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From Stack <st...@duboce.net>
Subject Re: Question on hbase.client.scanner.timeout.period
Date Thu, 27 Aug 2015 20:22:54 GMT
On Tue, Aug 25, 2015 at 8:03 AM, Eric Owhadi <eric.owhadi@esgyn.com> wrote:

> Hello St.Ack,
> Thanks for your pointer, but I had already investigated JIRA
> https://issues.apache.org/jira/browse/HBASE-13090
> Unfortunately, this heartbeat will protect against rpc timeout, not server
> side lease timeout that we are experiencing right now. I have not seen an
> active JIRA fixing our issue.
> Only https://issues.apache.org/jira/browse/HBASE6121 is complaining about
> the exact same issue, but was never resolved.
Which issue? https://issues.apache.org/jira/browse/HBASE-6121 seems

> The heartbeat JIRA in 13090 protect for situation where server scanner
> takes
> so long to retrieve the highly filtered information, that it exceeds the
> timeout (hbase.rpc.timeout).

> The timeout we are experiencing is the hbase.client.scanner.timeout.period,
> also deprecatedly known as hbase.regionserver.lease.period
> The mechanism is different: here, region server scanners wants to protect
> themselves against dead clients that would not perform "close", and allow
> releasing server side scanner resources. To do that, a lease mechanism is
> implemented, and if between 2 next() call, more than
> hbase.regionserver.lease.period occurs, the server side scanner will have
> been forced closed by this lease timeout safety mechanism. On late next()
> call, client will receive a DNRIOE of type unknownScannerException, and the
> client will assess that it is coming most likely from the lease timeout
> (and
> not from a region move), therefore throwing an exception instead of reset
> scanner (for the region move scenario).
> Hbase 1.1 does not address, as far as I have researched, the
> hbase.client.scanner.timeout.period issue we are facing.

Can you not have the high-level query that is being fed by a scan do
HBASE-13333? That is, tickle, the ongoing scan on occasion just to say that
I'm still alive?

Otherwise, what would you suggest? A scan that does not timeout? Or the
client being able to set a timeout in the Scan passed to the server?

Sorry for late reply,

> And yes, we will move to Hbase 1.1, and 1.0 as Cloudera and Hortonworks are
> having version mismatch on the next official builds trafodion will support.
> So my question is still open?
> Best regards,
> Eric Owhadi
> -----Original Message-----
> From: saint.ack@gmail.com [mailto:saint.ack@gmail.com] On Behalf Of Stack
> Sent: Monday, August 24, 2015 11:07 PM
> To: HBase Dev List
> Subject: Re: Question on hbase.client.scanner.timeout.period
> On Mon, Aug 24, 2015 at 4:48 PM, Eric Owhadi <eric.owhadi@esgyn.com>
> wrote:
> > Hello everyone,
> > We have been facing a situation on trafodion, where we are hitting the
> > hbase.client.scanner.timeout.period scenario:
> > basically, when doing queries that require spilling to disk because of
> > high complexity of what is involved, the underlying hbase scanner
> > serving one of the operation involved in the complex query cannot call
> > the next() withing the timeout specify... too busy taking care of other
> > business.
> > This is legit scenario, and I was wondering why in the code, special
> > care is done to make sure that client side, if a DNRIOE of type
> > unknownScannerException shows up, and the
> > hbase.client.scanner.timeout.period time elapsed, we make sure to
> > throw a scannerTimeoutException, instead of just let it go and reset
> > scanner.
> >
> > Scanners were redone in hbase 1.1. Can Trafodion come up onto hbase 1.1?
> See https://blogs.apache.org/hbase/entry/scan_improvements_in_hbase_1 for
> summary.
> St.Ack
> > I imagine that the lease time out implementation on region server side
> > is supposed to protect from resource leak of scanner object server
> > side. But I am not sure why we would make it so that client side throw
> > this timeout exception, when in fact what just happened was that
> > client was too busy to call next() on time.
> >
> > I am sure there is a reason, but cannot figure it out :-).
> >
> > BTW, I found this JIRA, talking about exact same thing:
> > https://issues.apache.org/jira/browse/HBASE61-21 but with no resolution.
> >
> > Any help understanding the reason of the timeout thrwown client side
> > instead of an automatic reset would be much appreciated, Best regards,
> > Eric Owhadi
> >

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