ramkrishna.s.vasudevan created HBASE-6438:
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Summary: RegionAlreadyInTransitionException needs to give more
info to avoid assignment inconsistencies
Key: HBASE-6438
URL: https://issues.apache.org/jira/browse/HBASE-6438
Project: HBase
Issue Type: Bug
Reporter: ramkrishna.s.vasudevan
Seeing some of the recent issues in region assignment,
RegionAlreadyInTransitionException is one reason after which the region
assignment may or may not happen(in the sense we need to wait for the TM to
assign).
In HBASE-6317 we got one problem due to RegionAlreadyInTransitionException on
master restart.
Consider the following case, due to some reason like master restart or external
assign call, we try to assign a region that is already getting opened in a RS.
Now the next call to assign has already changed the state of the znode and so
the current assign that is going on the RS is affected and it fails. The
second assignment that started also fails getting RAITE exception. Finally
both assignments not carrying on. Idea is to find whether any such RAITE
exception can be retried or not.
Here again we have following cases like where
-> The znode is yet to transitioned from OFFLINE to OPENING in RS
-> RS may be in the step of openRegion.
-> RS may be trying to transition OPENING to OPENED.
-> RS is yet to add to online regions in the RS side.
Here in openRegion() and updateMeta() any failures we are moving the znode to
FAILED_OPEN. So in these cases getting an RAITE should be ok. But in other
cases the assignment is stopped.
The idea is to just add the current state of the region assignment in the RIT
map in the RS side and using that info we can determine whether the assignment
can be retried or not on getting an RAITE.
Considering the current work going on in AM, pls do share if this is needed
atleast in the 0.92/0.94 versions?
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