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06 - Linking Apps Internally
We often need to connect individual apps together, for example: Sonarr and SABnzbd. This means we first need to know how to reach those Apps.
Linking Apps Internally
The backend for TrueNAS SCALE Apps is Kubernetes. Linking apps together in Kubernetes is done slightly differently than in other systems, as you can't point directly to other containers using their IP address.
Instead we need to use their internal(!) domain name. Please beware: this name is only available between Apps and can not be reached from the host/node or your own PC.
The format for internal domain name for the main service is explained bellow.
Please replace $NAME with the name you gave your App when installing and $APP with the name the app has on the catalog where is needed.
If your app has the same name as in the catalog, the format is as follows.
$NAME.ix-$NAME.svc.cluster.local
If your app has different name than in the catalog, the format is as follows
$NAME-$APP.ix-$NAME.svc.cluster.local
If you need to reach a different service (which is not often the case!), you need a slightly different format, where $SVCNAME is the name of the service you want to reach:
If your app has the same name as in the catalog, the format is as follows.
$NAME-$SVCNAME.ix-$NAME.svc.cluster.local
If your app has different name than in the catalog, the format is as follows
$NAME-$APPNAME-$SVCNAME.ix-$NAME.svc.cluster.local
Internal Domain Name generator
Example
To reach an app named "sabnzbd" (same name as the catalog app name) within Sonarr, we can use the following internal domain name:
sabnzbd.ix-sabnzbd.svc.cluster.localorsabnzbd.ix-sabnzbd
Video Guide
Additional Documentation
For more help troubleshooting DNS resolution in Kubernetes, review the official documentation: https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/