#Cassandra deployment on raspberry pi cluster# This ansible script installs cassandra on a cluster of raspberry pi's. The OS image from hypriot http://blog.hypriot.com/ has been installed on the authors cluster which does not have a copy of the jdk or python preinstalled. Hence the script also install's the jdk from oracle.

For controlling multiple nodes it is recommended that passwordless ssh login is used. Instructions can be found here http://www.thegeekstuff.com/2008/11/3-steps-to-perform-ssh-login-without-password-using-ssh-keygen-ssh-copy-id/

If the machine running ansible is macosx then https://github.com/brockgr/csshx is recommended. This allows bash commands to be entered onto multiple hosts. To invoke csshx enter

csshx root@172.16.2.[51-58]

Enter your own address range above.

Select the csshx master window and enter

apt-get install python

To install jdk and type the following from your ansible workstation command line

ansible-playbook -i production --tags=install_jdk,install_cassandra setup.yml

To remove jdk and cassandra type the following

ansible-playbook -i production --tags=remove_jdk,remove_cassandra setup.yml

To install only cassandra then type the following

ansible-playbook -i production --tags=install_cassandra setup.yml

To remove only cassandra then type the following

ansible-playbook -i production --tags=remove_cassandra setup.yml

User configurable variables are stored in /group_vars/all

The cassandra nodes are listed in /production in the appropriate groups. Any changes to reflect your node configuration need to be made there.

The apache cassandra logs are stored in /var/log/apache-cassandra.log

After the script has finished the seed nodes must be started first. type the following on each seed node

service cassandra start

type the folowing to see if the node has started and joined the cluster

/opt/cassandra/bin/nodetool status

Then you will see

Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address      Load       Tokens  Owns (effective)  Host ID                               Rack
UN  172.16.2.51  194.76 KB  256     25.1%             babe1a04-cabd-4a5d-b80e-e208dafcb606  rack1

Start the second seed node followed by

/opt/cassandra/bin/nodetool status

to see if the node has joined the cluster.

Repeat the steps until all the nodes are up and normal.

If the cluster needs restarting then ensure the seeds nodes are always started first, are up and normal, followed by the non seed nodes. If a node does not start then manually start it again.

www.datastax.com and planetcassandra.org are great sources of information. Also cassandra.apache.org has links to the mailing lists.

For information about ansible visit www.ansible.com