core, trie: intermediate mempool between trie and database (#15857)

This commit reduces database I/O by not writing every state trie to disk.

1 files changed, 355 insertions, 0 deletions

diff --git a/trie/database.go b/trie/database.go
new file mode 100644
index 000000000..d79120813
--- /dev/null
+++ b/trie/database.go
@@ -0,0 +1,355 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package trie
+
+import (
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+// secureKeyPrefix is the database key prefix used to store trie node preimages.
+var secureKeyPrefix = []byte("secure-key-")
+
+// secureKeyLength is the length of the above prefix + 32byte hash.
+const secureKeyLength = 11 + 32
+
+// DatabaseReader wraps the Get and Has method of a backing store for the trie.
+type DatabaseReader interface {
+	// Get retrieves the value associated with key form the database.
+	Get(key []byte) (value []byte, err error)
+
+	// Has retrieves whether a key is present in the database.
+	Has(key []byte) (bool, error)
+}
+
+// Database is an intermediate write layer between the trie data structures and
+// the disk database. The aim is to accumulate trie writes in-memory and only
+// periodically flush a couple tries to disk, garbage collecting the remainder.
+type Database struct {
+	diskdb ethdb.Database // Persistent storage for matured trie nodes
+
+	nodes     map[common.Hash]*cachedNode // Data and references relationships of a node
+	preimages map[common.Hash][]byte      // Preimages of nodes from the secure trie
+	seckeybuf [secureKeyLength]byte       // Ephemeral buffer for calculating preimage keys
+
+	gctime  time.Duration      // Time spent on garbage collection since last commit
+	gcnodes uint64             // Nodes garbage collected since last commit
+	gcsize  common.StorageSize // Data storage garbage collected since last commit
+
+	nodesSize     common.StorageSize // Storage size of the nodes cache
+	preimagesSize common.StorageSize // Storage size of the preimages cache
+
+	lock sync.RWMutex
+}
+
+// cachedNode is all the information we know about a single cached node in the
+// memory database write layer.
+type cachedNode struct {
+	blob     []byte              // Cached data block of the trie node
+	parents  int                 // Number of live nodes referencing this one
+	children map[common.Hash]int // Children referenced by this nodes
+}
+
+// NewDatabase creates a new trie database to store ephemeral trie content before
+// its written out to disk or garbage collected.
+func NewDatabase(diskdb ethdb.Database) *Database {
+	return &Database{
+		diskdb: diskdb,
+		nodes: map[common.Hash]*cachedNode{
+			{}: {children: make(map[common.Hash]int)},
+		},
+		preimages: make(map[common.Hash][]byte),
+	}
+}
+
+// DiskDB retrieves the persistent storage backing the trie database.
+func (db *Database) DiskDB() DatabaseReader {
+	return db.diskdb
+}
+
+// Insert writes a new trie node to the memory database if it's yet unknown. The
+// method will make a copy of the slice.
+func (db *Database) Insert(hash common.Hash, blob []byte) {
+	db.lock.Lock()
+	defer db.lock.Unlock()
+
+	db.insert(hash, blob)
+}
+
+// insert is the private locked version of Insert.
+func (db *Database) insert(hash common.Hash, blob []byte) {
+	if _, ok := db.nodes[hash]; ok {
+		return
+	}
+	db.nodes[hash] = &cachedNode{
+		blob:     common.CopyBytes(blob),
+		children: make(map[common.Hash]int),
+	}
+	db.nodesSize += common.StorageSize(common.HashLength + len(blob))
+}
+
+// insertPreimage writes a new trie node pre-image to the memory database if it's
+// yet unknown. The method will make a copy of the slice.
+//
+// Note, this method assumes that the database's lock is held!
+func (db *Database) insertPreimage(hash common.Hash, preimage []byte) {
+	if _, ok := db.preimages[hash]; ok {
+		return
+	}
+	db.preimages[hash] = common.CopyBytes(preimage)
+	db.preimagesSize += common.StorageSize(common.HashLength + len(preimage))
+}
+
+// Node retrieves a cached trie node from memory. If it cannot be found cached,
+// the method queries the persistent database for the content.
+func (db *Database) Node(hash common.Hash) ([]byte, error) {
+	// Retrieve the node from cache if available
+	db.lock.RLock()
+	node := db.nodes[hash]
+	db.lock.RUnlock()
+
+	if node != nil {
+		return node.blob, nil
+	}
+	// Content unavailable in memory, attempt to retrieve from disk
+	return db.diskdb.Get(hash[:])
+}
+
+// preimage retrieves a cached trie node pre-image from memory. If it cannot be
+// found cached, the method queries the persistent database for the content.
+func (db *Database) preimage(hash common.Hash) ([]byte, error) {
+	// Retrieve the node from cache if available
+	db.lock.RLock()
+	preimage := db.preimages[hash]
+	db.lock.RUnlock()
+
+	if preimage != nil {
+		return preimage, nil
+	}
+	// Content unavailable in memory, attempt to retrieve from disk
+	return db.diskdb.Get(db.secureKey(hash[:]))
+}
+
+// secureKey returns the database key for the preimage of key, as an ephemeral
+// buffer. The caller must not hold onto the return value because it will become
+// invalid on the next call.
+func (db *Database) secureKey(key []byte) []byte {
+	buf := append(db.seckeybuf[:0], secureKeyPrefix...)
+	buf = append(buf, key...)
+	return buf
+}
+
+// Nodes retrieves the hashes of all the nodes cached within the memory database.
+// This method is extremely expensive and should only be used to validate internal
+// states in test code.
+func (db *Database) Nodes() []common.Hash {
+	db.lock.RLock()
+	defer db.lock.RUnlock()
+
+	var hashes = make([]common.Hash, 0, len(db.nodes))
+	for hash := range db.nodes {
+		if hash != (common.Hash{}) { // Special case for "root" references/nodes
+			hashes = append(hashes, hash)
+		}
+	}
+	return hashes
+}
+
+// Reference adds a new reference from a parent node to a child node.
+func (db *Database) Reference(child common.Hash, parent common.Hash) {
+	db.lock.RLock()
+	defer db.lock.RUnlock()
+
+	db.reference(child, parent)
+}
+
+// reference is the private locked version of Reference.
+func (db *Database) reference(child common.Hash, parent common.Hash) {
+	// If the node does not exist, it's a node pulled from disk, skip
+	node, ok := db.nodes[child]
+	if !ok {
+		return
+	}
+	// If the reference already exists, only duplicate for roots
+	if _, ok = db.nodes[parent].children[child]; ok && parent != (common.Hash{}) {
+		return
+	}
+	node.parents++
+	db.nodes[parent].children[child]++
+}
+
+// Dereference removes an existing reference from a parent node to a child node.
+func (db *Database) Dereference(child common.Hash, parent common.Hash) {
+	db.lock.Lock()
+	defer db.lock.Unlock()
+
+	nodes, storage, start := len(db.nodes), db.nodesSize, time.Now()
+	db.dereference(child, parent)
+
+	db.gcnodes += uint64(nodes - len(db.nodes))
+	db.gcsize += storage - db.nodesSize
+	db.gctime += time.Since(start)
+
+	log.Debug("Dereferenced trie from memory database", "nodes", nodes-len(db.nodes), "size", storage-db.nodesSize, "time", time.Since(start),
+		"gcnodes", db.gcnodes, "gcsize", db.gcsize, "gctime", db.gctime, "livenodes", len(db.nodes), "livesize", db.nodesSize)
+}
+
+// dereference is the private locked version of Dereference.
+func (db *Database) dereference(child common.Hash, parent common.Hash) {
+	// Dereference the parent-child
+	node := db.nodes[parent]
+
+	node.children[child]--
+	if node.children[child] == 0 {
+		delete(node.children, child)
+	}
+	// If the node does not exist, it's a previously committed node.
+	node, ok := db.nodes[child]
+	if !ok {
+		return
+	}
+	// If there are no more references to the child, delete it and cascade
+	node.parents--
+	if node.parents == 0 {
+		for hash := range node.children {
+			db.dereference(hash, child)
+		}
+		delete(db.nodes, child)
+		db.nodesSize -= common.StorageSize(common.HashLength + len(node.blob))
+	}
+}
+
+// Commit iterates over all the children of a particular node, writes them out
+// to disk, forcefully tearing down all references in both directions.
+//
+// As a side effect, all pre-images accumulated up to this point are also written.
+func (db *Database) Commit(node common.Hash, report bool) error {
+	// Create a database batch to flush persistent data out. It is important that
+	// outside code doesn't see an inconsistent state (referenced data removed from
+	// memory cache during commit but not yet in persistent storage). This is ensured
+	// by only uncaching existing data when the database write finalizes.
+	db.lock.RLock()
+
+	start := time.Now()
+	batch := db.diskdb.NewBatch()
+
+	// Move all of the accumulated preimages into a write batch
+	for hash, preimage := range db.preimages {
+		if err := batch.Put(db.secureKey(hash[:]), preimage); err != nil {
+			log.Error("Failed to commit preimage from trie database", "err", err)
+			db.lock.RUnlock()
+			return err
+		}
+		if batch.ValueSize() > ethdb.IdealBatchSize {
+			if err := batch.Write(); err != nil {
+				return err
+			}
+			batch.Reset()
+		}
+	}
+	// Move the trie itself into the batch, flushing if enough data is accumulated
+	nodes, storage := len(db.nodes), db.nodesSize+db.preimagesSize
+	if err := db.commit(node, batch); err != nil {
+		log.Error("Failed to commit trie from trie database", "err", err)
+		db.lock.RUnlock()
+		return err
+	}
+	// Write batch ready, unlock for readers during persistence
+	if err := batch.Write(); err != nil {
+		log.Error("Failed to write trie to disk", "err", err)
+		db.lock.RUnlock()
+		return err
+	}
+	db.lock.RUnlock()
+
+	// Write successful, clear out the flushed data
+	db.lock.Lock()
+	defer db.lock.Unlock()
+
+	db.preimages = make(map[common.Hash][]byte)
+	db.preimagesSize = 0
+
+	db.uncache(node)
+
+	logger := log.Info
+	if !report {
+		logger = log.Debug
+	}
+	logger("Persisted trie from memory database", "nodes", nodes-len(db.nodes), "size", storage-db.nodesSize, "time", time.Since(start),
+		"gcnodes", db.gcnodes, "gcsize", db.gcsize, "gctime", db.gctime, "livenodes", len(db.nodes), "livesize", db.nodesSize)
+
+	// Reset the garbage collection statistics
+	db.gcnodes, db.gcsize, db.gctime = 0, 0, 0
+
+	return nil
+}
+
+// commit is the private locked version of Commit.
+func (db *Database) commit(hash common.Hash, batch ethdb.Batch) error {
+	// If the node does not exist, it's a previously committed node
+	node, ok := db.nodes[hash]
+	if !ok {
+		return nil
+	}
+	for child := range node.children {
+		if err := db.commit(child, batch); err != nil {
+			return err
+		}
+	}
+	if err := batch.Put(hash[:], node.blob); err != nil {
+		return err
+	}
+	// If we've reached an optimal match size, commit and start over
+	if batch.ValueSize() >= ethdb.IdealBatchSize {
+		if err := batch.Write(); err != nil {
+			return err
+		}
+		batch.Reset()
+	}
+	return nil
+}
+
+// uncache is the post-processing step of a commit operation where the already
+// persisted trie is removed from the cache. The reason behind the two-phase
+// commit is to ensure consistent data availability while moving from memory
+// to disk.
+func (db *Database) uncache(hash common.Hash) {
+	// If the node does not exist, we're done on this path
+	node, ok := db.nodes[hash]
+	if !ok {
+		return
+	}
+	// Otherwise uncache the node's subtries and remove the node itself too
+	for child := range node.children {
+		db.uncache(child)
+	}
+	delete(db.nodes, hash)
+	db.nodesSize -= common.StorageSize(common.HashLength + len(node.blob))
+}
+
+// Size returns the current storage size of the memory cache in front of the
+// persistent database layer.
+func (db *Database) Size() common.StorageSize {
+	db.lock.RLock()
+	defer db.lock.RUnlock()
+
+	return db.nodesSize + db.preimagesSize
+}