Distributed Key-Value Database

The following repository contains a simple distributed key-value database

Features

• Load Balancing - Utilizes Consistent Hashing
• Data Replication Mechanism - Data is lazily replicated on two other servers for every write request (Given 3 servers running)
• Graceful Server Failure Recovery - Data is automatically recovered in the case of server crashes
• HTTP Server - Running regex query operations for fetching/inserting/modifying key-value pairs

Refer to the linked design documents in the releases for an in-depth look into the performance and functionality of the database.

Client Communication API

connect <address> <port> - Eastablish a TCP connection to the storage server
disconnect- Disconnect from the connected server
put <key> <value> :

• Insert key-value pair into the storage system
• Update (overwrite) key-value pair into the storage system if the given key already exists
• Delete key-value pair if the <value> is null

get <key> - Retrieves given key from storage system
logLevel <level> - Sets log level for insepcting commands
help- Displays all commands available
quit - Tear down active connection and exit client program

Single Server Response

Request	Result	Response
put <key> <value>	Tuple Inserted	PUT_SUCCESS<key,value>
put <key> <value>	Tuple Updated	PUT_UPDATE<key,value>
put <key> <value>	Unable to Insert Tuple	PUT_ERROR<key,value>
put <key> <null>	Deleted Tuple	DELETE_SUCCESS<key,value>
put <key> <null>	Unable to Delete Tuple	DELETE_ERROR<key,value>
get <key>	Tuple Found	GET_SUCCESS<key,value>
get <key>	Tuple not Found	GET_ERROR<key,value>

Server Controller API - ECS

Responsible for adding/removing/stopping/starting servers in your distributed database

• addNodes <numberOfNodes> - Initializes the specified number of servers inserting them into a queue to be started
• start - Starts all initialized servers within the queue
• stop - Stops all servers currently running
• shutdown - Shutdown all servers currently running
• removeNode - removes a random server that is currently running

HTTP Server API (Executing Regex Query Expressions)

Find details on the the Regex API specifications here

Build/Run Instructions

Pre-requisites

• Java
• Ant
• Apache Zookeeper

Building the application

ant - Builds the project generating 4 jar files

• m4-client.jar
• m4-ecs.jar
• m4-http.jar
• m4-server.jar

Running the Client interface

java -jar m4-client.jar - Starts the terminal client interface

Running the ECS Contoller

1. Before starting ECS, you must ensure an instance of apache zookeeper is running. This can be done by navigating to the apache-zookeeper folder and running bin/zkServer.sh start

• You can stop apache-zookeeper by running the corresponding command: bin/zkServer.sh stop

2. Create a file called ecs.config which contains a list of: <server_name> <host> <port>
3. java -jar m4-ecs.jar ecs.config <apache-zookeeper port> - Note there is a default value provided for <apache-zookeeper port> and does not need to be provided

Running the HTTP Server

java -jar m4-server.jar <host> <port> - Starts the HTTP Server at the specified <host> <port>