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From baggio liu <baggi...@gmail.com>
Subject Re: Scan cause too many connection
Date Fri, 30 Jul 2010 08:05:29 GMT
Let me try . Thanks  very much for your help.
:D

Thanks & Best regards
LiuJinglong

在 2010年7月30日 下午3:35,Angus He <angushe@gmail.com>写道:

> Close the scannner will not close the store file.
>
> Probably you could increase the memstore size and region file size.
> And hbase.hstore.compactionThreshold and
> hbase.hstore.blockingStoreFiles might help too.
>
> 2010/7/30 baggio liu <baggioss@gmail.com>:
> > In our cluster,  there're thousands of region and each region has 5-8
> store
> > files, so the connection number is very terrible.
> > And if we close the store file after scanning , the connection number may
> > bring down some region servers. (In my cluster , my region server went
> down
> > caused by socket OOM, our fd limit set to 30000, and tcp_mem set to 2G).
> > We want to reuse these connections in DFSClient, do you have some more
> > graceful solutions ?
> >
> >
> > Thanks & Best regards
> > LiuJinglong
> >
> >
> > 在 2010年7月30日 下午2:51,Angus He <angushe@gmail.com>写道:
> >
> >> Hi Baggio,
> >>
> >>
> >> >   2. During scanning, it'll new StoreFile one by one. And in
> constructor
> >> of
> >> > StoreFile , HFile.Reader will be created. HFile.Reader act as
> DFSClient,
> >> > it'll keep a connection with DataNode when something should be read.
> >>
> >> Yes, There is a HFile.Reader opend in StoreFile constructor.
> >> But I am afraid there is only one instance in HBase for each
> >> StoreFile. And I just confirmed this
> >> in my dev machine. (HBase running in standalone mode). After many scan
> >> operations, still only one
> >> instance for each StoreFile.
> >>
> >> >   1.After checking code, and I've seen in scanner close method,
> >> > HFile.Reader has not been closed. Is that used for reuse HFile ?
> >> >      I try to close the scanner explictly, but it cause meta region
> can
> >> not
> >> > be loaded when start up. Both get() and scan()  use the same
> scanner...
> >>
> >> It seems there is only one HFile.Reader for each StoreFile, and the
> >> HFile.Reader instance is shared by multiple scannners.
> >>
> >> As for closing the scannner explicitly, it works all right in our
> >> case.  And really do not know what happened in your case.
> >>
> >> By the way, how do you get the scanner,by HTable or other ways?
> >>
> >>
> >> >
> >> > Thanks & Best regards
> >> > LiuJinglong
> >> >
> >> > 在 2010年7月30日 上午11:33,Angus He <angushe@gmail.com>写道:
> >> >
> >> >> 1. try to close the scanner explictly?
> >> >>
> >> >> 2. I do not think HBase will issue a new connection for each
> StoreFile
> >> >> for the scan operation.
> >> >>
> >> >> 2010/7/29 baggio liu <baggioss@gmail.com>:
> >> >> > Hi all,
> >> >> >    We have 53 machines in our hbase cluster and run 6 clients
to
> scan
> >> a
> >> >> > table. During scanning, we found when a region is scanning , it'll
> new
> >> >> > StoreFile object, create a connection to datanode (in fact , create
> >> HFile
> >> >> > Reader), so the number of connection increases by the number of
> store
> >> >> files.
> >> >> > We have many store files ,(cross several regions and has not reach
> >> minor
> >> >> > compaction thredshould), too many connections has been created.
And
> >> after
> >> >> > scanning, the connection will not closed.
> >> >> >    As the result of it , a machine which act as region server
has
> too
> >> >> high
> >> >> > system CPU, and hung for a long time.
> >> >> >    My question is :
> >> >> >   1. Why we don't close connection ( in fact, we don't close
> >> >> > HFile.Reader)after we complete to scan table ? We wanna to reuse
> >> >> connection
> >> >> > in the next scan ??
> >> >> >   2. How can we limit the connection number ?
> >> >> >
> >> >> > Thanks & Best regards
> >> >> > LiuJinglong
> >> >> >
> >> >>
> >> >>
> >> >>
> >> >> --
> >> >> Regards
> >> >> Angus
> >> >>
> >> >
> >>
> >>
> >>
> >> --
> >> Regards
> >> Angus
> >>
> >
>
>
>
> --
> Regards
> Angus
>

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