Jupyter can't connect to kernel

[talismanick]

I installed IHaskell with these commands:

cd ~
cabal install ihaskell
ihaskell install

Jupyter lists Haskell as a kernel option, but all attempts to start the kernel fail.
I'm on Void Linux, with GHC 8.6.5 and Cabal 3.0.0.0

[vaibhavsagar]

What is the console output after running jupyter notebook and selecting the Haskell kernel?

[talismanick]

[refusenick@box ~]$ jupyter notebook
[I 20:13:00.733 NotebookApp] The port 8888 is already in use, trying another port.
[I 20:13:00.744 NotebookApp] Serving notebooks from local directory: /home/refusenick
[I 20:13:00.744 NotebookApp] The Jupyter Notebook is running at:
[I 20:13:00.744 NotebookApp] http://localhost:8889/?token=9028e895c64f903b42543ad466714e28d7ea39b7f6ff0f82
[I 20:13:00.744 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[C 20:13:00.745 NotebookApp] 
    
    Copy/paste this URL into your browser when you connect for the first time,
    to login with a token:
        http://localhost:8889/?token=9028e895c64f903b42543ad466714e28d7ea39b7f6ff0f82
[I 20:13:02.057 NotebookApp] Accepting one-time-token-authenticated connection from ::1
[I 20:13:08.885 NotebookApp] Creating new notebook in 
[I 20:13:11.822 NotebookApp] Kernel started: c89ad20a-c977-4cda-ab9b-c32acef48f29
Loaded package environment from /home/refusenick/.ghc/x86_64-linux-8.6.5/environments/default
[W 20:13:12.231 NotebookApp] 404 GET /static/components/codemirror/mode/ihaskell/ihaskell.js?v=20191129201300 (::1) 37.55ms referer=http://localhost:8889/notebooks/Untitled4.ipynb?ke
rnel_name=haskell
ihaskell: Could not load module ‘IHaskell.Display’
It is a member of the hidden package ‘ihaskell-0.10.0.2’.
You can run ‘:set -package ihaskell’ to expose it.
(Note: this unloads all the modules in the current scope.)
Use -v to see a list of the files searched for.
Could not load module ‘IHaskell.Display’
It is a member of the hidden package ‘ihaskell-0.10.0.2’.
You can run ‘:set -package ihaskell’ to expose it.
(Note: this unloads all the modules in the current scope.)
Use -v to see a list of the files searched for.
Could not load module ‘IHaskell.IPython.Stdin’
It is a member of the hidden package ‘ihaskell-0.10.0.2’.
You can run ‘:set -package ihaskell’ to expose it.
(Note: this unloads all the modules in the current scope.)
Use -v to see a list of the files searched for.
Could not load module ‘IHaskell.Eval.Widgets’
It is a member of the hidden package ‘ihaskell-0.10.0.2’.
You can run ‘:set -package ihaskell’ to expose it.
(Note: this unloads all the modules in the current scope.)
Use -v to see a list of the files searched for.

It repeats the answer of it being a hidden package ad nauseam until it gives this:

[W 20:13:26.902 NotebookApp] KernelRestarter: restart failed
[W 20:13:26.902 NotebookApp] Kernel c89ad20a-c977-4cda-ab9b-c32acef48f29 died, removing from map.
[W 20:13:33.187 NotebookApp] Replacing stale connection: c89ad20a-c977-4cda-ab9b-c32acef48f29:49d85fdde06d4bde876daade7e1079a6
[W 20:13:55.235 NotebookApp] Replacing stale connection: c89ad20a-c977-4cda-ab9b-c32acef48f29:49d85fdde06d4bde876daade7e1079a6
[W 20:14:12.204 NotebookApp] Timeout waiting for kernel_info reply from c89ad20a-c977-4cda-ab9b-c32acef48f29
[E 20:14:12.210 NotebookApp] Error opening stream: HTTP 404: Not Found (Kernel does not exist: c89ad20a-c977-4cda-ab9b-c32acef48f29)
[W 20:14:12.215 NotebookApp] 404 GET /api/kernels/c89ad20a-c977-4cda-ab9b-c32acef48f29/channels?session_id=49d85fdde06d4bde876daade7e1079a6 (::1): Kernel does not exist: c89ad20a-c97
7-4cda-ab9b-c32acef48f29
[W 20:14:12.219 NotebookApp] 404 GET /api/kernels/c89ad20a-c977-4cda-ab9b-c32acef48f29/channels?session_id=49d85fdde06d4bde876daade7e1079a6 (::1) 39036.29ms referer=None
[W 20:14:12.219 NotebookApp] 404 GET /api/kernels/c89ad20a-c977-4cda-ab9b-c32acef48f29/channels?session_id=49d85fdde06d4bde876daade7e1079a6 (::1): Kernel does not exist: c89ad20a-c97
7-4cda-ab9b-c32acef48f29
[W 20:14:12.222 NotebookApp] 404 GET /api/kernels/c89ad20a-c977-4cda-ab9b-c32acef48f29/channels?session_id=49d85fdde06d4bde876daade7e1079a6 (::1) 16989.84ms referer=None
[W 20:14:16.255 NotebookApp] Replacing stale connection: c89ad20a-c977-4cda-ab9b-c32acef48f29:49d85fdde06d4bde876daade7e1079a6
[W 20:14:44.282 NotebookApp] Replacing stale connection: c89ad20a-c977-4cda-ab9b-c32acef48f29:49d85fdde06d4bde876daade7e1079a6

I can't start it from the globally-installed package?

[vaibhavsagar]

I think the issue is that IHaskell depends on the ihaskell library to work correctly, but your GHC_PACKAGE_PATH isn't set and so IHaskell fails to start. Can you try running ghc-pkg list, which should show you the package database you installed ihaskell to, and then using that as the value of GHC_PACKAGE_PATH when you run jupyter notebook? I'm guessing you might have to do something like

GHC_PACKAGE_PATH=~/.ghc/x86_64-linux-8.6.5/package.conf.d jupyter notebook

[talismanick]

It says my GHC_PACKAGE_PATH is /usr/lib/ghc-8.6.5/package.conf.d. Moreover, there is no package.conf.d folder in ~/.ghc/x86_64-linux-8.6.5/. Should I copy the existing package.conf.d to the home directory and chown it to my account? Will that break things?

[vaibhavsagar]

I don't think that's a good idea. Where did you install IHaskell to with cabal install ihaskell? Can you cabal exec -- jupyter notebook and see if that works?

Edit: cabal exec, not cabal run

[talismanick]

Where did you install IHaskell to with cabal install ihaskell?

It shows up as an installed binary in ~/.cabal/bin/.

Can you cabal exec -- jupyter notebook and see if that works?

It doesn't. It fails with the same error.

Should I remove the GHC package from my distro and reinstall it as a normal user with ghcup before reconfiguring cabal-install for it?

[vaibhavsagar]

No, there's no reason to blow up your whole Haskell setup just because this one package doesn't work. Can you try installing the ihaskell library with cabal install --lib ihaskell and doing cabal exec -- jupyter notebook?

[talismanick]

It says it's already installed, and I get the same error when running Jupyter again.

I don't have much of a Haskell setup right now - I'm new to the language. I might start all over again and give Stack another chance - everything assumes Stack usage, it seems.

[vaibhavsagar]

We have instructions for using Stack because it's commonly used, but there's no fundamental reason why IHaskell won't work with Cabal.

[vaibhavsagar]

Okay, here are instructions that worked for me:

1. cabal install ihaskell
2. ~/.cabal/bin/ihaskell install
3. Find out where your package database is, for me it was at ~/.cabal/store/ghc-8.6.5/package.db
4. Find out where your GHC boot packages are by running ghc-pkg | head -n1, for me this is /nix/store/xf5zihz12kszk0xiv6c0d0psc0mj10xs-ghc-8.6.5/lib/ghc-8.6.5/package.conf.d because I'm running NixOS but it will be different on your machine.
5. Use the output of steps 3 and 4 for the value of GHC_PACKAGE_PATH to run jupyter notebook:

$ GHC_PACKAGE_PATH=~/.cabal/store/ghc-8.6.5/package.db/:/nix/store/xf5zihz12kszk0xiv6c0d0psc0mj10xs-ghc-8.6.5/lib/ghc-8.6.5/package.conf.d jupyter notebook

Can you try this and see if it works for you?

[talismanick]

After reinstalling everything (luckily, I had the list of global packages in a reinstall script), the most recent solution worked!

Looks like I needed to fix the load paths. Hopefully, this will prevent other problems as well. Thanks for the help!