Using Radicale as read-only CalDAV proxy into third-party system via their API

[zimage]

We use a third-party service management system (ServiceNow) that allows users to create a calendar report (i.e. show all scheduled change tickets on a calendar), but doesn't allow ical or CalDAV access to that report. I am looking for a solution that will do the heavy lifting of doing the CalDAV piece, while I can use my knowledge to query the other system's API to return the calendar items and integrate this into the CalDAV front-end. Is this a use case that I could use Radicale for without a ton of refactoring?

[pbiering]

I assume the API queries towards ServiceNow are costly and change rate is not that high. Have you considered creating a cron job which pulls on regular basis ICS from ServiceNow and store them into Radicale's appropiate collection folder either as single items or one item containing all events? Even calling PUT from a trusted authenticated client can potentially do this upload.
In case of "single ICS" files you have to consider the sync-with-delete somehow - potentially by storing into a shadow collection which is wiped before and then run a rsync with delete job.

The async way would automatically introduce some kind of caching.

Automatic sync call of the API on each request I would not consider...because then one need also to program a caching layer.

[pbiering]

Another hint, as you have anyhow pull and process the events from ServiceNow you can generate an ICS all-in-one file and serve it as webcal by storing on a webserver (similar to the public holiday ICS services) + adding authentication requirement in webserver configuration.

Let user add the webcal URL into their calendar, then the events should be pulled (and synced therefore on every refresh) - No real need to have Radicale involved here.