CASSANDRA-20996 Use LWTs for all auto-repair history mutations

CHANGES.txt

@@ -1,4 +1,5 @@
 5.1
+ * Use LWTs for all auto-repair history mutations (CASSANDRA-20996)
  * Add cqlsh autocompletion for the identity mapping feature (CASSANDRA-20021)
  * Add DDL Guardrail enabling administrators to disallow creation/modification of keyspaces with durable_writes = false (CASSANDRA-20913)
  * Optimize Counter, Meter and Histogram metrics using thread local counters (CASSANDRA-20250)

src/java/org/apache/cassandra/repair/autorepair/AutoRepairUtils.java

@@ -150,27 +150,27 @@ public class AutoRepairUtils
     COL_DELETE_HOSTS, COL_DELETE_HOSTS_UPDATE_TIME, COL_REPAIR_TYPE, COL_HOST_ID);
 
     final static String DEL_AUTO_REPAIR_HISTORY = String.format(
-    "DELETE FROM %s.%s WHERE %s = ? AND %s = ?"
+    "DELETE FROM %s.%s WHERE %s = ? AND %s = ? IF EXISTS"
     , SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY, COL_REPAIR_TYPE,
     COL_HOST_ID);
 
     final static String RECORD_START_REPAIR_HISTORY = String.format(
-    "UPDATE %s.%s SET %s= ?, repair_turn = ? WHERE %s = ? AND %s = ?"
+    "UPDATE %s.%s SET %s= ?, repair_turn = ? WHERE %s = ? AND %s = ? IF EXISTS"
     , SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY, COL_REPAIR_START_TS,
     COL_REPAIR_TYPE, COL_HOST_ID);
 
     final static String RECORD_FINISH_REPAIR_HISTORY = String.format(
-    "UPDATE %s.%s SET %s= ?, %s=false WHERE %s = ? AND %s = ?"
+    "UPDATE %s.%s SET %s= ?, %s=false WHERE %s = ? AND %s = ? IF EXISTS"
     , SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY, COL_REPAIR_FINISH_TS,
     COL_FORCE_REPAIR, COL_REPAIR_TYPE, COL_HOST_ID);
 
     final static String CLEAR_DELETE_HOSTS = String.format(
-    "UPDATE %s.%s SET %s= {} WHERE %s = ? AND %s = ?"
+    "UPDATE %s.%s SET %s= {} WHERE %s = ? AND %s = ? IF EXISTS"
     , SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY, COL_DELETE_HOSTS,
     COL_REPAIR_TYPE, COL_HOST_ID);
 
     final static String SET_FORCE_REPAIR = String.format(
-    "UPDATE %s.%s SET %s=true  WHERE %s = ? AND %s = ?"
+    "UPDATE %s.%s SET %s=true  WHERE %s = ? AND %s = ? IF EXISTS"
     , SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY, COL_FORCE_REPAIR,
     COL_REPAIR_TYPE, COL_HOST_ID);
 

test/unit/org/apache/cassandra/repair/autorepair/AutoRepairUtilsTest.java

@@ -538,4 +538,42 @@ public void testSkipSystemTraces()
     {
         assertFalse(AutoRepairUtils.shouldConsiderKeyspace(Keyspace.open(SchemaConstants.TRACE_KEYSPACE_NAME)));
     }
+
+    @Test
+    public void testAutoRepairHistoryOutOfOrderDeleteRaceCondition()
+    {
+        // Setup: Create a node that will be deleted
+        UUID nodeToDelete = UUID.randomUUID();
+        UUID votingNode = UUID.randomUUID();
+
+        // Insert an initial row for the node to be deleted
+        QueryProcessor.executeInternal(String.format(
+        "INSERT INTO %s.%s (repair_type, host_id, repair_start_ts, repair_finish_ts) VALUES ('%s', %s, 100, 200)",
+        SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY,
+        repairType, nodeToDelete));
+
+        // Verify the row exists
+        UntypedResultSet beforeDelete = QueryProcessor.executeInternal(String.format(
+        "SELECT * FROM %s.%s WHERE repair_type = '%s' AND host_id = %s",
+        SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY,
+        repairType, nodeToDelete));
+        assertNotNull(beforeDelete);
+        assertEquals(1, beforeDelete.size());
+
+        // Simulate the race condition:
+        // 1. First, the delete is executed (this should create a tombstone)
+        AutoRepairUtils.deleteAutoRepairHistory(repairType, nodeToDelete);
+
+        // 2. Then, a vote to delete arrives after the row has already been deleted
+        AutoRepairUtils.addHostIdToDeleteHosts(repairType, votingNode, nodeToDelete);
+
+        // Verify that the row is still deleted despite the out-of-order vote
+        UntypedResultSet afterRace = QueryProcessor.executeInternal(String.format(
+        "SELECT * FROM %s.%s WHERE repair_type = '%s' AND host_id = %s",
+        SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY,
+        repairType, nodeToDelete));
+        assertNotNull(afterRace);
+        // The row should not exist - the delete should win despite the vote arriving later
+        assertEquals("Row should remain deleted despite out-of-order vote", 0, afterRace.size());
+    }
 }

test/unit/org/apache/cassandra/service/AutoRepairServiceSetterTest.java

@@ -132,6 +132,10 @@ public void prepare()
         QueryProcessor.executeInternal(String.format(
         "TRUNCATE %s.%s",
         SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_PRIORITY));
+        QueryProcessor.executeInternal(String.format(
+        "INSERT INTO %s.%s (host_id, repair_type) VALUES (%s, '%s')",
+        SchemaConstants.DISTRIBUTED_KEYSPACE_NAME, SystemDistributedKeyspace.AUTO_REPAIR_HISTORY,
+        StorageService.instance.getHostIdForEndpoint(InetAddressAndPort.getLocalHost()), repairTypeStr));
     }
 
     @Test