[HBASE-3777] Redefine Identity Of HBase Configuration

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.90.2
• Fix Version/s: 0.92.0
• Component/s: Client, IPC/RPC
• Hadoop Flags: Reviewed
• Assignee: Karthick Sankarachary
• Reporter: Karthick Sankarachary
• Created: 13/Apr/11 20:38
• Updated: 20/Nov/15 12:43
• Resolved: 03/May/11 04:44

Description

Judging from the javadoc in HConnectionManager, sharing connections across multiple clients going to the same cluster is supposedly a good thing. However, the fact that there is a one-to-one mapping between a configuration and connection instance, kind of works against that goal. Specifically, when you create HTable instances using a given Configuration instance and a copy thereof, we end up with two distinct HConnection instances under the covers. Is this really expected behavior, especially given that the configuration instance gets cloned a lot?

Here, I'd like to play devil's advocate and propose that we "deep-compare" HBaseConfiguration instances, so that multiple HBaseConfiguration instances that have the same properties map to the same HConnection instance. In case one is "concerned that a single HConnection is insufficient for sharing amongst clients", to quote the javadoc, then one should be able to mark a given HBaseConfiguration instance as being "uniquely identifiable".

Note that "sharing connections makes clean up of HConnection instances a little awkward", unless of course, you apply the change described in HBASE-3766.

Issue Links

• is depended upon by: HBASE-4508 Backport HBASE-3777 to 0.90 branch
• is related to: HBASE-3766 Manage Connections Through Reference Counts
• relates to: HBASE-2925 LRU of HConnectionManager.HBASE_INSTANCES breaks if HBaseConfiguration is changed
• relates to: HBASE-3792 TableInputFormat leaks ZK connections
• relates to: HBASE-3861 MiniZooKeeperCluster.startup() should refer to hbase.zookeeper.property.maxClientCnxns