Brain Code 2017 — JaVers meets DynamoDB hackathon

Your goal is to write JaversRepository for Amazon DynamoDB

If you succeeded, your code will be merged to JaVers master and released.
Thousands of JaVers users will be able to use DynamoDB with JaVers. This could be your first open source contribution. Awesome!

Intro

Amazon DynamoDB is a NoSQL database with a ColumnFamily data model, similar to Cassandra.

JaVers is an open source Java library for domain objects auditing. JaVers captures snapshots of domain objects (Entities) and persists them in a dedicated storage, called JaversRepository. Having some snapshots saved in a JaversRepository, it's easy to browse objects' history and check how they looked like in the past. See examples.

So far, JaVers provides two implementations of JaversRepository:

• SqlRepository,
• MongoRepository.

Our goal is to create the new implementation for DynamoDB.

Getting Started

DynamoDB

Firts, try to set up your DynamoDB. It's easier to start with DynamoDB running locally.

When you run it locally, launch Razor SQL and:

• type anything as AWS Access Key and AWS Secret Key
• set Max Results per Query to 1000

Create hello_world table with hash attribute my_id.

Run a few queries using unofficial, SQL-like, query language for DynamoDB, created by Razor.

Insert an item with String attribute:

insert into hello_world (my_id, my_text_col) values ('hello', 'world')

Insert another item with Number attribute:

insert into hello_world (my_id, my_int_col) values ('another', 5)

Select all items:

select * from hello_world

As you can see, item attributes are added dynamically.

See:

• Introduction to DynamoDB Concepts
• Getting Started - Java
• Data Types
• DynamoDB Documentation

JaVers development

Checkout our github repository:

git clone https://github.com/javers/javers.git
cd javers

Checkout the dynamoDb branch:

git checkout dynamoDb

Build & test

./gradlew test

Run integration test for DynamoDB:

./gradlew javers-persistence-dynamodb:integrationTest

DynamoDbSmokeTest should be green. DynamoRepositoryE2ETest should be red since DynamoRepository is not implemented yet.

Your task

Your task is to make all tests green.

• Fork the JaVers repository to dedicated space provided by BrainCode mentors.
• Implement DynamoRepository.
• Work in a team? That's great, but don't push the whole team work at once. We want to see individual commits of each team member.
• Create a pull request to dynamoDb branch in the javers repositorty.
• Make sure that CI is green, see travis-ci.org.
• Ask other attendee for the code review.

How we will evaluate your solution

• Code should be clean.
• End-to-end test is already there, but what about unit tests? Do we need them?
• Performance is the key. How you measure it? Provide performance tests and runtime statistics for various types of JaVers queries.
• Data model in DynamoDB should be well designed. Take a look how we designed database schemas for MongoDB and SQL.

Required tools

• Java8
• Git
• DynamoDB Downloadable Version or DynamoDB Web Service (as a part of AWS’s Free Tier).
• recommended IDE for Java: IntelliJ IDEA
  
• recommended GUI for DynamoDB: Razor SQL