PYTHON-4636 - Avoid blocking I/O calls in async code paths

pymongo/asynchronous/network.py

@@ -355,6 +355,7 @@ async def wait_for_read(conn: AsyncConnection, deadline: Optional[float]) -> Non
  """Block until at least one byte is read, or a timeout, or a cancel."""
  sock = conn.conn
  timed_out = False
+ timeout = _POLL_TIMEOUT
  # Check if the connection's socket has been manually closed
  if sock.fileno() == -1:
  return
@@ -373,16 +374,18 @@ async def wait_for_read(conn: AsyncConnection, deadline: Optional[float]) -> Non
  if remaining <= 0:
  timed_out = True
  timeout = max(min(remaining, _POLL_TIMEOUT), 0)
+ if _IS_SYNC:
+ readable = conn.socket_checker.select(sock, read=True, timeout=timeout)
  else:
- timeout = _POLL_TIMEOUT
- readable = conn.socket_checker.select(sock, read=True, timeout=timeout)
+ readable = conn.socket_checker.select(sock, read=True, timeout=0.0001)
  if conn.cancel_context.cancelled:
  raise _OperationCancelled("operation cancelled")
  if readable:
  return
  if timed_out:
  raise socket.timeout("timed out")
- await asyncio.sleep(0)
+ if not _IS_SYNC:
+ await asyncio.sleep(timeout / 100.0)
 
 
 async def _receive_data_on_socket(

pymongo/synchronous/network.py

@@ -352,6 +352,7 @@ def wait_for_read(conn: Connection, deadline: Optional[float]) -> None:
  """Block until at least one byte is read, or a timeout, or a cancel."""
  sock = conn.conn
  timed_out = False
+ timeout = _POLL_TIMEOUT
  # Check if the connection's socket has been manually closed
  if sock.fileno() == -1:
  return
@@ -370,15 +371,18 @@ def wait_for_read(conn: Connection, deadline: Optional[float]) -> None:
  if remaining <= 0:
  timed_out = True
  timeout = max(min(remaining, _POLL_TIMEOUT), 0)
+ if _IS_SYNC:
+ readable = conn.socket_checker.select(sock, read=True, timeout=timeout)
  else:
- timeout = _POLL_TIMEOUT
- readable = conn.socket_checker.select(sock, read=True, timeout=timeout)
+ readable = conn.socket_checker.select(sock, read=True, timeout=0.0001)
  if conn.cancel_context.cancelled:
  raise _OperationCancelled("operation cancelled")
  if readable:
  return
  if timed_out:
  raise socket.timeout("timed out")
+ if not _IS_SYNC:
+ time.sleep(timeout / 100.0)
 
 
 def _receive_data_on_socket(conn: Connection, length: int, deadline: Optional[float]) -> memoryview: