Clean up startup procedure

docs/ARCHITECTURE.rst

@@ -15,13 +15,13 @@ The components of the server are roughly like this::
              - ElectrumX -<<<<<- LocalRPC -
              -------------     ------------
               <      >
-    ----------        -------------------    ----------
+    ----------        -------------------    --------------
-    - Daemon -<<<<<<<<- Block processor ->>>>- Caches -
+    - Daemon -<<<<<<<<- Block processor ->>>>- UTXO Cache -
-    ----------        -------------------    ----------
+    ----------        -------------------    --------------
         <              <               >           <
-         --------------                 -----------
+         --------------                 ----------------
-         - Prefetcher -                 - Storage -
+         - Prefetcher -                 - FS + Storage -
-         --------------                 -----------
+         --------------                 ----------------
 
 
 Env

electrumx_server.py

@@ -20,20 +20,6 @@ from server.env import Env
 from server.protocol import BlockServer
 
 
-def close_loop(loop):
-    '''Close the loop down cleanly.  Cancel and collect remaining tasks.'''
-    tasks = asyncio.Task.all_tasks()
-    for task in tasks:
-        task.cancel()
-
-    try:
-        loop.run_until_complete(asyncio.gather(*tasks))
-    except asyncio.CancelledError:
-        pass
-
-    loop.close()
-
-
 def main_loop():
     '''Start the server.'''
     if os.geteuid() == 0:
@@ -45,9 +31,9 @@ def main_loop():
 
     def on_signal(signame):
         '''Call on receipt of a signal to cleanly shutdown.'''
-        logging.warning('received {} signal, preparing to shut down'
+        logging.warning('received {} signal, shutting down'.format(signame))
-                        .format(signame))
+        for task in asyncio.Task.all_tasks():
-        loop.stop()
+            task.cancel()
 
     # Install signal handlers
     for signame in ('SIGINT', 'SIGTERM'):
@@ -55,12 +41,14 @@ def main_loop():
                                 partial(on_signal, signame))
 
     server = BlockServer(Env())
-    server.start()
+    future = server.start()
     try:
-        loop.run_forever()
+        loop.run_until_complete(future)
+    except asyncio.CancelledError:
+        pass
     finally:
         server.stop()
-    close_loop(loop)
+        loop.close()
 
 
 def main():

server/block_processor.py

@@ -77,10 +77,6 @@ class Prefetcher(LoggedClass):
         else:
             return blocks, None
 
-    def start(self):
-        '''Start the prefetcher.'''
-        asyncio.ensure_future(self.main_loop())
-
     async def main_loop(self):
         '''Loop forever polling for more blocks.'''
         self.logger.info('starting daemon poll loop...')
@@ -179,7 +175,6 @@ class MemPool(LoggedClass):
         '''
         hex_hashes = set(hex_hashes)
         touched = set()
-
         initial = self.count < 0
         if initial:
             self.logger.info('beginning import of {:,d} mempool txs'
@@ -357,9 +352,9 @@ class BlockProcessor(server.db.DB):
         self.clean_db()
 
     def start(self):
-        '''Start the block processor.'''
+        '''Returns a future that starts the block processor when awaited.'''
-        asyncio.ensure_future(self.main_loop())
+        return asyncio.gather(self.main_loop(),
-        self.prefetcher.start()
+                              self.prefetcher.main_loop())
 
     async def main_loop(self):
         '''Main loop for block processing.