Master may assign META region twice to two regionservers when regionserver is
closed and started repeatedly in short time
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Key: HBASE-4590
URL: https://issues.apache.org/jira/browse/HBASE-4590
Project: HBase
Issue Type: Bug
Affects Versions: 0.90.2
Reporter: shenchunhui
In the following case:
1.first,kill all the regionservers
2.then, start all the regionservers immediately
3.then, kill all the regionservers immediately
4.then, start all the regionservers immediately
Master may assign META region twice , and make two regionserver carrying META
region.
Through logs, we find that:
Before 1, Regionserver A carrys the META region,
Between 2 and 3 , master receives Regionserver A startup message and is ready
to assign meta region to Regionserver B
But, it fails because of 3, and then reassign meta region to Regionserver
C,Then ,it is successful after 4,
when 4 , Regionserver C is started earlier than Regionserver A , and
Regionserver A is started earlier than Regionserver C successfully online the
META region. Therefore, when master receives Regionserver A startup message in
4, it consider Regionserver A carryed META region through CatalogTracker and
create a MetaServerShutdownHandler
In MetaServerShutdownHandler's process(), after completing split hlog,
Regionserver C has already onlined META region,
however it will execute the following code all the same where isCarryingMeta()
return true :
if (isCarryingMeta())this.services.getAssignmentManager().assignMeta();
After that, META region will online on two regionservers
In order to prevent it , we should verify meta region location before assign
Meta region .
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