Really thanks Georgy for your complete answer. My major concern on
openstack was HA on my legacy apps(I wanted to use cloudstack instead of
openstack becasue of its more attention to legacy apps and more HA
features). But now, I will check your listed HA solutions on openstack and
come back as soon as possible.
On Mon, Jun 9, 2014 at 8:53 PM, Georgy Okrokvertskhov <
gokrokvertsk...@mirantis.com> wrote:
> Hi,
>
> 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.
>
> Thanks
> Georgy
>
>
>
>
>
> On Mon, Jun 9, 2014 at 7:16 AM, Matthew Farina
> 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
>> wrote:
>> > Hi OpenStack Development Community,
>> > I know that the OpenStack interest is to become a cloud computing
>> operating
>> > 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
>> in
>> > 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!
>> >
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>> >
>>
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>
>
>
> --
> Georgy Okrokvertskhov
> Architect,
> OpenStack Platform Products,
> Mirantis
> http://www.mirantis.com
> Tel. +1 650 963 9828
> Mob. +1 650 996 3284
>
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>
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