Thank you Stack, Ted.
On Thu, Feb 6, 2014 at 10:53 PM, Stack <[email protected]> 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 <[email protected]> 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 <[email protected] > > >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 *
