GitHub Repository: Shadab998/ds-2pc

Two-Phase Commit (2PC) – Distributed Chat System

This project implements the Two-Phase Commit (2PC) protocol to guarantee atomic distributed transactions for the CreateRoom operation across a microservices-based chat platform.

With 2PC, either all services commit, or all abort, ensuring strong consistency.

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🏗️ Architecture Overview

Coordinator

• Gateway Service
• Orchestrates:
  • Phase 1: Voting
  • Phase 2: Global Commit / Abort

Participants

Services that take part in the distributed transaction:

Service	Description
Room Service	Stateful participant (SQLite)
Auth Service	Stateless participant
Presence Service	Stateless participant
Message Service	Stateless participant

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🚀 Running the System

Everything needed to run 2PC is in the deployment/ directory.
No build step is required because all images are already on Docker Hub.

1. Start all services

From inside deployment/:

docker-compose up

This launches:

• gateway (Coordinator)
• room
• auth
• presence
• message
• ui

When services are ready, you will see logs such as:

room-svc on :50052
presence-svc on :50053
message-svc on :50054
auth-svc on :50051
gateway-svc on :50055

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🧪 Testing 2PC

A test client is provided to validate the distributed CreateRoom transaction.

Open a new terminal at the ds-2pc/deployment/tests, then run:

python test_client.py

✔ Expected Output (Commit Case)

--- Sending CreateRoom request for test-room-1763... ---
--- SUCCESS: Gateway confirmed transaction COMMIT ---

You can also observe the docker terminal for detailed logs of Vote Decision by each node.

❌ Expected Output (Abort Case)

If any participant votes NO or times out:

--- ABORT: Gateway confirmed transaction ABORT {error-message} ---

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🎯 What This Demonstrates

• Full 2-Phase Commit protocol
• Atomic distributed room creation
• Coordinator-driven commit/abort flow
• Real RPC calls between microservices
• Fault-tolerant behavior (participant unavailable → abort)