[IPython-User] ipcontroller failover?

MinRK benjaminrk@gmail....
Sun Feb 12 14:06:24 CST 2012


On Sun, Feb 12, 2012 at 11:48, Darren Govoni <darren@ontrenet.com> wrote:

> On Sun, 2012-02-12 at 11:12 -0800, MinRK wrote:
> >
> >
> > On Sun, Feb 12, 2012 at 10:42, Darren Govoni <darren@ontrenet.com>
> > wrote:
> >         Thanks Min,
> >
> >         Is it possible to open a ticket for this capability for a
> >         (near) future
> >         release? It compliments that already amazing load balancing
> >         capability.
> >
> >
> > You are welcome to open an Issue.  I don't know if it will make it
> > into one of the next few releases, but it is on my todo list.  The
> > best way to get this sort of thing going is to start with a Pull
> > Request.
>
> Ok, I will open an issue. Thanks. In the meantime, is it possible for
> clients to 'know' when a controller is no longer available? For example,
> it would be nice if I can insert a callback handler for this sort of
> internal exception so I can provide some graceful recovery options.
>

It would be sensible to add a heartbeat mechanism on the controller->client
PUB channel for this information.  Until then, your main controller crash
detection is going to be simple timeouts.

ZeroMQ makes disconnect detection a challenge (because there are no
disconnect events, because a disconnected channel is still valid, as the
peer is allowed to just come back up).


>
> >
> >
> >         Perhaps a related but separate notion would be the ability to
> >         have
> >         clustered controllers for HA.
> >
> >
> > I do have a model in mind for this sort of thing, though not multiple
> > *controllers*, rather multiple Schedulers.  Our design with 0MQ would
> > make this pretty simple (just start another scheduler, and make an
> > extra call to socket.connect() on the Client and Engine is all that's
> > needed), and this should allow scaling to tens of thousands of
> > engines.
>
> Yes! That's what I'm after. In this cloud-scale age of computing, that
> would be ideal.
>
>
> Thanks Min.
>
> >
> >
> >         On Sun, 2012-02-12 at 08:32 -0800, Min RK wrote:
> >         > No, there is no failover mechanism.  When the controller
> >         goes down, further requests will simply hang.  We have almost
> >         all the information we need to bring up a new controller in
> >         its place (restart it), in which case the Client wouldn't even
> >         need to know that it went down, and would continue to just
> >         work, thanks to some zeromq magic.
> >         >
> >         > -MinRK
> >         >
> >         > On Feb 12, 2012, at 5:02, Darren Govoni
> >         <darren@ontrenet.com> wrote:
> >         >
> >         > > Hi,
> >         > >  Does ipython support any kind of clustering or failover
> >         for
> >         > > ipcontrollers? I'm wondering how situations are handled
> >         where a
> >         > > controller goes down when a client needs to perform
> >         something.
> >         > >
> >         > > thanks for any tips.
> >         > > Darren
> >         > >
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