websocket message size limitation introduced in tornadoweb causes kernel crashes

[AaronWatters]

I have some IPython widgets that stopped working for larger data sets recently and with the help of chatters in https://gitter.im/jupyter-widgets/Lobby in particular Jason Grout @jasongrout it turns out that the failures are due to a new limitation in tornadoweb zmq over websockets

See first entry here: http://www.tornadoweb.org/en/stable/releases/v4.5.0.html

This commit: tornadoweb/tornado@104a302

This issue: tornadoweb/tornado#1269

This new limitation results in kernel crashes that I didn't see before if (for example) a javascript widget attempts to transfer more than 10 megs of data in a message to a python kernel.

Is it possible to fix/work-around the limitation in a robust way in general within the Jupyter framework?

[takluyver]

It's possible to increase the limit, but you might just hit the higher limit anyway. There are probably good reasons to have some kind of limit on it - it's better to kill that kernel than use up memory until the server crashes.

[AaronWatters]

I agree. However it would be nice to have a way to send an arbitrary amount of data
from javascript to jupyter. One approach is to break large messages into smaller ones and
send those in sequence. I'm probably going to do this at the widget implementation level to allow my widget(s) to send large data to the kernel. I don't know if it makes sense to implement support for large data transfers further down the Jupyter stack (at the comm level or something) but it might.

By the way in the current implementation I have crashed the Jupyter server when attempting to send large enough messages. I believe I can reproduce this by uploading a 200meg file in a javascript widget and then cramming the contents across the websocket as a single message. Boom.

[maartenbreddels]

This is indeed quite a serious showstopper for widgets and binary transfers, did you find a good workaround for this?

[jasongrout]

Of course, you can reset websocket_max_message_size at the tornado level...

[harmon]

I'm also running into this I believe. Got a 12 MB iPyWidget Output field update being pushed from the kernel to the web browser, and it reliably closes the websocket connection with "Message too big (1009)". Can this "websocket_max_message_size " value be exposed so it's configurable?

[AaronWatters]

jp_proxy_widgets implements its own meta protocol to transfer data in chunks.
AaronWatters/jp_proxy_widget@45186ae

[cosmoscalibur]

Of course, you can reset websocket_max_message_size at the tornado level...

How can I reset this value launching notebook? Thia value is not present in notebook app tornado settings.

[cosmoscalibur]

For future reference:

Example to limit size in 100 MB.
Create config file

jupyter notebook --generate-config

Edit (uncomment) the following line in jupyter_notebook_config.py (generated file) and change the value (desired size in MB * 1024 * 1024):

c.NotebookApp.tornado_settings = {"websocket_max_message_size": 100 * 1024 * 1024}

Launch notebook with --config parameter pointing to config file:

jupyter notebook --config="jupyter_notebook_config.py" your_notebook.ipynb

[slw07g]

In addition to @cosmoscalibur's excellent instructions, you could alternatively store the config file in one of the paths jupyter watches, and it will load the config automatically.

To see the paths jupyter is configured to watch, run jupyter --paths

[ElisonSherton]

Hi @cosmoscalibur

Thanks for posting the solution above. I tried to do use that workaround. In this notebook below, I tried to upload a 99 MB file since I have improved the upload limit in the jupyter_notebook_config.py

Can you advise what could be going wrong here? Also, in the paths which jupyter looks for, there's the .jupyter folder which contains the jupyter_notebook_config.py file as mentioned by @slw07g but still the uploading is not happening properly...

I would be obliged if you could help with this issue please.

Thanks & Regards,
Vinayak.

[slw07g]

@ElisonSherton I notice you have 100*1024*1024 rather than 1000*1024*1024. If you add the zero, does it correct the issue?

[ElisonSherton]

@ElisonSherton I notice you have 100*1024*1024 rather than 1000*1024*1024. If you add the zero, does it correct the issue?

Hi @slw07g ,

Thanks for that advise. The upload now started working. However, as per @cosmoscalibur , the config needs to be changed to (desired size in MB * 1024 * 1024) right? Then I wonder why 99.1 MB file wouldn't get uploaded if I mention the limit as 100 * 1024 * 1024 instead of 1000 * 1024 * 1024?

The size of file for your reference is as follows

[slw07g]

@ElisonSherton This is because when you upload the file it gets encoded (Base64 I believe) which results in a payload that is larger than the actual file. There's some additional context on base-64 encoding here.

You can verify this yourself by using the developer tools in your browser and monitoring the messages sent over the websocket (make sure developer tools are open prior to loading the page so that it can capture the websocket).

If you increased the size to say 105MB, it'd probably be sufficient for the 99.1MB file.

Hope this helps.