Exchange rate API

GET /rate - get USD to UAH exchange rate

POST /subscribe - subscribe to exchange rate update (send application/x-www-form-urlencoded email address)

POST /unsubscribe - delete exchange rate subscription (send application/x-www-form-urlencoded email address)

Running application

Edit docker-compose.yml file and put your SMTP credentials, to be able to send updates to subscribers

To start http server and PostgreSQL service run: - docker compose up

Metrics

Application (each service at :8080/metrics in Prometheus format) exposes different metrics such as:

• total_email_sent
• customers_created_total{success=true|false}
• requests_total{method, path, status}
• total_subscribers{success=true|false}
• total_unsubscribers{success=true|false}

And other go_* and process_* metrics

To create metrics dashboards and view graphical representation go to localhost:3000 (Grafana)

Alerts

• total_subscribers{success=true} != customers_created_total{success=true} (Error in interservice communication, SAGA does not work)
• Anomaly rising of total_unsubscribers metric
• go_max_fd - go_total_fd < 100 (Small amount of open free file descriptors, connections leaks)
• total_email_sent < total_subscribers - total_unsubsribers (Not all emails were sent)

Architecture

Tests

To run unit tests for whole applicaton run go test -short ./... Run go test ./... to run all tests, including integration ones (require docker installed on your system)

TODO

• Graceful server shutdown
• SSL encryption
• Parallel emails sending