Josh Elser created HBASE-20028:
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Summary: NPE when comparing versions in AM after RS ZK expiration
Key: HBASE-20028
URL: https://issues.apache.org/jira/browse/HBASE-20028
Project: HBase
Issue Type: Bug
Components: master
Reporter: Josh Elser
Assignee: Josh Elser
Fix For: 2.0.0-beta-2
{noformat}
2018-02-20 16:36:41,794 ERROR [Thread-85] assignment.AssignmentManager:
java.lang.NullPointerException
java.lang.NullPointerException
at
org.apache.hadoop.hbase.util.VersionInfo.compareVersion(VersionInfo.java:122)
at
org.apache.hadoop.hbase.master.assignment.AssignmentManager.lambda$getExcludedServersForSystemTable$5(AssignmentManager.java:1860)
at java.util.Collections.max(Collections.java:712)
at
org.apache.hadoop.hbase.master.assignment.AssignmentManager.getExcludedServersForSystemTable(AssignmentManager.java:1859)
at
org.apache.hadoop.hbase.master.assignment.AssignmentManager.lambda$checkIfShouldMoveSystemRegionAsync$0(AssignmentManager.java:464){noformat}
Looks like a race condition around an RS losing its ZK lock. If AM tries to see
if it should move a Region to a server who we've seen that the lock was lost
but the RS hasn't yet been processed as "dead", we can get into a situation
where {{HMaster.getRegionServerVersion()}} returns null and causes this to fail.
Looks like a simple filter on the servers to preclude null versions would fix
the problem.
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