You have a patch for apache hbase Eric? Is there an apache hbase issue to add this in? St.Ack
On Thu, Sep 10, 2015 at 10:21 AM, Eric Owhadi <eric.owh...@esgyn.com> wrote: > Thanks for pointing me to HBase-13333, it is indeed supposed to address the > very same problem. With the drawback of requiring client side involvement, > of asynchronous nature. I still have not discovered any reason why just > doing it the way I proposed would lead to any negative side effect. Must > admit I feel uncomfortable since the patch is just about removing code that > usually is added with a purpose :-). > We have not yet run full QA, but at least 100% of trafodion regression test > pass. > As for when the patch will make it to trafodion, given that I did it only > for a CDH build of Trafodion with HBase 1.0 support, I still cannot check > it > in (trafodion is still on .98 and builds OK for Cloudera,Hortonworks,Mapr > and Apache). Trafodion would first need to have full support for HBase 1.0 > for all Hadoop distro we support, then I will need to redo the patch that > is > distro specific, and make sure the build process deals with this... It is > my > plan to do so... Hoping that I do not discover any issue with other distro > (like private attributes or functions that I cannot circumvent... but that > would just mean that the patch would not be available for a specific > distro) > Eric > > > -----Original Message----- > From: Jerry He [mailto:jerry...@gmail.com] > Sent: Saturday, September 5, 2015 1:47 PM > To: dev <dev@hbase.apache.org> > Subject: Re: Question on hbase.client.scanner.timeout.period > > You can take a look at HBASE-13333: Renew Scanner Lease without advancing > the RegionScanner, which may be helpful in this kind of case Your proposal > sounds like a good alternative approach as well. > We should add that JIRA to the blog link Stack mentioned. > > Jerry > > On Sat, Sep 5, 2015 at 9:07 AM, Stack <st...@duboce.net> wrote: > > > On Fri, Sep 4, 2015 at 5:06 PM, Eric Owhadi <eric.owh...@esgyn.com> > wrote: > > > > > OK so to answer the "is it easy to insert the patched scanner for > > > trafodion", the answer is no. > > > > > > > I suspected this. > > > > > > > > > Was easier on .98, but on 1.0 it was quite a challenge. All about > > > dealing with private attributes instead of protected that are not > > > visible to the PatchClentScanner class that extends ClientScanner. > > > Currently running the regression tests to see if there is no side > > effect... > > > Was able to demonstrate with breakpoint on next() waiting more than > > > 1 mn (the default lease timeout value) that with the patch things > > > gracefully reset and all is good, no row skipped or duplicated, > > > while without, I get the Scanner time out exception. Patch can be > > > turn on or off with a new > > key > > > in hbase-site.xml... > > > I will feel better when this will be deprecated :-). > > > > > > > Smile. > > > > Excellent. You have a patch for us then Eric? Sounds like the > > interjection of your new Scanner would be for pre-2.0. For 2.0 we > > should just turn on this behavior as the default. > > > > Thanks, > > St.Ack > > > > > > > > > Eric Owhadi > > > > > > -----Original Message----- > > > From: saint....@gmail.com [mailto:saint....@gmail.com] On Behalf Of > > Stack > > > Sent: Friday, August 28, 2015 6:35 PM > > > To: HBase Dev List <dev@hbase.apache.org> > > > Subject: Re: Question on hbase.client.scanner.timeout.period > > > > > > On Fri, Aug 28, 2015 at 11:31 AM, Eric Owhadi > > > <eric.owh...@esgyn.com> > > > wrote: > > > > > > > That sounds good, but given trafodion needs to work on current and > > > > future released version of HBase, unpatched, I will first > > > > implement a ClientScannerTrafodion (to be deprecated), inheriting > > > > from ClientScanner that will just overload the loadCache(),and > > > > make sure that the code that is picking up the right scanner based > > > > on scan object is bypassed to force getting the > > > > ClientScannerTrafodion when appropriate. > > > > Not very elegant, but need to take into consideration trafodion > > > > deployment requirements. > > > > Then, if we do not discover any side effect during our QA related > > > > to this code I will port the fix on HBase to deprecate the custom > > > > scanner (probably first on HBase 2.0, then will let the community > > > > decide if this fix is worth it for back porting...). It will be a > > > > first for me, but that's great, I'll take your offer to help ;-)... > > > > > > > > > > Sweet. Suggest opening an umbrellas issue in hbase to implement this > > > feature. Reference HBASE-2161 (it is closed now). Link trafodion > > > issue to it. A subtask could have implementation in hbase 2.0, > > > another could be backport. > > > > > > Is is easy to insert your T*ClientScanner? > > > St.Ack > > > > > > > > > > > > > Regards, > > > > Eric > > > > > > > > -----Original Message----- > > > > From: saint....@gmail.com [mailto:saint....@gmail.com] On Behalf > > > > Of Stack > > > > Sent: Thursday, August 27, 2015 3:55 PM > > > > To: HBase Dev List <dev@hbase.apache.org> > > > > Subject: Re: Question on hbase.client.scanner.timeout.period > > > > > > > > On Thu, Aug 27, 2015 at 1:39 PM, Eric Owhadi > > > > <eric.owh...@esgyn.com> > > > > wrote: > > > > > > > > > Oops, my bad, the related JIRA was : > > > > > https://issues.apache.org/jira/browse/HBASE-2161 > > > > > > > > > > I am suggesting that the special code client side in loadCache() > > > > > of ClientScanner that is trapping the UnknownScannerException, > > > > > then on purpose check if it is coming from a lease timeout (and > > > > > not by a region move) to decide that it would throw a > > > > > ScannerTimeoutException instead of letting the code go and just > > > > > reset the scanner and start from last successful retrieve (the > > > > > way it works for an unknowScannerException due to a region moving). > > > > > By just removing the special handling that tries to > > > > > differentiate from unkownScannerException due to lease timeout, > > > > > we should have a resolution to JIRA 2161- And to our trafodion > > > > > issue. > > > > > > > > > > We are still protecting against dead client that would cause > > > > > resource leak at region server, since we keep the lease timeout > > > > > mechanism. > > > > > > > > > > Not sure if I have overlooked something, as usually, code is > > > > > here for a reason :-)... > > > > > > > > > > > > > > Your proposal sounds good to me. > > > > > > > > Scanner works the way it does because it has always work this way > > > (smile). > > > > A while back, one of the lads suggested we do like dynamodb and > > > > have scanner have no state on the serverside, the scan next would > > > > just supply all necessary context. It was argued against because > > > > serverside setup is so costly. Your suggestion is similar only we > > > > do it only if Scanner has timed out. > > > > > > > > Suggest we keep the current semantic in 1.x at least. We could > > > > flip to your behavior in 2.x. Meantime, you'd have to ask for it > > > > when you set up your Scan object by setting a flag. > > > > > > > > Would that work? If you want to have a go at it, I could help out > > > > on the issue. > > > > > > > > St.Ack > > > > > > > > > > > > > > > > > > > > > Regards, > > > > > Eric > > > > > > > > > > > > > > > > > > > > -----Original Message----- > > > > > From: saint....@gmail.com [mailto:saint....@gmail.com] On Behalf > > > > > Of Stack > > > > > Sent: Thursday, August 27, 2015 3:23 PM > > > > > To: HBase Dev List <dev@hbase.apache.org> > > > > > Subject: Re: Question on hbase.client.scanner.timeout.period > > > > > > > > > > On Tue, Aug 25, 2015 at 8:03 AM, Eric Owhadi > > > > > <eric.owh...@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 unrelated. > > > > > > > > > > > > > > > > > > > > > The heartbeat JIRA in 13090 protect for situation where server > > > > > > scanner takes so long to retrieve the highly filtered > > > > > > information, that it exceeds the RPC 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, > > > > > St.Ack > > > > > > > > > > > > > > > > > > > > > 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....@gmail.com [mailto:saint....@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.owh...@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_hbas > > > > > > e_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 > > > > > > > > > > > > > > > > > > > > > > > > > > > >
