plugeth/triedb/pathdb/layertree.go

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// Copyright 2022 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 pathdb
import (
"errors"
"fmt"
"sync"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/trie/trienode"
"github.com/ethereum/go-ethereum/trie/triestate"
)
// layerTree is a group of state layers identified by the state root.
// This structure defines a few basic operations for manipulating
// state layers linked with each other in a tree structure. It's
// thread-safe to use. However, callers need to ensure the thread-safety
// of the referenced layer by themselves.
type layerTree struct {
lock sync.RWMutex
layers map[common.Hash]layer
}
// newLayerTree constructs the layerTree with the given head layer.
func newLayerTree(head layer) *layerTree {
tree := new(layerTree)
tree.reset(head)
return tree
}
// reset initializes the layerTree by the given head layer.
// All the ancestors will be iterated out and linked in the tree.
func (tree *layerTree) reset(head layer) {
tree.lock.Lock()
defer tree.lock.Unlock()
var layers = make(map[common.Hash]layer)
for head != nil {
layers[head.rootHash()] = head
head = head.parentLayer()
}
tree.layers = layers
}
// get retrieves a layer belonging to the given state root.
func (tree *layerTree) get(root common.Hash) layer {
tree.lock.RLock()
defer tree.lock.RUnlock()
return tree.layers[types.TrieRootHash(root)]
}
// forEach iterates the stored layers inside and applies the
// given callback on them.
func (tree *layerTree) forEach(onLayer func(layer)) {
tree.lock.RLock()
defer tree.lock.RUnlock()
for _, layer := range tree.layers {
onLayer(layer)
}
}
// len returns the number of layers cached.
func (tree *layerTree) len() int {
tree.lock.RLock()
defer tree.lock.RUnlock()
return len(tree.layers)
}
// add inserts a new layer into the tree if it can be linked to an existing old parent.
func (tree *layerTree) add(root common.Hash, parentRoot common.Hash, block uint64, nodes *trienode.MergedNodeSet, states *triestate.Set) error {
// Reject noop updates to avoid self-loops. This is a special case that can
// happen for clique networks and proof-of-stake networks where empty blocks
// don't modify the state (0 block subsidy).
//
// Although we could silently ignore this internally, it should be the caller's
// responsibility to avoid even attempting to insert such a layer.
root, parentRoot = types.TrieRootHash(root), types.TrieRootHash(parentRoot)
if root == parentRoot {
return errors.New("layer cycle")
}
parent := tree.get(parentRoot)
if parent == nil {
return fmt.Errorf("triedb parent [%#x] layer missing", parentRoot)
}
l := parent.update(root, parent.stateID()+1, block, nodes.Flatten(), states)
tree.lock.Lock()
tree.layers[l.rootHash()] = l
tree.lock.Unlock()
return nil
}
// cap traverses downwards the diff tree until the number of allowed diff layers
// are crossed. All diffs beyond the permitted number are flattened downwards.
func (tree *layerTree) cap(root common.Hash, layers int) error {
// Retrieve the head layer to cap from
root = types.TrieRootHash(root)
l := tree.get(root)
if l == nil {
return fmt.Errorf("triedb layer [%#x] missing", root)
}
diff, ok := l.(*diffLayer)
if !ok {
return fmt.Errorf("triedb layer [%#x] is disk layer", root)
}
tree.lock.Lock()
defer tree.lock.Unlock()
// If full commit was requested, flatten the diffs and merge onto disk
if layers == 0 {
base, err := diff.persist(true)
if err != nil {
return err
}
// Replace the entire layer tree with the flat base
tree.layers = map[common.Hash]layer{base.rootHash(): base}
return nil
}
// Dive until we run out of layers or reach the persistent database
for i := 0; i < layers-1; i++ {
// If we still have diff layers below, continue down
if parent, ok := diff.parentLayer().(*diffLayer); ok {
diff = parent
} else {
// Diff stack too shallow, return without modifications
return nil
}
}
// We're out of layers, flatten anything below, stopping if it's the disk or if
// the memory limit is not yet exceeded.
switch parent := diff.parentLayer().(type) {
case *diskLayer:
return nil
case *diffLayer:
// Hold the lock to prevent any read operations until the new
// parent is linked correctly.
diff.lock.Lock()
base, err := parent.persist(false)
if err != nil {
diff.lock.Unlock()
return err
}
tree.layers[base.rootHash()] = base
diff.parent = base
diff.lock.Unlock()
default:
panic(fmt.Sprintf("unknown data layer in triedb: %T", parent))
}
// Remove any layer that is stale or links into a stale layer
children := make(map[common.Hash][]common.Hash)
for root, layer := range tree.layers {
if dl, ok := layer.(*diffLayer); ok {
parent := dl.parentLayer().rootHash()
children[parent] = append(children[parent], root)
}
}
var remove func(root common.Hash)
remove = func(root common.Hash) {
delete(tree.layers, root)
for _, child := range children[root] {
remove(child)
}
delete(children, root)
}
for root, layer := range tree.layers {
if dl, ok := layer.(*diskLayer); ok && dl.isStale() {
remove(root)
}
}
return nil
}
// bottom returns the bottom-most disk layer in this tree.
func (tree *layerTree) bottom() *diskLayer {
tree.lock.RLock()
defer tree.lock.RUnlock()
if len(tree.layers) == 0 {
return nil // Shouldn't happen, empty tree
}
// pick a random one as the entry point
var current layer
for _, layer := range tree.layers {
current = layer
break
}
for current.parentLayer() != nil {
current = current.parentLayer()
}
return current.(*diskLayer)
}