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https://issues.apache.org/jira/browse/HBASE-6588?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13435716#comment-13435716
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zhou wenjian commented on HBASE-6588:
-------------------------------------
@Ted
i was doing some tests on table balancer, disable and then enable it.
howerver i mistake using drop table instead of enable,
Ctrl + c is immediately sent, and enable table is also closed behind, then i
found table is deleted, but i couldn't create it anymore. So i reproduce the
scenario.
> enable table throws npe and leaves trash in zk in competition with delete
> table
> -------------------------------------------------------------------------------
>
> Key: HBASE-6588
> URL: https://issues.apache.org/jira/browse/HBASE-6588
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.94.0
> Reporter: Zhou wenjian
> Fix For: 0.94.2
>
> Attachments: HBASE-6588-trunk.patch
>
>
> 2012-08-15 19:23:36,178 DEBUG org.apache.hadoop.hbase.client.ClientScanner:
> Creating scanner over .META. starting at key 'test,,'
> 2012-08-15 19:23:36,178 DEBUG org.apache.hadoop.hbase.client.ClientScanner:
> Advancing internal scanner to startKey at 'test,,'
> 2012-08-15 19:24:09,180 DEBUG org.apache.hadoop.hbase.client.ClientScanner:
> Creating scanner over .META. starting at key ''
> 2012-08-15 19:24:09,180 DEBUG org.apache.hadoop.hbase.client.ClientScanner:
> Advancing internal scanner to startKey at ''
> 2012-08-15 19:24:09,183 DEBUG org.apache.hadoop.hbase.client.ClientScanner:
> Finished with scanning at {NAME => '.META.,,1', STARTKEY => '', ENDKEY => '',
> ENCODED => 1028785192,}
> 2012-08-15 19:24:09,183 DEBUG org.apache.hadoop.hbase.master.CatalogJanitor:
> Scanned 2 catalog row(s) and gc'd 0 unreferenced parent region(s)
> 2012-08-15 19:25:12,260 DEBUG
> org.apache.hadoop.hbase.master.handler.DeleteTableHandler: Deleting region
> test,,1345029764571.d1e24b251ca6286c840a9a5f571b7db1. from META and FS
> 2012-08-15 19:25:12,263 INFO org.apache.hadoop.hbase.catalog.MetaEditor:
> Deleted region test,,1345029764571.d1e24b251ca6286c840a9a5f571b7db1. from META
> 2012-08-15 19:25:12,265 INFO
> org.apache.hadoop.hbase.master.handler.EnableTableHandler: Attemping to
> enable the table test
> 2012-08-15 19:25:12,265 WARN org.apache.hadoop.hbase.zookeeper.ZKTable:
> Moving table test state to enabling but was not first in disabled state: null
> 2012-08-15 19:25:12,267 DEBUG org.apache.hadoop.hbase.client.ClientScanner:
> Creating scanner over .META. starting at key 'test,,'
> 2012-08-15 19:25:12,267 DEBUG org.apache.hadoop.hbase.client.ClientScanner:
> Advancing internal scanner to startKey at 'test,,'
> 2012-08-15 19:25:12,270 DEBUG org.apache.hadoop.hbase.client.ClientScanner:
> Finished with scanning at {NAME => '.META.,,1', STARTKEY => '', ENDKEY => '',
> ENCODED => 1028785192,}
> 2012-08-15 19:25:12,270 ERROR org.apache.hadoop.hbase.executor.EventHandler:
> Caught throwable while processing event C_M_ENABLE_TABLE
> java.lang.NullPointerException
> at
> org.apache.hadoop.hbase.master.handler.EnableTableHandler.handleEnableTable(EnableTableHandler.java:116)
> at
> org.apache.hadoop.hbase.master.handler.EnableTableHandler.process(EnableTableHandler.java:97)
> at
> org.apache.hadoop.hbase.executor.EventHandler.run(EventHandler.java:169)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:662)
> table is disabled now, then we enable and delete the table at the same time.
> Since the thread num of MASTER_TABLE_OPERATIONS is 1 by default. The two
> operations are serial in master.Before deletetable deletes all the regions in
> meta, CreateTableHandler ships the check of tableExists,then it will block
> until deletetable finishs, then CreateTableHandler will set zk enabling, and
> find no data in meta:
> regionsInMeta = MetaReader.getTableRegions(this.ct, tableName, true);
> int countOfRegionsInTable = regionsInMeta.size();
> npe will be throwed here. And we could not create the same table anymore.
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