Custom Kernel JSON Configuration Variables

[timg512372]

Hi, I'm trying to create a custom kernel spec JSON file, and I would like the configuration variables to be available inside a custom gateway_provisioner. I'm looking at this line of documentation under System Architecture

Each kernel.json’s kernel_provisioner stanza can specify an optional config stanza that is converted into a dictionary of name/value pairs and passed as an argument to each kernel provisioner’s constructor relative to the provisioner identified by the provisioner_name entry.

but when I put variables under the config stanza and inspect the arguments passed into the kernel provisioner's constructor, I don't see any of my configuration variables. Do you know where I might be able to find the configuration variables?

kernel.json

{
  "argv": [
  ],
  "env": {},
  "display_name": "Python Custom",
  "language": "python",
  "interrupt_mode": "signal",
  "metadata": {
    "debugger": true,
    "kernel_provisioner": {
      "provisioner_name": "custom-provisioner",
      "config": {
        "launch_timeout": 30,
        "test": "test",
        "test2": "test2"
      }
    }
  }
}

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[kevin-bates]

Hi @timg512372 - thank you for opening this issue. I probably won't be able to take a closer look at this for a few days but wanted to get back to you.

The doc text you quoted could probably use some clarification, although I suspect it won't necessarily provide a solution. I think a better phrasing might be:

Each kernel.json’s kernel_provisioner stanza can specify an optional config stanza where its key/value pairs are included as keyword arguments to each kernel provisioner’s constructor relative to the provisioner identified by the provisioner_name entry.

This transformation is performed in the KernelProovisionerFactory in jupyter_client.

The idea is that each of the referenced keys in the config stanza correspond to configurable traits defined throughout the provisioner's class hierarchy (parent is such a trait, as are kernel_spec and kernel_id defined on KernelProvisionerBase).

When that's the case, I can't recall if they would appear as kwargs by the time the __init__() method is invoked as they may already be set into that class instance's traits and referenced via self.key. (The traitlets package provides lots of metadata-magic that can be a bit confusing IMO.)

I'm curious what keyword arguments you do see?

From what class does your custom provisioner derive?

[timg512372]

Hi @kevin-bates,

Thank you for your help! The key value pairs in the config stanza are indeed into the constructor as keyword arguments, and I can see them in kwargs in the __init__() method. For context, I was trying to derive off of DistributedProvisioner.

[kevin-bates]

Right on - glad to hear that. If you have any time, it would be great to have an update to the docs. No worries if not.