[Hawkular-dev] Sync with Inventory

Sat Jun 25 20:38:32 EDT 2016

yeah thanks for this :)
Lukas Krejci <lkrejci at redhat.com>於 2016年6月23日 週四，21:59寫道：

> On Thursday, June 23, 2016 10:27:12 AM Thomas Segismont wrote:
> > Hey Lukas,
> >
> > Thank you for pointing us in the sync endpoint. Austin will look into
> > this and will certainly come back with more questions.
> >
> > With respect to the user creating resources question, the difference
> > between Vert.x and Wildfly is that the user creates resources
> > grammatically. So in version 1 of the application, there might be two
> > HTTP servers as well as 7 event bus handlers, but only 1 http server in
> > version 2. And a named worker pool in version 3.
> >
> > In the end, I believe it doesn't matter if it's container which creates
> > resources or if it's the user himself. Does it?
> >
>
> It does not really (inventory has just a single API, so it does not really
> know who is talking to it - if a feed or if a user) - but resources inside
> and
> outside feeds have slightly different semantics.
>
> Right now the logic is this:
>
> Feeds are "agents" that don't care about anything else but their own little
> "world". That's why they can create their own resource types, metric types
> and
> they also declare resources and metrics of those types. Feed does not need
> to
> look "outside" of its own data and is in full charge of it.
>
> Hence the /sync endpoint applies to a feed nicely - since it is in charge,
> it
> merely declares what is the view it has currently of the "world" it sees
> and
> inventory will make sure it has the same picture - under that feed.
>
> Now if you have an application that spans multiple vms/machines and is
> composed of multiple processes, there is no such clear distinction of
> "ownership".
>
> While indeed a "real" user can just act like a feed, the envisioned
> workflow
> is that the user operates directly in environments and at the top level.
> I.e.
> a user assigns feeds to environments (i.e. this feed reports on my server
> in
> staging environment, etc) and the user creates "logical" resources in the
> environment (i.e. "My App" resource in staging env is composed of a load
> balancer managed by this feed, mongodb managed by another feed there and
> clustered wflys there, there and there).
>
> To model this, inventory supports 2 kinds of tree hierarchies - 1 created
> using the "contains" relationship, which expresses existential ownership -
> i.e. a feed contains its resources and if a feed disappears, so do the
> resources, because no one else can report on them. The entities bound by
> the
> contains relationship form a tree - no loops or diamonds in it (this is
> enforced by inventory). But there can also be a hierarchy created using an
> "isParentOf" relationship (which represents "logical" ownership). Resources
> bound by "isParentOf" can form an acyclic graph - i.e. 1 resource can have
> multiple parents as well as many children (isParentOf is applicable only to
> resources, not other types of entities).
>
> The hierarchies formed by "contains" and "isParentOf" are independent. So
> you
> can create a resource "My App" in the staging environment and declare it a
> parent (using "isParentOf") of the resources declared by feeds that manage
> the
> machines where the constituent servers live.
>
> That is the envisaged workflow for "apps". Now the downside to that is that
> (currently) there is no "sync" for that. The reason is that the application
> really is a logical concept and the underlying servers can be repurposed to
> serve different applications (so if app stops using it, it shouldn't really
> disappear from inventory, as is the case with /sync - because if a feed
> doesn't "see" a resource, then it really is just gone, because the feed is
> solely responsible for reporting on it).
>
> We can think about how to somehow help clients with "App sync" but I'm not
> sure if having a feed for vertx is the right thing to do. On the other
> hand I
> very well may not be seeing some obvious problems of the above or parallels
> that make the 2 approaches really the same because the above model is just
> ingrained in my brain after so many hours thinking about it ;)
>
> > As for the feed question, the Vert.x feed will be the Metrics SPI
> > implementation (vertx-hawkular-metrics project). Again I guess it's not
> > much different than the Hawkular Agent.
> >
>
> A feed would only be appropriate if vertx app never reported on something
> that
> would also be reported by other agents. I.e. if a part of a vertx
> application
> is also reported on by a wfly agent, because that part is running in a wfly
> server managed by us, then that will not work - 1 resource cannot be
> "contained" in 2 different feeds (not just API wise, but logically, too).
>
> > Maybe the wording around user creating resources was confusing? Did you
> > thought he would do so from application code? In this case, the answer
> > is no.
> >
>
> Yeah, we should probably get together and discuss what your plans are to
> get
> on the same page with everything.
>
> > Regards,
> > Thomas
> >
> > Le 23/06/2016 à 10:01, Austin Kuo a écrit :
> > > Yes, I’m gonna build the inventory for vertx applications.
> > > So I have to create a feed for it.
> > >
> > > Thanks!
> > >
> > > On Tue, Jun 21, 2016 at 7:55 PM Lukas Krejci <lkrejci at redhat.com
> > >
> > > <mailto:lkrejci at redhat.com>> wrote:
> > >     Hi Austin,
> > >
> > >     Inventory offers a /hawkular/inventory/sync endpoint that is used
> to
> > >     synchronize the "world view" of feeds (feed being something that
> > >     pushes data
> > >     into inventory).
> > >
> > >     You said though that a "user creates" the resources, so I am not
> > >     sure if /sync
> > >     would be applicable to your scenario. Would you please elaborate
> > >     more on where
> > >     in the inventory hierarchy you create your resources and how? I.e.
> > >     are you
> > >     using some sort of feed akin to Hawkular's Wildfly Agent or are you
> > >     just
> > >     creating your resources "manually" under environments?
> > >
> > >     On Tuesday, June 21, 2016 02:20:33 AM Austin Kuo wrote:
> > >     > Hi all,
> > >     >
> > >     > I’m currently investigating how to sync with inventory server.
> > >     > Here’s the example scenario:
> > >     > Consider the following problem. A user creates version 1 of the
> > >
> > >     app with
> > >
> > >     > two http servers, one listening on port 8080, the other on port
> > >
> > >     8181. In
> > >
> > >     > version 2, the http server listening on port 8181 is no longer
> > >     > needed.
> > >     > When the old version is stopped and the new version started,
> there
> > >
> > >     will be
> > >
> > >     > just one http server listening. The application is not aware of
> the
> > >     > previous state. What should we do so that the second http server
> > >
> > >     is removed
> > >
> > >     > from Inventory?
> > >     >
> > >     > Thanks in advance.
> > >
> > >     --
> > >     Lukas Krejci
> > >
> > >     _______________________________________________
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> > >     hawkular-dev at lists.jboss.org <mailto:hawkular-dev at lists.jboss.org>
> > >     https://lists.jboss.org/mailman/listinfo/hawkular-dev
> > >
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>
> --
> Lukas Krejci
>
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