Allow sasquatch datastore to add extra fields

python/lsst/analysis/tools/interfaces/datastore/_sasquatchDatastore.py

@@ -86,6 +86,16 @@ class SasquatchDatastore(GenericBaseDatastore):
     environment variable and "lsst.dm" if no environment variable is defined.
     """
 
+    extra_fields: dict[str, str | int | float] | None
+    """Extra key/value pairs that should be passed along with the metric
+    when storing in Sasquatch.
+
+    If not given extra key/value pairs can be obtained from the
+    ``$SASQUATCH_EXTRAS`` environment variable. This environment variable
+    must have the form of "k1=v2;k2=v2". If no environment variable is given
+    defaults can be read from the datastore configuration.
+    """
+
     def __init__(
         self,
         config: DatastoreConfig,
@@ -113,6 +123,16 @@ def __init__(
             ),
         )
 
+        extra_fields: dict[str, str | int | float] | None = None
+        if extras_str := os.environ.get("SASQUATCH_EXTRAS"):
+            extra_fields = {}
+            for item in extras_str.split(";"):
+                k, v = item.split("=")
+                extra_fields[k] = v
+            self.extra_fields = extra_fields
+        else:
+            self.extra_fields = self.config.get("extra_fields", extra_fields)
+
         self._dispatcher = SasquatchDispatcher(self.restProxyUrl, self.accessToken, self.namespace)
 
     @classmethod
@@ -133,7 +153,7 @@ def bridge(self) -> DatastoreRegistryBridge:
 
     def put(self, inMemoryDataset: Any, ref: DatasetRef) -> None:
         if self.constraints.isAcceptable(ref):
-            self._dispatcher.dispatchRef(inMemoryDataset, ref)
+            self._dispatcher.dispatchRef(inMemoryDataset, ref, extraFields=self.extra_fields)
         else:
             log.debug("Could not put dataset type %s with Sasquatch datastore", ref.datasetType)
             raise DatasetTypeNotSupportedError(