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retrieval.go
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retrieval.go
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// Copyright 2020 The Swarm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package retrieval provides the retrieval protocol
// implementation. The protocol is used to retrieve
// chunks over the network using forwarding-kademlia
// routing.
package retrieval
import (
"context"
"errors"
"fmt"
"strconv"
"time"
"github.com/ethersphere/bee/pkg/accounting"
"github.com/ethersphere/bee/pkg/cac"
"github.com/ethersphere/bee/pkg/logging"
"github.com/ethersphere/bee/pkg/p2p"
"github.com/ethersphere/bee/pkg/p2p/protobuf"
"github.com/ethersphere/bee/pkg/postage"
"github.com/ethersphere/bee/pkg/pricer"
pb "github.com/ethersphere/bee/pkg/retrieval/pb"
"github.com/ethersphere/bee/pkg/soc"
"github.com/ethersphere/bee/pkg/storage"
"github.com/ethersphere/bee/pkg/swarm"
"github.com/ethersphere/bee/pkg/topology"
"github.com/ethersphere/bee/pkg/tracing"
"github.com/opentracing/opentracing-go"
"golang.org/x/sync/singleflight"
)
type requestSourceContextKey struct{}
const (
protocolName = "retrieval"
protocolVersion = "1.0.0"
streamName = "retrieval"
)
var _ Interface = (*Service)(nil)
type Interface interface {
RetrieveChunk(ctx context.Context, addr swarm.Address, origin bool) (chunk swarm.Chunk, err error)
}
type retrievalResult struct {
chunk swarm.Chunk
peer swarm.Address
err error
retrieved bool
}
type Service struct {
addr swarm.Address
streamer p2p.Streamer
peerSuggester topology.EachPeerer
storer storage.Storer
singleflight singleflight.Group
logger logging.Logger
accounting accounting.Interface
metrics metrics
pricer pricer.Interface
tracer *tracing.Tracer
}
func New(addr swarm.Address, storer storage.Storer, streamer p2p.Streamer, chunkPeerer topology.EachPeerer, logger logging.Logger, accounting accounting.Interface, pricer pricer.Interface, tracer *tracing.Tracer) *Service {
return &Service{
addr: addr,
streamer: streamer,
peerSuggester: chunkPeerer,
storer: storer,
logger: logger,
accounting: accounting,
pricer: pricer,
metrics: newMetrics(),
tracer: tracer,
}
}
func (s *Service) Protocol() p2p.ProtocolSpec {
return p2p.ProtocolSpec{
Name: protocolName,
Version: protocolVersion,
StreamSpecs: []p2p.StreamSpec{
{
Name: streamName,
Handler: s.handler,
},
},
}
}
const (
retrieveChunkTimeout = 10 * time.Second
retrieveRetryIntervalDuration = 5 * time.Second
maxSelects = 8
originSuffix = "_origin"
)
func (s *Service) RetrieveChunk(ctx context.Context, addr swarm.Address, origin bool) (swarm.Chunk, error) {
s.metrics.RequestCounter.Inc()
flightRoute := addr.String()
if origin {
flightRoute = addr.String() + originSuffix
}
v, err, _ := s.singleflight.Do(flightRoute, func() (interface{}, error) {
maxPeers := 1
if origin {
maxPeers = maxSelects
}
span, logger, ctx := s.tracer.StartSpanFromContext(ctx, "retrieve-chunk", s.logger, opentracing.Tag{Key: "address", Value: addr.String()})
defer span.Finish()
sp := newSkipPeers()
ticker := time.NewTicker(retrieveRetryIntervalDuration)
defer ticker.Stop()
var (
peerAttempt int
peersResults int
resultC = make(chan retrievalResult, maxSelects)
)
requestAttempt := 0
lastTime := time.Now().Unix()
for requestAttempt < 5 {
if peerAttempt < maxSelects {
peerAttempt++
s.metrics.PeerRequestCounter.Inc()
go func() {
chunk, peer, requested, err := s.retrieveChunk(ctx, addr, sp)
resultC <- retrievalResult{
chunk: chunk,
peer: peer,
err: err,
retrieved: requested,
}
}()
} else {
resultC <- retrievalResult{}
}
select {
case <-ticker.C:
// break
case res := <-resultC:
if res.retrieved {
if res.err != nil {
if !res.peer.IsZero() {
logger.Debugf("retrieval: failed to get chunk %s from peer %s: %v", addr, res.peer, res.err)
}
peersResults++
} else {
return res.chunk, nil
}
}
case <-ctx.Done():
logger.Tracef("retrieval: failed to get chunk %s: %v", addr, ctx.Err())
return nil, fmt.Errorf("retrieval: %w", ctx.Err())
}
// all results received, only successfully attempted requests are counted
if peersResults >= maxPeers {
logger.Tracef("retrieval: failed to get chunk %s", addr)
return nil, storage.ErrNotFound
}
// if we have not counted enough successful attempts but out of selection amount, reset
if peerAttempt >= maxSelects {
if !origin {
return nil, storage.ErrNotFound
}
requestAttempt++
timeNow := time.Now().Unix()
if timeNow > lastTime {
lastTime = timeNow
peerAttempt = 0
sp.Reset()
} else {
select {
case <-time.After(600 * time.Millisecond):
case <-ctx.Done():
logger.Tracef("retrieval: failed to get chunk %s: %v", addr, ctx.Err())
return nil, fmt.Errorf("retrieval: %w", ctx.Err())
}
}
}
}
// if we have not managed to get results after 5 rounds of peer selections, give up
return nil, storage.ErrNotFound
})
if err != nil {
return nil, err
}
return v.(swarm.Chunk), nil
}
func (s *Service) retrieveChunk(ctx context.Context, addr swarm.Address, sp *skipPeers) (chunk swarm.Chunk, peer swarm.Address, requested bool, err error) {
startTimer := time.Now()
v := ctx.Value(requestSourceContextKey{})
sourcePeerAddr := swarm.Address{}
// allow upstream requests if this node is the source of the request
// i.e. the request was not forwarded, to improve retrieval
// if this node is the closest to he chunk but still does not contain it
allowUpstream := true
if src, ok := v.(string); ok {
sourcePeerAddr, err = swarm.ParseHexAddress(src)
if err == nil {
sp.Add(sourcePeerAddr)
}
// do not allow upstream requests if the request was forwarded to this node
// to avoid the request loops
allowUpstream = false
}
ctx, cancel := context.WithTimeout(ctx, retrieveChunkTimeout)
defer cancel()
peer, err = s.closestPeer(addr, sp.All(), allowUpstream)
if err != nil {
return nil, peer, false, fmt.Errorf("get closest for address %s, allow upstream %v: %w", addr.String(), allowUpstream, err)
}
peerPO := swarm.Proximity(s.addr.Bytes(), peer.Bytes())
if !sourcePeerAddr.IsZero() {
// is forwarded request
sourceAddrPO := swarm.Proximity(sourcePeerAddr.Bytes(), addr.Bytes())
addrPO := swarm.Proximity(peer.Bytes(), addr.Bytes())
poGain := int(addrPO) - int(sourceAddrPO)
s.metrics.RetrieveChunkPOGainCounter.
WithLabelValues(strconv.Itoa(poGain)).
Inc()
}
// compute the peer's price for this chunk for price header
chunkPrice := s.pricer.PeerPrice(peer, addr)
// Reserve to see whether we can request the chunk
err = s.accounting.Reserve(ctx, peer, chunkPrice)
if err != nil {
sp.AddOverdraft(peer)
return nil, peer, false, err
}
defer s.accounting.Release(peer, chunkPrice)
sp.Add(peer)
s.logger.Tracef("retrieval: requesting chunk %s from peer %s", addr, peer)
stream, err := s.streamer.NewStream(ctx, peer, nil, protocolName, protocolVersion, streamName)
if err != nil {
s.metrics.TotalErrors.Inc()
return nil, peer, false, fmt.Errorf("new stream: %w", err)
}
defer func() {
if err != nil {
_ = stream.Reset()
} else {
go stream.FullClose()
}
}()
w, r := protobuf.NewWriterAndReader(stream)
if err := w.WriteMsgWithContext(ctx, &pb.Request{
Addr: addr.Bytes(),
}); err != nil {
s.metrics.TotalErrors.Inc()
return nil, peer, false, fmt.Errorf("write request: %w peer %s", err, peer.String())
}
var d pb.Delivery
if err := r.ReadMsgWithContext(ctx, &d); err != nil {
s.metrics.TotalErrors.Inc()
return nil, peer, true, fmt.Errorf("read delivery: %w peer %s", err, peer.String())
}
s.metrics.RetrieveChunkPeerPOTimer.
WithLabelValues(strconv.Itoa(int(peerPO))).
Observe(time.Since(startTimer).Seconds())
s.metrics.TotalRetrieved.Inc()
stamp := new(postage.Stamp)
err = stamp.UnmarshalBinary(d.Stamp)
if err != nil {
return nil, peer, true, fmt.Errorf("stamp unmarshal: %w", err)
}
chunk = swarm.NewChunk(addr, d.Data).WithStamp(stamp)
if !cac.Valid(chunk) {
if !soc.Valid(chunk) {
s.metrics.InvalidChunkRetrieved.Inc()
s.metrics.TotalErrors.Inc()
return nil, peer, true, swarm.ErrInvalidChunk
}
}
// credit the peer after successful delivery
err = s.accounting.Credit(peer, chunkPrice)
if err != nil {
return nil, peer, true, err
}
s.metrics.ChunkPrice.Observe(float64(chunkPrice))
return chunk, peer, true, err
}
// closestPeer returns address of the peer that is closest to the chunk with
// provided address addr. This function will ignore peers with addresses
// provided in skipPeers and if allowUpstream is true, peers that are further of
// the chunk than this node is, could also be returned, allowing the upstream
// retrieve request.
func (s *Service) closestPeer(addr swarm.Address, skipPeers []swarm.Address, allowUpstream bool) (swarm.Address, error) {
closest := swarm.Address{}
err := s.peerSuggester.EachPeerRev(func(peer swarm.Address, po uint8) (bool, bool, error) {
for _, a := range skipPeers {
if a.Equal(peer) {
return false, false, nil
}
}
if closest.IsZero() {
closest = peer
return false, false, nil
}
dcmp, err := swarm.DistanceCmp(addr.Bytes(), closest.Bytes(), peer.Bytes())
if err != nil {
return false, false, fmt.Errorf("distance compare error. addr %s closest %s peer %s: %w", addr.String(), closest.String(), peer.String(), err)
}
switch dcmp {
case 0:
// do nothing
case -1:
// current peer is closer
closest = peer
case 1:
// closest is already closer to chunk
// do nothing
}
return false, false, nil
})
if err != nil {
return swarm.Address{}, err
}
// check if found
if closest.IsZero() {
return swarm.Address{}, topology.ErrNotFound
}
if allowUpstream {
return closest, nil
}
dcmp, err := swarm.DistanceCmp(addr.Bytes(), closest.Bytes(), s.addr.Bytes())
if err != nil {
return swarm.Address{}, fmt.Errorf("distance compare addr %s closest %s base address %s: %w", addr.String(), closest.String(), s.addr.String(), err)
}
if dcmp != 1 {
return swarm.Address{}, topology.ErrNotFound
}
return closest, nil
}
func (s *Service) handler(ctx context.Context, p p2p.Peer, stream p2p.Stream) (err error) {
w, r := protobuf.NewWriterAndReader(stream)
defer func() {
if err != nil {
_ = stream.Reset()
} else {
_ = stream.FullClose()
}
}()
var req pb.Request
if err := r.ReadMsgWithContext(ctx, &req); err != nil {
return fmt.Errorf("read request: %w peer %s", err, p.Address.String())
}
span, _, ctx := s.tracer.StartSpanFromContext(ctx, "handle-retrieve-chunk", s.logger, opentracing.Tag{Key: "address", Value: swarm.NewAddress(req.Addr).String()})
defer span.Finish()
ctx = context.WithValue(ctx, requestSourceContextKey{}, p.Address.String())
addr := swarm.NewAddress(req.Addr)
chunk, err := s.storer.Get(ctx, storage.ModeGetRequest, addr)
if err != nil {
if errors.Is(err, storage.ErrNotFound) {
// forward the request
chunk, err = s.RetrieveChunk(ctx, addr, false)
if err != nil {
return fmt.Errorf("retrieve chunk: %w", err)
}
} else {
return fmt.Errorf("get from store: %w", err)
}
}
stamp, err := chunk.Stamp().MarshalBinary()
if err != nil {
return fmt.Errorf("stamp marshal: %w", err)
}
chunkPrice := s.pricer.Price(chunk.Address())
debit := s.accounting.PrepareDebit(p.Address, chunkPrice)
defer debit.Cleanup()
if err := w.WriteMsgWithContext(ctx, &pb.Delivery{
Data: chunk.Data(),
Stamp: stamp,
}); err != nil {
return fmt.Errorf("write delivery: %w peer %s", err, p.Address.String())
}
s.logger.Tracef("retrieval protocol debiting peer %s", p.Address.String())
// debit price from p's balance
return debit.Apply()
}