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From Sreepathi <prasanna.sreepa...@gmail.com>
Subject Re: HBase 0.96 metrics
Date Fri, 07 Feb 2014 18:12:03 GMT
Thank you Stack, Ted.


On Thu, Feb 6, 2014 at 10:53 PM, Stack <stack@duboce.net> wrote:

> In case you didn't get what was just said:
>
> When a regionserver crashes, HBase needs to replay the contents of
> outstanding WAL logs (Write-Ahead-Logs A.K.A HLogs) before it can bring the
> regions the crashed server was hosting back on line again.  Replaying
> involves reading the WALs and then 'splitting' the edits by region so that
> when the region is opened in a new location, it has a nice neat file of its
> edits, only, to replay before it starts serving.
>
> The two metrics you cite are time and size histograms for this WAL split
> process.  The size histogram is updated with the size of all the WAL logs
> each time the splitting process is run.  The time histogram is updated w/
> how long the split process took. These metrics are sort of important.  You
> want the time to be little since it is time some of your data is offline...
> smaller log splitting sizes will usually mean less time so it is to try and
> keep the number of outstanding WALs low.
>
> Our metrics are better now, rationalized (though the num_ops suffix here
> seems 'off'). They could do with a bit of doc'ing.  What is in the refguide
> is a bit stale.
>
> Yours,
> St.Ack
>
>
> On Thu, Feb 6, 2014 at 5:31 PM, Ted Yu <yuzhihong@gmail.com> wrote:
>
> > These two metrics are the counter portion of MutableHistogram's for HLogs
> > split which give you histogram using hadoop2's metrics2 system.
> >
> > See
> >
> hbase-hadoop2-compat//src/main/java/org/apache/hadoop/hbase/master/MetricsMasterFilesystemSourceImpl.java
> >
> > Cheers
> >
> >
> > On Thu, Feb 6, 2014 at 4:59 PM, Sreepathi <prasanna.sreepathi@gmail.com
> > >wrote:
> >
> > > Hello,
> > >
> > > Could somebody explain what the following metrics mean and how they can
> > be
> > > used ?
> > >
> > > HlogSplitTime_num_ops
> > > HlogSplitSize_num_ops
> > >
> > > --
> > > *Regards,*
> > > --- *Sreepathi *
> > >
> >
>



-- 
*Regards,*
--- *Sreepathi *

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