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HBase, mail # user - Is "synchronized" required?


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Re: Is "synchronized" required?
Bing Li 2013-02-06, 10:31
Dear Lars,

I am now running HBase in the pseudo-distributed mode. The updated
HTable constructor also works?

Thanks so much!
Bing

On Wed, Feb 6, 2013 at 3:44 PM, lars hofhansl <[EMAIL PROTECTED]> wrote:
> Don't use a pool at all.
> With HBASE-4805 (https://issues.apache.org/jira/browse/HBASE-4805) you can precreate an HConnection and ExecutorService and then make HTable cheaply on demand every time you need one.
>
> Checkout HConnectionManager.createConnection(...) and the HTable constructors.
>
> I need to document this somewhere.
>
>
> -- Lars
>
>
>
> ________________________________
>  From: Bing Li <[EMAIL PROTECTED]>
> To: user <[EMAIL PROTECTED]>; lars hofhansl <[EMAIL PROTECTED]>; "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> Sent: Tuesday, February 5, 2013 10:36 PM
> Subject: Re: Is "synchronized" required?
>
> Lars,
>
> I found that at least the exceptions have nothing to do with shared HTable.
>
> To save the resources, I designed a pool for the classes that write
> and read from HBase. The primary resources consumed in the classes are
> HTable. The pool has some bugs.
>
> My question is whether it is necessary to design such a pool? Is it
> fine to create a instance of HTable for each thread?
>
> I noticed that HBase has a class, HTablePool. Maybe the pool I
> designed is NOT required?
>
> Thanks so much!
>
> Best wishes!
> Bing
>
> On Wed, Feb 6, 2013 at 1:05 PM, lars hofhansl <[EMAIL PROTECTED]> wrote:
>> Are you sharing this.rankTable between threads? HTable is not thread safe.
>>
>> -- Lars
>>
>>
>>
>> ________________________________
>>  From: Bing Li <[EMAIL PROTECTED]>
>> To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>; user <[EMAIL PROTECTED]>
>> Sent: Tuesday, February 5, 2013 8:54 AM
>> Subject: Re: Is "synchronized" required?
>>
>> Dear all,
>>
>> After "synchronized" is removed from the method of writing, I get the
>> following exceptions when reading. Before the removal, no such
>> exceptions.
>>
>> Could you help me how to solve it?
>>
>> Thanks so much!
>>
>> Best wishes,
>> Bing
>>
>>      [java] Feb 6, 2013 12:21:31 AM
>> org.apache.hadoop.hbase.ipc.HBaseClient$Connection run
>>      [java] WARNING: Unexpected exception receiving call responses
>>      [java] java.lang.NullPointerException
>>      [java]     at
>> org.apache.hadoop.hbase.io.HbaseObjectWritable.readObject(HbaseObjectWritable.java:521)
>>      [java]     at
>> org.apache.hadoop.hbase.io.HbaseObjectWritable.readFields(HbaseObjectWritable.java:297)
>>      [java]     at
>> org.apache.hadoop.hbase.ipc.HBaseClient$Connection.receiveResponse(HBaseClient.java:593)
>>      [java]     at
>> org.apache.hadoop.hbase.ipc.HBaseClient$Connection.run(HBaseClient.java:505)
>>      [java] Feb 6, 2013 12:21:31 AM
>> org.apache.hadoop.hbase.client.ScannerCallable close
>>      [java] WARNING: Ignore, probably already closed
>>      [java] java.io.IOException: Call to greatfreeweb/127.0.1.1:60020
>> failed on local exception: java.io.IOException: Unexpected exception
>> receiving call responses
>>      [java]     at
>> org.apache.hadoop.hbase.ipc.HBaseClient.wrapException(HBaseClient.java:934)
>>      [java]     at
>> org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:903)
>>      [java]     at
>> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Invoker.invoke(WritableRpcEngine.java:150)
>>      [java]     at $Proxy6.close(Unknown Source)
>>      [java]     at
>> org.apache.hadoop.hbase.client.ScannerCallable.close(ScannerCallable.java:112)
>>      [java]     at
>> org.apache.hadoop.hbase.client.ScannerCallable.call(ScannerCallable.java:74)
>>      [java]     at
>> org.apache.hadoop.hbase.client.ScannerCallable.call(ScannerCallable.java:39)
>>      [java]     at
>> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getRegionServerWithRetries(HConnectionManager.java:1325)
>>      [java]     at
>> org.apache.hadoop.hbase.client.HTable$ClientScanner.nextScanner(HTable.java:1167)
>>      [java]     at