network: close interfaces more aggressively (abort after 2 seconds)

fixes #7083

electrum/interface.py

@@ -686,12 +686,17 @@ class Interface(Logger):
             self.network.update_fee_estimates()
             await asyncio.sleep(60)
 
-    async def close(self):
+    async def close(self, *, force_after: int = None):
         """Closes the connection and waits for it to be closed.
         We try to flush buffered data to the wire, so this can take some time.
         """
+        if force_after is None:
+            # We give up after a while and just abort the connection.
+            # Note: specifically if the server is running Fulcrum, waiting seems hopeless,
+            #       the connection must be aborted (see https://github.com/cculianu/Fulcrum/issues/76)
+            force_after = 2  # seconds
         if self.session:
-            await self.session.close()
+            await self.session.close(force_after=force_after)
         # monitor_connection will cancel tasks
 
     async def run_fetch_blocks(self):

electrum/network.py

@@ -1220,7 +1220,8 @@ class Network(Logger, NetworkRetryManager[ServerAddr]):
     async def _stop(self, full_shutdown=False):
         self.logger.info("stopping network")
         try:
-            await asyncio.wait_for(self.taskgroup.cancel_remaining(), timeout=2)
+            # note: cancel_remaining ~cannot be cancelled, it suppresses CancelledError
+            await asyncio.wait_for(self.taskgroup.cancel_remaining(log=True), timeout=2)
         except (asyncio.TimeoutError, asyncio.CancelledError) as e:
             self.logger.info(f"exc during main_taskgroup cancellation: {repr(e)}")
         self.taskgroup = None