Make redis dependency of bokeh-server optional about bokeh

[bryevdv]

Redis is already an optional dependency, in the sense that Bokeh can be used to generate plots in static HTML output, or in inline IPython Notebook output, both without redis. I don't think the current server functionality can be reproduced with any of the tools you mention since the server requires two-way communication/notifications. Also the browser JS application is not going to have access to arbitrary local filesystem resources.

I am interested in exploring other communications/persistence options in the future (other databases, web sockets), but that is an entirely separate matter, so I am going to close this issue.

[ilanschnell]

But currently, when you run the bokeh-server, but do not have redis installed, you get:

$ ./bokeh-server -h
Traceback (most recent call last):
  File "./bokeh-server", line 4, in <module>
    from bokeh.server import start
  File "/Users/ilan/src/Bokeh/bokeh/server/start.py", line 9, in <module>
    import redis
ImportError: No module named redis

If redis is truly an optional dependency, it should either:

• print a message: "Redis needs to be installed to sun the bokeh-server"
• not include the bokeh-server script in setup.py when redis is not installed

[bryevdv]

After talking with Hugo, I have realized I have misunderstood the manner in which redis is used, so perhaps it can be made a truly optional dependency even for the server after all. But I don't know the time frame for adding this change, so in the mean time I will make it print a better message.

[pzwang]

Actually, it should be quite trivial to make the change so that on windows, the non-redis version just keeps all the objects around in a big global dict in the process, and it disappears when the process dies.

[filmor]

@pzwang That would be actually fine by me. Is this implemented?

[bryevdv]

@filmor here is a PR for this #388 It needs a little more cleanup and work (I'd like to add a shelve backend as well) but I should be able to merge it later today.

[bryevdv]

@filmor this PR has been merged. It currently supports an in-memory bokeh-server, which is used by default on windows. Will add a simple "shelve" based on later. It should work on Chrome and FF, there appears to be html/css problems on IE, the plot divs fail to expand. I am going to make a separate ticket for that. Please re-open this issue if you have any problems!