Google Colab notebook using IJava stuck at "Connecting" after installation + page reload

All of my notebooks with the IJava kernel that worked before now are stuck at “Connecting” after the initial IJava installation and browser page refresh.

What was working previously / expected behavior

1. Execute this first cell

!wget https://github.com/SpencerPark/IJava/releases/download/v1.3.0/ijava-1.3.0.zip 
!unzip ijava-1.3.0.zip 
!python install.py --sys-prefix

1. Wait for the Installed java kernel message

2. Refresh the browser page.

3. Execute any cell with Java code and see the output.

Now what happens is

I can execute the first cell and get the Installed java kernel message, seeing the notebook status as “Connected”.

But after refreshing the page, the status of the notebook is stuck at “Connecting” forever,

and thus no cells with Java code can be executed.

–

I’m using Google Colab for free, but since the initial installation still works, and the notebook status is “Connected” before the page is refreshed, I assume not being a paid subscriber should not be the problem.

Any idea what has been changed, and how I can get my Java notebooks to connect again?

Example https://colab.research.google.com/github/vistec-AI/colab/blob/master/ijava.ipynb

[SpencerPark]

Hello, author of that kernel here 😃 found my way over from the stack overflow question.

I was taking a peek into what is going on but I’m not too familiar with the colab infrastructure. Though I can verify that I can use the kernel within that workbook linked in that top comment, but cannot change the kernel type in colab. What I mean by that is I can run the following in a cell:

!jupyter console --kernel=java --simple-prompt

and the kernel starts up properly, jupyter client can connect, and I can execute code in that kernel.

Dec 09, 2022 7:40:21 AM io.github.spencerpark.jupyter.channels.Loop start
INFO: Loop starting...
Dec 09, 2022 7:40:21 AM io.github.spencerpark.jupyter.channels.Loop start
INFO: Loop started.
Dec 09, 2022 7:40:21 AM io.github.spencerpark.jupyter.channels.Loop start
INFO: Loop starting...
Dec 09, 2022 7:40:21 AM io.github.spencerpark.jupyter.channels.Loop start
INFO: Loop started.
Dec 09, 2022 7:40:21 AM io.github.spencerpark.jupyter.channels.Loop start
INFO: Loop starting...
Dec 09, 2022 7:40:21 AM io.github.spencerpark.jupyter.channels.Loop start
INFO: Loop started.
Jupyter console 6.1.0

Java 11.0.17+8-post-Ubuntu-1ubuntu218.04 :: IJava kernel 1.3.0 
Protocol v5.3 implementation by jupyter-jvm-basekernel 2.3.0
In [1]: System.out.println("test");
test

So there doesn’t seem to be an issue with starting the kernel in the container via jupyter but for whatever reason via colab has trouble connecting to it.

Also tried switching via getKernel().runtimeManager.changeKernelType('<session-id>', 'java') and saw the same successful startup logs in /var/colab/app.log:

Timestamp	Level	Message
Dec 9, 2022, 2:55:23 AM	WARNING	INFO: Loop started.
Dec 9, 2022, 2:55:23 AM	WARNING	Dec 09, 2022 7:55:23 AM io.github.spencerpark.jupyter.channels.Loop start
Dec 9, 2022, 2:55:23 AM	WARNING	INFO: Loop starting...
Dec 9, 2022, 2:55:23 AM	WARNING	Dec 09, 2022 7:55:23 AM io.github.spencerpark.jupyter.channels.Loop start
Dec 9, 2022, 2:55:23 AM	WARNING	INFO: Loop started.
Dec 9, 2022, 2:55:23 AM	WARNING	Dec 09, 2022 7:55:23 AM io.github.spencerpark.jupyter.channels.Loop start
Dec 9, 2022, 2:55:23 AM	WARNING	INFO: Loop starting...
Dec 9, 2022, 2:55:23 AM	WARNING	Dec 09, 2022 7:55:23 AM io.github.spencerpark.jupyter.channels.Loop start
Dec 9, 2022, 2:55:23 AM	WARNING	INFO: Loop started.
Dec 9, 2022, 2:55:23 AM	WARNING	Dec 09, 2022 7:55:23 AM io.github.spencerpark.jupyter.channels.Loop start
Dec 9, 2022, 2:55:23 AM	WARNING	INFO: Loop starting...
Dec 9, 2022, 2:55:23 AM	WARNING	Dec 09, 2022 7:55:23 AM io.github.spencerpark.jupyter.channels.Loop start
Dec 9, 2022, 2:55:22 AM	INFO	Kernel shutdown: 25522ba0-5629-428b-a3a6-29827234a5d0
Dec 9, 2022, 2:55:22 AM	INFO	Kernel started: 495f9ece-6927-4283-884f-ffc29915f72c

There are no errors and I do see the kernel connection file exists at /root/.local/share/jupyter/runtime/kernel-495f9ece-6927-4283-884f-ffc29915f72c.json so I presume it is still running. Note that 25522ba0-5629-428b-a3a6-29827234a5d0 is the id for the default python3 kernel that got created, and in the logs it shows that as shutting down when switching to the java kernel.

Don’t know if there is much else I can do to debug further on my end but happy to try anything if it will help!

[thomers]

@cperry-goog and @craigcitro , any feedback or news from your side regarding

_Do you know if this was another change in configuration on your side that rolled out with the 3.8 changes?

And is there something we could specify in the kernel metadata to say that a specific kernel prefers tpc as the transport?_