OpenTelemetry Python Lab

A FastAPI application with Celery workers using RabbitMQ for task queuing.

Features

• FastAPI Server with three endpoints:

  • GET / - Returns "Hello World"
  • GET /long-process - Simulates a long-running process (5 seconds)
  • POST /worker - Sends a number to Celery worker via RabbitMQ

• Celery Worker that processes numbers from RabbitMQ and prints "hello {number}"

Prerequisites

• Python 3.11+ (currently using Python 3.12)
• Docker and Docker Compose
• Virtual environment (already configured)

Setup Instructions

1. Start Infrastructure Services

Start RabbitMQ and Redis using Docker Compose:

docker-compose up -d

This will start:

• RabbitMQ on port 5672 (Management UI on port 15672)
• Redis on port 6379

2. Install Dependencies

Dependencies are already installed in the virtual environment, but if needed:

pip install -r requirements.txt

3. Start the Celery Worker

In one terminal, start the Celery worker:

celery -A worker worker --loglevel=info

4. Start the FastAPI Server

In another terminal, start the FastAPI server:

uvicorn app:app --reload --host 0.0.0.0 --port 8000

Or run directly:

python app.py

API Endpoints

GET /

Returns a simple "Hello World" message.

Example:

curl http://localhost:8000/

Response:

{
  "message": "Hello World"
}

GET /long-process

Simulates a long-running process that takes 5 seconds to complete.

Example:

curl http://localhost:8000/long-process

Response:

{
  "message": "Long process completed after 5 seconds"
}

POST /worker

Sends a number to the Celery worker via RabbitMQ. The worker will print "hello {number}".

Example:

curl -X POST http://localhost:8000/worker \
  -H "Content-Type: application/json" \
  -d '{"number": 42}'

Response:

{
  "message": "Task sent to worker with number: 42",
  "task_id": "12345678-1234-1234-1234-123456789012"
}

Monitoring

• RabbitMQ Management UI: http://localhost:15672 (guest/guest)
• FastAPI Docs: http://localhost:8000/docs
• FastAPI ReDoc: http://localhost:8000/redoc

Project Structure

.
├── app.py              # FastAPI application
├── worker.py           # Celery worker
├── requirements.txt    # Python dependencies
├── docker-compose.yml  # Docker services (RabbitMQ, Redis)
└── README.md          # This file

Stopping Services

To stop all services:

# Stop FastAPI and Celery worker (Ctrl+C in their terminals)
# Stop Docker services
docker-compose down

Troubleshooting

1. Connection refused errors: Make sure RabbitMQ and Redis are running via Docker Compose
2. Port conflicts: Check if ports 5672, 6379, 8000, or 15672 are already in use
3. Worker not receiving tasks: Ensure the Celery worker is running and connected to RabbitMQ