Clean up client notifications

- mempool informed of new block; it notifies controller synchronously
- controller notifies sessions synchronously
- sessions are notified of new height synchronously.  Any address touch
notifications are returned to the controller and scheduled
asynchronously.

Also, remove a redundant notification of height on initial header
subscriptions - the subscription response gives the current height;
we also used to send a notification as we didn't update our idea
of notified height.

server/block_processor.py

@@ -253,6 +253,8 @@ class BlockProcessor(server.db.DB):
                 self.logger.info('processed {:,d} block{} in {:.1f}s'
                                  .format(len(blocks), s,
                                          time.time() - start))
+                self.controller.mempool.on_new_block(self.touched)
+            self.touched.clear()
         elif hprevs[0] != chain[0]:
             await self.reorg_chain()
         else:
@@ -511,7 +513,6 @@ class BlockProcessor(server.db.DB):
         if self.caught_up_event.is_set():
             self.flush(True)
         else:
-            self.touched.clear()
             if time.time() > self.next_cache_check:
                 self.check_cache_size()
                 self.next_cache_check = time.time() + 30

server/controller.py

@@ -214,7 +214,6 @@ class Controller(ServerBase):
         self.ensure_future(self.log_start_external_servers())
         self.ensure_future(self.housekeeping())
         self.ensure_future(self.mempool.main_loop())
-        self.ensure_future(self.notify())
 
     def close_servers(self, kinds):
         '''Close the servers of the given kinds (TCP etc.).'''
@@ -272,27 +271,24 @@ class Controller(ServerBase):
             sslc.load_cert_chain(env.ssl_certfile, keyfile=env.ssl_keyfile)
             await self.start_server('SSL', host, env.ssl_port, ssl=sslc)
 
-    async def notify(self):
+    def notify_sessions(self, touched):
         '''Notify sessions about height changes and touched addresses.'''
-        while True:
-            await self.mempool.touched_event.wait()
-            touched = self.mempool.touched.copy()
-            self.mempool.touched.clear()
-            self.mempool.touched_event.clear()
-
         # Invalidate caches
         hc = self.history_cache
         for hashX in set(hc).intersection(touched):
             del hc[hashX]
-            if self.bp.db_height != self.cache_height:
+
-                self.cache_height = self.bp.db_height
+        height = self.bp.db_height
+        if height != self.cache_height:
+            self.cache_height = height
             self.header_cache.clear()
 
-            # Make a copy; self.sessions can change whilst await-ing
+        # Height notifications are synchronous.  Those sessions with
-            sessions = [s for s in self.sessions
+        # touched addresses are scheduled for asynchronous completion
-                        if isinstance(s, self.coin.SESSIONCLS)]
+        for session in self.sessions:
-            for session in sessions:
+            session_touched = session.notify(height, touched)
-                await session.notify(self.bp.db_height, touched)
+            if session_touched is not None:
+                self.ensure_future(session.notify_async(session_touched))
 
     def notify_peers(self, updates):
         '''Notify of peer updates.'''

server/mempool.py

@@ -37,8 +37,7 @@ class MemPool(util.LoggedClass):
         self.controller = controller
         self.coin = bp.coin
         self.db = bp
-        self.touched = bp.touched
+        self.touched = set()
-        self.touched_event = asyncio.Event()
         self.prioritized = set()
         self.stop = False
         self.txs = {}
@@ -101,7 +100,8 @@ class MemPool(util.LoggedClass):
         while True:
             # Avoid double notifications if processing a block
             if self.touched and not self.processing_new_block():
-                self.touched_event.set()
+                self.controller.notify_sessions(self.touched)
+                self.touched.clear()
 
             # Log progress / state
             todo = len(unfetched) + len(unprocessed)
@@ -177,6 +177,17 @@ class MemPool(util.LoggedClass):
 
         return process
 
+    def on_new_block(self, touched):
+        '''Called after processing one or more new blocks.
+
+        Touched is a set of hashXs touched by the transactions in the
+        block.  Caller must be aware it is modified by this function.
+        '''
+        # Minor race condition here with mempool processor thread
+        touched.update(self.touched)
+        self.touched.clear()
+        self.controller.notify_sessions(touched)
+
     def processing_new_block(self):
         '''Return True if we're processing a new block.'''
         return self.daemon.cached_height() > self.db.db_height

server/session.py

@@ -119,64 +119,70 @@ class ElectrumX(SessionBase):
     def sub_count(self):
         return len(self.hashX_subs)
 
-    async def notify(self, height, touched):
+    async def notify_async(self, our_touched):
-        '''Notify the client about changes in height and touched addresses.
+        changed = {}
-
-        Cache is a shared cache for this update.
-        '''
-        pairs = []
-        changed = []
 
-        matches = touched.intersection(self.hashX_subs)
+        for hashX in our_touched:
-        for hashX in matches:
             alias = self.hashX_subs[hashX]
             status = await self.address_status(hashX)
-            changed.append((alias, status))
+            changed[alias] = status
-
-        if height != self.notified_height:
-            self.notified_height = height
-            if self.subscribe_headers:
-                args = (self.controller.electrum_header(height), )
-                pairs.append(('blockchain.headers.subscribe', args))
-
-            if self.subscribe_height:
-                pairs.append(('blockchain.numblocks.subscribe', (height, )))
 
         # Check mempool hashXs - the status is a function of the
         # confirmed state of other transactions
-            for hashX in set(self.mempool_statuses).difference(matches):
+        for hashX, old_status in self.mempool_statuses.items():
-                old_status = self.mempool_statuses[hashX]
             status = await self.address_status(hashX)
             if status != old_status:
                 alias = self.hashX_subs[hashX]
-                    changed.append((alias, status))
+                changed[alias] = status
 
-        for alias_status in changed:
+        for alias, status in changed.items():
-            if len(alias_status[0]) == 64:
+            if len(alias) == 64:
                 method = 'blockchain.scripthash.subscribe'
             else:
                 method = 'blockchain.address.subscribe'
-            pairs.append((method, alias_status))
+            self.send_notification(method, (alias, status))
 
-        if pairs:
-            self.send_notifications(pairs)
         if changed:
             es = '' if len(changed) == 1 else 'es'
             self.log_info('notified of {:,d} address{}'
                           .format(len(changed), es))
 
+    def notify(self, height, touched):
+        '''Notify the client about changes to touched addresses (from mempool
+        updates or new blocks) and height.
+
+        Return the set of addresses the session needs to be
+        asyncronously notified about.  This can be empty if there are
+        possible mempool status updates.
+
+        Returns None if nothing needs to be notified asynchronously.
+        '''
+        height_changed = height != self.notified_height
+        if height_changed:
+            self.notified_height = height
+            if self.subscribe_headers:
+                args = (self.controller.electrum_header(height), )
+                self.send_notification('blockchain.headers.subscribe', args)
+            if self.subscribe_height:
+                args = (height, )
+                self.send_notification('blockchain.numblocks.subscribe', args)
+
+        our_touched = touched.intersection(self.hashX_subs)
+        if our_touched or (height_changed and self.mempool_statuses):
+            return our_touched
+
+        return None
+
     def height(self):
         '''Return the current flushed database height.'''
         return self.bp.db_height
 
-    def current_electrum_header(self):
-        '''Used as response to a headers subscription request.'''
-        return self.controller.electrum_header(self.height())
-
     def headers_subscribe(self):
         '''Subscribe to get headers of new blocks.'''
         self.subscribe_headers = True
-        return self.current_electrum_header()
+        height = self.height()
+        self.notified_height = height
+        return self.controller.electrum_header(height)
 
     def numblocks_subscribe(self):
         '''Subscribe to get height of new blocks.'''