Doodle-like REST API backed by Cassandra, used for Fribourg's University Advanced Databases System Course

Homework

The goal of the exercice is to build a REST API that will be able to create a poll, subscribe to the poll and retrieve the subsciptions.

In REST notation:

Create a new poll

POST /rest/polls
{ "label": "Afterwork", "choices": [ "Monday", "Tuesday", "Friday" ], "email": "[email protected]" }

Returns pollId (in Location header)

Subscribe to the poll

PUT /rest/polls/<pollId>
{ "name": "Benoit", "choices": [ "Monday", "Friday" ] }

Returns the updated poll, JSON encoded (see below)

GET /rest/polls/<pollId>

Returns the poll, JSON encoded

{ "poll": { "label": "Afterwork", "choices": [ "Monday", "Tuesday", "Friday" ], "email": "[email protected]", "subscribers": [ { "name": "Benoit", "choices": [ "Monday", "Friday" ] }, ... ] } }

Proposed Data Model

Keyspace

create keyspace doodle 
	with placement_strategy = 'org.apache.cassandra.locator.SimpleStrategy' 
	and  strategy_options = {replication_factor:1};

Column Families

polls

create column family polls 
	with key_validation_class = UUIDType 
	and comparator = AsciiType
	and default_validation_class = UTF8Type
	and column_metadata = [
		{column_name: label, validation_class: UTF8Type}
		{column_name: email, validation_class: UTF8Type}
		{column_name: choices, validation_class: UTF8Type}
	];

set polls[timeuuid()]['choices'] = '[ "Monday", "Tuesday", "Friday" ]';
set polls['0488b290-c153-11e2-b652-c56eefd2b5e3']['label'] = 'Afterwork';
set polls['0488b290-c153-11e2-b652-c56eefd2b5e3']['email'] = '[email protected]';

• choices is a JSON encoded list of strings.
• Polls are not intended to change often so they are put in a dedicated CF where for instance row caching could be turned on.

subscribers

create column family subscribers
	with key_validation_class = UUIDType
	and comparator = 'CompositeType(TimeUUIDType,UTF8Type)'
	and default_validation_class = UTF8Type;

set subscribers['0488b290-c153-11e2-b652-c56eefd2b5e3']['709f7180-c153-11e2-b652-c56eefd2b5e3:Benoit'] = '[ "Monday", "Friday" ]';

• The row key is the same UUID than the poll's row key.
• The column name is a TimeUUID to order the subscriptions, concatenated with (using CompositeType) a the name of the subscriber in UTF8 string
• The value is a JSON encoded list of strings representing the subscribed choices. Note that if the poll's administateur change the choices of the poll, either all the values need to be updated, or (btter) the removed choices are skipped (not displayed) at runtime.

Implementation

The current implementation use Hector client as high level connection to Cassandra.