231 lines
6.9 KiB
Go
231 lines
6.9 KiB
Go
// 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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"encoding/binary"
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"os"
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"time"
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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/storage"
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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
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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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nodeDBStartupKey = []byte("startup") // Time when the node discovery started (seed selection)
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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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nodeDBDiscoverBond = nodeDBDiscoverRoot + ":lastbond"
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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) (*nodeDB, error) {
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if path == "" {
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return newMemoryNodeDB()
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}
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return newPersistentNodeDB(path)
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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() (*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{lvl: db}, 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) (*nodeDB, error) {
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// Try to open the cache, recovering any corruption
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db, err := leveldb.OpenFile(path, nil)
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if _, iscorrupted := err.(leveldb.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, 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)
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}
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}
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return &nodeDB{lvl: db}, 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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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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// startup retrieves the time instance when the bootstrapping last begun. Its
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// purpose is to prevent contacting potential seed nodes multiple times in the
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// same boot cycle.
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func (db *nodeDB) startup() time.Time {
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return time.Unix(db.fetchInt64(nodeDBStartupKey), 0)
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}
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// updateStartup updates the bootstrap initiation time to the one specified.
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func (db *nodeDB) updateStartup(instance time.Time) error {
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return db.storeInt64(nodeDBStartupKey, instance.Unix())
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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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return nil
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}
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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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// 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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// lastBond retrieves the time of the last successful bonding with a remote node.
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func (db *nodeDB) lastBond(id NodeID) time.Time {
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return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverBond)), 0)
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}
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// updateLastBond updates the last time we successfully bound to a remote node.
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func (db *nodeDB) updateLastBond(id NodeID, instance time.Time) error {
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return db.storeInt64(makeKey(id, nodeDBDiscoverBond), instance.Unix())
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}
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// querySeeds retrieves a batch of nodes to be used as potential seed servers
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// during bootstrapping the node into the network.
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//
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// Ideal seeds are the most recently seen nodes (highest probability to be still
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// alive), but yet untried. However, since leveldb only supports dumb iteration
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// we will instead start pulling in potential seeds that haven't been yet pinged
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// since the start of the boot procedure.
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//
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// If the database runs out of potential seeds, we restart the startup counter
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// and start iterating over the peers again.
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func (db *nodeDB) querySeeds(n int) []*Node {
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startup := db.startup()
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it := db.lvl.NewIterator(nil, nil)
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defer it.Release()
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nodes := make([]*Node, 0, n)
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for len(nodes) < n && it.Next() {
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// Iterate until a discovery node is found
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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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// Retrieve the last ping time, and if older than startup, query
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lastPing := db.lastPing(id)
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if lastPing.Before(startup) {
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if node := db.node(id); node != nil {
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nodes = append(nodes, node)
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}
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}
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}
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// Reset the startup time if no seeds were found
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if len(nodes) == 0 {
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db.updateStartup(time.Now())
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}
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return nodes
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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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db.lvl.Close()
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}
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