core, eth, trie: direct state trie synchronization

1 files changed, 233 insertions, 0 deletions

diff --git a/trie/sync.go b/trie/sync.go
new file mode 100644
index 000000000..65cfd6ed8
--- /dev/null
+++ b/trie/sync.go
@@ -0,0 +1,233 @@
+// Copyright 2015 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 (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+	"gopkg.in/karalabe/cookiejar.v2/collections/prque"
+)
+
+// request represents a scheduled or already in-flight state retrieval request.
+type request struct {
+	hash   common.Hash // Hash of the node data content to retrieve
+	data   []byte      // Data content of the node, cached until all subtrees complete
+	object *node       // Target node to populate with retrieved data (hashnode originally)
+
+	parents []*request // Parent state nodes referencing this entry (notify all upon completion)
+	depth   int        // Depth level within the trie the node is located to prioritize DFS
+	deps    int        // Number of dependencies before allowed to commit this node
+
+	callback TrieSyncLeafCallback // Callback to invoke if a leaf node it reached on this branch
+}
+
+// SyncResult is a simple list to return missing nodes along with their request
+// hashes.
+type SyncResult struct {
+	Hash common.Hash // Hash of the originally unknown trie node
+	Data []byte      // Data content of the retrieved node
+}
+
+// TrieSyncLeafCallback is a callback type invoked when a trie sync reaches a
+// leaf node. It's used by state syncing to check if the leaf node requires some
+// further data syncing.
+type TrieSyncLeafCallback func(leaf []byte, parent common.Hash) error
+
+// TrieSync is the main state trie synchronisation scheduler, which provides yet
+// unknown trie hashes to retrieve, accepts node data associated with said hashes
+// and reconstructs the trie steb by step until all is done.
+type TrieSync struct {
+	database Database                 // State database for storing all the assembled node data
+	requests map[common.Hash]*request // Pending requests pertaining to a key hash
+	queue    *prque.Prque             // Priority queue with the pending requests
+}
+
+// NewTrieSync creates a new trie data download scheduler.
+func NewTrieSync(root common.Hash, database Database, callback TrieSyncLeafCallback) *TrieSync {
+	ts := &TrieSync{
+		database: database,
+		requests: make(map[common.Hash]*request),
+		queue:    prque.New(),
+	}
+	ts.AddSubTrie(root, 0, common.Hash{}, callback)
+	return ts
+}
+
+// AddSubTrie registers a new trie to the sync code, rooted at the designated parent.
+func (s *TrieSync) AddSubTrie(root common.Hash, depth int, parent common.Hash, callback TrieSyncLeafCallback) {
+	// Short circuit if the trie is empty
+	if root == emptyRoot {
+		return
+	}
+	// Assemble the new sub-trie sync request
+	node := node(hashNode(root.Bytes()))
+	req := &request{
+		object:   &node,
+		hash:     root,
+		depth:    depth,
+		callback: callback,
+	}
+	// If this sub-trie has a designated parent, link them together
+	if parent != (common.Hash{}) {
+		ancestor := s.requests[parent]
+		if ancestor == nil {
+			panic(fmt.Sprintf("sub-trie ancestor not found: %x", parent))
+		}
+		ancestor.deps++
+		req.parents = append(req.parents, ancestor)
+	}
+	s.schedule(req)
+}
+
+// Missing retrieves the known missing nodes from the trie for retrieval.
+func (s *TrieSync) Missing(max int) []common.Hash {
+	requests := []common.Hash{}
+	for !s.queue.Empty() && (max == 0 || len(requests) < max) {
+		requests = append(requests, s.queue.PopItem().(common.Hash))
+	}
+	return requests
+}
+
+// Process injects a batch of retrieved trie nodes data.
+func (s *TrieSync) Process(results []SyncResult) (int, error) {
+	for i, item := range results {
+		// If the item was not requested, bail out
+		request := s.requests[item.Hash]
+		if request == nil {
+			return i, fmt.Errorf("not requested: %x", item.Hash)
+		}
+		// Decode the node data content and update the request
+		node, err := decodeNode(item.Data)
+		if err != nil {
+			return i, err
+		}
+		*request.object = node
+		request.data = item.Data
+
+		// Create and schedule a request for all the children nodes
+		requests, err := s.children(request)
+		if err != nil {
+			return i, err
+		}
+		if len(requests) == 0 && request.deps == 0 {
+			s.commit(request)
+			continue
+		}
+		request.deps += len(requests)
+		for _, child := range requests {
+			s.schedule(child)
+		}
+	}
+	return 0, nil
+}
+
+// schedule inserts a new state retrieval request into the fetch queue. If there
+// is already a pending request for this node, the new request will be discarded
+// and only a parent reference added to the old one.
+func (s *TrieSync) schedule(req *request) {
+	// If we're already requesting this node, add a new reference and stop
+	if old, ok := s.requests[req.hash]; ok {
+		old.parents = append(old.parents, req.parents...)
+		return
+	}
+	// Schedule the request for future retrieval
+	s.queue.Push(req.hash, float32(req.depth))
+	s.requests[req.hash] = req
+}
+
+// children retrieves all the missing children of a state trie entry for future
+// retrieval scheduling.
+func (s *TrieSync) children(req *request) ([]*request, error) {
+	// Gather all the children of the node, irrelevant whether known or not
+	type child struct {
+		node  *node
+		depth int
+	}
+	children := []child{}
+
+	switch node := (*req.object).(type) {
+	case shortNode:
+		children = []child{{
+			node:  &node.Val,
+			depth: req.depth + len(node.Key),
+		}}
+	case fullNode:
+		for i := 0; i < 17; i++ {
+			if node[i] != nil {
+				children = append(children, child{
+					node:  &node[i],
+					depth: req.depth + 1,
+				})
+			}
+		}
+	default:
+		panic(fmt.Sprintf("unknown node: %+v", node))
+	}
+	// Iterate over the children, and request all unknown ones
+	requests := make([]*request, 0, len(children))
+	for _, child := range children {
+		// Notify any external watcher of a new key/value node
+		if req.callback != nil {
+			if node, ok := (*child.node).(valueNode); ok {
+				if err := req.callback(node, req.hash); err != nil {
+					return nil, err
+				}
+			}
+		}
+		// If the child references another node, resolve or schedule
+		if node, ok := (*child.node).(hashNode); ok {
+			// Try to resolve the node from the local database
+			blob, _ := s.database.Get(node)
+			if local, err := decodeNode(blob); local != nil && err == nil {
+				*child.node = local
+				continue
+			}
+			// Locally unknown node, schedule for retrieval
+			requests = append(requests, &request{
+				object:   child.node,
+				hash:     common.BytesToHash(node),
+				parents:  []*request{req},
+				depth:    child.depth,
+				callback: req.callback,
+			})
+		}
+	}
+	return requests, nil
+}
+
+// commit finalizes a retrieval request and stores it into the database. If any
+// of the referencing parent requests complete due to this commit, they are also
+// committed themselves.
+func (s *TrieSync) commit(req *request) error {
+	// Write the node content to disk
+	if err := s.database.Put(req.hash[:], req.data); err != nil {
+		return err
+	}
+	delete(s.requests, req.hash)
+
+	// Check all parents for completion
+	for _, parent := range req.parents {
+		parent.deps--
+		if parent.deps == 0 {
+			if err := s.commit(parent); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}