github.com/simplechain-org/go-simplechain@v1.0.6/p2p/discv5/database.go (about)

     1  // Copyright 2015 The go-simplechain Authors
     2  // This file is part of the go-simplechain library.
     3  //
     4  // The go-simplechain library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-simplechain library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-simplechain library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  // Contains the node database, storing previously seen nodes and any collected
    18  // metadata about them for QoS purposes.
    19  
    20  package discv5
    21  
    22  import (
    23  	"bytes"
    24  	"crypto/rand"
    25  	"encoding/binary"
    26  	"fmt"
    27  	"os"
    28  	"sync"
    29  	"time"
    30  
    31  	"github.com/simplechain-org/go-simplechain/crypto"
    32  	"github.com/simplechain-org/go-simplechain/log"
    33  	"github.com/simplechain-org/go-simplechain/rlp"
    34  	"github.com/syndtr/goleveldb/leveldb"
    35  	"github.com/syndtr/goleveldb/leveldb/errors"
    36  	"github.com/syndtr/goleveldb/leveldb/iterator"
    37  	"github.com/syndtr/goleveldb/leveldb/opt"
    38  	"github.com/syndtr/goleveldb/leveldb/storage"
    39  	"github.com/syndtr/goleveldb/leveldb/util"
    40  )
    41  
    42  var (
    43  	nodeDBNilNodeID      = NodeID{}       // Special node ID to use as a nil element.
    44  	nodeDBNodeExpiration = 24 * time.Hour // Time after which an unseen node should be dropped.
    45  	nodeDBCleanupCycle   = time.Hour      // Time period for running the expiration task.
    46  )
    47  
    48  // nodeDB stores all nodes we know about.
    49  type nodeDB struct {
    50  	lvl    *leveldb.DB   // Interface to the database itself
    51  	self   NodeID        // Own node id to prevent adding it into the database
    52  	runner sync.Once     // Ensures we can start at most one expirer
    53  	quit   chan struct{} // Channel to signal the expiring thread to stop
    54  }
    55  
    56  // Schema layout for the node database
    57  var (
    58  	nodeDBVersionKey = []byte("version") // Version of the database to flush if changes
    59  	nodeDBItemPrefix = []byte("n:")      // Identifier to prefix node entries with
    60  
    61  	nodeDBDiscoverRoot      = ":discover"
    62  	nodeDBDiscoverPing      = nodeDBDiscoverRoot + ":lastping"
    63  	nodeDBDiscoverPong      = nodeDBDiscoverRoot + ":lastpong"
    64  	nodeDBDiscoverFindFails = nodeDBDiscoverRoot + ":findfail"
    65  	nodeDBTopicRegTickets   = ":tickets"
    66  )
    67  
    68  // newNodeDB creates a new node database for storing and retrieving infos about
    69  // known peers in the network. If no path is given, an in-memory, temporary
    70  // database is constructed.
    71  func newNodeDB(path string, version int, self NodeID) (*nodeDB, error) {
    72  	if path == "" {
    73  		return newMemoryNodeDB(self)
    74  	}
    75  	return newPersistentNodeDB(path, version, self)
    76  }
    77  
    78  // newMemoryNodeDB creates a new in-memory node database without a persistent
    79  // backend.
    80  func newMemoryNodeDB(self NodeID) (*nodeDB, error) {
    81  	db, err := leveldb.Open(storage.NewMemStorage(), nil)
    82  	if err != nil {
    83  		return nil, err
    84  	}
    85  	return &nodeDB{
    86  		lvl:  db,
    87  		self: self,
    88  		quit: make(chan struct{}),
    89  	}, nil
    90  }
    91  
    92  // newPersistentNodeDB creates/opens a leveldb backed persistent node database,
    93  // also flushing its contents in case of a version mismatch.
    94  func newPersistentNodeDB(path string, version int, self NodeID) (*nodeDB, error) {
    95  	opts := &opt.Options{OpenFilesCacheCapacity: 5}
    96  	db, err := leveldb.OpenFile(path, opts)
    97  	if _, iscorrupted := err.(*errors.ErrCorrupted); iscorrupted {
    98  		db, err = leveldb.RecoverFile(path, nil)
    99  	}
   100  	if err != nil {
   101  		return nil, err
   102  	}
   103  	// The nodes contained in the cache correspond to a certain protocol version.
   104  	// Flush all nodes if the version doesn't match.
   105  	currentVer := make([]byte, binary.MaxVarintLen64)
   106  	currentVer = currentVer[:binary.PutVarint(currentVer, int64(version))]
   107  
   108  	blob, err := db.Get(nodeDBVersionKey, nil)
   109  	switch err {
   110  	case leveldb.ErrNotFound:
   111  		// Version not found (i.e. empty cache), insert it
   112  		if err := db.Put(nodeDBVersionKey, currentVer, nil); err != nil {
   113  			db.Close()
   114  			return nil, err
   115  		}
   116  
   117  	case nil:
   118  		// Version present, flush if different
   119  		if !bytes.Equal(blob, currentVer) {
   120  			db.Close()
   121  			if err = os.RemoveAll(path); err != nil {
   122  				return nil, err
   123  			}
   124  			return newPersistentNodeDB(path, version, self)
   125  		}
   126  	}
   127  	return &nodeDB{
   128  		lvl:  db,
   129  		self: self,
   130  		quit: make(chan struct{}),
   131  	}, nil
   132  }
   133  
   134  // makeKey generates the leveldb key-blob from a node id and its particular
   135  // field of interest.
   136  func makeKey(id NodeID, field string) []byte {
   137  	if bytes.Equal(id[:], nodeDBNilNodeID[:]) {
   138  		return []byte(field)
   139  	}
   140  	return append(nodeDBItemPrefix, append(id[:], field...)...)
   141  }
   142  
   143  // splitKey tries to split a database key into a node id and a field part.
   144  func splitKey(key []byte) (id NodeID, field string) {
   145  	// If the key is not of a node, return it plainly
   146  	if !bytes.HasPrefix(key, nodeDBItemPrefix) {
   147  		return NodeID{}, string(key)
   148  	}
   149  	// Otherwise split the id and field
   150  	item := key[len(nodeDBItemPrefix):]
   151  	copy(id[:], item[:len(id)])
   152  	field = string(item[len(id):])
   153  
   154  	return id, field
   155  }
   156  
   157  // fetchInt64 retrieves an integer instance associated with a particular
   158  // database key.
   159  func (db *nodeDB) fetchInt64(key []byte) int64 {
   160  	blob, err := db.lvl.Get(key, nil)
   161  	if err != nil {
   162  		return 0
   163  	}
   164  	val, read := binary.Varint(blob)
   165  	if read <= 0 {
   166  		return 0
   167  	}
   168  	return val
   169  }
   170  
   171  // storeInt64 update a specific database entry to the current time instance as a
   172  // unix timestamp.
   173  func (db *nodeDB) storeInt64(key []byte, n int64) error {
   174  	blob := make([]byte, binary.MaxVarintLen64)
   175  	blob = blob[:binary.PutVarint(blob, n)]
   176  	return db.lvl.Put(key, blob, nil)
   177  }
   178  
   179  func (db *nodeDB) storeRLP(key []byte, val interface{}) error {
   180  	blob, err := rlp.EncodeToBytes(val)
   181  	if err != nil {
   182  		return err
   183  	}
   184  	return db.lvl.Put(key, blob, nil)
   185  }
   186  
   187  func (db *nodeDB) fetchRLP(key []byte, val interface{}) error {
   188  	blob, err := db.lvl.Get(key, nil)
   189  	if err != nil {
   190  		return err
   191  	}
   192  	err = rlp.DecodeBytes(blob, val)
   193  	if err != nil {
   194  		log.Warn(fmt.Sprintf("key %x (%T) %v", key, val, err))
   195  	}
   196  	return err
   197  }
   198  
   199  // node retrieves a node with a given id from the database.
   200  func (db *nodeDB) node(id NodeID) *Node {
   201  	var node Node
   202  	if err := db.fetchRLP(makeKey(id, nodeDBDiscoverRoot), &node); err != nil {
   203  		return nil
   204  	}
   205  	node.sha = crypto.Keccak256Hash(node.ID[:])
   206  	return &node
   207  }
   208  
   209  // updateNode inserts - potentially overwriting - a node into the peer database.
   210  func (db *nodeDB) updateNode(node *Node) error {
   211  	return db.storeRLP(makeKey(node.ID, nodeDBDiscoverRoot), node)
   212  }
   213  
   214  // deleteNode deletes all information/keys associated with a node.
   215  func (db *nodeDB) deleteNode(id NodeID) error {
   216  	deleter := db.lvl.NewIterator(util.BytesPrefix(makeKey(id, "")), nil)
   217  	for deleter.Next() {
   218  		if err := db.lvl.Delete(deleter.Key(), nil); err != nil {
   219  			return err
   220  		}
   221  	}
   222  	return nil
   223  }
   224  
   225  // ensureExpirer is a small helper method ensuring that the data expiration
   226  // mechanism is running. If the expiration goroutine is already running, this
   227  // method simply returns.
   228  //
   229  // The goal is to start the data evacuation only after the network successfully
   230  // bootstrapped itself (to prevent dumping potentially useful seed nodes). Since
   231  // it would require significant overhead to exactly trace the first successful
   232  // convergence, it's simpler to "ensure" the correct state when an appropriate
   233  // condition occurs (i.e. a successful bonding), and discard further events.
   234  func (db *nodeDB) ensureExpirer() {
   235  	db.runner.Do(func() { go db.expirer() })
   236  }
   237  
   238  // expirer should be started in a go routine, and is responsible for looping ad
   239  // infinitum and dropping stale data from the database.
   240  func (db *nodeDB) expirer() {
   241  	tick := time.NewTicker(nodeDBCleanupCycle)
   242  	defer tick.Stop()
   243  	for {
   244  		select {
   245  		case <-tick.C:
   246  			if err := db.expireNodes(); err != nil {
   247  				log.Error(fmt.Sprintf("Failed to expire nodedb items: %v", err))
   248  			}
   249  		case <-db.quit:
   250  			return
   251  		}
   252  	}
   253  }
   254  
   255  // expireNodes iterates over the database and deletes all nodes that have not
   256  // been seen (i.e. received a pong from) for some allotted time.
   257  func (db *nodeDB) expireNodes() error {
   258  	threshold := time.Now().Add(-nodeDBNodeExpiration)
   259  
   260  	// Find discovered nodes that are older than the allowance
   261  	it := db.lvl.NewIterator(nil, nil)
   262  	defer it.Release()
   263  
   264  	for it.Next() {
   265  		// Skip the item if not a discovery node
   266  		id, field := splitKey(it.Key())
   267  		if field != nodeDBDiscoverRoot {
   268  			continue
   269  		}
   270  		// Skip the node if not expired yet (and not self)
   271  		if !bytes.Equal(id[:], db.self[:]) {
   272  			if seen := db.lastPong(id); seen.After(threshold) {
   273  				continue
   274  			}
   275  		}
   276  		// Otherwise delete all associated information
   277  		db.deleteNode(id)
   278  	}
   279  	return nil
   280  }
   281  
   282  // lastPing retrieves the time of the last ping packet send to a remote node,
   283  // requesting binding.
   284  func (db *nodeDB) lastPing(id NodeID) time.Time {
   285  	return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPing)), 0)
   286  }
   287  
   288  // updateLastPing updates the last time we tried contacting a remote node.
   289  func (db *nodeDB) updateLastPing(id NodeID, instance time.Time) error {
   290  	return db.storeInt64(makeKey(id, nodeDBDiscoverPing), instance.Unix())
   291  }
   292  
   293  // lastPong retrieves the time of the last successful contact from remote node.
   294  func (db *nodeDB) lastPong(id NodeID) time.Time {
   295  	return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPong)), 0)
   296  }
   297  
   298  // updateLastPong updates the last time a remote node successfully contacted.
   299  func (db *nodeDB) updateLastPong(id NodeID, instance time.Time) error {
   300  	return db.storeInt64(makeKey(id, nodeDBDiscoverPong), instance.Unix())
   301  }
   302  
   303  // findFails retrieves the number of findnode failures since bonding.
   304  func (db *nodeDB) findFails(id NodeID) int {
   305  	return int(db.fetchInt64(makeKey(id, nodeDBDiscoverFindFails)))
   306  }
   307  
   308  // updateFindFails updates the number of findnode failures since bonding.
   309  func (db *nodeDB) updateFindFails(id NodeID, fails int) error {
   310  	return db.storeInt64(makeKey(id, nodeDBDiscoverFindFails), int64(fails))
   311  }
   312  
   313  // querySeeds retrieves random nodes to be used as potential seed nodes
   314  // for bootstrapping.
   315  func (db *nodeDB) querySeeds(n int, maxAge time.Duration) []*Node {
   316  	var (
   317  		now   = time.Now()
   318  		nodes = make([]*Node, 0, n)
   319  		it    = db.lvl.NewIterator(nil, nil)
   320  		id    NodeID
   321  	)
   322  	defer it.Release()
   323  
   324  seek:
   325  	for seeks := 0; len(nodes) < n && seeks < n*5; seeks++ {
   326  		// Seek to a random entry. The first byte is incremented by a
   327  		// random amount each time in order to increase the likelihood
   328  		// of hitting all existing nodes in very small databases.
   329  		ctr := id[0]
   330  		rand.Read(id[:])
   331  		id[0] = ctr + id[0]%16
   332  		it.Seek(makeKey(id, nodeDBDiscoverRoot))
   333  
   334  		n := nextNode(it)
   335  		if n == nil {
   336  			id[0] = 0
   337  			continue seek // iterator exhausted
   338  		}
   339  		if n.ID == db.self {
   340  			continue seek
   341  		}
   342  		if now.Sub(db.lastPong(n.ID)) > maxAge {
   343  			continue seek
   344  		}
   345  		for i := range nodes {
   346  			if nodes[i].ID == n.ID {
   347  				continue seek // duplicate
   348  			}
   349  		}
   350  		nodes = append(nodes, n)
   351  	}
   352  	return nodes
   353  }
   354  
   355  func (db *nodeDB) fetchTopicRegTickets(id NodeID) (issued, used uint32) {
   356  	key := makeKey(id, nodeDBTopicRegTickets)
   357  	blob, _ := db.lvl.Get(key, nil)
   358  	if len(blob) != 8 {
   359  		return 0, 0
   360  	}
   361  	issued = binary.BigEndian.Uint32(blob[0:4])
   362  	used = binary.BigEndian.Uint32(blob[4:8])
   363  	return
   364  }
   365  
   366  func (db *nodeDB) updateTopicRegTickets(id NodeID, issued, used uint32) error {
   367  	key := makeKey(id, nodeDBTopicRegTickets)
   368  	blob := make([]byte, 8)
   369  	binary.BigEndian.PutUint32(blob[0:4], issued)
   370  	binary.BigEndian.PutUint32(blob[4:8], used)
   371  	return db.lvl.Put(key, blob, nil)
   372  }
   373  
   374  // reads the next node record from the iterator, skipping over other
   375  // database entries.
   376  func nextNode(it iterator.Iterator) *Node {
   377  	for end := false; !end; end = !it.Next() {
   378  		id, field := splitKey(it.Key())
   379  		if field != nodeDBDiscoverRoot {
   380  			continue
   381  		}
   382  		var n Node
   383  		if err := rlp.DecodeBytes(it.Value(), &n); err != nil {
   384  			log.Warn(fmt.Sprintf("invalid node %x: %v", id, err))
   385  			continue
   386  		}
   387  		return &n
   388  	}
   389  	return nil
   390  }
   391  
   392  // close flushes and closes the database files.
   393  func (db *nodeDB) close() {
   394  	close(db.quit)
   395  	db.lvl.Close()
   396  }