API: Eid sorting

dp3/api/routers/entity.py

@@ -144,6 +144,7 @@ def _validate_sort_params(etype: str, sort: list[str] | None) -> list[tuple[str,
         sort: list of sort specifications in format 'attribute:direction'
               where direction is 1 (ascending) or -1 (descending)
               e.g., ['hostname:-1', 'ip:1']
+              Special attribute 'eid' is also supported for sorting by entity ID.
 
     Returns:
         List of (attribute, direction) tuples for sorting, or None if no sorting specified
@@ -172,6 +173,11 @@ def _validate_sort_params(etype: str, sort: list[str] | None) -> list[tuple[str,
         attr, direction_str = match.groups()
         direction = int(direction_str) if direction_str else 1  # Default to ascending (1)
 
+        # Support sorting by entity ID using pseudo-attribute 'eid'
+        if attr == "eid":
+            sort_criteria.append((attr, direction))
+            continue
+
         # Check if attribute exists
         if attr not in entity_attribs:
             raise RequestValidationError(
@@ -306,11 +312,13 @@ async def get_entity_type_eids(
 
     Generic and fulltext filters are merged - fulltext overrides conflicting keys.
 
-    Sorting is supported for plain and observations attributes with primitive data types
-    (excluding json and multi_value observations). To sort by multiple attributes, provide
-    multiple sort parameters in the format 'attribute:direction' where direction is 1 (ascending)
-    or -1 (descending). Direction defaults to 1 (ascending) if not provided. Example:
-    `?sort=hostname:-1&sort=ip:1`
+    Sorting is supported by entity ID using the special attribute name `eid`,
+    as well as for plain and observations attributes with primitive data types
+    (excluding json and multi_value observations). To sort by multiple attributes,
+    provide multiple sort parameters in the format 'attribute:direction' where
+    direction is 1 (ascending) or -1 (descending). Direction defaults to 1 (ascending)
+    if not provided. Examples:
+    `?sort=eid:1`, `?sort=hostname:-1&sort=ip:1`
     """
     fulltext_filters, generic_filter = _validate_snapshot_filters(fulltext_filters, generic_filter)
     sort_criteria = _validate_sort_params(etype, sort)

tests/test_api/test_get_entity_eids.py

@@ -60,3 +60,69 @@ def test_get_entity_eids_generic_filters_eid(self):
             {5, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59},
             {x["eid"] for x in eids.data},
         )
+
+    def test_get_entity_eids_sort_by_eid_asc(self):
+        eids = self.get_entity_data("entity/A/get", EntityEidList, sort="eid:1", limit=0)
+        self.assertEqual(100, len(eids.data))
+        self.assertEqual(list(range(100)), [x["eid"] for x in eids.data])
+
+    def test_get_entity_eids_sort_by_eid_desc(self):
+        eids = self.get_entity_data("entity/A/get", EntityEidList, sort="eid:-1", limit=0)
+        self.assertEqual(100, len(eids.data))
+        self.assertEqual(list(range(99, -1, -1)), [x["eid"] for x in eids.data])
+
+    def test_get_entity_eids_pagination_with_sort(self):
+        received_eids = []
+        for i in range(0, 100, 10):
+            eids = self.get_entity_data(
+                "entity/A/get", EntityEidList, sort="eid:1", skip=i, limit=10
+            )
+            self.assertEqual(10, len(eids.data), f"Failed at {i}")
+            received_eids.extend(x["eid"] for x in eids.data)
+        self.assertEqual(list(range(100)), received_eids)
+
+        received_eids = []
+        for i in range(0, 100, 10):
+            eids = self.get_entity_data(
+                "entity/A/get", EntityEidList, sort="eid:-1", skip=i, limit=10
+            )
+            self.assertEqual(10, len(eids.data), f"Failed at {i}")
+            received_eids.extend(x["eid"] for x in eids.data)
+        self.assertEqual(list(range(99, -1, -1)), received_eids)
+
+    def _get_sorted_eids(self, sort_params: list[str], **kwargs) -> EntityEidList:
+        """Fetch entity EIDs with multiple sort query parameters.
+
+        The shared `get_request` helper joins kwargs with '&' and cannot emit
+        multiple values for the same key, which is required for multi-column
+        sorting. Build the query string explicitly here.
+        """
+        query_parts = [f"sort={param}" for param in sort_params]
+        for key, value in kwargs.items():
+            query_parts.append(f"{key}={value}")
+        response = self.get_request(f"entity/A/get?{'&'.join(query_parts)}")
+        self.assertEqual(response.status_code, 200)
+        return EntityEidList.model_validate_json(response.content)
+
+    def test_get_entity_eids_sort_by_multiple_attrs(self):
+        res = self.push_datapoints(
+            [
+                {"src": "setup@test", "attr": "data2", "type": "A", "id": i, "v": f"g{i % 5}"}
+                for i in range(0, 100)
+            ]
+        )
+        self.assertEqual(res.status_code, 200)
+        sleep(8)
+        self.get_request("control/make_snapshots")
+        sleep(6)
+
+        expected = sorted(range(100), key=lambda i: (f"g{i % 5}", i))
+        # omit :1 if sort is ascending
+        eids = self._get_sorted_eids(["data2", "eid"], limit=0)
+        self.assertEqual(100, len(eids.data))
+        self.assertEqual(expected, [x["eid"] for x in eids.data])
+
+        expected = sorted(range(100), key=lambda i: (f"g{i % 5}", -i))
+        eids = self._get_sorted_eids(["data2:1", "eid:-1"], limit=0)
+        self.assertEqual(100, len(eids.data))
+        self.assertEqual(expected, [x["eid"] for x in eids.data])