Download fixes

- don't make empty requests
- don't make requests if all objects are pending already

src/network/downloadthread.py

@@ -62,6 +62,8 @@ class DownloadThread(threading.Thread, StoppableThread):
                         continue
                     payload.extend(chunk)
                     missingObjects[chunk] = now
+                if not payload:
+                    continue
                 i.append_write_buf(protocol.CreatePacket('getdata', payload))
                 logger.debug("%s:%i Requesting %i objects", i.destination.host, i.destination.port, len(request))
                 requested += len(request)

src/randomtrackingdict.py

@@ -71,8 +71,9 @@ class RandomTrackingDict(object):
         self.pendingTimeout = pendingTimeout
 
     def randomKeys(self, count=1):
-        if self.len == 0 or (self.pendingLen >= self.maxPending and
-                self.lastPoll + self.pendingTimeout > time()):
+        if self.len == 0 or ((self.pendingLen >= self.maxPending or
+            self.pendingLen == self.len) and self.lastPoll +
+            self.pendingTimeout > time()):
             raise KeyError
         # reset if we've requested all
         with self.lock: