Don't emit a Prometheus error for empty tables (#80)

Fixes #79

Causes #81

Author: jcjones

partitionmanager/cli.py

@@ -360,6 +360,8 @@ def do_partition(conf):
         except partitionmanager.types.DatabaseCommandException as e:
             log.warning("Failed to automatically handle %s: %s", table, e)
             metrics.add("alter_errors", table.name, 1)
+        except partitionmanager.types.TableEmptyException:
+            log.warning("Table %s appears to be empty. Skipping.", table)
         except (ValueError, Exception) as e:
             log.warning("Failed to handle %s: %s", table, e)
             metrics.add("alter_errors", table.name, 1)

partitionmanager/database_helpers_test.py

@@ -9,6 +9,7 @@
     SqlInput,
     SqlQuery,
     Table,
+    TableEmptyException,
 )
 
 
@@ -46,6 +47,16 @@ def test_position_of_table(self):
         pos = get_position_of_table(db, table, data)
         self.assertEqual(pos.as_list(), [90210])
 
+    def test_empty_table(self):
+        db = MockDatabase()
+        db.add_response("SELECT id FROM `burgers` ORDER BY", [])
+
+        table = Table("burgers")
+        data = {"range_cols": ["id"]}
+
+        with self.assertRaises(TableEmptyException):
+            get_position_of_table(db, table, data)
+
     def test_exact_timestamp_no_query(self):
         db = MockDatabase()
         db.add_response("SELECT id FROM `burgers` ORDER BY", [{"id": 42}])

partitionmanager/table_append_partition.py

@@ -61,7 +61,7 @@ def get_current_positions(database, table, columns):
                 f"Expected one result from {table.name}"
             )
         if not rows:
-            raise partitionmanager.types.TableInformationException(
+            raise partitionmanager.types.TableEmptyException(
                 f"Table {table.name} appears to be empty. (No results)"
             )
         positions[column] = rows[0][column]

partitionmanager/types.py

@@ -611,6 +611,10 @@ class TableInformationException(Exception):
     """Raised when the table's status doesn't include the information we need."""
 
 
+class TableEmptyException(Exception):
+    """Raised when the table is empty."""
+
+
 class NoEmptyPartitionsAvailableException(Exception):
     """Raised if no empty partitions are available to safely modify."""
 

pyproject.toml

@@ -116,4 +116,4 @@ max-complexity = 16  # default is 10
 [tool.ruff.lint.pylint]
 max-args = 7  # default is 5
 max-branches = 15  # default is 12
-max-statements = 52  # default is 50
+max-statements = 54  # default is 50