[SimGrid-user] adding/removing hosts during simulation

Martin Quinson martin.quinson at ens-rennes.fr
Wed Nov 14 15:20:11 CET 2018


ah, but you want to create VM instances at run time? Yes, this is
possible of course, but that's not exactly the same question as
creating hosts, is it?

If I misuderstood and you really need creating hosts, please note that
I did not disminish this need. I just said that someone has to do so.
You could open a bug, I could pledge to do the work myself, but given
my current workload, it'd be faster for you to just implement this new
routing algorithm yourself and contribute it back to this open-source

Sorry for not having enough funding to pay enough workforce on SimGrid.
Believe me, I'd love to :)


On Wed, Nov 14, 2018 at 01:02:16PM +0300, Oleg Sukhoroslov wrote:
> Dear Martin,
> Thanks for a quick reply.
> The use case I have in mind is to model the execution of a single
> cloud-based application. From the point of view of an application developer
> (a cloud user), the cloud allows to flexibly add/remove nodes (VM instances)
> to the application on-demand during the run time. Indeed, it is possible to
> add all physical hosts at the beginning of the simulation and to model the
> cloud infrastructure itself (or its part that could be allocated at most to
> run the application). However, there is actually no need to model the
> internals of the cloud in my use case. Since there could by many possible
> instance types and configurations in a cloud, it would be much more
> convenient just to dynamically add the instances with specific
> configurations as hosts to the simulation instead of dealing with placement
> of them to a static set of physical hosts, invisible to the application.
> Essentially, from the point of view of a cloud user, it should have its
> personal dynamically reconfigurable distributed system.
> So, in my case, the problem is not a large number of hosts, but rather in
> development convenience and a large number of possible instance
> configurations.
> Hope my description is clear. Any advices are more than welcome.
> Regards,
> Oleg
> On 11/14/18 12:39 AM, Martin Quinson wrote:
> > Hello Oleg,
> > 
> > unfortunately, it is not possible to add or remove hosts from the simulation right now. That's something we should fix in the future. In the meanwhile what people usually do to overcome this is that they just add all the hosts that they may need at start up, and they simply turn off the machines when they should not be part of the platform.
> > 
> > The extreme of this approach was some users simulating wifi networks and roaming by creating one host per potential location of their users. That's rather brutal, as they ended up with thousands of hosts, but it seems that SimGrid can deal with the load induced on the simulation core.
> > 
> > Maybe you can use this trick for the time being?
> > 
> > And if you really need that feature (eg because you'd need millions of hosts with this trick), just say so. I'd love to help you implementing a new routing algorithm that allows to add and remove hosts in your platform.
> > 
> > Take care,
> > Mt
> > 
> > ----- Le 13 Nov 18, à 21:59, Oleg Sukhoroslov oleg.sukhoroslov at gmail.com a écrit :
> > 
> > > Hi,
> > > 
> > > Is it possible to dynamically add/remove hosts during the simulation
> > > with SimGrid?
> > > It seems that S4U API is lacking such functionality at the moment, but I
> > > noticed that previously there were functions like addHost()/delHost(),
> > > which are removed now.
> > > 
> > > Regards,
> > > Oleg
> > > 
> > > _______________________________________________
> > > Simgrid-user mailing list
> > > Simgrid-user at lists.gforge.inria.fr
> > > https://lists.gforge.inria.fr/mailman/listinfo/simgrid-user

To a great extent the act of coding is one of organization.
Refactoring. Simplifying. Figuring out how to remove extraneous
manipulations here and there.  -- http://prog21.dadgum.com/177.html
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