Accept server connections from any origin

I get errors like the following from my bokeh server application:

bokeh.server.views.ws - ERROR - Refusing websocket connection from Origin 'http://127.0.0.1:8789';                       use --allow-websocket-origin=127.0.0.1:8789 to permit this; currently we allow origins {'localhost:8789'}

There may be two problems here:

1. (minor) localhost is often synonymous with 127.0.0.1. It might be good to whitelist 127.0.0.1 generally.
2. (major) I have started my Bokeh server with the argument Server(..., host=['*']) which in previous versions ensured that my server could be accessed regardless of what the caller called my server address.

The second point is more important to me (and to others). It is critical in many applications to be able to robustly view a bokeh server even if we don’t know, at the time of setting up the server, what that server’s address will be. This was the intent of https://github.com/bokeh/bokeh/pull/4052

In [2]: bokeh.__version__
Out[2]: '0.12.5dev15'

[mrocklin]

@bryevdv and I chatted about this privately. On my side I can add allow_websocket_origin=["*"] to my application. Bokeh may dump the old hosts= keyword into allow_websocket_origin= to facilitate a smoother transition if developer time allows.

My fix in Dask is here: https://github.com/dask/distributed/pull/957

[bryevdv]

After discussion with @mrocklin the problem was discovered. Previously --host=* updated the host whitelist, but it also updated the allow_websocket_origin as a side effect. Now that it is completely ignored, anything that relied on --host=whatever to allow ws connections too, will have a probelm.

So the proposal is this:

Don’t completely ignore host. But simply immediately transfer its contents to the allow_websocket_origin so that old usages will not break. The deprecation message should be updated to reflect that --allow_websocket_origin may now be explicitly needed.