daemon.py: work around aiohttp bug

Also log unexpected exceptions in the prefetcher

electrumx/server/block_processor.py

@@ -55,6 +55,9 @@ class Prefetcher(object):
                     await asyncio.sleep(self.polling_delay)
             except DaemonError as e:
                 self.logger.info(f'ignoring daemon error: {e}')
+            except Exception:
+                self.logger.exception(f'unexpected exception')
+                raise
 
     def get_prefetched_blocks(self):
         '''Called by block processor when it is processing queued blocks.'''

electrumx/server/daemon.py

@@ -150,6 +150,14 @@ class Daemon(object):
             except WorkQueueFullError:
                 log_error('work queue full.')
                 on_good_message = 'running normally'
+            except CancelledError as e:
+                # aiohttp bug - it raises a CancelledError (!!) if the transport is
+                # closing; presumably bitcoind is busy and closes the connection early.
+                # See https://github.com/aio-libs/aiohttp/issues/2499
+                if 'closing transport' not in str(e):
+                    raise
+                log_error('disconnected.')
+                on_good_message = 'connection restored'
 
             await asyncio.sleep(retry)
             retry = max(min(self.max_retry, retry * 2), self.init_retry)