Fix Gate/Binance memory regression and roll stop offset from avg.

Stop fetch_tickers fallback for volume rank and keep stale cache on failed refresh. Compute roll unified stop as merge-average plus offset percent instead of break-even.

Co-authored-by: Cursor <cursoragent@cursor.com>

hub_volume_rank_lib.py

@@ -292,8 +292,7 @@ def _scores_from_binance(exchange) -> list[tuple[str, str, float]]:
                     return _merge_scores(by_base)
         except Exception:
             pass
-    tickers = exchange.fetch_tickers()
-    return _scores_from_markets(exchange, tickers or {}, "binance")
+    return []
 
 
 def _scores_from_gate(exchange) -> list[tuple[str, str, float]]:
@@ -330,8 +329,7 @@ def _scores_from_gate(exchange) -> list[tuple[str, str, float]]:
                     return _merge_scores(by_base)
         except Exception:
             continue
-    tickers = exchange.fetch_tickers()
-    return _scores_from_markets(exchange, tickers or {}, "gateio")
+    return []
 
 
 def _scores_from_markets(
@@ -373,6 +371,11 @@ def _collect_scores(exchange, exchange_id: str) -> list[tuple[str, str, float]]:
     return _scores_from_markets(exchange, tickers or {}, ex_id)
 
 
+def _uses_lightweight_volume_scores(exchange_id: str) -> bool:
+    ex_id = str(exchange_id or "").lower()
+    return ex_id in ("okx", "binance", "gateio", "gate", "gate_bot")
+
+
 def build_usdt_swap_volume_ranks(
     exchange,
     ensure_markets_loaded: Callable[[], None],
@@ -383,8 +386,9 @@ def build_usdt_swap_volume_ranks(
     全市场 USDT 永续 24h 成交额排名（base -> rank）。
     优先各所轻量 ticker API，避免 fetch_tickers() 拉全市场（Gate/Binance 内存优化）。
     """
-    ensure_markets_loaded()
     ex_id = str(exchange_id or getattr(exchange, "id", "") or "").lower()
+    if not _uses_lightweight_volume_scores(ex_id):
+        ensure_markets_loaded()
     scored = _collect_scores(exchange, ex_id)
     ranks: dict[str, int] = {}
     for idx, (_sym, base, _qv) in enumerate(scored, 1):
@@ -417,10 +421,11 @@ def resolve_daily_volume_rank(
                 ensure_markets_loaded,
                 exchange_id=exchange_id,
             )
-            cache["ranks"] = ranks
-            cache["total"] = total
-            cache["version"] = cache_version
-            cache["updated_at"] = now_ts
+            if total > 0 and ranks:
+                cache["ranks"] = ranks
+                cache["total"] = total
+                cache["version"] = cache_version
+                cache["updated_at"] = now_ts
         except Exception:
             pass
     ranks = cache.get("ranks") or {}