Align external kernel connections with jupyter-server (#352)

jupyverse_api/jupyverse_api/kernels/__init__.py

@@ -4,6 +4,7 @@
 
 from fastapi import APIRouter, Depends, Request
 from jupyverse_api import Router, Config
+from pydantic import Field
 
 from ..app import App
 from ..auth import Auth, User
@@ -239,5 +240,19 @@ async def kernel_channels(
 
 class KernelsConfig(Config):
     default_kernel: str = "python3"
-    connection_path: Optional[str] = None
+    allow_external_kernels: bool = Field(
+        description=(
+            "Whether or not to allow external kernels, whose connection files are placed in "
+            "external_connection_dir."
+        ),
+        default=False,
+    )
+    external_connection_dir: Optional[str] = Field(
+        description=(
+            "The directory to look at for external kernel connection files, if "
+            "allow_external_kernels is True. Defaults to Jupyter runtime_dir/external_kernels. "
+            "Make sure that this directory is not filled with left-over connection files."
+        ),
+        default=None,
+    )
     require_yjs: bool = False

plugins/kernels/fps_kernels/main.py

@@ -12,6 +12,7 @@
 from jupyverse_api.yjs import Yjs
 from jupyverse_api.app import App
 
+from .kernel_driver.paths import jupyter_runtime_dir
 from .routes import _Kernels
 
 
@@ -38,13 +39,17 @@ async def start(
         kernels = _Kernels(app, self.kernels_config, auth, frontend_config, yjs)
         ctx.add_resource(kernels, types=Kernels)
 
-        if self.kernels_config.connection_path is not None:
-            path = Path(self.kernels_config.connection_path)
+        if self.kernels_config.allow_external_kernels:
+            external_connection_dir = self.kernels_config.external_connection_dir
+            if external_connection_dir is None:
+                path = Path(jupyter_runtime_dir()) / "external_kernels"
+            else:
+                path = Path(external_connection_dir)
             task = asyncio.create_task(kernels.watch_connection_files(path))
 
         yield
 
-        if self.kernels_config.connection_path is not None:
+        if self.kernels_config.allow_external_kernels:
             task.cancel()
         for kernel in kernels.kernels.values():
             await kernel["server"].stop()