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HBase >> mail # user >> Is "synchronized" required?


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Re: Is "synchronized" required?
Yes, HTable is not thread safe, and using synchronized around them could
work, but would be implementation dependent.
You can have one HTable per request at a reasonable cost since
https://issues.apache.org/jira/browse/HBASE-4805. It's seems to be
available in 0.92 as well.

Cheers,

Nicolas
On Mon, Feb 4, 2013 at 10:13 PM, Adrien Mogenet <[EMAIL PROTECTED]>wrote:

> Beware, HTablePool is not totally thread-safe as well:
> https://issues.apache.org/jira/browse/HBASE-6651.
>
>
> On Mon, Feb 4, 2013 at 9:42 PM, Haijia Zhou <[EMAIL PROTECTED]> wrote:
>
> > Hi, Bing,
> >
> >  Not sure about your scenario but HTable class is not thread safe for
> > neither reads nor write.
> >  If you consider writing/reading from a table in a multiple-threaded way,
> > you can consider using HTablePool.
> >
> >  Hope it helps
> >
> > HJ
> >
> >
> > On Mon, Feb 4, 2013 at 3:32 PM, Bing Li <[EMAIL PROTECTED]> wrote:
> >
> > > Dear Ted and Harsh,
> > >
> > > I am sorry I didn't keep the exceptions. It occurred many days ago. My
> > > current version is 0.92.
> > >
> > > Now "synchronized" is removed. Is it correct?
> > >
> > > I will test if such exceptions are raised. I will let you know.
> > >
> > > Thanks!
> > >
> > > Best wishes,
> > > Bing
> > >
> > >
> > > On Tue, Feb 5, 2013 at 4:25 AM, Ted Yu <[EMAIL PROTECTED]> wrote:
> > > > Bing:
> > > > Use pastebin.com instead of attaching exception report.
> > > >
> > > > What version of HBase are you using ?
> > > >
> > > > Thanks
> > > >
> > > >
> > > > On Mon, Feb 4, 2013 at 12:21 PM, Harsh J <[EMAIL PROTECTED]> wrote:
> > > >>
> > > >> What exceptions do you actually receive - can you send them here?
> > > >> Knowing that is key to addressing your issue.
> > > >>
> > > >> On Tue, Feb 5, 2013 at 1:50 AM, Bing Li <[EMAIL PROTECTED]> wrote:
> > > >> > Dear all,
> > > >> >
> > > >> > When writing data into HBase, sometimes I got exceptions. I guess
> > they
> > > >> > might be caused by concurrent writings. But I am not sure.
> > > >> >
> > > >> > My question is whether it is necessary to put "synchronized"
> before
> > > >> > the writing methods? The following lines are the sample code.
> > > >> >
> > > >> > I think the directive, synchronized, must lower the performance of
> > > >> > writing. Sometimes concurrent writing is needed in my system.
> > > >> >
> > > >> > Thanks so much!
> > > >> >
> > > >> > Best wishes,
> > > >> > Bing
> > > >> >
> > > >> > public synchronized void AddDomainNodeRanks(String domainKey, int
> > > >> > timingScale, Map<String, Double> nodeRankMap)
> > > >> > {
> > > >> >       List<Put> puts = new ArrayList<Put>();
> > > >> >       Put domainKeyPut;
> > > >> >       Put timingScalePut;
> > > >> >       Put nodeKeyPut;
> > > >> >       Put rankPut;
> > > >> >
> > > >> >       byte[] domainNodeRankRowKey;
> > > >> >
> > > >> >       for (Map.Entry<String, Double> nodeRankEntry :
> > > >> > nodeRankMap.entrySet())
> > > >> >       {
> > > >> >           domainNodeRankRowKey > > > >> > Bytes.toBytes(RankStructure.DOMAIN_NODE_RANK_ROW +
> > > >> > Tools.GetAHash(domainKey + timingScale + nodeRankEntry.getKey()));
> > > >> >
> > > >> >          domainKeyPut = new Put(domainNodeRankRowKey);
> > > >> >          domainKeyPut.add(RankStructure.DOMAIN_NODE_RANK_FAMILY,
> > > >> > RankStructure.DOMAIN_NODE_RANK_DOMAIN_KEY_COLUMN,
> > > >> > Bytes.toBytes(domainKey));
> > > >> >          puts.add(domainKeyPut);
> > > >> >
> > > >> >          timingScalePut = new Put(domainNodeRankRowKey);
> > > >> >          timingScalePut.add(RankStructure.DOMAIN_NODE_RANK_FAMILY,
> > > >> > RankStructure.DOMAIN_NODE_RANK_TIMING_SCALE_COLUMN,
> > > >> > Bytes.toBytes(timingScale));
> > > >> >         puts.add(timingScalePut);
> > > >> >
> > > >> >         nodeKeyPut = new Put(domainNodeRankRowKey);
> > > >> >         nodeKeyPut.add(RankStructure.DOMAIN_NODE_RANK_FAMILY,
> > > >> > RankStructure.DOMAIN_NODE_RANK_NODE_KEY_COLUMN,
> > > >> > Bytes.toBytes(nodeRankEntry.getKey()));
> > > >> >         puts.add(nodeKeyPut);