News Archive

Hadoop on OpenStack

The latest project to be incubated in OpenStack for the Icehouse (2014.1) release cycle is Savanna, which provides MapReduce as a service using Apache Hadoop. Savanna was approved for incubation by the OpenStack Technical Committee in a vote last night.

In what is becoming a recurring theme, much of the discussion centred around potential overlap with other programs—specifically Heat (orchestration) and Trove (database provisioning). The main goal of Savanna should be to provide a MapReduce API, but in order to do so it has to implement a cluster provisioning service as well.

The Savanna team have done a fair amount of work to determine that Hadoop is too complex a workload for Heat to handle at present, but they have not approached the Heat team about closing the gap. That is unfortunate, because we are currently engaged in an effort to extend Heat to more complex workloads, and Hadoop is a canonical example of the kind of thing we would like to support. (It is doubly unfortunate, given that the obstacles cited appear comparatively minor.) This will have to change, because there was universal agreement that Savanna should move to integrating with Heat rather than roll-your-own orchestration.

The final form of any integration with Trove, however, remains unclear. The Savanna team maintain that there is no overlap because Trove provides a database as a service and Hadoop is not a database, but this is too glib for my liking. Trove is essentially a pretty generic provisioning service, and while its user-facing function is to provision databases, that would be a poor excuse for maintaining multiple provisioning implementations in OpenStack. And, while it would be wrong to describe Hadoop as a database per se, it would be fair to say that Hadoop has a database. Trove is already planning a clustering API. In my opinion, the two teams will need to work together to come up with a common implmentation, whether in the form of a common library, a common service or a direct dependency on Trove.

The idea of allowing Savanna to remain part of the wider OpenStack ecosystem without officially adopting it was, of course, considered. Hadoop can be considered part of the Platform rather than the Infrastructure layer, so naturally there was inquiry into whether it makes sense for OpenStack to annoint that particular platform rather than implement a more generic service (though it is by no means clear that the latter is feasible). Leaving aside that Amazon already implments Hadoop in the form of its Elastic MapReduce service, the Hadoop ecosystem is so big and diverse that worrying about locking users in to it is a bit like worrying about OpenStack locking users in to Linux. It does, of course, but there is still a world of choice there.

The final source of differing opinions simply related to timing. Some folks on the committee felt that an integration plan for Heat and/or Trove should be developed prior to accepting Savanna into incubation. Incubation confers integration with the OpenStack infrastructure (instead of StackForge) and Design Summit session slots, both of which would be highly desirable. The Technical Committee’s responsibility is to bless a team and a rough scope, so the issue was whether the latter is sufficiently clear to proceed.

This objection was overcome, as the committee voted to accept Savanna for incubation, albeit by a smaller margin than some previous votes. The team now has their work cut out to integrate with the other OpenStack projects, and nobody should be surprised if Savanna ends up remaining in incubation through the J cycle. Nonetheless, we welcome them to the OpenStack family and look forward to working with them before and during the upcoming Summit to develop the roadmap for integration.