feat: keep Docker images on computes consistent with the controller host

Only relying on the image name lets a moved tag (e.g. a newer :latest)
silently serve stale content from a compute that already has an image
under the same name. When creating a Docker node, the controller now
pins the image id (Id from the Docker daemon on the controller host)
into the create payload. A compute holding a different image under the
same tag reports the image as missing, which routes it through the
image sync added by the previous commit and re-aligns the tag.

No new template fields or database changes: the controller host daemon
remains the source of truth and the pin is resolved per creation. When
the image is not available on the controller host the pin is omitted
and behavior is unchanged (the compute pulls from the repository).

gns3server/api/routes/compute/docker_nodes.py

@@ -81,6 +81,7 @@ async def create_docker_node(project_id: UUID, node_data: schemas.DockerCreate)
         extra_configs=node_data.get("extra_configs"),
         memory=node_data.get("memory", 0),
         cpus=node_data.get("cpus", 0),
+        image_digest=node_data.get("image_digest"),
     )
     # Pop keys already consumed by create_node above so the setattr
     # fallback loop below only applies truly extra keys and does not
@@ -89,7 +90,7 @@ async def create_docker_node(project_id: UUID, node_data: schemas.DockerCreate)
         "console", "console_type", "console_resolution", "console_http_port",
         "console_http_path", "aux", "aux_type", "start_command", "environment",
         "adapters", "mac_address", "extra_hosts", "extra_volumes", "extra_configs",
-        "memory", "cpus",
+        "memory", "cpus", "image_digest",
     ):
         node_data.pop(key, None)
     for name, value in node_data.items():

gns3server/compute/docker/docker_vm.py

@@ -122,6 +122,7 @@ class DockerVM(BaseNode):
         extra_configs=None,
         memory=0,
         cpus=0,
+        image_digest=None,
     ):
 
         if not is_rfc1123_hostname_valid(name):
@@ -135,6 +136,10 @@ class DockerVM(BaseNode):
         if ":" not in image:
             image = f"{image}:latest"
         self._image = image
+        # image id expected by the controller (set when the image is available on
+        # the controller host): a different local image under the same tag is
+        # treated as missing so the controller re-syncs the expected version
+        self._image_digest = image_digest
         # assign through the property setters so creation and updates apply
         # the same value normalization (e.g. "" -> None)
         self.start_command = start_command
@@ -583,6 +588,16 @@ class DockerVM(BaseNode):
         if image_infos is None:
             raise DockerError(f"Cannot get information for image '{self._image}', please try again.")
 
+        if self._image_digest and image_infos.get("Id") != self._image_digest:
+            # the tag exists but points to a different image (e.g. a moved :latest):
+            # report it as missing so the controller re-syncs the expected version
+            local_id = image_infos.get("Id")
+            log.info(
+                f"Image '{self._image}' version mismatch on this compute: "
+                f"local id '{local_id}' != expected '{self._image_digest}'"
+            )
+            raise ImageMissingError(self._image)
+
         available_cpus = psutil.cpu_count(logical=True)
         if self._cpus > available_cpus:
             raise DockerError(

gns3server/controller/node.py

@@ -465,6 +465,7 @@ class Node:
         data["node_id"] = self._id
         if self._node_type == "docker":
             timeout = None
+            await self._add_docker_image_digest(data)
         else:
             timeout = 1200
         trial = 0
@@ -788,6 +789,29 @@ class Node:
                 return True
         return False
 
+    async def _add_docker_image_digest(self, data):
+        """
+        Pin the Docker image of a node to the image id found on the Docker daemon
+        of the controller host, so that a compute holding a different image under
+        the same tag (e.g. a moved :latest) gets it re-synced instead of silently
+        reusing the stale copy. Not set when the image is not on the controller host.
+        """
+
+        from gns3server.compute.docker import Docker
+        from gns3server.compute.docker.docker_error import DockerError
+
+        image = data.get("image")
+        if not image:
+            return
+        try:
+            image_info = await Docker.instance().query("GET", f"images/{image}/json")
+        except DockerError:
+            # not available on the controller host: nothing to pin against
+            return
+        image_id = image_info.get("Id")
+        if image_id:
+            data["image_digest"] = image_id
+
     async def _sync_missing_docker_image(self, image):
         """
         Export a Docker image from the Docker daemon on the controller host and

gns3server/schemas/compute/docker_nodes.py

@@ -75,6 +75,12 @@ class DockerCreate(DockerBase):
     application_id: Optional[int] = Field(
         None, ge=1, le=1022, description="IOL application ID for iol-runner images (allocated by the controller)"
     )
+    image_digest: Optional[str] = Field(
+        None, pattern=r"^sha256:[a-f0-9]{64}$",
+        description="Image id the controller expects for 'image' (sha256:<hex>, resolved from the Docker "
+                    "daemon on the controller host). When set and the compute holds a different image "
+                    "under the same tag, the image is reported as missing so the controller re-syncs it"
+    )
 
 
 class DockerUpdate(DockerBase):

tests/compute/docker/test_docker_vm.py

@@ -564,6 +564,38 @@ async def test_create_image_not_available(compute_project, manager):
         query_mock.assert_not_called()
 
 
+@pytest.mark.asyncio
+async def test_create_image_digest_match(compute_project, manager):
+
+    response = {
+        "Id": "sha256:" + "a" * 64,
+        "Warnings": []
+    }
+    with asyncio_patch("gns3server.compute.docker.Docker.query", return_value=response) as mock:
+        vm = DockerVM("test", str(uuid.uuid4()), compute_project, manager, "ubuntu:latest",
+                      image_digest="sha256:" + "a" * 64)
+        await vm.create()
+        # the last query is the container creation: the digest check let it through
+        assert mock.call_args[0] == ("POST", "containers/create?name={}".format(vm.docker_name))
+        assert vm._cid == "sha256:" + "a" * 64
+
+
+@pytest.mark.asyncio
+async def test_create_image_digest_mismatch(compute_project, manager):
+
+    response = {
+        "Id": "sha256:" + "b" * 64,
+        "Warnings": []
+    }
+    vm = DockerVM("test", str(uuid.uuid4()), compute_project, manager, "ubuntu:latest",
+                  image_digest="sha256:" + "a" * 64)
+    with asyncio_patch("gns3server.compute.docker.Docker.query", return_value=response) as query_mock:
+        with pytest.raises(ImageMissingError, match="ubuntu:latest"):
+            await vm.create()
+        # only the image inspect happened: no container was created from the stale image
+        query_mock.assert_called_once_with("GET", "images/ubuntu:latest/json")
+
+
 @pytest.mark.asyncio
 async def test_create_with_user(compute_project, manager):
 

tests/controller/test_node.py

@@ -726,6 +726,28 @@ async def test_sync_missing_docker_image_pull_fallback(compute, controller):
     compute.post.assert_called_with("/docker/images/pull", data={"image": "nginx:latest"}, timeout=None)
 
 
+@pytest.mark.asyncio
+async def test_create_docker_node_pins_image_digest(compute, controller):
+
+    project = Project(str(uuid.uuid4()), controller=controller)
+    node = Node(project, compute, "demo",
+                node_id=str(uuid.uuid4()),
+                node_type="docker",
+                properties={"image": "gns3/frr:latest", "adapters": 1})
+
+    response = MagicMock()
+    response.status = 200
+    response.json = {}
+    compute.post = AsyncioMagicMock(return_value=response)
+
+    image_id = "sha256:" + "a" * 64
+    with asyncio_patch("gns3server.compute.docker.Docker.query", return_value={"Id": image_id}):
+        assert await node.create() is True
+    # the image id from the controller host daemon is pinned into the create payload
+    data = compute.post.call_args[1]["data"]
+    assert data["image_digest"] == image_id
+
+
 def test_update_label(node):
     """
     The text in label need to be always the