Added refresh endpoint w/ token

[joeherm]

• Add /refresh?token=specified_token endpoint that sends SIGHUP

[joeherm]

Apologies- meant to open this on our fork.

[brendan-ward]

@joeherm we're open to considering something like this in the base repo too; there was some discussion on the related filesystem-based reloader.

However, using SIGHUP from an API endpoint feels a little awkward ("hey server please restart yourself"). Instead, I think I'd want to implement something that sets a mutex (so multiple calls to /reload in separate threads don't collide), then uses something similar to what we're doing here to rescan the registered directories and re-add those that exist.

This could also be extended to take a service ID and reload just that, which would likely be nice for certain cases too.

We didn't (yet) have those specific use cases, so I haven't put further thought into supporting a reload HTTP API. One thing that we didn't work out was how to handle authentication for this:

• shared secret (your token); which is nice and lightweight but also risky, it could get logged as plaintext anywhere in between caller and mbtileserver and potentially used to do a DOS attack
• HTTP Basic Auth based on credentials provided at server startup
• something else?

[joeherm]

Apologies for the late response! I meant to respond earlier and it got a bit lost in the holiday shuffle. I agree with what you're saying here about the awkwardness of the having the server restart itself, though we did implement the above (with slight changes) as a workaround for our short-term needs.

If there is interest in having that merged happy to do so, otherwise perhaps I should file an issue? If I get some downtime it's something I would be happy to work on and contribute back :) .

[brendan-ward]

Added #133 for this idea