DM-41880: Support ChainedDatastore for Butler server

doc/changes/DM-41880.feature.rst

@@ -0,0 +1 @@
+Butler server can now be configured to use a ChainedDatastore.

doc/changes/DM-41880.perf.rst

@@ -0,0 +1 @@
+``FileDatastore.knows()`` no longer requires database I/O if its input ``DatasetRef`` has datastore records attached.

python/lsst/daf/butler/_dataset_ref.py

@@ -60,7 +60,7 @@
 
 # Per-dataset records grouped by opaque table name, usually there is just one
 # opaque table.
-DatasetDatastoreRecords: TypeAlias = Mapping[str, Iterable[StoredDatastoreItemInfo]]
+DatasetDatastoreRecords: TypeAlias = Mapping[str, list[StoredDatastoreItemInfo]]
 
 
 class AmbiguousDatasetError(Exception):

python/lsst/daf/butler/datastores/chainedDatastore.py

@@ -399,6 +399,17 @@ def get(
 
         raise FileNotFoundError(f"Dataset {ref} could not be found in any of the datastores")
 
+    def prepare_get_for_external_client(self, ref: DatasetRef) -> object:
+        return self._get_matching_datastore(ref).prepare_get_for_external_client(ref)
+
+    def _get_matching_datastore(self, ref: DatasetRef) -> Datastore:
+        """Return the first child datastore that owns the specified dataset."""
+        for datastore in self.datastores:
+            if datastore.knows(ref):
+                return datastore
+
+        raise FileNotFoundError(f"Dataset {ref} could not be found in any of the datastores")
+
     def put(self, inMemoryDataset: Any, ref: DatasetRef) -> None:
         """Write a InMemoryDataset with a given `DatasetRef` to each
         datastore.

python/lsst/daf/butler/datastores/fileDatastore.py

@@ -40,6 +40,7 @@
 
 from lsst.daf.butler import (
     Config,
+    DatasetDatastoreRecords,
     DatasetId,
     DatasetRef,
     DatasetType,
@@ -457,12 +458,12 @@
         """
         # Try to get them from the ref first.
         if ref._datastore_records is not None and not ignore_datastore_records:
-            if (ref_records := ref._datastore_records.get(self._table.name)) is not None:
-                # Need to make sure they have correct type.
-                for record in ref_records:
-                    if not isinstance(record, StoredFileInfo):
-                        raise TypeError(f"Datastore record has unexpected type {record.__class__.__name__}")
-                return cast(list[StoredFileInfo], ref_records)
+            ref_records = ref._datastore_records.get(self._table.name, [])
+            # Need to make sure they have correct type.
+            for record in ref_records:
+                if not isinstance(record, StoredFileInfo):
+                    raise TypeError(f"Datastore record has unexpected type {record.__class__.__name__}")
+            return cast(list[StoredFileInfo], ref_records)
 
         # Look for the dataset_id -- there might be multiple matches
         # if we have disassembled the dataset.
@@ -1333,9 +1334,7 @@
         exists : `bool`
             `True` if the dataset is known to the datastore.
         """
-        # We cannot trust datastore records from ref, as many unit tests delete
-        # datasets and check their existence.
-        fileLocations = self._get_dataset_locations_info(ref, ignore_datastore_records=True)
+        fileLocations = self._get_dataset_locations_info(ref)
         if fileLocations:
             return True
         return False
@@ -2065,10 +2064,14 @@
                 datastoreRecords=file_info.to_simple(),
             )
 
+        locations = self._get_dataset_locations_info(ref)
+        if len(locations) == 0:
+            raise FileNotFoundError(f"No artifacts found for DatasetId '{ref.id}'")
+
         return FileDatastoreGetPayload(
             datastore_type="file",
             dataset_ref=ref.to_simple(),
-            file_info=[to_file_info_payload(info) for info in self._get_dataset_locations_info(ref)],
+            file_info=[to_file_info_payload(info) for info in locations],
         )
 
     @transactional
@@ -2153,7 +2156,7 @@
             storedInfo = self._write_in_memory_to_artifact(in_memory_dataset, ref)
             artifacts.append((ref, storedInfo))
 
-        ref_records = {self._opaque_table_name: [info for _, info in artifacts]}
+        ref_records: DatasetDatastoreRecords = {self._opaque_table_name: [info for _, info in artifacts]}
         ref = ref.replace(datastore_records=ref_records)
         return {self.name: ref}
 

tests/config/basic/server.yaml

@@ -0,0 +1,26 @@
+# This is a rough approximation of the configuration on the idfprod environment
+datastore:
+  cls: lsst.daf.butler.datastores.chainedDatastore.ChainedDatastore
+  datastore_constraints:
+    # One entry per datastore in datastores section
+    # Use empty `-` if no constraint override required
+    - constraints:
+        reject:
+          - all
+    - constraints:
+        accept:
+          - all
+  datastores:
+    - datastore:
+        name: FileDatastore@s3://immutable-bucket/dc2
+        cls: lsst.daf.butler.datastores.fileDatastore.FileDatastore
+        root: s3://immutable-bucket/dc2
+    - datastore:
+        name: FileDatastore@s3://mutable-bucket
+        cls: lsst.daf.butler.datastores.fileDatastore.FileDatastore
+        root: s3://mutable-bucket/
+        records:
+          table: user_datastore_records
+        formatters: !include formatters.yaml
+        composites: !include composites.yaml
+storageClasses: !include storageClasses.yaml

tests/test_datastore.py

@@ -1086,6 +1086,17 @@ def test_roots(self):
             if root is not None:
                 self.assertTrue(root.exists())
 
+    def test_prepare_get_for_external_client(self):
+        datastore = self.makeDatastore()
+        storageClass = self.storageClassFactory.getStorageClass("StructuredData")
+        dimensions = self.universe.conform(("visit", "physical_filter"))
+        dataId = {"instrument": "dummy", "visit": 52, "physical_filter": "V", "band": "v"}
+        ref = self.makeDatasetRef("metric", dimensions, storageClass, dataId)
+        with self.assertRaises(FileNotFoundError):
+            # Most of the coverage for this function is in test_server.py,
+            # because it requires a file backend that supports URL signing.
+            datastore.prepare_get_for_external_client(ref)
+
 
 class PosixDatastoreNoChecksumsTestCase(PosixDatastoreTestCase):
     """Posix datastore tests but with checksums disabled."""

tests/test_server.py

@@ -105,16 +105,18 @@ def setUpClass(cls):
         # Note that all files are stored in memory.
         cls.enterClassContext(clean_test_environment_for_s3())
         cls.enterClassContext(mock_aws())
-        bucket_name = "anybucketname"  # matches s3Datastore.yaml
-        getS3Client().create_bucket(Bucket=bucket_name)
+
+        # matches server.yaml
+        for bucket in ["mutable-bucket", "immutable-bucket"]:
+            getS3Client().create_bucket(Bucket=bucket)
 
         cls.storageClassFactory = StorageClassFactory()
 
         # First create a butler and populate it.
         cls.root = makeTestTempDir(TESTDIR)
         cls.repo = MetricTestRepo(
             root=cls.root,
-            configFile=os.path.join(TESTDIR, "config/basic/butler-s3store.yaml"),
+            configFile=os.path.join(TESTDIR, "config/basic/server.yaml"),
             forceConfigRoot=False,
         )
         # Add a file with corrupted data for testing error conditions