From c39ba74249738d84022ae8163caab5d5a2e9f0e8 Mon Sep 17 00:00:00 2001
From: "J.C. Jones" <jc@letsencrypt.org>
Date: Thu, 29 Feb 2024 12:54:50 -0700
Subject: [PATCH] Don't emit a Prometheus error for empty tables

Fixes #79

Causes #81
---
 partitionmanager/cli.py                    |  2 ++
 partitionmanager/database_helpers_test.py  | 11 +++++++++++
 partitionmanager/table_append_partition.py |  2 +-
 partitionmanager/types.py                  |  4 ++++
 pyproject.toml                             |  2 +-
 5 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/partitionmanager/cli.py b/partitionmanager/cli.py
index 723b650..c8f03e0 100644
--- a/partitionmanager/cli.py
+++ b/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)
diff --git a/partitionmanager/database_helpers_test.py b/partitionmanager/database_helpers_test.py
index 188752c..280ae17 100644
--- a/partitionmanager/database_helpers_test.py
+++ b/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}])
diff --git a/partitionmanager/table_append_partition.py b/partitionmanager/table_append_partition.py
index 266bdd0..521b9f0 100644
--- a/partitionmanager/table_append_partition.py
+++ b/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]
diff --git a/partitionmanager/types.py b/partitionmanager/types.py
index cf1e3ca..d630cf7 100644
--- a/partitionmanager/types.py
+++ b/partitionmanager/types.py
@@ -596,6 +596,10 @@ 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."""
 
diff --git a/pyproject.toml b/pyproject.toml
index ebb928b..29e78dd 100644
--- a/pyproject.toml
+++ b/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