This is the first of the multi part series on Cassandra. In each part I will cover one aspect amount setting up, managing and monitoring Cassandra on Amazon Web Services.

In this first part I will focus on the setup of Cassandra on AWS.

#Deployment Model

Cassandra will be set up as a multi-node cluster on AWS. AWS is spread over multiple regions and each region has multiple availability zones(AZ) within them.

Each region will start with at-least 3 nodes in a cluster. The nodes will be spread across different AZ’s. Most of the AWS regions have atleast 3 different AZ.

In regions where there are less than 3 AZ’s, two nodes will share the same AZ.

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#Setup

##AWS

• Choose a region which has three availability zones. For the purpose of this post, I have choosen us-west-2.
• Spin up one EC2 instance in each availability zone.
• Databased should always be on private subnets of VPC and should not be open to internet.

• Update the firewall setting on the secutiry group associated with the EC2 instance to allow incomming traffinc on the following ports:

  9042 CQL Client port 7000 Inter node communication on cluster

##Installable

• Download Cassandra 2.2.4V from the below URL.

  http://downloads.datastax.com/community/dsc-cassandra-2.2.4-bin.tar.gz

• Unzip it to a location on the EC2 machine.
• Do this on all three nodes.

##Cassandra Configuration

Make the below changes in the files present in the

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/conf

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File : cassandra-rackdc.properties

dc_suffix = 2a_cassandra   # Uniquely identify a node in a datacenter(DC).DC names are automatically assiged by Cassandra using EC2Snitch/EC2MultiRegionSnitch.
prefer_local = true

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File : cassandra.yaml

partitioner: org.apache.cassandra.dht.Murmur3Partitioner  # This is the default and we will keep it as it is. Used to hash and distribute the keys across differnt nodes.

endpoint_snitch: Ec2Snitch  # Use EC2MultiRegionSnitch if you are setting up multiple clusters spanning different regions. Otherwise use Ec2Snitch

listen_address: 10.101.212.201  # This will be the private IP address of the EC2 instance. Will vary from instance to instance.

broadcast_address: 10.101.212.201  # private IP address of the EC2 instance.

rpc_address: 10.101.212.201  # private IP address of the EC2 instance

seeds: "10.101.212.206,10.101.214.60"   ## IP address of the nodes acting as seeds

key_cache_size_in_mb: 100000

data_file_directories:   # location where database files needs to be stored. 
   -/local/mnt/cassandra/data
   
commitlog_directory: /local/mnt/cassandra/commitlog  #location where the commit logs needs to be stored.

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Reference : 

https://en.wikipedia.org/wiki/Constrained_Application_Protocol

http://coap.technology/](http://coap.technology/

CoAP (Constrained Application protocol) is an application layer protocol intended for use in resource constrained environments like in low power electronic devices and other electrical appliances which need to be able to send and receive instructions remotely.

CoAP is a good candidate to build a IoT (Internet of Things) framework to help devices talk to remote application or servers.

Californium is a Java Library which can be used to setup API endpoints in your application which operate using the Constrained Application Protocol.

Jmeter-coap-Sampler is a Jmeter plugin which can be used for Automation testing or Load testing your API endpoints implemented in CoAP.

There are separate samplers to test DTLS endpoints and non DTLS endpoints.

Pre-requisite

1. Java 7
2. Maven 2.x+
3. Jmeter 2.10+

Installation Instructions:

1. Get the code.
2. Execute the following maven code

mvn dependency:copy-dependencies install -DexcludeGroupIds=org.apache.jmeter

1. Copy the following jars from target/dependency to /jmeter_install_path/lib

2. californium-core-1.0.0-SNAPSHOT.jar
3. scandium-1.0.0-SNAPSHOT.jar

4. element-connector-1.0.0-SNAPSHOT.jar

5. Execute the following maven code

mvn clean package 

1. Copy the following jar from target/ to /jmeter_install_path/lib/ext

2. jmeter-coap-sampler-1.0.0.jar

Using the Sampler

1. Open JMeter.
2. Add a new Thread Group.
3. Right click on the Thread Group -> Add -> Sampler -> Java Request
4. Choose the Java Request from the navigation panel.

5. Click on the ‘classname’ drop down and choose between

   1 2	org.jmeter.plugin.CoapDtlsConnectionSampler org.jmeter.plugin.CoapConnectionSampler

Screenshots

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