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https://issues.apache.org/jira/browse/HBASE-26596?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17464273#comment-17464273
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Yutong Xiao commented on HBASE-26596:
-------------------------------------
In branch-2, the unloadRegion function directly get all online regions
{code:java}
// Get Online RegionServers
List<ServerName> regionServers = new ArrayList<>();
regionServers.addAll(admin.getRegionServers());
// Remove the host Region server from target Region Servers list
ServerName server = stripServer(regionServers, hostname, port);
if (server == null) {
LOG.info("Could not find server '{}:{}' in the set of region servers.
giving up.",
hostname, port);
LOG.debug("List of region servers: {}", regionServers);
return false;
}
{code}
But one question is, what if all the other servers are not in the same rsgroup
with the unloadedregionserver. Is that the region will be moved back after a
failed move? But for null rsgroup problem, as there is no rsgroup operations,
the problem does not exists at branch-2 I think.
> region_mover should gracefully ignore null response from
> RSGroupAdmin#getRSGroupOfServer
> ----------------------------------------------------------------------------------------
>
> Key: HBASE-26596
> URL: https://issues.apache.org/jira/browse/HBASE-26596
> Project: HBase
> Issue Type: Bug
> Components: mover, rsgroup
> Affects Versions: 1.7.1
> Reporter: Viraj Jasani
> Assignee: Yutong Xiao
> Priority: Major
>
> If regionserver has any non-daemon thread running even after it's own
> shutdown, the running non-daemon thread can prevent clean JVM exit and
> regionserver could be stuck in the zombie state. We have recently provided a
> workaround for this in HBASE-26468 for regionserver exit hook to wait 30s for
> all non-daemon threads to get stopped before terminating JVM abnormally.
> However, if regionserver is stuck in such state, region_mover unload fails
> with:
> {code:java}
> NoMethodError: undefined method `getName` for nil:NilClass
> getSameRSGroupServers at /bin/region_mover.rb:503
> __ensure__ at /bin/region_mover.rb:313
> unloadRegions at /bin/region_mover.rb:310
> (root) at /bin/region_mover.rb:572
> {code}
> This happens if the cluster has RSGroup enabled and the given server is
> already stopped, hence RSGroupAdmin#getRSGroupOfServer would return null (as
> the server is not running anymore so it is not part of any RSGroup).
> region_mover should ride over this null response and gracefully exit from
> unloadRegions() call.
>
> We should also check if the fix is applicable to branch-2 and above.
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