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https://issues.apache.org/jira/browse/HBASE-14190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14687390#comment-14687390
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Vandana Ayyalasomayajula commented on HBASE-14190:
--------------------------------------------------
In the MetaTableAccessor class, getSystemTableRegionsAndLocations() method,
since we know that we need system table region information and they start with
NamespaceDescriptor.SYSTEM_NAMESPACE_NAME_STR string, can we optimize this :
{quote}
+ scanMeta(connection, HConstants.EMPTY_START_ROW, HConstants.EMPTY_END_ROW,
+ QueryType.REGION, visitor);
{quote}
In this way we will avoid scanning the entire meta table.
> 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
> Reporter: Ted Yu
> Assignee: Ted Yu
> Priority: Critical
> Attachments: 14190-v6.txt, 14190-v7.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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