Added troubleshooting guide for Application Bad Gateway - Closes #199

Author: ShadowArcanist

docs/.vitepress/config.mts

@@ -519,6 +519,13 @@ export default defineConfig({
         collapsed: true,
         items: [
           { text: 'Overview', link: '/troubleshoot/overview' },
+          {
+            text: 'Applications',
+            collapsed: true,
+            items: [
+              { text: 'Bad Gateway', link: '/troubleshoot/applications/bad-gateway.md' },
+            ]
+          },
           {
             text: 'Dashboard',
             collapsed: true,

docs/public/images/troubleshoot/applications/bad-gateway/1.webp

@@ -0,0 +1,46 @@
+---
+title: Bad Gateway Error 
+---
+
+# Bad Gateway Error  
+If your deployed application works when you access it via your server’s IP address and port but shows a **Bad Gateway** error on your domain, the issue is most often due to misconfigured port settings, incorrect host mapping, or your app listening only on localhost.
+
+
+## Symptoms 
+- The application is accessible via the server IP with a port but not via the domain.  
+- You might also run into a **No Available Server** error.
+
+
+## Diagnosis
+- **Port Configuration:** Check the port your application is listening on and see if the correct port is entered in the **Port Expose** field on the Coolify dashboard.  
+
+- **Host Mapping:** Check if the application’s port is mapped to the host system.
+
+- **Listening Address:** Check if the app is only listening to `localhost` inside the container.
+
+- **Domain Port Inclusion:** Check your domain URL has a port number at the end.
+
+- **Container Status:** Check the status of the container where your app is running (Is it unhealthy? Stuck at Starting?).
+
+
+## Solution
+- **Update Port Settings:** Enter the correct port number in the **Port Expose** field on the Coolify dashboard and restart your app.  
+    
+    <ZoomableImage src="/docs/images/troubleshoot/applications/bad-gateway/1.webp" />
+- **Remove Host Port Mapping:** If the port is mapped to the host system, remove the mapping so the proxy can route traffic correctly, then restart your app.  
+    
+    <ZoomableImage src="/docs/images/troubleshoot/applications/bad-gateway/2.webp" />
+- **Adjust Listening Address:** Change your application so it listens on all network interfaces (`0.0.0.0`) instead of just `localhost`.  
+
+    <ZoomableImage src="/docs/images/troubleshoot/applications/bad-gateway/3.webp" />
+- **Correct Domain URL:** Add the correct port number at the end of your domain URL if needed, and restart your application.
+
+    <ZoomableImage src="/docs/images/troubleshoot/applications/bad-gateway/4.webp" />
+- **Restart Container / Check Logs:** Try restarting the container to see if it fixes the issue, or check the container logs to find out what's causing it to be unhealthy. 
+    - Often, a failing health check might be the problem, and removing the health check could fix it.
+   
+       <ZoomableImage src="/docs/images/troubleshoot/applications/bad-gateway/5.webp" />
+
+
+## Support
+If these steps don’t solve the issue, consider reaching out for further assistance by joining our [Discord community ↗](https://coolify.io/discord) and sharing your app logs, coolify proxy logs, configuration screenshots, and details of the troubleshooting steps you’ve already tried.