JustinDB

Distributed Key-Value Storage built on top of Scala/Akka

JustinDB KV is an eventually consistent key-value database that favours write availability. It’s a faithful implementation of Amazon’s Dynamo, with advanced features such as vector clocks for conflict resolution. JustinDB is also fault-tolerant. Servers can go up or down at any moment with no single point of failure.

➜  JustinDB git:(master) ✗ docker exec -it justindb /bin/bash
   ___              _    _        ______ ______
  |_  |            | |  (_)       |  _  \| ___ \
    | | _   _  ___ | |_  _  _ __  | | | || |_/ /
    | || | | |/ __|| __|| || '_ \ | | | || ___ \
/\__/ /| |_| |\__ \| |_ | || | | || |/ / | |_/ /
\____/  \__,_||___/ \__||_||_| |_||___/  \____/

Cli:
    cli help
More documentation available at:
    https://github.com/speedcom/JustinDB
    https://speedcom.github.io/

Summary of techniques

Problem	Technique	Advantage
Partitioning	Consistent Hashing	Incremental Scalability
Membership and failure detection	Gossip-based membership protocol and failure detection	Preserves symmetry and avoids having a centralized registry for storing membership and node liveness information
High Availability for writes	Vector clocks with reconciliation during reads	Version size is decoupled from update rites
Recovering from permanent failures	Anti-entropy using Merkle trees	Synchronizes divergent replicas in the background

Why akka

Its a toolkit and runtime for building highly concurrent applications which comes with ideas that have been around from some time - actor model. Besides that it has many welcome features around clustering:

1. load balancing
2. location transparency
3. self maintenance
4. fault tolerance

Authentication, authorization, validation

In case it's not obvious, Justin performs no authentication, authorization, or any validation of input data. Clients must implement those things themselves.

System Requirements

JustinDB works with Java 8 and newer.

Bunch of posts about JustinDB

1. JustinDB - Modern REACTIVE NoSQL database
2. JustinDB - Database Model
3. JustinDB - Pluggable persistent and in-memory storage engines
4. JustinDB - More than 700 commits!
5. JustinDB - Serialization that greatly improves performance
6. JustinDB - Replication and Partitioning
7. JustinDB - Why Scala and Akka?
8. JustinDB - Data versioning: Vector Clocks
9. JustinDB - HTTP API
10. JustinDB - The Ring
11. JustinDB - Preference list
12. JustinDB - Solving data entropy: Read Repair
13. JustinDB - Solving data entropy: Active-Anti Entropy
14. JustinDB - Executable JAR
15. JustinDB - Multi-Datacenter Replication