From 0ebc0573446a0f48a1e849cbde3bb05f183b7096 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adri=C3=A1n=20Chaves?= <adrian@chaves.io>
Date: Wed, 12 Mar 2025 21:21:36 +0100
Subject: [PATCH] =?UTF-8?q?Replace=20RuntimeError=20handling=20with=20Andr?=
 =?UTF-8?q?ey=E2=80=99s=20lock-based=20approach?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 scrapy/core/engine.py | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/scrapy/core/engine.py b/scrapy/core/engine.py
index 7383fc0e0..05f8a266a 100644
--- a/scrapy/core/engine.py
+++ b/scrapy/core/engine.py
@@ -113,6 +113,7 @@ class ExecutionEngine:
         self.start_time: float | None = None
         self._load_seeding_policy()
         self._seeds: AsyncIterable[Any] | None = None
+        self._waiting_for_seed: bool = False
 
     def _load_seeding_policy(self) -> None:
         try:
@@ -192,15 +193,13 @@ class ExecutionEngine:
 
     @inlineCallbacks
     def _process_next_seed(self):
+        if self._waiting_for_seed:
+            return
+        self._waiting_for_seed = True
         try:
             seed = yield deferred_from_coro(self._seeds.__anext__())
         except StopAsyncIteration:
             self._seeds = None
-        except RuntimeError:
-            # “RuntimeError: anext(): asynchronous generator is already
-            # running” happens if yield_seeds is taking long to yield the
-            # next seed.
-            pass
         except Exception:
             self._seeds = None
             logger.error(
@@ -214,6 +213,8 @@ class ExecutionEngine:
             else:
                 self.scraper.start_itemproc(seed, response=None)
                 self._slot.nextcall.schedule()
+        finally:
+            self._waiting_for_seed = False
 
     @inlineCallbacks
     def _start_next_requests(self) -> Generator[Deferred[Any], Any, None]: