ObjectRocket, the provider of cloud-based, MongoDB database services which has its sales offices in Pleasanton, has been acquired by cloud hosting provider Rackspace, Rackspace announced Wednesday morning. Financial details of the buy were not disclosed. MOngoDB provides the MongoDB, NoSQL database as a cloud-based service. NoSQL is used heavily in the big data area. Rackspace said the buy will help broaden its Openstack-based open cloud platform.