Returns the internal HTTP base URL for a given plugin, without a trailing slash.
The returned URL should point to an internal endpoint for the plugin, with the shortest route possible. The URL should be used for service-to-service communication within a Backstage backend deployment.
This method must always be called just before making each request, as opposed to fetching the URL once when constructing an API client. That is to ensure that more flexible routing patterns can be supported where a different result might be returned each time.
For example, asking for the URL for catalog may return something
like http://10.1.2.3/api/catalog
Returns the external HTTP base backend URL for a given plugin, without a trailing slash.
The returned URL should point to an external endpoint for the plugin, such that it is reachable from the Backstage frontend and other external services. The returned URL should be usable for example as a callback / webhook URL.
The returned URL should be stable and in general not change unless other static or external configuration is changed. Changes should not come as a surprise to an operator of the Backstage backend.
For example, asking for the URL for catalog may return something
like https://backstage.example.com/api/catalog
The DiscoveryService is used to provide a mechanism for backend plugins to discover the endpoints for itself or other backend plugins.
See the service documentation for more details.
Remarks
The purpose of the discovery API is to allow for many different deployment setups and routing methods through a central configuration, instead of letting each individual plugin manage that configuration.
Implementations of the discovery API can be as simple as a URL pattern using the pluginId, but could also have overrides for individual plugins, or query a separate discovery service.