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Khder,
Sorry for the late response.
You can certainly experiment with extending the code to include more advanced
scheduling functions. The existing ranking of computers is something like
this:
1) generate a set of all computers meeting the minimum requirements of the
image, that the user has access to, and that the image is mapped to; order
that list by node specs from low to high
2) remove from that set any computers that are already assigned reservations
3) if the image is virtual, remove any VMs for which the host doesn't have
enough memory to load the VM (without overbooking)
4) assign the new reservation the first computer from that set for which an
active management node can be found
There's actually 3 sets of computers being tracked - those already loaded with
the image being requested, those set aside for a block allocation of which the
user is a member, and then a set of both of those plus any available computers
that are currently loaded with another image.
There is a configuration option (SCHEDULER_ALLOCATE_RANDOM_COMPUTER) in
conf.php that allows the sets of computers to be randomized. The motivation
behind this option is for sites that have homogeneous virtual machines and
hosts. Randomizing the assigned computer should help spread the load equally
among all existing hosts.
I hope that helps.
Josh
On Tuesday, October 21, 2014 9:01:17 PM Khder Omar wrote:
> Hi Josh,
>
> Thanks for your reaction. I have checked the code source and I think the
> only function which might fulfill my question is function allocComputer(...)
>
> Eventually, the function a piece test schedule code
>
> if(SCHEDULER_ALLOCATE_RANDOM_COMPUTER) {
>
> shuffle($blockids);
> shuffle($currentids);
> shuffle($computerids);
>
> }
>
>
> I might assume if it was correctly understood that VCL scheduler process
> determines in first place a computer to be assigned to a management node
> from a given array or table in order otherwise it can be randomly chosen!
> Then, we can assume that the scheduling decision is still using a basic
> order as FCFS or a chance/Random order! It that assumed be correct ? if so,
> is there a way to extend the code by including more advanced scheduling
> functions ?
>
> Best regards,
> PhD Team
>
> 2014-10-21 16:11 GMT+01:00 Josh Thompson <[email protected]>:
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> > Khder,
> >
> > The scheduling of reservations is actually done in the web code. Have a
> > look
> > at the isAvailable function in the web/.ht-inc/utils.php file.
> >
> > https://svn.apache.org/repos/asf/vcl/trunk/web/.ht-inc/utils.php
> >
> > Josh
> >
> > On Tuesday, October 21, 2014 4:39:05 PM Khder Omar wrote:
> > > Dear all,
> > >
> > > We were wondering what kind of scheduler algorithms VCL might use ? Any
> > > hints about the scheduler source code will be appreciated. The idea is
> > > actually to check how VCL will perform while changing the scheduler
> > > algorithm [in management node].
> > >
> > >
> > > Thanks in advance
> > >
> > > Best regards,
> > > Phd team
> >
> > - --
> > - -------------------------------
> > Josh Thompson
> > VCL Developer
> > North Carolina State University
> >
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Josh Thompson
VCL Developer
North Carolina State University
my GPG/PGP key can be found at pgp.mit.edu
All electronic mail messages in connection with State business which
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