[Go-essp-tech] Replica support in Gateway 2.0

Kettleborough, Jamie jamie.kettleborough at metoffice.gov.uk
Mon Nov 14 08:56:33 MST 2011 

Hello,

There is a lot going on here and I don't really know how to start - particularly as I'm aware that the way I phrased my previous post wasn't great, as it put the wrong thing first.  (I was out Friday, and so fell behind in all the discussions).

I'm still trying to get my head round what is going on between the different interfaces on the data in ESG (OAI, gateway Hessian, Thredds, web based portal) so maybe first I should just explain how I came across the problem with stale replicas.  We've simply been using the gateway Hessian API to compare what the BADC and the DKRZ gateways know about (initially to try and understand what was going on).  When doing this it was clear that DKRZ knew about some of our datasets that were no longer at BADC.  (I've included the full list as an attachment - Estani if you look for the section 'in WDCC but not BADC', and then regex search for cmip5.*MOHC you'll see a full list).

Does this tie in with the bug as you have have described it at the web portal view of the data (I think my uncertainty here is where the web portal gets its list of data sets from - does it go to all the gateway Hessian interfaces, or does it use the OAI stuff? I have to admit to being really ignorant about the OAI stuff - I only really started to play with it this morning).

Jamie

> -----Original Message-----
> From: Estanislao Gonzalez [mailto:gonzalez at dkrz.de] 
> Sent: 10 November 2011 23:03
> To: Kettleborough, Jamie
> Cc: martin.juckes at stfc.ac.uk; go-essp-tech at ucar.edu; 
> esg-gateway-dev at earthsystemgrid.org
> Subject: RE: [Go-essp-tech] Replica support in Gateway 2.0
> 
> Hi Jamie,
> 
> I wasn't aware of the "stale" datasets. Well, that is a 
> *major* Gateway Bug, because it should know already about a 
> newer version, so as it is designed right now "should" point 
> just to the original because there's no replica for this.
> [What now happens is that if you select BADC as the Gateway 
> to download to, you end up with the new version, although at 
> DKRZ said the version was the older one. - It looks like a 
> major bug to me]
> 
> The fact that the new version does not get immediately 
> replicated it's not a problem but a particularity of any 
> distributed system. It's impossible to have a replica of the 
> all archive synchronized to the minute. What we can do, is 
> "hide" things that are outdated.
> Basically:
> 1) If the user searches for an id, that resolves to the 
> latest version. 
> (If no version is given, we might safely presume the latest is
> requested)
> 2) Only replicas of that version should be displayed if 
> available (this should be already possible)
> 3) If the user searches for a particular version, she/he 
> should be getting exactly this (feature not implemented)
> 4) Same as 2, display only known replicas of that version.
> 
> I don't think this is complicated. And regarding the "few 
> years [from now]" I don't think that's the case, and not only 
> because of bandwidth (which IS an issue already, as well as 
> server load). I'm pretty sure papers are getting written "as 
> we speak", even before a DOI gets out there. So these people 
> "need" to cite something, right? The only thing they can hold 
> to is a bunch of URLs AND checksums. It's the only thing you 
> can "cite" at the moment, without this no papers could be 
> written and not only in the CMIP5 context (and thus a large 
> AR5 share).
> That's the reason the archives are there. You can cite what 
> you find at DKRZ, or BADC, or PCMDI. What's in there is 
> guaranteed to remain exactly where it was found for the next 
> 10+ years, other institutions do not have this commitment (nor can).
> 
> Again 2c. Thanks,
> Estani
> 
> On 10.11.2011 09:14, Kettleborough, Jamie wrote:
> > Hello,
> >
> > I know this thread has moved on, but can we rewind just a bit.  I 
> > think Nathan asked for use cases around this issue.
> >
> > As far as I'm aware there are two main user use cases here 
> (there may 
> > be others obviously).
> >
> > 1. User wants to get data *now* (even if its only 'preprint' in 
> > Bryan's language) in a way that suites their particular needs 
> > (functional and non-functional)
> >
> > 2. In a few years (not sure how long - could be months) time user 
> > wants to get a copy of the data to verify or extend some previous 
> > analysis.
> >
> > I'm sure someone will correct me if I have this wrong, but 
> I *think* 
> > most of the discussion so far has centered around the 
> second of these.
> > I think the first one needs some discusion too though 
> doesn't it - it 
> > feels more urgent to me?
> >
> > I think it needs reviewing in the light of replication as 
> when there 
> > is replication a user *may* choose to go to a particular 
> data-node as 
> > it suites them better - they may see faster downloads 
> because of the 
> > network route betweent them and the servers, or it might 
> support some 
> > data service they want.  Something in the system has to have the 
> > responsibility of choosing which replica to download.  To 
> be honest I 
> > think this is best left to the user.  If this is the case then the 
> > user has to have a good view of *where* the data is through their 
> > interface.  Nate - I think your proposed implementation 
> would expose 
> > the information no?
> >
> > The other issue for replication I can think of coming out 
> of use case
> > 1 is versioning.  Data will be revised by data providers (we have 
> > examples of this), so I think that the replication system 
> has to keep 
> > up and the interfaces have to be able to communicate this 
> to the user.
> >  A case I'm worried about is if a replica goes stale (sorry 
> Estani, I
> > *think* we have examples of these e.g.
> > 
> > 
> cmip5.output1.MOHC.HadGEM2-ES.historicalGHG.day.atmos.day.r1i1p1.v2011
> > 032 at DKRZ is stale - we've resubmitted as v20111102.  I only 
> > discovered this yesterday, and understood what *might* be happening 
> > today, I can send more examples if you need them).  I think a user 
> > needs to be able to tell (without too much hard work) what 
> really is a 
> > replica, and what is a replica of a previous version.  Nate 
> - can you 
> > cope with this situation in your proposed implementation?
> >
> > (Are there any issues around authorisation when it comes to replicas
> > - would a new published version mean all replicas of 
> previous versions 
> > are no longer 'authorisable' against, or would stale replicas be
> > available?)
> >
> > I know that replication has started to happen - but is this 
> the right 
> > thing now?  Is everything in place to do this in a way that 
> is *safe* 
> > and not going to confuse users?
> >
> > Jamie
> >
> > (I guess if you have a client that only uses the data nodes 
> you know 
> > what node you were talking to, and see the full version information 
> > from the outset, so these aren't such big issues).
> >
> > ps yes I know I still have to answer some questions from Sebastien 
> > about our client.
> >
> >> -----Original Message-----
> >> From: go-essp-tech-bounces at ucar.edu
> >> [mailto:go-essp-tech-bounces at ucar.edu] On Behalf Of 
> >> martin.juckes at stfc.ac.uk
> >> Sent: 10 November 2011 16:26
> >> To: gonzalez at dkrz.de; go-essp-tech at ucar.edu; 
> >> esg-gateway-dev at earthsystemgrid.org
> >> Subject: Re: [Go-essp-tech] Replica support in Gateway 2.0
> >>
> >> Hi Estani,
> >>
> >> You missed the start -- the bit which is not achievable is 
> publishing 
> >> a replica to the same gateway used for the original publication of 
> >> that data. E.g. IPSL data published to BADC,
> >>
> >> Cheers,
> >> Martin
> >>
> >> > >-----Original Message-----
> >> > >From: go-essp-tech-bounces at ucar.edu [mailto:go-essp-tech- 
> >> > >bounces at ucar.edu] On Behalf Of Estanislao Gonzalez
> >> > >Sent: 10 November 2011 16:20
> >> > >To: go-essp-tech at ucar.edu; esg-gateway-dev at earthsystemgrid.org
> >> > >Subject: Re: [Go-essp-tech] Replica support in Gateway 2.0
> >> > >
> >> > >Hi,
> >> > >
> >> > >this analogy seams perfect. Now regarding to the options
> >> we have at
> >> > >the
> >> > >moment:
> >> > >1) How "unique" is the dataset id in a Gateway? 
> Federation wide, 
> >> > >local gAteway or project unique?
> >> > >2) Depending on one, the procedure could involve "moving" the 
> >> > >published data to some other project, Gateway, Federation :-)
> >> > >
> >> > >I think this could be achievable:
> >> > >1) Data gets replicated to some Gateway (redundancy enforced)
> >> > >2) The originated Gateway, if it's also replicating,
> >> should replicate
> >> > >(just data, no publication yet) from the QC checked replica.
> >> > >3) The "pre-print" gets removed (which either mean move to a 
> >> > >different project, Gateway, etc or really completely
> >> delete it from
> >> > >the Gateway)
> >> > >4) The replica gets published.
> >> > >
> >> > >I might be omitting something, but it seams achievable 
> right now.
> >> > >
> >> > >My 2c,
> >> > >Estani
> >> > >
> >> > >Am 10.11.2011 07:15, schrieb Bryan Lawrence:
> >> > >> Martin has been quite vociferous (quite rightly) in
> >> personal email
> >> > >to me that as far as QC goes, the dataset which gets
> >> through QC2 will
> >> > >*not* be the original dataset - we have no control over
> >> the original
> >> > >dataset's permanence and/or immutability.
> >> > >>
> >> > >> This raises some interesting issues about the role of
> >> ESGF ... and
> >> > >it's interaction with the data owner and the 
> publication process 
> >> > >which is governed by DKRZ as the Publisher (and in the future 
> >> > >probably multiple publication processes and multiple
> >> Publishers). The
> >> > >correct analogy here, as I said on an earlier email 
> today, is to 
> >> > >consider the original dataset as a preprint, of a
> >> Published dataset
> >> > >(at QC level 3).
> >> > >>
> >> > >> Incidentally, this disctinction might offer us a possible
> >> > >> (distinct)
> >> > >future for two different types of gateways into ESGF: the
> >> Published
> >> > >datasets view (which makes pre-eminent the QC'd copy) and the 
> >> > >published view (which makes pre-eminenent whatever someone
> >> sticks on
> >> > >a data node).
> >> > >>
> >> > >> But meanwhile, I think we can live with what you
> >> proposed, as long
> >> > >as the QC status of the replicas is clearly visible - 
> and the DOI 
> >> > >points to a landing page that somehow prioritises those 
> versions, 
> >> > >which would be trivial if your page was organised in 
> the same way 
> >> > >(prioritising the replicants of QC level 3, then 
> replicants of QC 
> >> > >level 2, and then originals).
> >> > >>
> >> > >> Cheers
> >> > >> Bryan
> >> > >>
> >> > >>
> >> > >>> Hi Stephen,
> >> > >>>
> >> > >>> On 11/10/2011 05:23 AM, stephen.pascoe at stfc.ac.uk wrote:
> >> > >>>> Hi Eric,
> >> > >>>>
> >> > >>>> Replicas are beginning to show up in CMIP5 and this is
> >> exposing
> >> > >some
> >> > >>>> gaps in what Gateway 1.x can do. I know you are
> >> reimplementing
> >> > >replica
> >> > >>>> support in Gateway 2.0 so I'd like to raise these 
> issues now.
> >> > >>>>
> >> > >>>> We need to be able to publish a replica to the same
> >> Gateway that
> >> > >hosts
> >> > >>>> the original. I can't imagine this being possible with
> >> Gateway
> >> > >>>> 1.x
> >> > >since
> >> > >>>> the URL http://<GATEWAY>/dataset/<dataset-id>.html
> >> only points to
> >> > >one
> >> > >>>> dataset on that Gateway. Either that page needs to link to
> >> the
> >> > >original
> >> > >>>> and all replicas for that dataset or we need separate URLs
> >> for
> >> > >each
> >> > >>>> replica/original, or both.
> >> > >>> The current direction for the implementation would be
> >> to have a 1
> >> > >page
> >> > >>> for the original dataset and have that page list where
> >> replicas
> >> > >>> are located.
> >> > >>>
> >> > >>> If there are use cases for the other options we should get
> >> those
> >> > >identified.
> >> > >>>
> >> > >>> Thanks!
> >> > >>> -Nate
> >> > >>>
> >> > >>>
> >> > >>>> Is this part of your design for Gateway 2.0's replica
> >> support?
> >> > >>>>
> >> > >>>> Thanks,
> >> > >>>>
> >> > >>>> Stephen.
> >> > >>>>
> >> > >>>> ---
> >> > >>>>
> >> > >>>> Stephen Pascoe +44 (0)1235 445980
> >> > >>>>
> >> > >>>> Centre of Environmental Data Archival
> >> > >>>>
> >> > >>>> STFC Rutherford Appleton Laboratory, Harwell Oxford,
> >> Didcot OX11
> >> > >0QX, UK
> >> > >>>>
> >> > >>>>
> >> > >>>> --
> >> > >>>> Scanned by iCritical.
> >> > >>>>
> >> > >>>>
> >> > >>>>
> >> > >>>>
> >> > >>>> _______________________________________________
> >> > >>>> GO-ESSP-TECH mailing list
> >> > >>>> GO-ESSP-TECH at ucar.edu
> >> > >>>> http://mailman.ucar.edu/mailman/listinfo/go-essp-tech
> >> > >>> _______________________________________________
> >> > >>> GO-ESSP-TECH mailing list
> >> > >>> GO-ESSP-TECH at ucar.edu
> >> > >>> http://mailman.ucar.edu/mailman/listinfo/go-essp-tech
> >> > >>>
> >> > >> --
> >> > >> Bryan Lawrence
> >> > >> University of Reading:  Professor of Weather and Climate
> >> Computing.
> >> > >> National Centre for Atmospheric Science: Director of 
> Models and
> >> > >Data.
> >> > >> STFC: Director of the Centre for Environmental Data Archival.
> >> > >> Ph: +44 118 3786507 or 1235 445012;
> >> Web:home.badc.rl.ac.uk/lawrence
> >> > >> _______________________________________________
> >> > >> GO-ESSP-TECH mailing list
> >> > >> GO-ESSP-TECH at ucar.edu
> >> > >> http://mailman.ucar.edu/mailman/listinfo/go-essp-tech
> >> > >
> >> > >
> >> > >--
> >> > >Estanislao Gonzalez
> >> > >
> >> > >Max-Planck-Institut für Meteorologie (MPI-M) Deutsches 
> >> > >Klimarechenzentrum (DKRZ) - German Climate Computing
> >> Centre Room 108
> >> > >- Bundesstrasse 45a, D-20146 Hamburg, Germany
> >> > >
> >> > >Phone:   +49 (40) 46 00 94-126
> >> > >E-Mail:  gonzalez at dkrz.de
> >> > >
> >> > >_______________________________________________
> >> > >GO-ESSP-TECH mailing list
> >> > >GO-ESSP-TECH at ucar.edu
> >> > >http://mailman.ucar.edu/mailman/listinfo/go-essp-tech
> >> --
> >> Scanned by iCritical.
> >> _______________________________________________
> >> GO-ESSP-TECH mailing list
> >> GO-ESSP-TECH at ucar.edu
> >> http://mailman.ucar.edu/mailman/listinfo/go-essp-tech
> >>
> 
> --
> Estanislao Gonzalez
> 
> Max-Planck-Institut für Meteorologie (MPI-M) Deutsches 
> Klimarechenzentrum (DKRZ) - German Climate Computing Centre 
> Room 108 - Bundesstrasse 45a, D-20146 Hamburg, Germany
> 
> Phone:   +49 (40) 46 00 94-126
> E-Mail:  gonzalez at dkrz.de
> 
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