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From Anup Bishnoi <pixelsallo...@gmail.com>
Subject Re: Update conflicts?
Date Wed, 06 Apr 2011 06:40:10 GMT
Or just use a list function for the node_status view, if all you want is
that html response with all the information about one particular node.
Though you'll have to model the keys emitted from that view slightly
differently

On Wed, Apr 6, 2011 at 12:04 PM, Anup Bishnoi <pixelsallover@gmail.com>wrote:

> you could join the different pieces of information about the node (which
> you get by one query on the view suggested above) on the page itself with
> javascript, instead of asking couch for everything embedded in an html
> response
>
>
> On Wed, Apr 6, 2011 at 11:53 AM, Luis Miguel Silva <
> luismiguelferreirasilva@gmail.com> wrote:
>
>> Sorry if my last email was too big :o).
>>
>> Well, one reason i wanted to avoid doing that is because it didn't
>> seem as easy to maintain as my original approach but i'll discuss your
>> suggestion with my team to see what they have to say.
>> Also, i just couldn't get join to work :o\...
>>
>> How would you create a view that joins data from those different types
>> of documents to create a single complete view of a node?
>> I've read the documentation on view joins but simply could not get it
>> to work :o\...
>>
>> Thank you,
>> Luis
>>
>> On Tue, Apr 5, 2011 at 9:12 PM, Ryan Ramage <ryan.ramage@gmail.com>
>> wrote:
>> > Luis,
>> >
>> > Thats a lot to take in, but a quick suggestion.
>> >
>> > Have a parent doc that looks like this:
>> > {
>> >    id: node1,
>> >        type: node,
>> >    location: blah,
>> > }
>> >
>> > and some 'children' docs that look like this
>> >
>> > {
>> >    id: 3232323323223-32323232322-3232,
>> >        timestamp: 1299794532000,
>> >    type: cpu,
>> >    node: node1,
>> >    cpu: 0.94,
>> >    ccores: 4,
>> >     acores: 4,
>> >     cmemory: 4096,
>> >    amemory: 1024
>> > }
>> >
>> > and
>> > {
>> >    id: 3232323323223-32323232322-3232,
>> >        timestamp: 1299794532000,
>> >    type: disk,
>> >    node: node1,
>> >    disk: 100000
>> > }
>> > and
>> > {
>> >    id: 433432323323223-3232323322332,
>> >        timestamp: 1299794532000,
>> >    type: netio,
>> >    node: node1,
>> >    in: 100,
>> >    out: 200
>> > }
>> > and
>> > {
>> >    id: 323432423432534534-534534-543534534
>> >        timestamp: 1299794532000,
>> >    type: generic,
>> >    node: node1,
>> >    name: "foo",
>> >    value: "bar"
>> > }
>> >
>> > create a status view
>> > "node_status" : function (doc) {
>> >        if (doc.type != 'node') {
>> >                emit([doc.node, doc.type, doc.timestamp],null);
>> >        }
>> > }
>> >
>> > This allows you to not have to ever update a doc. Just keep inserting.
>> > Couchdb is good at that.
>> >
>> >
>> >
>> >
>> > On Tue, Apr 5, 2011 at 7:20 PM, Luis Miguel Silva
>> > <luismiguelferreirasilva@gmail.com> wrote:
>> >> Thanks for your email Ryan.
>> >>
>> >> Let me give you some more information on what i'm trying to do...
>> >> Essentially, i have to create a "sort of CMDB" system that stores, not
>> only configuration data, but also operational data (so...i guess you could
>> call it a OMDB instead).
>> >>
>> >> Either way, my company develops a meta-scheduler that can be used for
>> HPC or Cloud environments. It will guarantee that your resources are used
>> the best way possible, maximizing their usage, based on the policies you set
>> up in it.
>> >>
>> >> To do that, our software needs to be aware of how the environment looks
>> and this is why an OMDB piece is very important for us (as it allows us to
>> store information on the environment).
>> >>
>> >> Also, our software talks with external resource managers by a protocol
>> we developed more than a dozen years ago called "WIKI" (not as in
>> "wikipedia" but, WIKI as in the hawayan word for fast). That protocol is
>> heavily based around key/value pairs so this is one of the reasons i was
>> EXTREMELY excited to find out that, with CouchDB's "view" functionality, i
>> would be able to map document attributes to more meaningful attributes that
>> our software understands (i.e. map the document's "available_cores"
>> attribute to "ccores" [the "consumable cores" parameter our software
>> understands]).
>> >>
>> >> Another important thing to notice is that resources can be off
>> different types: node (for bare metal nodes), vm (for vms running on nodes)
>> and storage (we can actually have more data types but those are enough to
>> exemplify what i'm talking about).
>> >>
>> >> This is why i created those "big documents" instead of smaller ones!
>> >> For instance, each document would represent an entire node (i.e. procs,
>> memory, etc).
>> >>
>> >> So my idea was to have an external process initially populate the
>> database with documents representing ALL the nodes we are managing (hence
>> why i started my benchmarks with 100K increments) and OTHER external
>> processes (i.e. other types of resource managers) would update individual
>> attributes in each document.
>> >>
>> >> Let's imagine a document with id "node01":
>> >> These fields would be updated by an agent that collected some of the
>> hardware specs:\
>> >>        ccores: 4 // total cores on machine
>> >>        acores: 4 // available cores on machine
>> >>        cmemory: 4096 // total memory on machine
>> >>        amemory: 1024 // available memory
>> >>        cpuload: 94%
>> >> This field would be updated by our storage resource manager:
>> >>        GMETRIC["disk"]: 1000000
>> >> And, for instance, these fields would be updated by a network resource
>> manager:
>> >>        GMETRIC["NETIO"]: { "in":100, "out":200 }
>> >>
>> >> So, as you can see, different processes would manage the same document
>> (just different attributes in it).
>> >>
>> >> And the REALLY cool thing about the Views is the fact that our
>> customers could VERY easily adapt the database so that it would store THEIR
>> extra data and shove it in a generic parameter that our software woulder
>> understand [i.e. the GMETRIC parameters are generic metrics...).
>> >>
>> >> So, based on these requirements, do you have any suggestions on how we
>> should store our data (keeping its structure easy enough for external
>> consumers to maintain it without having to bust their heads figuring out the
>> logic behind the document attributes)?? :o)
>> >>
>> >> Thank you!
>> >> Luis Miguel Silva
>> >>
>> >> On Apr 5, 2011, at 6:45 PM, Ryan Ramage <ryan.ramage@gmail.com> wrote:
>> >>
>> >>> Luis,
>> >>>
>> >>> Having the rev is very important when you update a doc. It lets you
>> >>> know that your piece of information is out of date. This is a good
>> >>> thing....
>> >>>
>> >>> I am wondering if the way you are modeling your data is not leading
>> >>> you to do this update with less chance of conflict. See if you can
>> >>> break your docs into even smaller docs. For example, I noticed from
a
>> >>> prior post you had a lot of Arrays in your docs. If multiple processes
>> >>> are changing that array, you might be better served by making each
>> >>> element in the array a separate doc.
>> >>>
>> >>> Ryan
>> >>>
>> >>> On Tue, Apr 5, 2011 at 4:41 PM, Luis Miguel Silva
>> >>> <luismiguelferreirasilva@gmail.com> wrote:
>> >>>> More or less!
>> >>>>
>> >>>> The most common scenario will be:
>> >>>> - two or more processes writing to the same document, but only to
a
>> >>>> specific attribute (not overwriting the whole document)
>> >>>>
>> >>>> If, by any chance, two processes overwrite the same field, i'm ok
>> with
>> >>>> the last one always winning.
>> >>>>
>> >>>> Thanks,
>> >>>> Luis
>> >>>>
>> >>>> On Tue, Apr 5, 2011 at 4:26 PM, Robert Newson <
>> robert.newson@gmail.com> wrote:
>> >>>>> "Ideally, we would be able to update without specifying the
_rev,
>> just
>> >>>>> posting (or, in this case PUTting) to the document..."
>> >>>>>
>> >>>>> So you want to blindly overwrite some unknown data?
>> >>>>>
>> >>>>> B.
>> >>>>>
>> >>>>> On 5 April 2011 22:57, Zachary Zolton <zachary.zolton@gmail.com>
>> wrote:
>> >>>>>> Luis,
>> >>>>>>
>> >>>>>> Checkout _update handlers:
>> >>>>>>
>> >>>>>> http://wiki.apache.org/couchdb/Document_Update_Handlers
>> >>>>>>
>> >>>>>>
>> >>>>>> Cheers,
>> >>>>>>
>> >>>>>> Zach
>> >>>>>>
>> >>>>>> On Tue, Apr 5, 2011 at 4:46 PM, Luis Miguel Silva
>> >>>>>> <luismiguelferreirasilva@gmail.com> wrote:
>> >>>>>>> Dear all,
>> >>>>>>>
>> >>>>>>> I'm trying to play around with updates and i'm bumping
into some
>> problems.
>> >>>>>>>
>> >>>>>>> Let's image we have to clients that poll a document
from the
>> server at
>> >>>>>>> the same time and get the same _rev.
>> >>>>>>> Then one of them updates the doc based on the _rev it
got:
>> >>>>>>> [root@xkitten ~]# curl -X PUT -d
>> >>>>>>> '{"_rev":"3-0d519bcf08130bf784f3c35d79760740","hello2":"fred2"}'
>> >>>>>>> http://localhost:5984/benchmark/test?conflicts=true
>> >>>>>>> {"ok":true,"id":"test","rev":"4-03640ebafbb4fcaf127844671f8e2de7"}
>> >>>>>>> Then another one tries to update the doc based on the
same exact
>> _rev:
>> >>>>>>> [root@xkitten ~]# curl -X PUT -d
>> >>>>>>> '{"_rev":"3-0d519bcf08130bf784f3c35d79760740","hello3":"fred3"}'
>> >>>>>>> http://localhost:5984/benchmark/test?conflicts=true
>> >>>>>>> {"error":"conflict","reason":"Document update conflict."}
>> >>>>>>> [root@xkitten ~]#
>> >>>>>>>
>> >>>>>>> Is there a way to avoid this?! (like...make the update
just create
>> a
>> >>>>>>> new _rev or something)??
>> >>>>>>>
>> >>>>>>> Ideally, we would be able to update without specifying
the _rev,
>> just
>> >>>>>>> posting (or, in this case PUTting) to the document...
>> >>>>>>>
>> >>>>>>> Thoughts??
>> >>>>>>>
>> >>>>>>> Thank you,
>> >>>>>>> Luis
>> >>>>>>>
>> >>>>>>
>> >>>>>
>> >>>>
>> >>
>> >
>>
>
>

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