or not? Directly
using the 'new HTable()' method.
If the answer is 'yes', then why I still need the HConnectionManager to create
a shared connection?
I am talking about 0.98.6.
I googled for days, and even try to read HBase src code, but still get really
confused. I try to do some tests also, but since I am too newbie, I don't know
how to verify the difference, I really don't know what a HConnection do under
the hood. I counted the ZooKeeper client requests, and I found some difference.
If this ZooKeeper requests difference is a correct metrics, it means to me that
two HTable do not share HConnetion even using same 'configuration' in the
constructor. So it confused me more and more....
Please someone kindly help me for this newbie question and thanks in advance.
Thanks,
Ming
