[IPython-dev] ipython with sync

[Brian Granger]

William,

Thanks for notes.  This is really exciting and we are very interested
in getting live sync to work with IPython itself.  I am traveling this
week, but will try to have a look soon.  Is the code available
somewhere to look at?

Cheers,

Brian

On Tue, Sep 10, 2013 at 9:11 AM, William Stein <wstein at gmail.com> wrote:
> Hi,
>
> Somewhat by accident I spent the last two weeks implementing hosted
> IPython notebooks with sync for https://cloud.sagemath.com.
> Initially I had just plan to simplify the port forwarding setup, since
> what Ondrej Certik was doing with multiple forward and reverse port
> forwards seemed complicated.  But then I became concerned about
> multiple users (or users with multiple browsers) overwriting each
> other's notebooks, because cloud.sagemath projects are frequently
> shared between multiple people, and everything else does realtime
> sync.    I had planned just to add some very minimal merge-on-save
> functionality to avoid major issues, but somehow got sucked into
> realtime sync (even with the other person's cursor showing).
>
> It would be enormously helpful to me if a couple of expert IPython
> users were to try out what I implemented and just ask a bunch of
> questions.
>
> 1. Go to https://cloud.sagemath.com and make an account; this is
> completely free, and is hosted on computers at University of
> Washington.
>
> 2. Create a new project.
>
> 3. Click +New, then click "IPython" (or paste in a link to an ipython
> notebook, or upload a file).
>
> 4. An IPython notebook server will start, the given .ipynb file should
> load in a same-domain iframe, and then some of the ipython notebook
> code is and iframe contents are monkey patched, in order to support
> sync and better integration with https://cloud.sagemath.com.
>
> 5. Open the ipynb file in multiple browsers, and see that changes in
> one appear in the other, including moving cells around, creating new
> cells, editing markdown (the rendered version appears elsewhere), etc.
>   Anything that sets the notebook.dirty flag in IPython causes a sync
> (evaluating a cell that creates no output doesn't set this flag, at
> least in 1.0.0, which is a bug in IPython, I guess).
>
> Since this is all very new and the first (I guess) realtime sync
> implementation on top of IPython, there are probably a lot of issues.
>  Note that if you click the "i" info button to the right, you'll get a
> link to the standard IPython
>
> The other thing of interest is a little Python script called
> "ipython-notebook", which I wrote.  It basically makes it easy to run
> an IPython notebook server as a daemon, get the port it is running on,
> etc.  It's pretty simple but satisfies my use case, and has
> JSON-output, to make it web friendly.    As I've written it, my script
> passes several base_url options through by default, which are needed
> for cloud.sagemath.  Anyway, I've attached it to this email (with a
> BSD license) in case there is any interest.
>
> Regarding the monkey patching in 4 above, the right thing to do would
> be to explain exactly what hooks/changes in the IPython html client I
> need in order to do sync, etc., make sure these makes sense to the
> IPython devs, and send a pull request (or have a coding sprint in
> Seattle or Berkeley?).  As an example, in order to do sync
> *efficiently*, I have to be able to set a given cell from JSON -- it's
> critical to do this in place when possible, since the overhead of
> creating a new cell is huge (due probably to the overhead of creating
> CodeMirror editors); however, the fromJSON method in IPython assumes
> that the cell is brand new -- it would be nice to add an option to
> make a cell fromJSON without assuming it is empty.
>
> The ultimate outcome of this could be a clean well-defined way of
> doing sync for IPython notebooks using any third-party sync
> implementation.  IPython might provide their own sync service and
> there are starting to be others available these days -- e.g., Google
> has one: https://developers.google.com/drive/realtime/, and maybe
> Guido van Rosum helped write one for Dropbox recently?
>
> Subdirectories:   I noticed, incidentally, that the wakari version of
> the IPython notebook server allows one to load ipynb files that are in
> any subdirectory, whereas the standard IPython notebook server
> doesn't.  For cloud.sagemath, I just spawn a new IPython notebook
> server for each directory that a user accesses files in right now.
> This seems cludgy, so I'm interested in the situation regarding adding
> support for subdirectories.
>
> -- William
>
>
>
> --
> William Stein
> Professor of Mathematics
> University of Washington
> http://wstein.org
>
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-- 
Brian E. Granger
Cal Poly State University, San Luis Obispo
bgranger at calpoly.edu and ellisonbg at gmail.com