Updated Kafka role for 0.10.x

[andrewkcarter]

This updates the Kafka role from Kafka 0.9.x to 0.10.x. There are a series of steps to follow to perform a rolling upgrade of a functioning cluster. They are explained in the documentation linked below. I've distilled it it down the following specific steps.

https://kafka.apache.org/documentation/#upgrade

1. Add the two following ansible variables so they apply to all brokers (i.e. production group vars file):

#### KAFKA VARS ####
kafka_inter_broker_protocol_version: "0.9.0"
kafka_log_message_format_version: "0.9.0"

These pin the message formats between brokers and the clients to our current versions.

For each broker in the Kafka cluster execute steps 2 - 4:

2. Tail the broker logs to monitor the upgrade, shutdown, and restart:

tail -f /var/log/kafka/server.log

3. Run the Kafka 0.10 role:

ansible-playbook -i <inventory> --limit <broker-node> --tags deps-kafka,site-kafka site-infrastructure.yml

4. If the role didn't restart the Kafka broker after the update, then manually restart it.

supervisorctl restart kafka

-- GOTO Step 2 ---

Now the all brokers are running Kafka 0.10, we can now change the protocol versions to the latest.

5. Remove the two Ansible variables introduced in step 1.

6. Repeat steps 2 - 4 again for each broker to apply the protocol version change.

This process was tested on a two VM cluster running a series of Storm topologies actively using Kafka during the upgrade.

[andrewkcarter]

#58 (comment)