[openstack-dev] Stateful Applications on OpenStack
gokrokvertskhov at mirantis.com
Mon Jun 9 16:23:32 UTC 2014
You still can run legacy application on OpenStack with HA and DR using the
same good old school tools like pacemaker, heartbeat, DRBD etc. There are
all necessary features available in latest OpenStack. The most important
feature for HA - secondary IP address was implemented in Havana. Now you
can assign multiple IP addresses to the single VM port. Secondary IP can be
used as a VIP in pacemaker so it is possible to create classic
Active-Passive setup for any application. HAProxy is still there an you can
use it for any application which uses IP based transport for communication.
This secondary IP feature allows you to run even Windows cluster
applications without any significant changes in setup in comparison to the
running cluster on physical nodes.
There is no shared volumes (yet as I know) but you can use DRBD on VM to
sync two volumes attached to two different VMs and shared network
filesystems as a service is almost there. Using these approaches it is
possible to have data resilience for legacy applications too.
There is no automagic things which make legacy apps resilient, but it is
still possible to do with using known tools as there are no limitations
from OpenStack infrastructure side for that. As I know there were
discussions about exposing HA clusters on hypervisors that will allow some
kind of resilience automatically (through automatic migrations or
evacuation) but there is no active work on it visible.
On Mon, Jun 9, 2014 at 7:16 AM, Matthew Farina <matt at mattfarina.com> wrote:
> In my experience building apps that run in OpenStack, you don't give
> up state. You shift how you handle state.
> For example, instead of always routing a user to the same instance and
> that instance holding the session data there is a common session store
> for the app (possibly synced between regions). If you store session on
> each instance and loose an instance you'll run into problems. If
> sessions is more of a service for each instance than an instance
> coming and going isn't a big deal.
> A good database as a service, swift (object storage), and maybe a
> microservice architecture may be helpful.
> Legacy applications might have some issues with the architecture
> changes and some may not be a good fit for cloud architectures. One
> way to help legacy applications is to use block storage, keep the
> latest snapshot of the instance in glance (image service), and monitor
> an instance. If an instance goes offline you can easily create a new
> one from the image and mount block storage with the data.
> - Matt
> On Mon, Jun 9, 2014 at 7:27 AM, hossein zabolzadeh <zabolzadeh at gmail.com>
> > Hi OpenStack Development Community,
> > I know that the OpenStack interest is to become a cloud computing
> > system. And this simple sentence means: "Say goodbye to Statefull
> > Applications".
> > But, as you know we are in the transition phase from stateful apps to
> > stateless apps(Remember Pets and Cattle Example). Legacy apps are still
> > used and how openstack can address the problems of running stateful
> > applications(e.g. HA, DR, FT, R,...)?
> > HA: High Availability
> > DR: Disaster Recovery
> > FT: Fault Tolerance
> > R: Resiliancy!
> > _______________________________________________
> > OpenStack-dev mailing list
> > OpenStack-dev at lists.openstack.org
> > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
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