Why You Get Connect Econnrefused Azure Error in Azure Functions

You're experiencing the dreaded ECONNREFUSED Azure error in your Azure Functions, huh? This error can be frustrating, especially when you're not sure what's causing it.

The ECONNREFUSED error typically occurs when a client (in this case, your Azure Function) attempts to connect to a server (like a database or API) but the server is not listening on the specified port.

This error can happen when the server is down, not configured correctly, or simply not available. A common scenario is when an Azure Function tries to connect to a database that's not configured to accept connections from the function's host.

Azure Functions rely on a connection to a server to perform tasks, so if that connection is refused, the function will fail with an ECONNREFUSED error.

Azure Functions Troubleshooting can be a real challenge.

If you're experiencing a "connect ECONNREFUSED 127.0.0.1:9091" error when running Azure Functions with VS Code, it's likely a network issue.

VS Code not opening a terminal displaying "Executing task [...]" is a red flag.

You can still browse the extension marketplace and run "pip install" within the terminal in VS Code.

HTTP errors are a common issue when working with Azure, and understanding what they mean can help you troubleshoot and resolve the problem.

HTTP errors in the 500-599 range are typically thrown by an Application Gateway or Layer-7 Load balancer, indicating an issue accessing the backend.

These errors can be caused by a lack of healthy backend instances, where the gateway cannot proceed with the request.

It's also possible that the backend is another load balancer throwing an HTTP 5xx error itself, in which case the problem lies downstream.

The Application Gateway may have lost network connectivity towards backend servers or a Firewall is blocking it, resulting in an HTTP error.

A proper health probe configuration is crucial to ensure the backend server is healthy and can respond to requests.

Here are some possible causes of HTTP errors in Azure:

If the connection is timing out, it's likely a network issue, possibly due to a Firewall (NSG) blocking connectivity. You can run a TCP connectivity test to rule out application layer issues.

A connection troubleshoot can help identify configuration issues impacting reachability and provide hop-by-hop paths from source to destination. This functionality requires the Network Watcher extension to be installed on your Virtual Machines.

Connection pool timeouts can occur if many users access your app simultaneously or if you send a large number of queries in parallel. If you experience connection pool timeouts, you can tune the connection_limit and pool_timeout parameters.

Some troubleshooting tools are available to help investigate connectivity issues under the “Network Watcher” resource in the Azure Portal. These tools can help identify network issues and provide a comprehensive troubleshooting analysis for a connection.

If telnet from one VM to another works, but telnet from a pool member VM to the internal load balancer's IP address times out, it's likely due to SNAT not being offered by internal load balancer configurations.