electrum

commit 152c6abb86f41e3fdf0992501f500571e806091b
parent 9505a203d8de6596f7bd9e04900652a613a7d998
Author: SomberNight <somber.night@protonmail.com>
Date:   Wed, 12 Sep 2018 16:58:15 +0200

network: fix another race in session.subscribe

key in session.subscriptions does not imply key in session.cache

Diffstat:
M
electrum/interface.py
 | 
10
++++++----

1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/electrum/interface.py b/electrum/interface.py
@@ -29,6 +29,7 @@ import sys
 import traceback
 import asyncio
 from typing import Tuple, Union
+from collections import defaultdict
 
 import aiorpcx
 from aiorpcx import ClientSession, Notification
@@ -46,7 +47,7 @@ class NotificationSession(ClientSession):
 
     def __init__(self, *args, **kwargs):
         super(NotificationSession, self).__init__(*args, **kwargs)
-        self.subscriptions = {}
+        self.subscriptions = defaultdict(list)
         self.cache = {}
 
     async def handle_request(self, request):
@@ -70,12 +71,13 @@ class NotificationSession(ClientSession):
             timeout)
 
     async def subscribe(self, method, params, queue):
+        # note: until the cache is written for the first time,
+        # each 'subscribe' call might make a request on the network.
         key = self.get_index(method, params)
-        if key in self.subscriptions:
-            self.subscriptions[key].append(queue)
+        self.subscriptions[key].append(queue)
+        if key in self.cache:
             result = self.cache[key]
         else:
-            self.subscriptions[key] = [queue]
             result = await self.send_request(method, params)
             self.cache[key] = result
         await queue.put(params + [result])