Merge branch 'no_dup_log' into develop

server/server.py

@@ -75,13 +75,16 @@ class BlockCache(object):
                          .format(self.cache_limit))
 
         last_log = 0
+        prior_height = self.db.height
         while await self.maybe_prefill():
             now = time.time()
-            if now > last_log + 15:
+            count = self.fetched_height - prior_height
+            if now > last_log + 15 and count:
                 last_log = now
-                self.logger.info('prefilled blocks to height {:,d} '
+                prior_height = self.fetched_height
+                self.logger.info('prefilled {:,d} blocks to height {:,d} '
                                  'daemon height: {:,d}'
-                                 .format(self.fetched_height,
+                                 .format(count, self.fetched_height,
                                          self.daemon_height))
             await asyncio.sleep(1)