366 lines
11 KiB
Go
366 lines
11 KiB
Go
// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Contains the node database, storing previously seen nodes and any collected
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// metadata about them for QoS purposes.
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package discover
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import (
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"bytes"
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"crypto/rand"
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"encoding/binary"
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"os"
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"sync"
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"time"
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"github.com/ethereum/go-ethereum/crypto"
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"github.com/ethereum/go-ethereum/log"
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"github.com/ethereum/go-ethereum/rlp"
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"github.com/syndtr/goleveldb/leveldb"
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"github.com/syndtr/goleveldb/leveldb/errors"
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"github.com/syndtr/goleveldb/leveldb/iterator"
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"github.com/syndtr/goleveldb/leveldb/opt"
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"github.com/syndtr/goleveldb/leveldb/storage"
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"github.com/syndtr/goleveldb/leveldb/util"
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)
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var (
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nodeDBNilNodeID = NodeID{} // Special node ID to use as a nil element.
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nodeDBNodeExpiration = 24 * time.Hour // Time after which an unseen node should be dropped.
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nodeDBCleanupCycle = time.Hour // Time period for running the expiration task.
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)
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// nodeDB stores all nodes we know about.
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type nodeDB struct {
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lvl *leveldb.DB // Interface to the database itself
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self NodeID // Own node id to prevent adding it into the database
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runner sync.Once // Ensures we can start at most one expirer
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quit chan struct{} // Channel to signal the expiring thread to stop
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}
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// Schema layout for the node database
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var (
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nodeDBVersionKey = []byte("version") // Version of the database to flush if changes
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nodeDBItemPrefix = []byte("n:") // Identifier to prefix node entries with
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nodeDBDiscoverRoot = ":discover"
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nodeDBDiscoverPing = nodeDBDiscoverRoot + ":lastping"
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nodeDBDiscoverPong = nodeDBDiscoverRoot + ":lastpong"
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nodeDBDiscoverFindFails = nodeDBDiscoverRoot + ":findfail"
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)
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// newNodeDB creates a new node database for storing and retrieving infos about
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// known peers in the network. If no path is given, an in-memory, temporary
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// database is constructed.
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func newNodeDB(path string, version int, self NodeID) (*nodeDB, error) {
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if path == "" {
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return newMemoryNodeDB(self)
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}
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return newPersistentNodeDB(path, version, self)
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}
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// newMemoryNodeDB creates a new in-memory node database without a persistent
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// backend.
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func newMemoryNodeDB(self NodeID) (*nodeDB, error) {
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db, err := leveldb.Open(storage.NewMemStorage(), nil)
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if err != nil {
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return nil, err
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}
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return &nodeDB{
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lvl: db,
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self: self,
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quit: make(chan struct{}),
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}, nil
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}
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// newPersistentNodeDB creates/opens a leveldb backed persistent node database,
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// also flushing its contents in case of a version mismatch.
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func newPersistentNodeDB(path string, version int, self NodeID) (*nodeDB, error) {
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opts := &opt.Options{OpenFilesCacheCapacity: 5}
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db, err := leveldb.OpenFile(path, opts)
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if _, iscorrupted := err.(*errors.ErrCorrupted); iscorrupted {
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db, err = leveldb.RecoverFile(path, nil)
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}
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if err != nil {
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return nil, err
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}
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// The nodes contained in the cache correspond to a certain protocol version.
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// Flush all nodes if the version doesn't match.
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currentVer := make([]byte, binary.MaxVarintLen64)
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currentVer = currentVer[:binary.PutVarint(currentVer, int64(version))]
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blob, err := db.Get(nodeDBVersionKey, nil)
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switch err {
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case leveldb.ErrNotFound:
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// Version not found (i.e. empty cache), insert it
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if err := db.Put(nodeDBVersionKey, currentVer, nil); err != nil {
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db.Close()
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return nil, err
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}
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case nil:
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// Version present, flush if different
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if !bytes.Equal(blob, currentVer) {
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db.Close()
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if err = os.RemoveAll(path); err != nil {
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return nil, err
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}
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return newPersistentNodeDB(path, version, self)
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}
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}
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return &nodeDB{
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lvl: db,
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self: self,
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quit: make(chan struct{}),
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}, nil
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}
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// makeKey generates the leveldb key-blob from a node id and its particular
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// field of interest.
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func makeKey(id NodeID, field string) []byte {
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if bytes.Equal(id[:], nodeDBNilNodeID[:]) {
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return []byte(field)
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}
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return append(nodeDBItemPrefix, append(id[:], field...)...)
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}
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// splitKey tries to split a database key into a node id and a field part.
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func splitKey(key []byte) (id NodeID, field string) {
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// If the key is not of a node, return it plainly
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if !bytes.HasPrefix(key, nodeDBItemPrefix) {
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return NodeID{}, string(key)
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}
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// Otherwise split the id and field
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item := key[len(nodeDBItemPrefix):]
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copy(id[:], item[:len(id)])
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field = string(item[len(id):])
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return id, field
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}
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// fetchInt64 retrieves an integer instance associated with a particular
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// database key.
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func (db *nodeDB) fetchInt64(key []byte) int64 {
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blob, err := db.lvl.Get(key, nil)
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if err != nil {
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return 0
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}
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val, read := binary.Varint(blob)
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if read <= 0 {
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return 0
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}
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return val
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}
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// storeInt64 update a specific database entry to the current time instance as a
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// unix timestamp.
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func (db *nodeDB) storeInt64(key []byte, n int64) error {
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blob := make([]byte, binary.MaxVarintLen64)
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blob = blob[:binary.PutVarint(blob, n)]
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return db.lvl.Put(key, blob, nil)
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}
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// node retrieves a node with a given id from the database.
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func (db *nodeDB) node(id NodeID) *Node {
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blob, err := db.lvl.Get(makeKey(id, nodeDBDiscoverRoot), nil)
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if err != nil {
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return nil
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}
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node := new(Node)
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if err := rlp.DecodeBytes(blob, node); err != nil {
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log.Error("Failed to decode node RLP", "err", err)
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return nil
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}
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node.sha = crypto.Keccak256Hash(node.ID[:])
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return node
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}
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// updateNode inserts - potentially overwriting - a node into the peer database.
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func (db *nodeDB) updateNode(node *Node) error {
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blob, err := rlp.EncodeToBytes(node)
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if err != nil {
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return err
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}
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return db.lvl.Put(makeKey(node.ID, nodeDBDiscoverRoot), blob, nil)
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}
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// deleteNode deletes all information/keys associated with a node.
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func (db *nodeDB) deleteNode(id NodeID) error {
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deleter := db.lvl.NewIterator(util.BytesPrefix(makeKey(id, "")), nil)
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for deleter.Next() {
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if err := db.lvl.Delete(deleter.Key(), nil); err != nil {
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return err
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}
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}
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return nil
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}
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// ensureExpirer is a small helper method ensuring that the data expiration
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// mechanism is running. If the expiration goroutine is already running, this
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// method simply returns.
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//
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// The goal is to start the data evacuation only after the network successfully
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// bootstrapped itself (to prevent dumping potentially useful seed nodes). Since
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// it would require significant overhead to exactly trace the first successful
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// convergence, it's simpler to "ensure" the correct state when an appropriate
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// condition occurs (i.e. a successful bonding), and discard further events.
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func (db *nodeDB) ensureExpirer() {
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db.runner.Do(func() { go db.expirer() })
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}
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// expirer should be started in a go routine, and is responsible for looping ad
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// infinitum and dropping stale data from the database.
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func (db *nodeDB) expirer() {
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tick := time.Tick(nodeDBCleanupCycle)
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for {
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select {
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case <-tick:
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if err := db.expireNodes(); err != nil {
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log.Error("Failed to expire nodedb items", "err", err)
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}
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case <-db.quit:
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return
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}
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}
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}
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// expireNodes iterates over the database and deletes all nodes that have not
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// been seen (i.e. received a pong from) for some allotted time.
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func (db *nodeDB) expireNodes() error {
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threshold := time.Now().Add(-nodeDBNodeExpiration)
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// Find discovered nodes that are older than the allowance
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it := db.lvl.NewIterator(nil, nil)
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defer it.Release()
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for it.Next() {
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// Skip the item if not a discovery node
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id, field := splitKey(it.Key())
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if field != nodeDBDiscoverRoot {
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continue
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}
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// Skip the node if not expired yet (and not self)
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if !bytes.Equal(id[:], db.self[:]) {
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if seen := db.lastPong(id); seen.After(threshold) {
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continue
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}
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}
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// Otherwise delete all associated information
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db.deleteNode(id)
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}
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return nil
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}
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// lastPing retrieves the time of the last ping packet send to a remote node,
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// requesting binding.
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func (db *nodeDB) lastPing(id NodeID) time.Time {
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return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPing)), 0)
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}
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// updateLastPing updates the last time we tried contacting a remote node.
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func (db *nodeDB) updateLastPing(id NodeID, instance time.Time) error {
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return db.storeInt64(makeKey(id, nodeDBDiscoverPing), instance.Unix())
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}
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// lastPong retrieves the time of the last successful contact from remote node.
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func (db *nodeDB) lastPong(id NodeID) time.Time {
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return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPong)), 0)
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}
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// updateLastPong updates the last time a remote node successfully contacted.
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func (db *nodeDB) updateLastPong(id NodeID, instance time.Time) error {
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return db.storeInt64(makeKey(id, nodeDBDiscoverPong), instance.Unix())
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}
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// findFails retrieves the number of findnode failures since bonding.
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func (db *nodeDB) findFails(id NodeID) int {
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return int(db.fetchInt64(makeKey(id, nodeDBDiscoverFindFails)))
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}
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// updateFindFails updates the number of findnode failures since bonding.
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func (db *nodeDB) updateFindFails(id NodeID, fails int) error {
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return db.storeInt64(makeKey(id, nodeDBDiscoverFindFails), int64(fails))
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}
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// querySeeds retrieves random nodes to be used as potential seed nodes
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// for bootstrapping.
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func (db *nodeDB) querySeeds(n int, maxAge time.Duration) []*Node {
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var (
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now = time.Now()
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nodes = make([]*Node, 0, n)
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it = db.lvl.NewIterator(nil, nil)
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id NodeID
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)
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defer it.Release()
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seek:
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for seeks := 0; len(nodes) < n && seeks < n*5; seeks++ {
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// Seek to a random entry. The first byte is incremented by a
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// random amount each time in order to increase the likelihood
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// of hitting all existing nodes in very small databases.
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ctr := id[0]
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rand.Read(id[:])
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id[0] = ctr + id[0]%16
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it.Seek(makeKey(id, nodeDBDiscoverRoot))
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n := nextNode(it)
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if n == nil {
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id[0] = 0
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continue seek // iterator exhausted
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}
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if n.ID == db.self {
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continue seek
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}
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if now.Sub(db.lastPong(n.ID)) > maxAge {
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continue seek
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}
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for i := range nodes {
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if nodes[i].ID == n.ID {
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continue seek // duplicate
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}
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}
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nodes = append(nodes, n)
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}
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return nodes
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}
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// reads the next node record from the iterator, skipping over other
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// database entries.
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func nextNode(it iterator.Iterator) *Node {
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for end := false; !end; end = !it.Next() {
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id, field := splitKey(it.Key())
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if field != nodeDBDiscoverRoot {
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continue
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}
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var n Node
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if err := rlp.DecodeBytes(it.Value(), &n); err != nil {
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log.Warn("Failed to decode node RLP", "id", id, "err", err)
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continue
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}
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return &n
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}
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return nil
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}
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// close flushes and closes the database files.
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func (db *nodeDB) close() {
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close(db.quit)
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db.lvl.Close()
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}
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