propagation support for bind mounts (once docker-py supports it officially)

dockerspawner/dockerspawner.py

@@ -1429,12 +1429,15 @@ def _fmt(v):
             return self.format_volume_name(v, self)
 
         for k, v in volumes.items():
-            m = mode
+            rw = mode
+            p = 'rprivate'
             if isinstance(v, dict):
                 if "mode" in v:
-                    m = v["mode"]
+                    rw = v["mode"]
+                if "propagation" in v:
+                    p = v["propagation"]
                 v = v["bind"]
-            binds[_fmt(k)] = {"bind": _fmt(v), "mode": m}
+            binds[_fmt(k)] = {"bind": _fmt(v), "mode": rw, 'propagation': p}
         return binds
 
     def _render_templates(self, obj, ns=None):

dockerspawner/systemuserspawner.py

@@ -34,6 +34,21 @@ class SystemUserSpawner(DockerSpawner):
         ),
     )
 
+    image_homedir_propagation = Unicode(
+        "rprivate",
+        config=True,
+        help=dedent(
+            """
+            Mode for bind mount propagation. Possible values are
+            `rshared`,`shared`,`rprivate`, `private`, `rslave`, `slave`.
+            default is `rprivate`.
+            This is only interpreted by docker-py if patched  (see:
+            https://github.com/jannefleischer/docker-py/commit/786d55de465e72d0bb4b318272a2d020e43ff54a
+            ) and run on linux - no support for Docker Desktop.
+            """
+        ),
+    )
+
     run_as_root = Bool(
         False,
         config=True,
@@ -117,6 +132,23 @@ def volume_mount_points(self):
         mount_points.append(self.homedir)
         return mount_points
 
+    @property
+    def homedirpropagation(self):
+        """
+        Setting for the propagation mode for home dir. Wrong values are defaulted to `rprivate`.
+        """
+        if self.image_homedir_propagation in (
+            'rshared',
+            'shared',
+            'rprivate',
+            'private',
+            'rslave',
+            'slave',
+        ):
+            return self.image_homedir_propagation
+        else:
+            return 'rprivate'
+
     @property
     def volume_binds(self):
         """
@@ -129,7 +161,11 @@ def volume_binds(self):
             }
         """
         volumes = super().volume_binds
-        volumes[self.host_homedir] = {'bind': self.homedir, 'ro': False}
+        volumes[self.host_homedir] = {
+            'bind': self.homedir,
+            'ro': False,
+            'propagation': self.homedirpropagation,
+        }
         return volumes
 
     def get_env(self):

tests/volumes_test.py

@@ -14,13 +14,15 @@ def test_binds(monkeypatch):
     d.user = types.SimpleNamespace(name="xyz")
     d.volumes = {"a": "b", "c": {"bind": "d", "mode": "Z"}}
     assert d.volume_binds == {
-        "a": {"bind": "b", "mode": "rw"},
-        "c": {"bind": "d", "mode": "Z"},
+        "a": {"bind": "b", "mode": "rw", "propagation": 'rprivate'},
+        "c": {"bind": "d", "mode": "Z", "propagation": 'rprivate'},
     }
     d.volumes = {"a": "b", "c": "d", "e": "f"}
     assert d.volume_mount_points == ["b", "d", "f"]
     d.volumes = {"/nfs/{username}": {"bind": "/home/{username}", "mode": "z"}}
-    assert d.volume_binds == {"/nfs/xyz": {"bind": "/home/xyz", "mode": "z"}}
+    assert d.volume_binds == {
+        "/nfs/xyz": {"bind": "/home/xyz", "mode": "z", "propagation": 'rprivate'}
+    }
     assert d.volume_mount_points == ["/home/xyz"]
 
 
@@ -35,7 +37,13 @@ def test_format(label_template, spawner):
         return "THIS IS A TEST"
 
     d.format_volume_name = test_format
-    assert d.volume_binds == {"THIS IS A TEST": {"bind": "THIS IS A TEST", "mode": "z"}}
+    assert d.volume_binds == {
+        "THIS IS A TEST": {
+            "bind": "THIS IS A TEST",
+            "mode": "z",
+            "propagation": 'rprivate',
+        }
+    }
     assert d.volume_mount_points == ["THIS IS A TEST"]
 
 
@@ -46,7 +54,11 @@ def test_default_format_volume_name(monkeypatch):
     d.user = types.SimpleNamespace(name="user@email.com")
     d.volumes = {"data/{username}": {"bind": "/home/{raw_username}", "mode": "z"}}
     assert d.volume_binds == {
-        "data/user-40email-2ecom": {"bind": "/home/user@email.com", "mode": "z"}
+        "data/user-40email-2ecom": {
+            "bind": "/home/user@email.com",
+            "mode": "z",
+            "propagation": 'rprivate',
+        }
     }
     assert d.volume_mount_points == ["/home/user@email.com"]
 
@@ -60,7 +72,11 @@ def test_escaped_format_volume_name(monkeypatch):
     d.volumes = {"data/{username}": {"bind": "/home/{username}", "mode": "z"}}
     d.format_volume_name = dockerspawner.volumenamingstrategy.escaped_format_volume_name
     assert d.volume_binds == {
-        "data/user-40email-2ecom": {"bind": "/home/user-40email-2ecom", "mode": "z"}
+        "data/user-40email-2ecom": {
+            "bind": "/home/user-40email-2ecom",
+            "mode": "z",
+            "propagation": 'rprivate',
+        }
     }
     assert d.volume_mount_points == ["/home/user-40email-2ecom"]