This is just semantics for now but it might be better to think of the number of
things being allocated as requests rather than machines. This will allow for
block requests of cluster images.
Regarding the return code... it might be useful to return the number of requests
that haven't been successfully allocated for the block time. A return code of 0
would mean all of the resources for the block time have been successfully allocated.
The backend wouldn't need to worry about the total number of requests that are
needed nor would it care how many were successfully allocated during this stage.
It would only have to know if the number which couldn't be allocated is
greater than 0.
This would make it easy to add some failure recovery features in the future. If
the number which hasn't yet been allocated is greater than 0, the backend
process could make multiple attempts by sleeping and looping.
-Andy
Josh Thompson wrote:
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For the frontend, one function works as well as two would. However, I can see
how it would simplify code on the backend to just pass a blockTimes id since
it wouldn't have to determine all of the other information (blockTimes
entries include blockrequestids; so, the blockrequestid wouldn't need to be
passed as well).
So, how about this, keep the function already described except drop
the 'blockTimeid' parameter and add this function as well:
function: XMLRPCproccessBlockTime
parameters:
blockTimesid - id from the blockTimes table
ignoreprivileges - 0 (false) or 1 (true) - set to 1 to select computers from
any that are mapped to be able to run the image; set to 0 to only select
computers from ones that are both mapped and that users in the usergroup
assigned to this block request have been granted access to through the
privilege tree.
returns: the number of machines that were successfully allocated, with 0
indicating a complete failure of not being able to allocate any computers
I just realized a problem in the return part of both functions. What if the
function is called too close to the start time to be able to preload the
computers by then? Should it just return 0 and not try to load any of them?
It may be that the functions need to return an array containing both a return
code and the number of computers that were successfully allocated. Thoughts?
Josh
On Thursday February 05, 2009, Aaron Peeler wrote:
Would it make sense to break this into two functions?
Have this function XMLRPCblockAllocation with only two parameters
blockrequestid and blockTimeid.
The second function would be to create the Block Allocation -
XMLRPCcreateBlockAllocation.
Aaron
--On February 4, 2009 4:39:30 PM -0500 Josh Thompson
<josh_thomp...@ncsu.edu> wrote:
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I'm going to start work on VCL-78 which is an addition to the frontend
XML RPC API to allow the backend to call the frontend for allocating
computers for block reservations. Currently, the block reservations are
created in the frontend, but computers are not allocated to fulfill them
because the requested time(s) could be at any point in the future. So,
around 6 hours before a requested time, the backend picks up that block
reservation time slot, allocates computers for it, and then inserts
reload reservations early enough for the computers to be preloaded by
the start of the time slot.
This results in a fair amount of duplicated code, since the frontend
currently handles computer allocation in all other cases.
This is how I am planning on implementing it. Please reply with any
comments on doing it differently or tweaking it somehow. I'm open to
any suggestions.
The backend could just call the frontend with the blockTimes id to
process, but I'll make it more generic to be more useful in other cases
and require that the backend specify several items.
function name: XMLRPCblockAllocation
parameters:
imageid - id of the image to be used
start - unix timestamp for the start time (i.e. machines should be
prep'd and ready by this time)
end - unix timestamp for the end time
machinecount - number of computers to allocate
usergroupid - id of user group for checking user access to machines
ignoreprivileges - 0 (false) or 1 (true) - set to 1 to select computers
from any that are mapped to be able to run the image; set to 0 to only
select computers from ones that are both mapped and that users in
usergroupid have been granted access to through the privilege tree. If
this is set to 1, usergroupid is ignored (more on this below).
blockTimeid - id from blockTimes table that this will fulfill or 0 if
there is not an existing block reservation related to this call
returns: the number of machines that were successfully allocated, with 0
indicating a complete failure of not being able to allocate any computers
Description of how it will work:
The frontend will use the normal scheduling functions to allocate
computers and insert them into the blockComputers table. If blockTimeid
is 0, new entries will be created in the blockRequest and blockTimes
tables. It will create reload reservations for the computers early
enough for them to be loaded by the start time based on historical
loading times.
The ignoreprivileges flag exists to allow more machines to be available
for fulfilling block reservations than just those that the user group
has access to. The current implementation with the backend doing the
processing functions as if ignoreprivileges were set to 1.
That's pretty much it.
Josh
- --
- -------------------------------
Josh Thompson
Systems Programmer
Virtual Computing Lab (VCL)
North Carolina State University
josh_thomp...@ncsu.edu
919-515-5323
my GPG/PGP key can be found at pgp.mit.edu
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Aaron Peeler
OIT Advanced Computing
College of Engineering-NCSU
919.513.4571
http://vcl.ncsu.edu
- --
- -------------------------------
Josh Thompson
Systems Programmer
Virtual Computing Lab (VCL)
North Carolina State University
josh_thomp...@ncsu.edu
919-515-5323
my GPG/PGP key can be found at pgp.mit.edu
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--
Andy Kurth
Virtual Computing Lab
Office of Information Technology
North Carolina State University
andy_ku...@ncsu.edu
919.513.4090
