[Openais] CSI, SI and SU, Component ??? Totally confused.

[harish kulkarni]

Thanks for your clarification.

Let me just re-iterate just to correct myself,

Component: is logical stuff
Component Service Instance: Is a process
Service Unit: Logical stuff
Service Instance: set of CSI's.

Now say, i have two executable's  (x1 and x2) which provide two different
functionalities say y1 and y2, and are interdependable so i define them as
components under one service unit.

Till now it's all logical binding.

Now when i define CSI, i can have multiple CSI's of each component. say for
example i may have x1-csi-1 and x1-csi-2 and y1-csi-1, y1-csi-2.

And i can have two SI's

si-A and si-B, si-A will have two csi's  x1-csi-1 and y1-csi-1, similarly
under si-B will have x1-csi-2 and y1-csi-2.

And under sg i define one su, but two si's.

When i bring up this kind of a setup on two blades (box;s) , we end-up of
seeing two si's which means four processes on one box and 4 on other box.

two instances of x1 process with x1-csi-1 and x1-csi-2 specific arguments

two instances of y1 process with y1-csi-1 and y1-csi-2 specific arguments.

and each si will have have it's own HA state.

And both are independent, which means si-A could be active on blade-1 and
si-B could be active on blade blade-2.

Please correct if i have missed something.

-Thanks
Harish


On Fri, Jun 12, 2009 at 2:26 PM, Steven Dake <sdake at redhat.com> wrote:

> On Fri, 2009-06-12 at 12:39 +0530, harish kulkarni wrote:
> > Hello All,
>
> First, AMF in openais is experimental and you likely wont be happy with
> the results.
> >
> > I need your help in getting an understanding about these terms with an
> > example, i saw few examples on this mailing list which were helpful.
> > But not close to realistic situations.
> >
> > I understand the service unit and component concept well but i didn't
> > get component service instance(CSI), service instance (SI) and
> > service group (SG) logic well, i read specs and other presentations
> > on
>
> A component can provide multiple instantiations of a service unit's
> workload.  For example consider a webserver which hosts 5 domains.  Each
> domain would be a separate CSI but serviced by 1
> component(component=webserver process of a SU).
>
> The CSI abstraction essentially allows a component to have separate
> contexts (also known as instances).  A service instance is a collection
> of the CSIs that define a SU's running instances.  In a typical
> application, there is only one component providing all processing for a
> service unit.  If the case is in my hypothetical example above, there is
> 1 web server component and 1 database component, they could be combined
> into 1 SU.  Then each of the 5 domain names would get a separate SI (5
> SIs (load1-load5), 2 components (webserver, db), and each component in
> the SI would get a seperate CSI (5 CSIs per component in the SU)
> CSIs(comp1-load1->comp1-load5->comp1 and
> comp1-load2->comp2-load2->comp2)
>
> > web but failed to grab the said.
> >
> > Please help me with your thoughts.
> >
> > Use Case:
> >
> > Assume i have 3 processes/components, which constitute my service
> > Process-1 Provides DB interface for persistent data storage
> > Process-2 Call Control Logic (CCL)
> > Process-4 Billing
> >
> > Let's say i have two physical box's (blades) on which i am building
> > the service.
> >
> > I want to have CCL and Billing on same blade always, so i define both
> > of them under single SU (SU-1) as two components,
> > one CCL component (COMP-1) and other Billing component (COMP-2).
> >
> > From my understanding, within a service unit, if a component goes down
> > the whole SU gets switch-overed, in normal active-standby setup.
> >
> > And i define DB component (COMP-3) within another SU (SU-2)
> >
> > When my system runs, i see on active blade (blade-1) all components
> > COMP-1, COMP-2,COMP-3 getting active status and on standby blade
> > (blade-2)
> >
> > i see all the components getting standby status.
> >
> > Where does this CSI (component service instance), SI (service
> > instance) and SG (service group) come into picture and why do we need
> > them?.
>
> see above for example.  If it isn't clear from that, ask again and I'll
> rephrase.
>
> You might have a look at pacemaker (which is an availability manager
> developed in open source and an offshoot of the linux-ha effort) if you
> want something compatible with openais and corosync that you can use
> today.
>
> >
> > Might be that my requirements don't really need  CSI,SI,SG, but
> > according to my knowledge most telco box's have what i have explained
> > might be few more components and SU additional accordingly.
> >
>
> Finally a SG is just a grouping of SUs into one logical entity.
>
> > -Thanks for your time.
> > Harish
> >
> > _______________________________________________
> > Openais mailing list
> > Openais at lists.linux-foundation.org
> > https://lists.linux-foundation.org/mailman/listinfo/openais
>
>
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