Drop hardcoded Nebius InfiniBand fabrics

src/dstack/_internal/core/backends/nebius/compute.py

@@ -28,8 +28,11 @@
     get_offers_disk_modifier,
 )
 from dstack._internal.core.backends.nebius import resources
-from dstack._internal.core.backends.nebius.fabrics import get_suitable_infiniband_fabrics
-from dstack._internal.core.backends.nebius.models import NebiusConfig, NebiusServiceAccountCreds
+from dstack._internal.core.backends.nebius.models import (
+    NebiusConfig,
+    NebiusOfferBackendData,
+    NebiusServiceAccountCreds,
+)
 from dstack._internal.core.errors import (
     BackendError,
     NotYetTerminated,
@@ -281,23 +284,30 @@ def create_placement_group(
         master_instance_offer: InstanceOffer,
     ) -> PlacementGroupProvisioningData:
         assert placement_group.configuration.placement_strategy == PlacementStrategy.CLUSTER
-        backend_data = NebiusPlacementGroupBackendData(cluster=None)
+        master_instance_offer_backend_data: NebiusOfferBackendData = (
+            NebiusOfferBackendData.__response__.parse_obj(master_instance_offer.backend_data)
+        )
+        fabrics = list(master_instance_offer_backend_data.fabrics)
+        if self.config.fabrics is not None:
+            fabrics = [f for f in fabrics if f in self.config.fabrics]
+        placement_group_backend_data = NebiusPlacementGroupBackendData(cluster=None)
         # Only create a Nebius cluster if the instance supports it.
         # For other instances, return dummy PlacementGroupProvisioningData.
-        if fabrics := get_suitable_infiniband_fabrics(
-            master_instance_offer, allowed_fabrics=self.config.fabrics
-        ):
+        if fabrics:
             fabric = random.choice(fabrics)
             op = resources.create_cluster(
                 self._sdk,
                 name=placement_group.name,
                 project_id=self._region_to_project_id[placement_group.configuration.region],
                 fabric=fabric,
             )
-            backend_data.cluster = NebiusClusterBackendData(id=op.resource_id, fabric=fabric)
+            placement_group_backend_data.cluster = NebiusClusterBackendData(
+                id=op.resource_id,
+                fabric=fabric,
+            )
         return PlacementGroupProvisioningData(
             backend=BackendType.NEBIUS,
-            backend_data=backend_data.json(),
+            backend_data=placement_group_backend_data.json(),
         )
 
     def delete_placement_group(self, placement_group: PlacementGroup) -> None:
@@ -317,16 +327,15 @@ def is_suitable_placement_group(
         if placement_group.configuration.region != instance_offer.region:
             return False
         assert placement_group.provisioning_data is not None
-        backend_data = NebiusPlacementGroupBackendData.load(
+        placement_group_backend_data = NebiusPlacementGroupBackendData.load(
             placement_group.provisioning_data.backend_data
         )
+        instance_offer_backend_data: NebiusOfferBackendData = (
+            NebiusOfferBackendData.__response__.parse_obj(instance_offer.backend_data)
+        )
         return (
-            backend_data.cluster is None
-            or backend_data.cluster.fabric
-            in get_suitable_infiniband_fabrics(
-                instance_offer,
-                allowed_fabrics=None,  # enforced at cluster creation time, no need to enforce here
-            )
+            placement_group_backend_data.cluster is None
+            or placement_group_backend_data.cluster.fabric in instance_offer_backend_data.fabrics
         )
 
 

src/dstack/_internal/core/backends/nebius/configurator.py

@@ -10,7 +10,6 @@
 )
 from dstack._internal.core.backends.nebius import resources
 from dstack._internal.core.backends.nebius.backend import NebiusBackend
-from dstack._internal.core.backends.nebius.fabrics import get_all_infiniband_fabrics
 from dstack._internal.core.backends.nebius.models import (
     NebiusBackendConfig,
     NebiusBackendConfigWithCreds,
@@ -19,6 +18,7 @@
     NebiusServiceAccountCreds,
     NebiusStoredConfig,
 )
+from dstack._internal.core.backends.nebius.resources import get_all_infiniband_fabrics
 from dstack._internal.core.errors import BackendError, ServerClientError
 from dstack._internal.core.models.backends.base import BackendType
 

src/dstack/_internal/core/backends/nebius/models.py

@@ -179,3 +179,7 @@ class NebiusConfig(NebiusStoredConfig):
     """
 
     creds: AnyNebiusCreds
+
+
+class NebiusOfferBackendData(CoreModel):
+    fabrics: set[str] = set()

src/dstack/_internal/core/backends/nebius/resources.py

@@ -50,11 +50,14 @@
 from nebius.sdk import SDK
 
 from dstack._internal.core.backends.base.configurator import raise_invalid_credentials_error
+from dstack._internal.core.backends.base.offers import get_catalog_offers
 from dstack._internal.core.backends.nebius.models import (
     DEFAULT_PROJECT_NAME_PREFIX,
+    NebiusOfferBackendData,
     NebiusServiceAccountCreds,
 )
 from dstack._internal.core.errors import BackendError, NoCapacityError
+from dstack._internal.core.models.backends.base import BackendType
 from dstack._internal.utils.event_loop import DaemonEventLoop
 from dstack._internal.utils.logging import get_logger
 
@@ -249,6 +252,17 @@ def get_default_subnet(sdk: SDK, project_id: str) -> Subnet:
     raise BackendError(f"Could not find default subnet in project {project_id}")
 
 
+def get_all_infiniband_fabrics() -> set[str]:
+    offers = get_catalog_offers(backend=BackendType.NEBIUS)
+    result = set()
+    for offer in offers:
+        backend_data: NebiusOfferBackendData = NebiusOfferBackendData.__response__.parse_obj(
+            offer.backend_data
+        )
+        result |= backend_data.fabrics
+    return result
+
+
 def create_disk(
     sdk: SDK, name: str, project_id: str, size_mib: int, image_family: str, labels: Dict[str, str]
 ) -> SDKOperation[Operation]:

src/tests/_internal/server/routers/test_backends.py

@@ -13,7 +13,13 @@
 
 from dstack._internal.core.backends.oci import region as oci_region
 from dstack._internal.core.models.backends.base import BackendType
-from dstack._internal.core.models.instances import InstanceStatus
+from dstack._internal.core.models.instances import (
+    Gpu,
+    InstanceOffer,
+    InstanceStatus,
+    InstanceType,
+    Resources,
+)
 from dstack._internal.core.models.users import GlobalRole, ProjectRole
 from dstack._internal.core.models.volumes import VolumeStatus
 from dstack._internal.server.models import BackendModel
@@ -212,6 +218,30 @@ async def test_creates_lambda_backend(
     @pytest.mark.skipif(sys.version_info < (3, 10), reason="Nebius requires Python 3.10")
     @pytest.mark.parametrize("test_db", ["sqlite", "postgres"], indirect=True)
     class TestNebius:
+        @pytest.fixture(autouse=True)
+        def patch_catalog(self):
+            with patch(
+                "dstack._internal.core.backends.nebius.resources.get_catalog_offers"
+            ) as get_catalog_offers_mock:
+                get_catalog_offers_mock.return_value = [
+                    InstanceOffer(
+                        backend=BackendType.NEBIUS,
+                        instance=InstanceType(
+                            name="gpu-h100-sxm 8gpu-128vcpu-1600gb",
+                            resources=Resources(
+                                cpus=128,
+                                memory_mib=1600 * 1024,
+                                gpus=[Gpu(name="H100", memory_mib=80 * 1024)] * 8,
+                                spot=False,
+                            ),
+                        ),
+                        region="eu-north1",
+                        price=23.6,
+                        backend_data={"fabrics": ["fabric-2", "fabric-3"]},
+                    )
+                ]
+                yield
+
         async def test_not_creates_with_invalid_creds(
             self, test_db, session: AsyncSession, client: AsyncClient
         ):
@@ -238,18 +268,16 @@ async def test_not_creates_with_invalid_creds(
             assert len(res.scalars().all()) == 0
 
         @pytest.mark.parametrize(
-            ("config_regions", "config_projects", "mocked_projects", "error"),
+            ("config_extra", "mocked_projects", "error"),
             [
                 pytest.param(
-                    None,
-                    None,
+                    {},
                     [_nebius_project()],
                     None,
                     id="default",
                 ),
                 pytest.param(
-                    ["eu-north1"],
-                    None,
+                    {"regions": ["eu-north1"]},
                     [
                         _nebius_project(
                             "project-e00test", "default-project-eu-north1", "eu-north1"
@@ -260,15 +288,13 @@ async def test_not_creates_with_invalid_creds(
                     id="with-regions",
                 ),
                 pytest.param(
-                    ["xx-xxxx1"],
-                    None,
+                    {"regions": ["xx-xxxx1"]},
                     [_nebius_project()],
                     "do not exist in this Nebius tenancy",
                     id="error-invalid-regions",
                 ),
                 pytest.param(
-                    ["eu-north1"],
-                    None,
+                    {"regions": ["eu-north1"]},
                     [
                         _nebius_project(
                             "project-e00test0", "default-project-eu-north1", "eu-north1"
@@ -279,8 +305,7 @@ async def test_not_creates_with_invalid_creds(
                     id="finds-default-project-among-many",
                 ),
                 pytest.param(
-                    ["eu-north1"],
-                    None,
+                    {"regions": ["eu-north1"]},
                     [
                         _nebius_project("project-e00test0", "non-default-project-0", "eu-north1"),
                         _nebius_project("project-e00test1", "non-default-project-1", "eu-north1"),
@@ -289,8 +314,7 @@ async def test_not_creates_with_invalid_creds(
                     id="error-no-default-project",
                 ),
                 pytest.param(
-                    None,
-                    ["project-e00test0"],
+                    {"projects": ["project-e00test0"]},
                     [
                         _nebius_project("project-e00test0", "non-default-project-0", "eu-north1"),
                         _nebius_project("project-e00test1", "non-default-project-1", "eu-north1"),
@@ -299,15 +323,13 @@ async def test_not_creates_with_invalid_creds(
                     id="with-projects",
                 ),
                 pytest.param(
-                    None,
-                    ["project-e00xxxx"],
+                    {"projects": ["project-e00xxxx"]},
                     [_nebius_project()],
                     "not found in this Nebius tenancy",
                     id="error-invalid-projects",
                 ),
                 pytest.param(
-                    None,
-                    ["project-e00test0", "project-e00test1"],
+                    {"projects": ["project-e00test0", "project-e00test1"]},
                     [
                         _nebius_project("project-e00test0", "non-default-project-0", "eu-north1"),
                         _nebius_project("project-e00test1", "non-default-project-1", "eu-north1"),
@@ -316,8 +338,10 @@ async def test_not_creates_with_invalid_creds(
                     id="error-multiple-projects-in-same-region",
                 ),
                 pytest.param(
-                    ["eu-north1"],
-                    ["project-e00test"],
+                    {
+                        "regions": ["eu-north1"],
+                        "projects": ["project-e00test"],
+                    },
                     [
                         _nebius_project(
                             "project-e00test", "default-project-eu-north1", "eu-north1"
@@ -327,15 +351,26 @@ async def test_not_creates_with_invalid_creds(
                     None,
                     id="with-regions-and-projects",
                 ),
+                pytest.param(
+                    {"fabrics": ["fabric-2", "fabric-3"]},
+                    [_nebius_project()],
+                    None,
+                    id="with-valid-fabrics",
+                ),
+                pytest.param(
+                    {"fabrics": ["fabric-2", "fabric-invalid"]},
+                    [_nebius_project()],
+                    "InfiniBand fabrics do not exist",
+                    id="with-invalid-fabrics",
+                ),
             ],
         )
         async def test_create(
             self,
             test_db,
             session: AsyncSession,
             client: AsyncClient,
-            config_regions: Optional[list[str]],
-            config_projects: Optional[list[str]],
+            config_extra: dict[str, Any],
             mocked_projects: Sequence[Any],
             error: Optional[str],
         ):
@@ -347,8 +382,7 @@ async def test_create(
             body = {
                 "type": "nebius",
                 "creds": FAKE_NEBIUS_SERVICE_ACCOUNT_CREDS,
-                "regions": config_regions,
-                "projects": config_projects,
+                **config_extra,
             }
             with patch(
                 "dstack._internal.core.backends.nebius.resources.list_tenant_projects"