[release/1.4.18] core: print import stats more often

If geth is busy importing 2048 heavy blocks it can take a while before
it prints anything. This change ensures that a message gets printed
every 8s.

(cherry picked from commit e66b158)

core/blockchain.go

@@ -824,19 +824,16 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 	// faster than direct delivery and requires much less mutex
 	// acquiring.
 	var (
-		stats         struct{ queued, processed, ignored int }
+		stats         = insertStats{startTime: time.Now()}
 		events        = make([]interface{}, 0, len(chain))
 		coalescedLogs vm.Logs
-		tstart        = time.Now()
-
-		nonceChecked = make([]bool, len(chain))
+		nonceChecked  = make([]bool, len(chain))
 	)
 
 	// Start the parallel nonce verifier.
 	nonceAbort, nonceResults := verifyNoncesFromBlocks(self.pow, chain)
 	defer close(nonceAbort)
 
-	txcount := 0
 	for i, block := range chain {
 		if atomic.LoadInt32(&self.procInterrupt) == 1 {
 			glog.V(logger.Debug).Infoln("Premature abort during block chain processing")
@@ -931,7 +928,6 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 			return i, err
 		}
 
-		txcount += len(block.Transactions())
 		// write the block to the chain and get the status
 		status, err := self.WriteBlock(block)
 		if err != nil {
@@ -966,19 +962,54 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 		case SplitStatTy:
 			events = append(events, ChainSplitEvent{block, logs})
 		}
+
 		stats.processed++
+		if glog.V(logger.Info) {
+			stats.report(chain, i)
+		}
 	}
 
-	if (stats.queued > 0 || stats.processed > 0 || stats.ignored > 0) && bool(glog.V(logger.Info)) {
-		tend := time.Since(tstart)
-		start, end := chain[0], chain[len(chain)-1]
-		glog.Infof("imported %d block(s) (%d queued %d ignored) including %d txs in %v. #%v [%x / %x]\n", stats.processed, stats.queued, stats.ignored, txcount, tend, end.Number(), start.Hash().Bytes()[:4], end.Hash().Bytes()[:4])
-	}
 	go self.postChainEvents(events, coalescedLogs)
 
 	return 0, nil
 }
 
+// insertStats tracks and reports on block insertion.
+type insertStats struct {
+	queued, processed, ignored int
+	lastIndex                  int
+	startTime                  time.Time
+}
+
+const (
+	statsReportLimit     = 1024
+	statsReportTimeLimit = 8 * time.Second
+)
+
+// report prints statistics if some number of blocks have been processed
+// or more than a few seconds have passed since the last message.
+func (st *insertStats) report(chain []*types.Block, index int) {
+	limit := statsReportLimit
+	if index == len(chain)-1 {
+		limit = 0 // Always print a message for the last block.
+	}
+	now := time.Now()
+	duration := now.Sub(st.startTime)
+	if duration > statsReportTimeLimit || st.queued > limit || st.processed > limit || st.ignored > limit {
+		start, end := chain[st.lastIndex], chain[index]
+		txcount := countTransactions(chain[st.lastIndex:index])
+		glog.Infof("imported %d block(s) (%d queued %d ignored) including %d txs in %v. #%v [%x / %x]\n", st.processed, st.queued, st.ignored, txcount, duration, end.Number(), start.Hash().Bytes()[:4], end.Hash().Bytes()[:4])
+		*st = insertStats{startTime: now, lastIndex: index}
+	}
+}
+
+func countTransactions(chain []*types.Block) (c int) {
+	for _, b := range chain {
+		c += len(b.Transactions())
+	}
+	return c
+}
+
 // reorgs takes two blocks, an old chain and a new chain and will reconstruct the blocks and inserts them
 // to be part of the new canonical chain and accumulates potential missing transactions and post an
 // event about them