Stock Price Listener System

This project implements a distributed stock price listener system using Elixir technologies such as GenServer, Agent, libcluster, and Phoenix.PubSub.

It also includes a stock price generator that simulates an external service sending price updates. When a price is received, it is propagated to all subscribed users in real time.

Features

• Users can subscribe and unsubscribe to individual stock tickers or all at once.
• Supports crash simulation to test fault tolerance and automatic recovery.
• On recovery, the system restores previous subscriptions.
• Distributed across multiple nodes using libcluster.

Available Stock Tickers

FB, AMZ, AAPL, NVDA, GOOG

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Getting Started

1. Install Dependencies

Install asdf and run:

asdf install

2. Start the Cluster

Open four terminal instances and run the following commands in each:

iex --name [email protected] -S mix
iex --name [email protected] -S mix
iex --name [email protected] -S mix
iex --name [email protected] -S mix

Ensure epmd is running and nodes can connect via Erlang distribution.

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Usage

Subscribe to Stock Tickers

StockPriceListenerClient.subscribe("AMZ")
StockPriceListenerClient.subscribe_all()

Unsubscribe from Stock Tickers

StockPriceListenerClient.unsubscribe("GOOG")
StockPriceListenerClient.unsubscribe_all()

Start the Price Generator

{:ok, pid} = GenServer.start(StockPriceGenerator, 5000)
# The number is the update interval in milliseconds

Stop the Generator

GenServer.stop(pid)

Simulate a Crash

StockPriceListenerServer.crash()

At least one user must be subscribed to "AMZ" for the crash to be meaningful.

Manually Broadcast a Stock Price

Phoenix.PubSub.broadcast(StockPriceListener.PubSub, "AAPL", {"AAPL", 31245})

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Notes

• The system demonstrates how to build a resilient Elixir application that can handle failures and recover gracefully.
• Useful for learning supervision trees, clustering, process recovery, and real-time messaging.