[HBASE-8473] add note to ref guide about snapshots and ec2 reverse dns requirements.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.98.0, 0.94.6.1, 0.95.0
• Fix Version/s: 2.0.0
• Component/s: documentation, snapshots
• Hadoop Flags: Reviewed
• Assignee: M Linville
• Reporter: Jonathan Hsieh
• Created: 01/May/13 01:15
• Updated: 16/Jun/22 16:59
• Resolved: 14/Jul/14 04:57

Description

From IRC from mighty Jeremy Carroll.

17:10 <jeremy_carroll> jmhsieh: I think I found the root cuase. All my region servers reach the barrier, but it does not continue.
17:11 <jeremy_carroll> jmhsieh: All RS have this in their logs: 2013-05-01 00:04:56,356 DEBUG org.apache.hadoop.hbase.procedure.Subprocedure: Subprocedure 'backup1' coordinator notified of 'acquire', waiting on 'reached' or 'abort' from coordinator.
17:11 <jeremy_carroll> jmhsieh: Then the coordinator (Master) never sends anything. They just sit until the timeout.
17:12 <jeremy_carroll> jmhsieh: So basically 'reached' is never obtained. Then abort it set, and it fails.
...
17:24 <jeremy_carroll> jmhsieh: Found the bug. The hostnames dont match the master due to DNS resolution
17:25 <jeremy_carroll> jmhsieh: The barrier aquired is putting in the local hostname from the regionservers. In EC2 (Where reverse DNS does not work well), the master hands the internal name to the client.
17:25 <jeremy_carroll> jmhsieh: https://s3.amazonaws.com/uploads.hipchat.com/23947/185789/au94meik0h3y5ii/Screen%20Shot%202013-04-30%20at%2017.25.50.png 
17:26 <jeremy_carroll> jmhsieh: So it's waiting for something like 'ip-10-155-208-202.ec2.internal,60020,1367366580066' zNode to show up, but instead 'hbasemetaclustera-d1b0a484,60020,1367366580066,' is being inserted. Barrier is not reached
17:27 <jeremy_carroll> jmhsieh: Reason being in our environment the master does not have a reverse DNS entry. So we get stuff like this on RegionServer startup in our logs.
17:27 <jeremy_carroll> jmhsieh: 2013-05-01 00:03:00,614 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: Master passed us hostname to use. Was=hbasemetaclustera-d1b0a484, Now=ip-10-155-208-202.ec2.internal
17:54 <jeremy_carroll> jmhsieh: That was it. Verified. Now that Reverse DNS is working, snapshots are working. Now how to figure out how to get Reverse DNS working on Route53. I wished there was something like 'slave.host.name' inside of Hadoop for this. Looking at source code.