network: cache subscription responses

lib/network.py

@@ -168,6 +168,7 @@ class Network(util.DaemonThread):
         self.utxo_roots = {}
         # callbacks passed with subscriptions
         self.subscriptions = defaultdict(list)
+        self.sub_cache = {}
         # callbacks set by the GUI
         self.callbacks = defaultdict(list)
 
@@ -275,6 +276,7 @@ class Network(util.DaemonThread):
 
     def send_subscriptions(self):
         self.print_error('sending subscriptions to', self.interface.server, len(self.unanswered_requests), len(self.subscribed_addresses))
+        self.sub_cache.clear()
         # Resend unanswered requests
         requests = self.unanswered_requests.values()
         self.unanswered_requests = {}
@@ -462,6 +464,7 @@ class Network(util.DaemonThread):
         error = response.get('error')
         result = response.get('result')
         method = response.get('method')
+        params = response.get('params')
 
         # We handle some responses; return the rest to the client.
         if method == 'server.version':
@@ -486,9 +489,11 @@ class Network(util.DaemonThread):
             self.on_get_chunk(interface, response)
         elif method == 'blockchain.block.get_header':
             self.on_get_header(interface, response)
-        else:
-            params = response['params']
-            callbacks = self.subscriptions.get(repr((method, params)), [])
+
+        elif method.endswith('.subscribe'):
+            k = repr((method, params))
+            self.sub_cache[k] = response
+            callbacks = self.subscriptions.get(k, [])
             for callback in callbacks:
                 callback(response)
 
@@ -496,7 +501,6 @@ class Network(util.DaemonThread):
         responses = interface.get_responses()
 
         for request, response in responses:
-            callback = None
             if request:
                 method, params, message_id = request
                 # client requests go through self.send() with a
@@ -505,7 +509,6 @@ class Network(util.DaemonThread):
                 client_req = self.unanswered_requests.pop(message_id, None)
                 if client_req:
                     assert interface == self.interface
-
                 # Copy the request method and params to the response
                 response['method'] = method
                 response['params'] = params
@@ -534,14 +537,23 @@ class Network(util.DaemonThread):
         '''Messages is a list of (method, params) tuples'''
         with self.lock:
             subs = filter(lambda (m,v): m.endswith('.subscribe'), messages)
-            for method, params in subs:
-                k = repr((method, params))
-                l = self.subscriptions.get(k, [])
-                if callback not in l:
-                    l.append(callback)
-                self.subscriptions[k] = l
-
-            self.pending_sends += messages
+            for message in messages:
+                method, params = message
+                if method.endswith('.subscribe'):
+                    k = repr((method, params))
+                    l = self.subscriptions.get(k, [])
+                    if callback not in l:
+                        l.append(callback)
+                    self.subscriptions[k] = l
+                    # check cached response
+                    r = self.sub_cache.get(k)
+                    if r is not None:
+                        util.print_error("cache hit", k)
+                        callback(r)
+                    else:
+                        self.pending_sends.append(message)
+                else:
+                    self.pending_sends.append(message)
 
 
     def process_pending_sends(self):