The error connection refused typically occurs when the MongoDB server is not running or is not accessible at the URL specified in the connection string. Here are a few common causes:
Incorrect Connection URL: Make sure the URL specified in the MONGODB_CONNECTION_URL environment variable is correct and reachable.
MongoDB Server Not Running: Verify that the MongoDB server is running and accessible on the network. You can do this by using the mongo command in the terminal to connect to the database.
Firewall Blocking the Connection: If the MongoDB server is running on a different machine, make sure the firewall on that machine is not blocking the connection. You can check the firewall rules and allow incoming connections on the MongoDB port (27017 by default).
Network Configuration: If the MongoDB server and the client are on different networks, make sure that the network configuration allows connections between the two.
Try resolving these issues and see if the error persists. If the error continues, try updating the MongoDB driver version or checking the MongoDB logs for more information.