maas-devel team mailing list archive

[Julian Edwards <julian.edwards@xxxxxxxxxxxxx>]

Here's the updated architecture based on the conversations we've had.

https://docs.google.com/document/d/1PtFKcizW3bmP3QBv771tSGMO4VaCiLkWlr-oDzn-
FqU/edit

Anyone outside Canonical can view it this time.

Follow up with comments here please.

On Friday 04 May 2012 15:50:15 Julian Edwards wrote:
> Hi
> 
> Gavin also has a proposal to come, but this is the basis of what I discussed
> with Robert earlier.
> 
> The main aim is hyperscale. That is, we want to support hundreds of
> thousands of nodes.  Cobbler simply doesn't allow us to do that.  In
> addition we are currently tied into driving it synchronously so that we can
> be sure it synced its own database, which causes bugs like:
> https://bugs.launchpad.net/maas/+bug/989355
> 
> The other main issue surrounds DHCP/TFTP and PXE booting.  When we write out
> config files for these services we need to make sure there are no conflicts
> with multiple processes/threads doing the same thing.
> 
> Finally, we need to separate appserver requests from provisioning tasks
> because the latter can be long running (as per the above bug).
> 
> To this end we discussed:
> 
>  * Use Celery as a task queue (can use Rabbit or Django's DB as a broker)
>   → Django has a Celery plugin which makes this very easy
>  * Have one queue per pserv process
>  * Each pserv is responsible for servicing the tasks on that queue
>  * It scales by having multiple queues each with another pserv, or just
> multiple pservs pulling from one queue.
>  * The pserv can read the database by using Django's ORM, and write to it by
> sending API requests back to Django's appserver threads (again, scalable).
> 
> We also talked about batching requests on the Rabbit task queues because we
> might want to accumulate several requests that change the configs for DHCP
> etc.  For now though we can process serially and optimise later.  We'd need
> to think about how to implement locking though if there are multiple
> writers to the same files.
> 
> J