🚀 Resolving Azure App Service Connectivity Issues with Supabase PostgreSQL

Recently, I faced an interesting connectivity issue while deploying a .NET Core application hosted on Azure App Service, trying to connect to a Supabase PostgreSQL database. While the app worked fine locally, it failed when deployed to Azure. Here's how I identified the problem and fixed it.

🔍 The Problem

My application was using this PostgreSQL connection string:

Host=db.zovrkyywxdlnkqglddaz.supabase.co;Port=5432;Database=postgres;Username=****;Password=****;Ssl Mode=Require;Trust Server Certificate=true

Locally, everything worked perfectly. But once deployed to Azure App Service, the application failed to connect, throwing errors such as:

No such host is known: Error Log

fail: Microsoft.EntityFrameworkCore.Database.Connection[20004] An error occurred using the connection to database 'postgres' on server 'tcp://db.zovrkyywxdlnkqglddaz.supabase.co:5432'.

fail: Microsoft.EntityFrameworkCore.Query[10100] An exception occurred while iterating over the results of a query for context type 'sdonboarding.Server.Models.SalesManagementContext'.

System.Net.Sockets.SocketException (11004): The requested name is valid, but no data of the requested type was found. at System.Net.NameResolutionPal.ProcessResult(SocketError errorCode, GetAddrInfoExContext* context) at System.Net.NameResolutionPal.GetAddressInfoExCallback(Int32 error, Int32 bytes, NativeOverlapped* overlapped) --- End of stack trace from previous location ---

🧪 Investigation Steps

1. Log Setup: Since I was using Free tier and I did not get anything even after enabling the logs via App Service Logs in Azure. I was not clear what was wrong. I was using Deployment Center and had configured GitHub workflow for continuous deployment. So I did below things to see the logs:

   1. In the .yml file add below code after dotnet publish to get the logs at C:\home\site\wwwroot\logs:

      • name: Enable stdout logging in generated web.config run: | $configPath = ".\publish_output\web.config" (Get-Content $configPath) -replace 'stdoutLogEnabled="false"', 'stdoutLogEnabled="true"' | Set-Content $configPath

   2. Doing this will put stdoutLogEnabled\=”true” in web.config before deploying.

   3. You will be able to check the logs now as I have given in the problem section.

2. In Azure App Service search Advanced Tools(kudu) => Debug console.

3. In the kudu console do Using nslookup, I discovered the database resolved to an IPv6 address:

   nslookup db.zovrkyywxxdlnkqglddaz.supabase.co

   1. *** UnKnown can't find db.zovrkyywxxdlnkqglddaz.supabase.co: Non-existent domain

      Server: UnKnown

      Address: 168.63.125.16

Root Cause

The original Direct Connection hostname (db.zovrkyywxdlnkqglddaz.supabase.co) did not resolve to a valid IPv4 address, and Azure App Service only supports outbound IPv4. This means that:

• From within Azure, the app could not reach the database — DNS resolution succeeded (AAAA), but there was no routable IPv4 (A) address.

• Even though your local machine could connect (supporting both IPv4 and IPv6), Azure could not — resulting in errors like:

  System.Net.Sockets.SocketException (11004): The requested name is valid, but no data of the requested type was found.

✅ The Fix

Supabase provides a session pooler endpoint (e.g., aws-0-ap-southeast-2.pooler.supabase.com) that:

• Is designed for better compatibility, especially in IPv4-only environments

• Exposes a public IPv4 address that Azure App Service can connect to

• Supabase => Project Settings => Database => Connect => Session pooler

When I updated the connection string to use this session pooler hostname, Username, Password remians same, DNS resolution succeeded with an IPv4 address, and the app connected successfully.