core, eth/downloader: fix chain sync eta

Author: rjl493456442

core/blockchain_test.go

@@ -4339,6 +4339,13 @@ func testInsertChainWithCutoff(t *testing.T, cutoff uint64, ancientLimit uint64)
 		if header.Hash() != hash {
 			t.Errorf("block #%d: header mismatch: want: %v, got: %v", num, hash, header.Hash())
 		}
+		tail, err := db.Tail()
+		if err != nil {
+			t.Fatalf("Failed to get chain tail, %v", err)
+		}
+		if tail != cutoffBlock.NumberU64() {
+			t.Fatalf("Unexpected chain tail, want: %d, got: %d", cutoffBlock.NumberU64(), tail)
+		}
 		// Block bodies and receipts before the cutoff should be non-existent
 		if num < cutoffBlock.NumberU64() {
 			body := chain.GetBody(hash)

eth/downloader/downloader.go

@@ -1133,10 +1133,20 @@ func (d *Downloader) reportSnapSyncProgress(force bool) {
 		header = d.blockchain.CurrentHeader()
 		block  = d.blockchain.CurrentSnapBlock()
 	)
-	syncedBlocks := block.Number.Uint64() - d.syncStartBlock
-	if syncedBlocks == 0 {
+	// Prevent reporting if nothing has been synchronized yet
+	if block.Number.Uint64() <= d.syncStartBlock {
 		return
 	}
+	// Prevent reporting noise if the actual chain synchronization (headers
+	// and bodies) hasn't started yet. Inserting the ancient header chain is
+	// fast enough and would introduce significant bias if included in the count.
+	if d.chainCutoffNumber != 0 && block.Number.Uint64() < d.chainCutoffNumber {
+		return
+	}
+	fetchedBlocks := block.Number.Uint64() - d.syncStartBlock
+	if d.chainCutoffNumber != 0 {
+		fetchedBlocks = block.Number.Uint64() - d.chainCutoffNumber
+	}
 	// Retrieve the current chain head and calculate the ETA
 	latest, _, _, err := d.skeleton.Bounds()
 	if err != nil {
@@ -1151,9 +1161,7 @@ func (d *Downloader) reportSnapSyncProgress(force bool) {
 	}
 	var (
 		left = latest.Number.Uint64() - block.Number.Uint64()
-
-		// TODO(rjl493456442) fix the ETA in the pruning mode.
-		eta = time.Since(d.syncStartTime) / time.Duration(syncedBlocks) * time.Duration(left)
+		eta  = time.Since(d.syncStartTime) / time.Duration(fetchedBlocks) * time.Duration(left)
 
 		progress = fmt.Sprintf("%.2f%%", float64(block.Number.Uint64())*100/float64(latest.Number.Uint64()))
 		headers  = fmt.Sprintf("%v@%v", log.FormatLogfmtUint64(header.Number.Uint64()), common.StorageSize(headerBytes).TerminalString())