Bokeh 2.0 issue persisting

[thvasilo]

Related to PR #180, issue #179

Hello @xhochy , I just tried serving a panel application through jupyter-server-proxy on a SageMaker instance (Tornado 6.0.4, jupyter-server-proxy 1.3.2, panel 0.9.5, bokeh 2.0.2) but I got the same error that the linked PR was fixing:

sh-4.2$ panel serve gallery/simple/iris_kmeans.ipynb
2020-05-04 23:30:38,708 Starting Bokeh server version 2.0.2 (running on Tornado 6.0.4)
2020-05-04 23:30:38,709 User authentication hooks NOT provided (default user enabled)
2020-05-04 23:30:38,712 Bokeh app running at: http://localhost:5006/iris_kmeans
2020-05-04 23:30:38,712 Starting Bokeh server with process id: 5175
2020-05-04 23:30:51,541 WebSocket connection opened
2020-05-04 23:30:51,542 Uncaught exception GET /iris_kmeans/ws (127.0.0.1)
HTTPServerRequest(protocol='http', host='<IP.REDACTED>:8443', method='GET', uri='/iris_kmeans/ws', version='HTTP/1.1', remote_ip='127.0.0.1')
Traceback (most recent call last):
  File "/home/ec2-user/anaconda3/envs/python3/lib/python3.6/site-packages/tornado/websocket.py", line 956, in _accept_connection
    open_result = handler.open(*handler.open_args, **handler.open_kwargs)
  File "/home/ec2-user/anaconda3/envs/python3/lib/python3.6/site-packages/bokeh/server/views/ws.py", line 123, in open
    raise ProtocolError("Subprotocol header is not 'bokeh'")
bokeh.protocol.exceptions.ProtocolError: Subprotocol header is not 'bokeh'

Any ideas on what the cause might be and how to fix?

[thvasilo]

Note that serving the same exact notebook through Voila works, but the interactive aspect of the webapp breaks (i.e. changing values/sliders in the interface has no effect on the output).

So I'm curious as to why Bokeh Server insists on the subprotocol header being bokeh, maybe I should report over there?

[xhochy]

Can you try running this locally without SageMaker? It could be that SageMaker itself does some proxying that breaks this too.

[thvasilo]

Locally this seems to work.

What I did:

• Launch a Jupyter notebook server locally, on port 8888. This is only used for the proxy.
• Serve a Panel webapp on port 5006, using panel serve --allow-websocket-origin=localhost:8888 gallery/simple/iris_kmeans.ipynb (had to add the allow websocket origin because bokeh server was complaining:
  • Refusing websocket connection from Origin 'http://localhost:8888'; use --allow-websocket-origin=localhost:8888 or set BOKEH_ALLOW_WS_ORIGIN=localhost:8888 to permit this; currently we allow origins {'localhost:5006'}
• Navigate to http://localhost:8888/proxy/5006/iris_kmeans. The app works as expected.

Any ideas on what I could look into for SageMaker. What could be interfering in such a particular way, changing the subprotocol header?

[evanfwelch]

Also having this exact issue still in SageMaker notebooks despite the fixes to jupyter-server-proxy... any ideas for debugging?