[openstack-dev] [savanna] scalable architecture

Ruslan Kamaldinov rkamaldinov at mirantis.com
Tue Jul 30 10:56:07 UTC 2013

This question was asked several times. So we decided to provide a
detailed response.

1. The first question is “Why doesn’t Savanna use Heat to provision VMs?”

Generally using Heat underneath for infrastructure provisioning looks
reasonable. In a tactic perspective there are few factors making Heat
usage underneath Savanna problematic:
* Heat stability for Grizzly release. Savanna currently maintains
Grizzly+ compatibility.
* Installation of large Hadoop clusters (100+ nodes). Will be
addressed by proposed architecture changes.
* Anti-affinity support for HDFS redundancy in cloud environment
* Circular dependencies - we should generate ‘/etc/hosts’ for all
instances in provisioned cluster. We can’t use cloud init for this
directly. There are a couple possible solutions using Heat, but none
of them looks like a straightforward solution.
* Level of complexity. We try to keep things as simple as possible.
Adding extra layer will increase overall complexity of the solution.
In addition both Savanna and Heat under active development changing
lots of internals and even APIs and will require extra effort to

Here is what we’ll do:
* Create a wiki page with text from this email
* Create a list of requirements for Heat

Once Heat fulfills all the requirements we will be able and should use
Heat for VM provisioning.

2. Let’s answer the second question - why we need Savanna? Can’t we
use Heat to do what Savanna does?

* Savanna provides bunch of Hadoop-specific features. It’ll be hard to
provide them as Heat plugin
* Savanna provides Hadoop-specific APIs and functionality. Heat use
cases are mostly around provisioning/deployment.
* Savanna provides integration with various Hadoop distributions
through pluggable mechanism

Now, more details on each item.
Hadoop specific features:
* Tight Swift integration. Hadoop can read and write from/to Swift
object storage. Savanna provides required configs for the Hadoop
* Usage of anti-affinity to preserve data-redundancy of HDFS nodes

Hadoop-specific APIs and functionality:
* Hadoop cluster scaling
* Elastic Data Processing: https://wiki.openstack.org/wiki/Savanna/EDP

Integration with Hadoop distributions through pluggable mechanism:
- Usually Hadoop cluster deployment is a multi-step operation. First
step is to install management console (for instance Apache Ambari).
Second step is to communicate with management console through REST API
to provision Hadoop on the cluster. Savanna wraps all this operations
under well-defined API.

I hope all the items above explain why we need Savanna as a separate
OpenStack service.

3. Why can’t Savanna be used as a plugin for Heat?
It should be and it will be someday.


On Thu, Jul 25, 2013 at 7:42 PM, Joe Gordon <joe.gordon0 at gmail.com> wrote:
> On Jul 23, 2013 12:34 PM, "Sergey Lukjanov" <slukjanov at mirantis.com> wrote:
>> Hi evereyone,
>> We’ve started working on upgrading Savanna architecture in version 0.3 to
>> make it horizontally scalable.
>> The most part of information is in the wiki page -
>> https://wiki.openstack.org/wiki/Savanna/NextGenArchitecture.
>> Additionally there are several blueprints created for this activity -
>> https://blueprints.launchpad.net/savanna?searchtext=ng-
>> We are looking for comments / questions / suggestions.
> This sounds like most of this can be built around Heat, except maybe the
> rest api to hadoop.  So why not use heat for the deploy part?
>> P.S. The another thing that we’re working on in Savanna 0.3 is EDP
>> (Elastic Data Processing).
>> Thank you!
>> Sincerely yours,
>> Sergey Lukjanov
>> Savanna Technical Lead
>> Mirantis Inc.
>> _______________________________________________
>> OpenStack-dev mailing list
>> OpenStack-dev at lists.openstack.org
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
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