Would be awesome to get this merged!

Without checking if this is already done: would be great if the code saved a snapshot of the most recently retrieved content for the config and targets, so that if the backend should be down, or someone uploaded a bad config, the checks still keep working.

Also: does this watch for changes and automatically reapplies, like with local files?

Note about this change: It will increase convenience but it will make cloudprober run dependent on external configs. For the most part it's okay -- it will only make debugging a bit harder as you'll have to find the external file content when cloudprober started running. Maybe, as @theduke suggested above, we can cache file contents locally, which will be useful in two cases:

a. to debug.
b. for the restarts where external file service is unavailable and you need to restart. Note, ideally, you don't want to start if you cannot get the latest content, so maybe we'll provide a flag to use cache if actual file is not available -- it will not be the default behavior.

I'll consider hashing this out and implementing it in a different pull request / issue.