Merge pull request #61 from coreos/master

Fix two problems

log.go

@@ -273,12 +273,16 @@ func (l *Log) getEntryResult(entry *LogEntry, clear bool) (interface{}, error) {
 	// If a result exists for the entry then return it with its error.
 	if entry.Index > 0 && entry.Index <= uint64(len(l.results)) {
 		if result := l.results[entry.Index-1]; result != nil {
+
+			// keep the records before remove it
+			returnValue, err := result.returnValue, result.err
+
 			// Remove reference to result if it's being cleared after retrieval.
 			if clear {
 				result.returnValue = nil
 			}
 
-			return result.returnValue, result.err
+			return returnValue, err
 		}
 	}
 

server.go

@@ -723,7 +723,17 @@ func (s *Server) processAppendEntriesResponse(resp *AppendEntriesResponse) {
 		s.debugln("commit index ", commitIndex)
 		for i := committedIndex; i < commitIndex; i++ {
 			if entry := s.log.getEntry(i + 1); entry != nil {
-				entry.commit <- true
+				// if the leader is a new one and the entry came from the 
+				// old leader, the commit channel will be nil and no go routine
+				// is waiting from this channel
+				// if we try to send to it, the new leader will get stuck
+				if entry.commit != nil {
+					select {
+					case entry.commit <- true:
+					default:
+						panic("server unable to send signal to commit channel")
+					}
+				}
 			}
 		}
 	}