Kernel fails to send config sometimes

[impact27]

Issue Report Checklist

• Searched the issues page for similar reports
• Read the relevant sections of the Spyder Troubleshooting Guide and followed its advice
• Reproduced the issue after updating with conda update spyder (or pip, if not using Anaconda)
• Could not reproduce inside jupyter qtconsole (if console-related)
• Tried basic troubleshooting (if a bug/error)
  • Restarted Spyder
  • Reset preferences with spyder --reset
  • Reinstalled the latest version of Anaconda
  • Tried the other applicable steps from the Troubleshooting Guide
• Completed the Problem Description, Steps to Reproduce and Version sections below

Problem Description

The kernel is supposed to send the config when opening:

https://github.com/spyder-ide/spyder-kernels/blob/05476b35cf9e55787521c43f91dd5eedcb56c7a2/spyder_kernels/comms/frontendcomm.py#L183

But sometimes it doesn't! And it is known because I added this line:

https://github.com/spyder-ide/spyder-kernels/blob/05476b35cf9e55787521c43f91dd5eedcb56c7a2/spyder_kernels/comms/frontendcomm.py#L163

Which solves this exact problem.

I found a workaround in #12134 that I could include in a standalone PR. But the problem remains: it should not be needed.

What steps reproduce the problem?

1. The kernel connects to the comm but fails to send the configuration
2. The kernel sends a blocking request to the frontend (debugging / runfile / ...)
3. The frontend doesn't know the port to which the reply should be sent and the kernel is not listening to the shell channel (because it is waiting for a reply)

What is the expected output? What do you see instead?

This causes a comm timeout error. I have no idea why the kernel fails to send the config.

Solutions

1 - Figure out why the config is not sent
2 - Always send the config with every message

Versions

• Spyder version:
• Python version:
• Qt version:
• PyQt version:
• Operating System name/version:

Dependencies

PASTE DEPENDENCIES HERE

[ccordoba12]

I found a workaround in #12134 that I could include in a standalone PR

Please do, so I can include it for 4.1.4.

But the problem remains: it should not be needed.

Perhaps things could be solved if we moved to use the control channel instead of our own (dedicated) commsn channel? I say it because that channel is present by default (which could be part of the issue, since we have to create our comms channel).

[impact27]

spyder-ide/spyder-kernels#230

[ccordoba12]

Thanks a lot @impact27!

[impact27]

#13166

[impact27]

I think #13174 is a more reliable way of fixing this issue

[ccordoba12]

Ok, thanks for your work on this. I'll review it and try to include it for 4.1.4