Minimal Raft Implementation

Implemtation of Raft consensus algorithm in JavaScript.

How to run

1. Environment: Open the project in n terminal windows, where n is the number of nodes in the system.
2. Execution: In each of n terminal windows, run node index.js [n] [m] where n is the total nodes and m is the current node id.
3. Communication: Upon reaching consensus, the system is ready for interaction via RESTful endpoints:

• Execute: localhost:300[m]/ where m is the id of the leader, used to give new command to execute and store.
• Retrieve: localhost:300[m]/log where m can be any node, used to retrieve the current state of the system.

Quick Demo [MacOS only]

1. Open project in terminal, set node.js 21 environment (if needed, nvm use 21 for Node Version Manager)
2. run ./raft_demo.sh 3 to launch 3 nodes. Find out the id of current leader from launched terminal windows.
3. Use Postman or any API testing tool to issue commands and retrive state.
4. You may simulate a node failure by using the localhost:300[m]/kill endpoint to kill the node with id = m.

Consensus Algorithms Overview

Consensus algorithms are protocols used in distributed systems to achieve agreement on a single data value among distributed processes or systems. This is crucial for ensuring consistency and reliability in environments where multiple nodes or machines must work together.

Basic Concepts

• Nodes: Independent processes or machines that participate in the consensus.
• Proposals: Values that nodes suggest to be agreed upon.
• Quorum: The minimum number of nodes that must agree for the decision to be valid.
• Fault Tolerance: The ability of the system to continue functioning correctly even when some nodes fail or act maliciously.

Common Steps in Consensus Algorithms

1. Propose: Nodes propose values to be agreed upon.
2. Vote: Nodes vote on the proposed values.
3. Decision: Once a quorum is reached, the decision is made.
4. Broadcast: The agreed-upon value is broadcast to all nodes.

Important Properties

• Consistency: All nodes agree on the same value.
• Availability: The system can continue to operate even if some nodes fail.
• Partition Tolerance: The system can handle network partitions where some nodes cannot communicate.

Applications

• Blockchain: Ensures all nodes in the network agree on the state of the ledger.
• Distributed Databases: Ensures data consistency across different nodes.
• Fault-Tolerant Systems: Provides reliability and availability in critical systems.