Spark 1.2 with Cassandra 2.1: Setting up a SparkSQL + Cassandra environment

In my previous post on Cassandra and Spark I showed how to get a development environment setup with Vagrant/Ansible/VirtualBox without installing Cassandra/Spark on your dev station.

This update will get us to a point where we can run SQL (yes, SQL, not CQL) on Cassandra. It is just a trivial example to show the setup working.

The previous article was back in the days of Spark 1.0. With Spark 1.1+ we can now run SparkSQL directly against Cassandra.

I've updated the Vagrant/Ansible provisioning to install Spark 1.2 and Cassandra 2.1, and I've added a new "fatjar" with the latest Cassandra Spark connector so that we can use it in the Spark shell and show this magic working. The 1.2 connector isn't released yet so I have built against the Alpha, see here for details. We're just that cutting edge here...

So, once you have ran vagrant up (this will take a while as it downloads + install all of the above) you'll need to SSH in we can get into Spark shell.

I've setup the following alias so no worrying about classpaths:

alias spark-shell='spark-shell --jars /vagrant/spark-connector-1.2.0-alpha1-driver-2.1.4-1.0.0-SNAPSHOT-fat.jar

First lets jump into cqlsh and create a keyspace and table to play with:


Not the most exciting schema you'll ever see, but this is all about getting the Hello World of SparkSQL on Cassandra working!

Now we have some data to play with lets access it from Spark shell.


Lets go through what has happened here:

• Lines 3-6: Mandatory Spark ASCII art
• Line 12: Import the connector so we can access Cassandra
• Line 15: Create a CassandraSQLContext
• Line 18: Set it to our test Keyspace we created above
• Line 20: Select the whole table (very exciting I know!)
• Line 21: Get Spark to execute an action so all the magic happens

That's all for now, tune in later for a more complicated example :)

Here's the link to all the Vagrant/Ansible code.

Installing Cassandra and Spark with Ansible

I am currently doing a proof of concept with Spark and Cassandra. I quickly need to be able to create and start Cassandra and Spark clusters. Ansible to the rescue!

I split this my ansible playbook into three roles:

• Cassandra
• Ops center
• Spark

My main playbook is very simple:

I have some hosts defined in a separate hosts file called m25-cassandra. I've decided to install htop, I could have out this in a general server role.

I also define a few variables, these of course course could be defined else where per role:

• cluster_name - this will replace the cluser name in each of the hosts cassandra.yaml
• seeds - as above

So lets take a look at each role.

Cassandra

Here are the tasks:

This is doing the following:

• Installing a JRE
• Adding the Apache Cassandra debian repository
• Adding the keys for the debian repository
• Installing the latest version of Cassandra
• Replacing the cassandra.yaml (details later)
• Ensuring Cassandra is started

The template cassandra.yaml uses the following variables:

• cluster_name: '{{ cluster_name }}' - So we can rename the cluster
• - seeds: "{{ seeds }}" - So when we add a new node it connects to the cluster
• listen_address: {{ inventory_hostname }} - Listen on the nodes external IP so other nodes can communicate with it
• rpc_address: {{ inventory_hostname }} - So we can connect ops center and cqlsh to the nodes

Magic! Now adding new hosts to my hosts file with the tag m25_cassandra will get Cassandra installed, connected to the cluster and started.

Ops Center

The tasks file for ops center:

This is doing the following:

• Adding the Datastax community debian repository
• Adding the key for the repo
• Installing Ops Center
• Starting Ops Center

No templates here as all the default configuration is fine.

Spark

The spark maven build can build a debian package but I didn't find a public debian repo with it in so the following just downloads and unzips the Spark package:

I start the workers using the start-slaves.sh script from my local master do don't need to start anything on the nodes that have Cassandra on.

Conclusion

Ansible makes it very easy to install distributed systems like Cassandra. The thought of doing it manually fills me with pain! This is just got a PoC, I don't suggest downloading Spark from the public internet or always installing the latest version of Cassandra for your production systems. The full souce including templates and directory structure is here.