Concurrent replicated transaction key-value store

Overview

This is a project developed within the course of Design and Implementation of Distributed Applications (DIDA) at Instituto Superior Técnico, University of Lisbon. The project consists of a replicated consistent key-value store that uses the Vertical Paxos algorithm to ensure fault tolerance and flexibility of reconfiguration.

The system is composed of a set of servers that replicate the state of the key-value store and a client that issues transactions to the servers. The client can read and write keys in the key-value store, and the servers ensure that all transactions are executed in a linearizable order. The system is also able to reconfigure itself by adding or removing servers, and the servers can elect a leader to coordinate the reconfiguration process.

For simplicity, the current implementation assumes that there is one single client and 5 servers and all modules run on the same physical machine. Moreover, each server, as well as the client, knows the address of all other servers.

Co-authors: Daniela Camarinha & Joana Matias and special thanks to Mestre André for the blessing 🙏.

Table of contents

• Getting started
• Building
• Deployment
  • Servers
  • Client
  • ConsoleClient
  • Server coordination master
• Usage
• Feedback
• License

Getting started

This project requires Java 22+ and Maven 3.9.x to be installed on your machine to build and run the project.

Building

To build the project, run the following command in the root directory:

mvn clean install

Maven will download all dependencies and compile the project.

Deployment

The project is composed of four main components, please deploy them in the following order:

Note: For Windows machines, we have a script that automatically launches all components. Run the following command in the root directory:

./run.bat

Servers

The servers run the base implementation. They are executed running the following command in the server directory:

mvn exec:java -D exec.args="8080 {id}"

Note: On Windows, it is necessary to use mvn exec:java -D "exec.args"="8080 {id}" instead.

Where you must fill in the following argument:

• {id}: Sequential id of the server. Current implementation requires servers to be ID'ed starting from 0 to 4 servers.

Client

A client that executes transactions. It is executed by running the following command in the client directory:

mvn exec:java

ConsoleClient

The debug console to control the servers. It is executed by running the following command in the consoleclient directory:

mvn exec:java

Server coordination master

The master module is the Master in Vertical Paxos. It is executed by running the following command in the master directory:

mvn exec:java

Usage

The client module opens a terminal from where students may issue commands. The following commands are available:

• help - Shows the full command list;
• read {read_key} - Reads a key (useful for debug);
• tx {read_key_1} {read_key_2} {write_key} - Takes as input 3 keys and executes a transaction with 2 reads and 1 write respectively;
• loop - Runs multiple transactions, one after another, in a loop, defined by the following parameters;
• lenght {loop-lenght} - Defines the number of transactions executed when looping;
• time {sleep-range} - Slows down transactions by sleeping a random amount of time in sleep-range between reads and commit;
• exit - Gracefully finishes the client.

The console client opens a terminal from where students may issue configuration changes to servers. The following commands are available:

• help - Shows the full command list;
• leader on {server_id} - Instructs a server to start acting as a Paxos leader;
• debug {mode} {server_id} - Activates debug on a given server;
• reconfig {configuration} - Executes a transaction on key 0 to change the configuration;
• reconfleader {leader_id} {configuration} - Activates the leader with the given id and changes the configuration;
• exit - Gracefully finishes the console.

Feedback

For any questions or feedback, please feel free to reach out to me at wangxiting01917@gmail.com.

License

This project is licensed under the MIT License - see the LICENSE file for details.