blockchain: Optimize stake node pruning.

blockchain/blockindex.go

@@ -1069,6 +1069,23 @@ func (bi *blockIndex) maybeUpdateBestHeaderForTip(tip *blockNode) {
 	}
 }
 
+// BestHeader returns the header with the most cumulative work that is NOT known
+// to be invalid.  This is not necessarily the same as the active best chain,
+// especially when block data is not yet known.  However, since block nodes are
+// only added to the index for block headers that pass all sanity and positional
+// checks, which include checking proof of work, it does represent the tip of
+// the header chain with the highest known work that has a reasonably high
+// chance of becoming the best chain tip and is useful for things such as
+// reporting progress and discovering the most suitable blocks to download.
+//
+// This function is safe for concurrent access.
+func (bi *blockIndex) BestHeader() *blockNode {
+	bi.RLock()
+	bestHeader := bi.bestHeader
+	bi.RUnlock()
+	return bestHeader
+}
+
 // MarkBlockFailedValidation marks the passed node as having failed validation
 // and then marks all of its descendants (if any) as having a failed ancestor.
 //
@@ -1362,9 +1379,11 @@ func (bi *blockIndex) FindBestChainCandidate() *blockNode {
 	return bestCandidate
 }
 
-// flush writes all of the modified block nodes to the database and clears the
+// Flush writes all of the modified block nodes to the database and clears the
 // set of modified nodes if it succeeds.
-func (bi *blockIndex) flush() error {
+//
+// This function is safe for concurrent access.
+func (bi *blockIndex) Flush() error {
 	// Nothing to flush if there are no modified nodes.
 	bi.Lock()
 	if len(bi.modified) == 0 {

blockchain/chain.go

@@ -828,14 +828,15 @@ func (b *BlockChain) connectBlock(node *blockNode, block, parent *dcrutil.Block,
 			})
 	}
 
-	// Optimization: Before checkpoints, immediately dump the parent's stake
-	// node because we no longer need it.
-	var latestCheckpointHeight int64
-	if b.latestCheckpoint != nil {
-		latestCheckpointHeight = b.latestCheckpoint.Height
-	}
-	if node.height < latestCheckpointHeight {
-		parent := b.bestChain.Tip().parent
+	// Optimization:  Immediately prune the parent's stake node when it is no
+	// longer needed due to being too far behind the best known header.
+	var pruneHeight int64
+	bestHeader := b.index.BestHeader()
+	if bestHeader.height > minMemoryStakeNodes {
+		pruneHeight = bestHeader.height - minMemoryStakeNodes
+	}
+	if node.height < pruneHeight {
+		parent := node.parent
 		parent.stakeNode = nil
 		parent.newTickets = nil
 		parent.ticketsVoted = nil
@@ -1531,7 +1532,7 @@ func (b *BlockChain) flushBlockIndex() error {
 			return err
 		}
 	}
-	return b.index.flush()
+	return b.index.Flush()
 }
 
 // flushBlockIndexWarnOnly attempts to flush any modified block index nodes to
@@ -1578,9 +1579,7 @@ func (b *BlockChain) maybeUpdateIsCurrent(curBest *blockNode) {
 
 		// Not current if the best block is not synced to the header with the
 		// most cumulative work that is not known to be invalid.
-		b.index.RLock()
-		bestHeader := b.index.bestHeader
-		b.index.RUnlock()
+		bestHeader := b.index.BestHeader()
 		syncedToBestHeader := curBest.height == bestHeader.height ||
 			bestHeader.IsAncestorOf(curBest)
 		if !syncedToBestHeader {
@@ -2412,9 +2411,7 @@ func New(ctx context.Context, config *Config) (*BlockChain, error) {
 	log.Infof("UTXO database version info: version: %d, compression: %d, utxo "+
 		"set: %d", utxoDbInfo.version, utxoDbInfo.compVer, utxoDbInfo.utxoVer)
 
-	b.index.RLock()
-	bestHdr := b.index.bestHeader
-	b.index.RUnlock()
+	bestHdr := b.index.BestHeader()
 	log.Infof("Best known header: height %d, hash %v", bestHdr.height,
 		bestHdr.hash)
 

blockchain/chainquery.go

@@ -141,9 +141,7 @@ func (b *BlockChain) ChainTips() []ChainTipInfo {
 //
 // This function is safe for concurrent access.
 func (b *BlockChain) BestHeader() (chainhash.Hash, int64) {
-	b.index.RLock()
-	header := b.index.bestHeader
-	b.index.RUnlock()
+	header := b.index.BestHeader()
 	return header.hash, header.height
 }
 
@@ -244,9 +242,7 @@ func (b *BlockChain) PutNextNeededBlocks(out []chainhash.Hash) []chainhash.Hash
 //
 // This function is safe for concurrent access.
 func (b *BlockChain) VerifyProgress() float64 {
-	b.index.RLock()
-	bestHdr := b.index.bestHeader
-	b.index.RUnlock()
+	bestHdr := b.index.BestHeader()
 	if bestHdr.height == 0 {
 		return 0.0
 	}

blockchain/process.go

@@ -89,9 +89,7 @@ func (b *BlockChain) isAssumeValidAncestor(node *blockNode) bool {
 	}
 
 	// Return false if the node is not an ancestor of the best header.
-	b.index.RLock()
-	bestHeader := b.index.bestHeader
-	b.index.RUnlock()
+	bestHeader := b.index.BestHeader()
 	if !node.IsAncestorOf(bestHeader) {
 		return false
 	}