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From NNever <nnever...@gmail.com>
Subject Re: Is HBase Thread-Safety?
Date Fri, 13 Apr 2012 02:50:05 GMT
1. A pre-row lock is here during the update, so other clients will block
whild on client performs an update.(see HRegion.put 's annotaion), no
exception.
In the client side, while a process is updating, it may not reach the
buffersize so the other process may read the original value, I think.

2. What kind of inconsistency? different value on the same row's qualifier?

3.I don't know the truely realize in code. There Is caching, but everytime
you call methods like Htable.get, it still need connect to server to
retrieve data——so, not as fast as in memory, isn't it?

Best regards,
nn

2012/4/13 Bing Li <lblabs@gmail.com>

> Dear Iars,
>
> Thanks so much for your reply!
>
> In my case, I need to overwrite or update a HTable. If reading during the
> process of updating or overwriting, any exceptions will be thrown by HBase?
>
> If multiple instances for a HTable are used by multiple threads, there must
> be inconsistency among them, right?
>
> I guess caching must be done in HBase. So retrieving in HTable must be
> almost as fast as in memory?
>
> Best regards,
> Bing
>
> On Fri, Apr 13, 2012 at 6:17 AM, lars hofhansl <lhofhansl@yahoo.com>
> wrote:
>
> > Hi Bing,
> >
> > Which part? The server certainly is thread safe.
> > The client is not, at least not all the way through.
> >
> > The main consideration is HTable, which is not thread safe, you need to
> > create one instance for each thread
> > (HBASE-4805 makes that much cheaper), store the HTable in a ThreadLocal
> > after creation, or use HTablePool.
> >
> > Please let me know if that answers your question.
> >
> > Thanks.
> >
> > -- Lars
> >
> >
> > ----- Original Message -----
> > From: Bing Li <lblabs@gmail.com>
> > To: hbase-user@hadoop.apache.org; user <user@hbase.apache.org>
> > Cc:
> > Sent: Thursday, April 12, 2012 3:10 PM
> > Subject: Is HBase Thread-Safety?
> >
> > Dear all,
> >
> > Is HBase thread-safety? Do I need to consider the consistency issue when
> > manipulating HBase?
> >
> > Thanks so much!
> >
> > Best regards,
> > Bing
> >
> >
>

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