fix(storage): address code quality comments

backend/packages/storage/store/repositories/db/run_event.py

@@ -17,20 +17,25 @@ _SEQ_PROCESS_BITS = 9
 _SEQ_PROCESS_SALT = secrets.randbits(_SEQ_PROCESS_BITS)
 _SEQ_COUNTER_LIMIT = 1 << _SEQ_COUNTER_BITS
 _SEQ_TIMESTAMP_SHIFT = _SEQ_COUNTER_BITS + _SEQ_PROCESS_BITS
-_last_seq_millis = 0
-_seq_lock = threading.Lock()
 
 
-def _allocate_sequence_base(batch_size: int) -> int:
-    if batch_size >= _SEQ_COUNTER_LIMIT:
-        raise ValueError(f"Run event batch is too large: {batch_size} >= {_SEQ_COUNTER_LIMIT}")
+class _SequenceAllocator:
+    def __init__(self) -> None:
+        self._last_millis = 0
+        self._lock = threading.Lock()
 
-    global _last_seq_millis
-    now_ms = time.time_ns() // 1_000_000
-    with _seq_lock:
-        seq_ms = max(now_ms, _last_seq_millis + 1)
-        _last_seq_millis = seq_ms
-    return (seq_ms << _SEQ_TIMESTAMP_SHIFT) | (_SEQ_PROCESS_SALT << _SEQ_COUNTER_BITS)
+    def allocate_base(self, batch_size: int) -> int:
+        if batch_size >= _SEQ_COUNTER_LIMIT:
+            raise ValueError(f"Run event batch is too large: {batch_size} >= {_SEQ_COUNTER_LIMIT}")
+
+        now_ms = time.time_ns() // 1_000_000
+        with self._lock:
+            seq_ms = max(now_ms, self._last_millis + 1)
+            self._last_millis = seq_ms
+        return (seq_ms << _SEQ_TIMESTAMP_SHIFT) | (_SEQ_PROCESS_SALT << _SEQ_COUNTER_BITS)
+
+
+_sequence_allocator = _SequenceAllocator()
 
 
 def _serialize_content(content: Any, metadata: dict[str, Any]) -> tuple[str, dict[str, Any]]:
@@ -75,7 +80,7 @@ class DbRunEventRepository(RunEventRepositoryProtocol):
         if not events:
             return []
 
-        seq_base = _allocate_sequence_base(len(events))
+        seq_base = _sequence_allocator.allocate_base(len(events))
 
         rows: list[RunEventModel] = []