Add support for tornado.

[jmcarp]

AFAICT this doesn't require anything silly, so should be acceptable based on conversation in #114.

[Resolves #114]

[brian-brazil]

Could you re-use the WSGI handler rather than implementing something tornado specific? Then there's only docs to maintain.

[jmcarp]

Yes, but according to https://www.tornadoweb.org/en/stable/wsgi.html#running-wsgi-apps-on-tornado-servers,

WSGI is a synchronous interface, while Tornado’s concurrency model is based on single-threaded asynchronous execution. This means that running a WSGI app with Tornado’s WSGIContainer is less scalable than running the same app in a multi-threaded WSGI server like gunicorn or uwsgi. Use WSGIContainer only when there are benefits to combining Tornado and WSGI in the same process that outweigh the reduced scalability.

Which reminds me that I might also need async versions of generate_latest and collect so that slow collectors don't block the event loop. Which it sounds like don't belong in this library. Will think about this more.

[vribeiro1]

Are there any plans on merging this pull request? It's very useful for a project of mine.

[brian-brazil]

There's not, but you're free to host it in another repository.

[luiscoms]

+1

[luiscoms]

It could be added in the documentation as an example

[FullDataAlchemist]

+1