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https://issues.apache.org/jira/browse/HBASE-14190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16067819#comment-16067819
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Allan Yang edited comment on HBASE-14190 at 6/29/17 6:27 AM:
-------------------------------------------------------------
{quote}
Sounds reasonable to me. Do we need change in the meta region opener in case
namespace gets scheduled ahead of meta?
{quote}
in current design, the only case the namespace gets scheduled ahead of meta is
that, namespace and meta region are host on different rs, and they crashed at
the same time, and then the SSH assign both meta region and meta to the same
server, and open namespace region request arrivals before open meta region
request... That's nearly impossible
wait a minute... If this happens, open namespace region will stuck since meta
region is not online, and assign meta will stuck also because there only one
thread for meta hander. maybe this is not a good idea.
was (Author: allan163):
{quote}
Sounds reasonable to me. Do we need change in the meta region opener in case
namespace gets scheduled ahead of meta?
{quote}
No need, in current design, the only case the namespace gets scheduled ahead of
meta is that, namespace and meta region are host on different rs, and they
crashed at the same time, and then the SSH assign both meta region and meta to
the same server, and open namespace region request arrivals before open meta
region request... That's nearly impossible
If no objection, I will open a new issue
> Assign system tables ahead of user region assignment
> ----------------------------------------------------
>
> Key: HBASE-14190
> URL: https://issues.apache.org/jira/browse/HBASE-14190
> Project: HBase
> Issue Type: Bug
> Components: Region Assignment
> Reporter: Ted Yu
> Assignee: Ted Yu
> Priority: Critical
> Attachments: 14190-system-wal-v1.txt, 14190-v12.4.txt, 14190-v12.txt
>
>
> Currently the namespace table region is assigned like user regions.
> I spent several hours working with a customer where master couldn't finish
> initialization.
> Even though master was restarted quite a few times, it went down with the
> following:
> {code}
> 2015-08-05 17:16:57,530 FATAL [hdpmaster1:60000.activeMasterManager]
> master.HMaster: Master server abort: loaded coprocessors are: []
> 2015-08-05 17:16:57,530 FATAL [hdpmaster1:60000.activeMasterManager]
> master.HMaster: Unhandled exception. Starting shutdown.
> java.io.IOException: Timedout 300000ms waiting for namespace table to be
> assigned
> at
> org.apache.hadoop.hbase.master.TableNamespaceManager.start(TableNamespaceManager.java:104)
> at org.apache.hadoop.hbase.master.HMaster.initNamespace(HMaster.java:985)
> at
> org.apache.hadoop.hbase.master.HMaster.finishActiveMasterInitialization(HMaster.java:779)
> at org.apache.hadoop.hbase.master.HMaster.access$500(HMaster.java:182)
> at org.apache.hadoop.hbase.master.HMaster$1.run(HMaster.java:1646)
> at java.lang.Thread.run(Thread.java:744)
> {code}
> During previous run(s), namespace table was created, hence leaving an entry
> in hbase:meta.
> The following if block in TableNamespaceManager#start() was skipped:
> {code}
> if (!MetaTableAccessor.tableExists(masterServices.getConnection(),
> TableName.NAMESPACE_TABLE_NAME)) {
> {code}
> TableNamespaceManager#start() spins, waiting for namespace region to be
> assigned.
> There was issue in master assigning user regions.
> We tried issuing 'assign' command from hbase shell which didn't work because
> of the following check in MasterRpcServices#assignRegion():
> {code}
> master.checkInitialized();
> {code}
> This scenario can be avoided if we assign hbase:namespace table after
> hbase:meta is assigned but before user table region assignment.
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