homer/docs/troubleshooting.md

Troubleshooting

My custom service card doesn't work, nothing appears or offline status is displayed (pi-hole, sonarr, ping, ...)

You might by facing a CORS (Cross Origin Request Sharing) issue. It happens when the targeted service is hosted on a different domain or port. Web browsers will not allow to fetch information from a different site without explicit permissions (the targeted service must include a special Access-Control-Allow-Origin: * HTTP headers). If this happens your web console (ctrl+shit+i or F12) will be filled with this kind of errors:

Access to fetch at 'https://<target-service>' from origin 'https://<homer>' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

To resolve this, you can either:

• Host all your target service under the same domain & port.
• Modify the target sever configuration so that the response of the server included following header- Access-Control-Allow-Origin: * (https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#simple_requests). It might be an option in the targeted service, otherwise depending on how the service is hosted, the proxy or web server can seamlessly add it.
• Use a cors proxy sever like cors-container, cors-anywhere or many others.