Spark Plugin
============

The Spark Sahara plugin provides a way to provision Apache Spark clusters on
OpenStack in a single click and in an easily repeatable fashion.

Currently Spark is installed in standalone mode, with no YARN or Mesos support.

Images
------

For cluster provisioning prepared images should be used. The Spark plugin
has been developed and tested with the images generated by the :doc:`diskimagebuilder`.
Those Ubuntu images already have Cloudera CDH4 HDFS and Apache Spark installed.

The Spark plugin requires an image to be tagged in Sahara Image Registry with
two tags: 'spark' and '<Spark version>' (e.g. '1.0.0').

Also you should specify the username of the default cloud-user used in the image. For
images generated with the DIB it is 'ubuntu'.

Note that the Spark cluster is deployed using the scripts available in the
Spark distribution, which allow to start all services (master and slaves), stop
all services and so on. As such (and as opposed to CDH HDFS daemons), Spark is
not deployed as a standard Ubuntu service and if the virtual machines are
rebooted, Spark will not be restarted.

Spark configuration
-------------------

Spark needs few parameters to work and has sensible defaults. If needed they
can be changed when creating the Sahara cluster template. No node group options
are available.

Once the cluster is ready, connect with ssh to the master using the 'ubuntu'
user and the appropriate ssh key. Spark is installed in /opt/spark and should
be completely configured and ready to start executing jobs. At the bottom of
the cluster information page from the OpenStack dashboard, a link to the Spark
web interface is provided.

Cluster Validation
------------------

When a user creates an Hadoop cluster using the Spark plugin,
the cluster topology requested by user is verified for consistency.

Currently there are the following limitations in cluster topology for the Spark plugin:

  + Cluster must contain exactly one HDFS namenode
  + Cluster must contain exactly one Spark master
  + Cluster must contain at least one Spark slave
  + Cluster must contain at least one HDFS datanode

The tested configuration puts the NameNode co-located with the master and a DataNode
with each slave to maximize data locality.

Limitations
-----------

For now scaling and EDP are not supported.

Swift support is not available in Spark. Once it is developed there, it will be
possible to add it to this plugin.
