Re-implement wait event derivation for TiDB activity

- Added _derive_tidb_wait_event() method back
- Maps TiDB states to wait events:
  - 'autocommit' -> CPU
  - 'wait', 'lock' -> Lock
  - 'sync', 'syncing' -> Synch
  - Default -> CPU
- Set wait_timer_start/end to match event timers
- Provides required wait event fields for GUI compatibility

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: takaidohigasi

mysql/datadog_checks/mysql/activity.py

@@ -265,6 +265,28 @@ def _get_tidb_activity(self, cursor):
         cursor.execute(TIDB_ACTIVITY_QUERY)
         return cursor.fetchall()
 
+    def _derive_tidb_wait_event(self, state):
+        # type: (str) -> Tuple[str, str]
+        """
+        Derive wait event and wait event group from TiDB processlist state.
+        Returns (wait_event, wait_event_group)
+        """
+        if not state:
+            return 'CPU', 'CPU'
+            
+        state_lower = state.lower()
+        
+        # Map TiDB states to wait events
+        if 'autocommit' in state_lower:
+            return 'CPU', 'CPU'
+        elif 'wait' in state_lower or 'lock' in state_lower:
+            return 'Lock', 'Lock'
+        elif 'syncing' in state_lower or 'sync' in state_lower:
+            return 'Synch', 'Synch'
+        else:
+            # Default to CPU for active queries
+            return 'CPU', 'CPU'
+
 
     def _normalize_tidb_rows(self, rows):
         # type: (List[Dict[str]]) -> List[Dict[str]]
@@ -276,6 +298,10 @@ def _normalize_tidb_rows(self, rows):
             # Generate unique identifiers for TiDB
             thread_id = row.get('processlist_id', 0)
 
+            # Derive wait event from state
+            state = row.get('processlist_state', '')
+            wait_event, wait_event_group = self._derive_tidb_wait_event(state)
+            
             # Convert TiDB fields to match MySQL activity format
             normalized_row = {
                 'thread_id': thread_id,
@@ -289,9 +315,9 @@ def _normalize_tidb_rows(self, rows):
                 'query_time': row.get('query_time', 0),
                 'memory_usage': row.get('memory_usage', 0),
                 'txn_start_time': row.get('txn_start_time'),
-                # TiDB doesn't have wait events - leave as None
-                'wait_event': None,
-                'wait_event_type': None,
+                # Derived wait events
+                'wait_event': wait_event,
+                'wait_event_type': wait_event_group,
             }
 
             # Add query truncation state
@@ -349,10 +375,10 @@ def _create_tidb_activity_event(self, active_sessions, tags):
                 'event_timer_start': event_start_ms * 1000000,  # Convert to nanoseconds
                 'event_timer_end': current_time_ms * 1000000,   # Convert to nanoseconds
                 'lock_time': 0,  # TiDB doesn't provide lock time in CLUSTER_PROCESSLIST
-                # Wait event info - TiDB doesn't have this information
-                'wait_event': row.get('wait_event'),  # Will be None
-                'wait_timer_start': None,
-                'wait_timer_end': None,
+                # Wait event info
+                'wait_event': row.get('wait_event', 'CPU'),
+                'wait_timer_start': event_start_ms * 1000000,  # Same as event timer
+                'wait_timer_end': current_time_ms * 1000000,
                 # Additional MySQL compatibility fields
                 'object_name': None,  # TiDB doesn't track file operations
                 'object_type': None,