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From Karthik Kambatla <kkamb...@cs.purdue.edu>
Subject Re: Flaky tableExists()
Date Wed, 21 Jul 2010 17:43:57 GMT
Thanks a lot for the prompt help. [I had sent an immediate reply but from
the wrong address... hopefully, you would receive this.]

I am running HBase 0.20.5. I have cleaned the whole cluster and re-setup
everything (HDFS, MapReduce, and HBase). Here is the transcript -- from when
the HBase cluster has been started.


[kambatla@mercado-2 ~]$ hbase shell
HBase Shell; enter 'help<RETURN>' for list of supported commands.
Version: 0.20.5, rUnknown, Thu Jul 15 22:27:05 PDT 2010

hbase(main):001:0> list
0 row(s) in 0.0910 seconds

hbase(main):002:0> create 'Test'
0 row(s) in 1.0990 seconds

hbase(main):003:0> list
Test


1 row(s) in 0.0070 seconds

hbase(main):004:0> exit


[kambatla@mercado-2 ~]$ hbase shell
HBase Shell; enter 'help<RETURN>' for list of supported commands.
Version: 0.20.5, rUnknown, Thu Jul 15 22:27:05 PDT 2010

hbase(main):001:0> list
0 row(s) in 0.0860 seconds

hbase(main):004:0> scan '.META.'
ROW
COLUMN+CELL

 Test,,1279665697803         column=info:server, timestamp=1279668781099,
value=15.25.119.96:60020
 Test,,1279665697803         column=info:serverstartcode,
timestamp=1279668781099, value=1279665651801
1 row(s) in 0.0260 seconds

hbase(main):005:0> create 'Test1'
0 row(s) in 1.1050 seconds

hbase(main):006:0> list
0 row(s) in 0.0060 seconds

hbase(main):007:0> scan '.META.'
ROW
COLUMN+CELL

 Test,,1279665697803         column=info:server, timestamp=1279668781099,
value=15.25.119.96:60020
 Test,,1279665697803         column=info:serverstartcode,
timestamp=1279668781099, value=1279665651801
1 row(s) in 0.0100 seconds

hbase(main):008:0> exit


[kambatla@mercado-2 ~]$ hbase shell
HBase Shell; enter 'help<RETURN>' for list of supported commands.
Version: 0.20.5, rUnknown, Thu Jul 15 22:27:05 PDT 2010

hbase(main):001:0> list
0 row(s) in 0.0900 seconds

hbase(main):002:0> scan '.META.'
ROW
COLUMN+CELL

0 row(s) in 0.0130 seconds

hbase(main):003:0> scan '.META.'
ROW
COLUMN+CELL

0 row(s) in 0.0070 seconds

Thanks
Karthik


On Tue, Jul 20, 2010 at 4:15 PM, Jonathan Gray <jgray@facebook.com> wrote:

> Also, I'm not sure this will be fixed with the master changes.
>
> tableExists() actually makes a call to listTables() and then checks if the
> table you are looking for is in the list.
>
> listTables() uses a MetaScanner/MetaVisitor.  Though the master changes
> de-emphasize the general use of meta scanning, it would not necessarily
> change the implementation of these client (to RS) calls.
>
> Hard to say what would make this flakey besides some of the older bugs
> around lots of META StoreFiles.
>
> What version of HBase are you running?
>
> JG
>
> > -----Original Message-----
> > From: Jonathan Gray [mailto:jgray@facebook.com]
> > Sent: Tuesday, July 20, 2010 4:06 PM
> > To: user@hbase.apache.org
> > Subject: RE: Flaky tableExists()
> >
> > I've personally never seen a flaky tableExists() but it's not something
> > I've used heavily.
> >
> > Could you do the same operations you did below in the shell but also
> > run:  scan '.META.'
> >
> > > -----Original Message-----
> > > From: Karthik Kambatla [mailto:karthik.shashank.kambatla@gmail.com]
> > > Sent: Tuesday, July 20, 2010 3:26 PM
> > > To: user@hbase.apache.org
> > > Subject: Re: Flaky tableExists()
> > >
> > > Thanks Ryan for understanding the pain :)
> > >
> > > Is there a work-around for the time being? I haven't experienced any
> > > such
> > > issues with earlier versions of HBase. Was I just lucky or would it
> > > make
> > > sense to revert to earlier questions?
> > >
> > > Thanks
> > > Karthik
> > >
> > > On Tue, Jul 20, 2010 at 2:54 PM, Ryan Rawson <ryanobjc@gmail.com>
> > > wrote:
> > >
> > > > This sucks, and there are being substantial reworks to master
> > > > functions in 0.90 :-)
> > > >
> > > > Hopefully that will permanently address these kinds of bugs.
> > > >
> > > > Hopefully within a few weeks there'll be a developer preview (0.89
> > > > series) that has that code.
> > > >
> > > > -ryan
> > > >
> > > > On Tue, Jul 20, 2010 at 2:52 PM, Karthik Kambatla
> > > > <kkambatl@cs.purdue.edu> wrote:
> > > > > Hi all
> > > > >
> > > > > I have been noticing a slightly flaky behavior with respect to
> > > > > HBaseAdmin.tableExists(). After I have created the table, it
> > > returns
> > > > > true/false every time when called. In hbase shell, the list
> > command
> > > > prints
> > > > > out all the tables sometimes, and shows no tables on other
> > > occasions. Any
> > > > > ideas as to why this happens?
> > > > >
> > > > > The master on my cluster runs the HDFS - namenode, secondary
> > > namenode;
> > > > HBase
> > > > > - HMaster, HQuorumPeer. The 12 slaves run the HDFS datanode and
> > > HBase
> > > > > HRegionServer. Below is the transcript of operations on hbase
> > > shell...
> > > > Every
> > > > > time I exit and enter hbase shell, the output changes.
> > > > >
> > > > > Thanks
> > > > > Karthik
> > > > >
> > > > > hbase(main):002:0> count 'SUBSCRIPTIONS'
> > > > > 0 row(s) in 6.0560 seconds
> > > > > hbase(main):003:0> create 'Test'
> > > > > 0 row(s) in 1.0840 seconds
> > > > > hbase(main):004:0> list
> > > > > SUBSCRIPTIONS
> > > > >
> > > > >
> > > > > 1 row(s) in 0.0090 seconds
> > > > >
> > > > > hbase(main):010:0> create 'Test'
> > > > > NativeException: org.apache.hadoop.hbase.TableExistsException:
> > > > > org.apache.hadoop.hbase.TableExistsException: Test
> > > > >    at
> > > >
> > org.apache.hadoop.hbase.master.HMaster.createTable(HMaster.java:798)
> > > > >    at
> > > >
> > org.apache.hadoop.hbase.master.HMaster.createTable(HMaster.java:762)
> > > > >    at sun.reflect.GeneratedMethodAccessor13.invoke(Unknown
> > Source)
> > > > >    at
> > > > >
> > > >
> > >
> > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccesso
> > > rImpl.java:25)
> > > > >    at java.lang.reflect.Method.invoke(Method.java:597)
> > > > >    at
> > > org.apache.hadoop.hbase.ipc.HBaseRPC$Server.call(HBaseRPC.java:657)
> > > > >    at
> > > > >
> > >
> > org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:91
> > > 5)
> > > > >
> > > > >
> > > > > hbase(main):011:0> list
> > > > > SUBSCRIPTIONS
> > > > >
> > > > > 1 row(s) in 0.0070 seconds
> > > > > hbase(main):012:0> exit
> > > > >
> > > > > [kambatla@mercado-2 ~]$ hbase shell
> > > > > HBase Shell; enter 'help<RETURN>' for list of supported commands.
> > > > > Version: 0.20.5, rUnknown, Thu Jul 15 22:27:05 PDT 2010
> > > > > hbase(main):001:0> list
> > > > > TOPICS
> > > > >
> > > > > Test
> > > > >
> > > > > TestTable
> > > > >
> > > > > USERS
> > > > >
> > > > > 4 row(s) in 0.0930 seconds
> > > > > hbase(main):005:0> exit
> > > > >
> > > > > [kambatla@mercado-2 ~]$ hbase shell
> > > > > HBase Shell; enter 'help<RETURN>' for list of supported commands.
> > > > > Version: 0.20.5, rUnknown, Thu Jul 15 22:27:05 PDT 2010
> > > > > hbase(main):001:0> list
> > > > > EVENTS
> > > > >
> > > > > SUBSCRIPTIONS
> > > > >
> > > > > TOPICS
> > > > >
> > > > > TestTable
> > > > >
> > > > > USERS
> > > > >
> > > > > 5 row(s) in 0.1000 seconds
> > > > >
> > > >
>

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