Azure App Service
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Getting 500 Internal Server Error on /admin-portal/landing via Azure Application Gateway (Next.js app)
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Vivin Kumar
0
Reputation points
Hi all,
I'm currently hosting a Next.js application behind Azure Application Gateway (App Gateway), and I'm facing a persistent issue where requests to:
http://
Azure App Service
{count} votes
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Prabhavathi Manchala 2,470 Reputation points Microsoft External Staff Moderator2025-06-25T09:06:15.4+00:00 Hi Vivin Kumar,
You're seeing a 500 Internal Server Error on
/admin-portal/landingwhen accessing your Next.js app through Azure Application Gateway. This usually points to an issue in the app itself, not the gateway.Common causes include missing
basePathinnext.config.jswhen hosting under a sub-path like/admin-portal, incorrect path forwarding by the gateway (e.g., sending/landinginstead), missing rewrite rules or headers needed for dynamic pages, or the backend being unhealthy, slow, or crashing.1). Update
next.config.jsin your Next.js AppIf your app is hosted under
/admin-portal, add:module.exports = { basePath: '/admin-portal', trailingSlash: true, // optional, if routing issues continue };Then, rebuild and redeploy the app.
2). Check Application Gateway Path-Based Routing Rules
Ensure that Azure Application Gateway is not stripping or incorrectly forwarding the
/admin-portalprefix, use a path rule like/admin-portal/*and avoid overriding or rewriting the path unless it's intentional.URL path-based routing in Azure Application Gateway
3). Enable Diagnostic Logs to Debug Further
Enable diagnostics on Azure Application Gateway to monitor backend status codes and request traces by navigating to Application Gateway -> Diagnostics Settings in the Azure Portal, enabling logging to Log Analytics or a Storage Account, and reviewing the
ApplicationGatewayAccessLogandApplicationGatewayPerformanceLog.Monitor Application Gateway with logs
4). Ensure Backend Health & Next.js API Routes Work
Test the route by accessing
https://<backend-hostname>/admin-portal/landingdirectly to see if it works or throws an error, and make sure server-side rendering isn't failing due to auth, database, or runtime issues.curl -i https://<backend-host>/admin-portal/landingOnce the routing configuration is aligned between your App Gateway and the Next.js
basePath, and you ensure that the route/admin-portal/landingis valid and working directly, the 500 error will be resolved. -
Vivin Kumar 0 Reputation points
2025-06-26T03:26:54.1833333+00:00 Hello Prabhavathi
Thanks for your response. We have the same code deployed for another site called 'Agent-Assist', which is accessible via `gateway-ip/Agent-Assist`. However, we are currently unable to access the 'Admin-Portal' site. -
Prabhavathi Manchala 2,470 Reputation points Microsoft External Staff Moderator
2025-06-26T10:49:11.0133333+00:00 Hi Vivin Kumar,
Since both
Agent-AssistandAdmin-Portaluse the same code and are behind the same Azure Application Gateway, but onlyAdmin-Portalshows a 500 error, it’s likely not a code issue. The problem is probably due to deployment or configuration differences.1). Double-check Path-Based Routing for Admin-Portal
Even though
Agent-Assistis working, it’s possible that the routing rule forAdmin-Portalis missing, misconfigured, or unintentionally rewriting the path.Please verify that your Application Gateway has a
path-based routing rulelike:Path: /admin-portal/* → Backend Pool: [Admin-Portal Backend App]Also, ensure that no rewrite rule is stripping
/admin-portalfrom the path, and that Admin-Portal is using the same backend pool as Agent-Assist, if applicable.2). Compare Deployment Slots or App Settings
If Agent-Assist and Admin-Portal are deployed to different Azure Web Apps or slots, check App Service -> Configuration for differences such as the
basePathinnext.config.js(which should be/admin-portal), environment variables likeNODE_ENVorNEXT_PUBLIC_*, and ensure the deployment source and last build version match, sometimes Admin-Portal may not have received the latest build properly.Deploying Next.js apps to Azure App Service
Since
Agent-Assistworks and both share the same base code, this almost certainly comes down to arouting rule mismatch, incorrect basePath, or astale/failed deploymenton the Admin-Portal backend.
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