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Which of the following sequences will it traverse to find the region serving the row range of interest?

Your client application connects to HBase for the first time to perform a write. Which of the
following sequences will it traverse to find the region serving the row range of interest?

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A.
ZooKeeper -> RegionServer -> Region

B.
ZooKeeper ->.META. -> RegionServer -> Region

C.
ZooKeeper -> ROOT -> .META. -> RegionServer -> Region

D.
ZooKeeper -> HMaster -> -ROOT- -> .META. -> RegionServer -> Region

Explanation:
The general flow is that a new client contacts the Zookeeper quorum (a separate
cluster of Zookeeper nodes) first to find a particular row key. It does so by retrieving the server
name (i.e. host name) that hosts the -ROOT- region from Zookeeper. With that information it can
query that server to get the server that hosts the .META. table. Both of these two details are
cached and only looked up once. Lastly it can query the .META. server and retrieve the server that
has the row the client is looking for.

Note:
*The .META. table keeps a list of all regions in the system. The .META. table structure is as
follows:
Key:
Region key of the format ([table],[region start key],[region id])
Values:
info:regioninfo (serialized HRegionInfo instance for this region)
info:server (server:port of the RegionServer containing this region)
info:serverstartcode (start-time of the RegionServer process containing this region)
Reference:HBase Architecture 101 – Storage

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