// Copyright 2018 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
}
