[3.12] gh-131325: fix sendfile fallback implementation to drain data after writing to transport (GH-131376) (#131378)

miss-islington · kumaraditya303 · web-flow · commit c1faeadd8293 · 2025-03-17T19:40:43.000Z
gh-131325: fix sendfile fallback implementation to drain data after writing to transport (GH-131376) (cherry picked from commit 94f4d87) Co-authored-by: Kumar Aditya <kumaraditya@python.org>
diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
@@ -1264,8 +1264,8 @@ async def _sendfile_fallback(self, transp, file, offset, count):
                 read = await self.run_in_executor(None, file.readinto, view)
                 if not read:
                     return total_sent  # EOF
-                await proto.drain()
                 transp.write(view[:read])
+                await proto.drain()
                 total_sent += read
         finally:
             if total_sent > 0 and hasattr(file, 'seek'):
diff --git a/Misc/NEWS.d/next/Library/2025-03-17-18-50-39.gh-issue-131325.wlasMF.rst b/Misc/NEWS.d/next/Library/2025-03-17-18-50-39.gh-issue-131325.wlasMF.rst
@@ -0,0 +1 @@
+Fix sendfile fallback implementation to drain data after writing to transport in :mod:`asyncio`.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+Fix sendfile fallback implementation to drain data after writing to transport in :mod:`asyncio`.