Better handling of kernel crashes (dead kernels)

[claudiaregio]

[DonJayamanne]

I think we've fixed these issues in interactive window

[DonJayamanne]

Current state

• Today we just bomb out and log errors in cell output (session cannot be created)
• Error message is very confusing to the user (no indication that kernel is dead)
  • Users are used to seeing errors from kernels in output (not extension), hence they might be under the impression these are errors from kernel & attempt to re-execute cells
• User needs to manually restart the kernel

Proposed Solution

• Notify user when kernel dies (like jupyter)
• Allow user to restart kernel (like jupyter)
• Include error message from kernel (so users know what went wrong)
  • E.g. if kernel fails due to some package, or the like, then they know what caused it
  • Else all they know is kernel died and could end up just blaming vscode extension
  • I.e. we need to provide the user with tools necessary to resolve the issue themselves
• If we were able to successfully run a cell (or start the kernel), then ask user to inspect the particular cell that caused the issue
  • E.g. we've found kernels crash when users have busted packages
  • This way users will know what to look at and diagnose the issue.
  • Plenty of examples
  • Error: Direct kernel connection broken #1706
  • Kernel crashes when importing tensorflow #7600
  • Bad conda environment causes a notebook to not be able to be opened #4855
• Warn users when files override built in packages that could have caused the kernel to fail #7538
• Prompt the user to restart the kernel when running a cell against a dead kernel #7399
• Kernel issues with Python 2.7 #4680
• Display warning when user selects outdated versions of Python #7960
• Recommend renaming python file if python file it overwrites builtins #8195

[DonJayamanne]

Closing in favor of #7901