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HBase >> mail # user >> Scanner timeout -- any reason not to raise?


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Re: Scanner timeout -- any reason not to raise?
Bryan:
Interesting idea.

You can log a JIRA with the following two suggestions.

On Wed, Mar 20, 2013 at 10:39 AM, Bryan Beaudreault <
[EMAIL PROTECTED]> wrote:

> I was thinking something like this:
>
> Scan scan = new Scan(startRow, endRow);
>
> scan.setCaching(someVal); // based on what we expect most rows to take for
> processing time
>
>  ResultScanner scanner = table.getScanner(scan);
>
>   for (Result r : scanner) {
>
>   // usual processing, the time for which we accounted for in our caching
> and global lease timeout settings
>
>   if (someCondition) {
>
>     // More time-intensive processing necessary on this record, which is
> hard to account for in the caching
>
>     scanner.progress();
>
>   }
>
>  }
>
>
> --
>
> I'm not sure how we could expose this in the context of a hadoop job, since
> I don't believe we have access to the underlying scanner, but that would be
> great also.
>
>
> On Wed, Mar 20, 2013 at 1:11 PM, Ted Yu <[EMAIL PROTECTED]> wrote:
>
> > bq.  if HBase provided a way to manually refresh a lease similar to
> > Hadoop's context.progress()
> >
> > Can you outline how the above works for long scan ?
> >
> > bq. Even being able to override the timeout on a per-scan basis would be
> > nice.
> >
> > Agreed.
> >
> > On Wed, Mar 20, 2013 at 10:05 AM, Bryan Beaudreault <
> > [EMAIL PROTECTED]> wrote:
> >
> > > Typically it is better to use caching and batch size to limit the
> number
> > of
> > > rows returned and thus the amount of processing required between calls
> to
> > > next() during a scan, but it would be nice if HBase provided a way to
> > > manually refresh a lease similar to Hadoop's context.progress().  In a
> > > cluster that is used for many different applications, upping the global
> > > lease timeout is a heavy handed solution.  Even being able to override
> > the
> > > timeout on a per-scan basis would be nice.
> > >
> > > Thoughts on that, Ted?
> > >
> > >
> > > On Wed, Mar 20, 2013 at 1:00 PM, Ted Yu <[EMAIL PROTECTED]> wrote:
> > >
> > > > In 0.94, there is only one setting.
> > > > See release notes of HBASE-6170 which is in 0.95
> > > >
> > > > Looks like this should help (in 0.95):
> > > >
> > > > https://issues.apache.org/jira/browse/HBASE-2214
> > > > Do HBASE-1996 -- setting size to return in scan rather than count of
> > rows
> > > > -- properly
> > > >
> > > > From your description, you should be able to raise the timeout since
> > the
> > > > writes are relatively fast.
> > > >
> > > > Cheers
> > > >
> > > > On Wed, Mar 20, 2013 at 9:32 AM, Dan Crosta <[EMAIL PROTECTED]>
> wrote:
> > > >
> > > > > I'm confused -- I only see one setting in CDH manager, what is the
> > name
> > > > of
> > > > > the other setting?
> > > > >
> > > > > Our load is moderately frequent small writes (in batches of 1000
> > cells
> > > at
> > > > > a time, typically split over a few hundred rows -- these complete
> > very
> > > > > fast, we haven't seen any timeouts there), and infrequent batches
> of
> > > > large
> > > > > reads (scans), which is where we do see timeouts. My guess is that
> > the
> > > > > timeout is more due to our application taking some time --
> apparently
> > > > more
> > > > > than 60s -- to process the results of each scan's output, rather
> than
> > > due
> > > > > to slowness in HBase itself, which tends to be only moderately
> loaded
> > > > > (judging by CPU, network, and disk) while we do the reads.
> > > > >
> > > > > Thanks,
> > > > > - Dan
> > > > >
> > > > > On Mar 17, 2013, at 2:20 PM, Ted Yu wrote:
> > > > >
> > > > > > The lease timeout is used by row locking too.
> > > > > > That's the reason behind splitting the setting into two config
> > > > > parameters.
> > > > > >
> > > > > > How is your load composition ? Do you mostly serve reads from
> > HBase ?
> > > > > >
> > > > > > Cheers
> > > > > >
> > > > > > On Sun, Mar 17, 2013 at 1:56 PM, Dan Crosta <[EMAIL PROTECTED]>
> > > wrote:
> > > > > >
> > > > > >> Ah, thanks Ted -- I was wondering what that setting was for.