Forex Exchange Rate API with Prometheus & Grafana

This project is a Go-based Forex exchange rate service with real-time metrics exposed via Prometheus and visualized in Grafana.
It supports retrieving the latest rates, historical data, and currency conversions.

Features

• REST API for:
  • Latest Forex rates
  • Historical Forex rates over a time range
  • Currency conversion
• Metrics for:
  • Request counts
  • Error counts
  • Request duration histograms
• Dockerized deployment for:
  • Go API
  • Prometheus
  • Grafana
  • Redis
• Configurable via .env file

---

Project Structure

.
├── cache/                   # In-memory caching
├── cmd/                     # Application entry point
├── handlers/                # HTTP request handlers
├── metrics/                 # Prometheus metrics definitions
├── models/                  # Data models
├── services/                # Business logic & integrations
├── prometheus.yml           # Prometheus configuration
├── docker-compose.yml       # Orchestrates services
├── dockerfile               # Builds the Go app
├── go.mod / go.sum          # Go module dependencies
├── .env                     # Set environment variables
└── .gitignore               # Git ignore rules

Setup & Installation

1. Clone the repository

git clone https://github.com/Radheshg04/GreedyGame.git
cd GreedyGame

2. Configure environment variables

Create a .env file in the project root with the required variables:

EXCHANGE_RATE_API_KEY="FOREX_API_KEY"
EXCHANGE_HOST_API_KEY="FALLBACK_API_KEY"

Where to get them:

• Sign up for a free account at ExchangeRate API here. Get an API key from the dashboard after signing in.

• For the fallback API, register at ExchangeRates.host here.

Paste the obtained keys into the .env file in the project root.

3. Build and start the containers

docker compose up --build

This will start:

Go API (port 8080)

Prometheus (port 9090)

Grafana (port 3000)

Redis (port 6379)

4. Access the services

• API: http://localhost:8080
• Prometheus: http://localhost:9090
• Grafana: http://localhost:3000 (login: admin / pass: admin)

---

Monitoring & Metrics

Prometheus

Prometheus scrapes metrics from the Go service at:

http://go_app:2112/metrics

Grafana

1. Open Grafana at http://localhost:3000.
2. Add Prometheus as a data source:
   • URL: http://prometheus:9090
   • Access: Server
3. Import dashboards or create custom ones.

---

API Endpoints

Method	Endpoint	Query Parameters	Description
GET	/rates/latest	None	Get the latest exchange rates for all supported currencies.
GET	/rates/historical	currency1 (string) — Base currency currency2 (string) — Target currency from (YYYY-MM-DD) — Start date to (YYYY-MM-DD) — End date	Get historical exchange rates for a currency pair over a specified time range.
GET	/convert	from (string) — Base currency to (string) — Target currency date (YYYY-MM-DD, optional) — Historical date	Convert between currencies. If date is provided, returns the historical conversion rate; otherwise, returns the current rate.

Assumptions

• Supports only: USD, INR, EUR, JPY, GBP.
• Latest rates are refreshed every 1 hour and cached in memory to reduce API calls.
• Fallback API is used only when the primary API fails.
• Historical data is only available for the last 90 days. Requests beyond that return an error.

Example Requests

Get Latest Rates

curl -X GET 'http://localhost:8080/rates/latest'

Expected Output:

{
  "EUR": 0.85529477,
  "GBP": 0.73664008,
  "INR": 87.54853587,
  "JPY": 146.63268885,
  "USD": 1
}

Convert Currencies (Current)

curl -X GET 'http://localhost:8080/convert?from=USD&to=INR'

Expected Output:

{
  "amount": 87.54853587
}

Convert Currencies (Historical)

curl -X GET 'http://localhost:8080/convert?from=USD&to=INR&date=2025-08-10'

Expected Output:

{
  "amount": 87.6119484
}

Get Historical Rates

curl -X GET 'http://localhost:8080/rates/historical?currency1=USD&currency2=INR&from=2025-08-10&to=2025-08-14'

Expected Output:

{
  "conversion rates": [
    87.6119484,
    87.66770623,
    87.67856445,
    87.68494592,
    87.54853587
  ]
}

Bonus

• Integrated Prometheus metrics and Grafana dashboards for real-time monitoring.

To import the provided dashboard:

1. Go to Grafana → Dashboards → Import
2. Upload `grafana-dashboard.json` from 'examples' folder in this repo.
3. Select the Prometheus data source and click Import.

Stopping the services

docker compose down