requesting.go

   1 package torrent
   2
   3 import (
   4         "container/heap"
   5         "context"
   6         "encoding/gob"
   7         "fmt"
   8         "reflect"
   9         "runtime/pprof"
  10         "time"
  11         "unsafe"
  12
  13         "github.com/anacrolix/log"
  14         "github.com/anacrolix/multiless"
  15
  16         request_strategy "github.com/anacrolix/torrent/request-strategy"
  17 )
  18
  19 func (t *Torrent) requestStrategyPieceOrderState(i int) request_strategy.PieceRequestOrderState {
  20         return request_strategy.PieceRequestOrderState{
  21                 Priority:     t.piece(i).purePriority(),
  22                 Partial:      t.piecePartiallyDownloaded(i),
  23                 Availability: t.piece(i).availability(),
  24         }
  25 }
  26
  27 func init() {
  28         gob.Register(peerId{})
  29 }
  30
  31 type peerId struct {
  32         *Peer
  33         ptr uintptr
  34 }
  35
  36 func (p peerId) Uintptr() uintptr {
  37         return p.ptr
  38 }
  39
  40 func (p peerId) GobEncode() (b []byte, _ error) {
  41         *(*reflect.SliceHeader)(unsafe.Pointer(&b)) = reflect.SliceHeader{
  42                 Data: uintptr(unsafe.Pointer(&p.ptr)),
  43                 Len:  int(unsafe.Sizeof(p.ptr)),
  44                 Cap:  int(unsafe.Sizeof(p.ptr)),
  45         }
  46         return
  47 }
  48
  49 func (p *peerId) GobDecode(b []byte) error {
  50         if uintptr(len(b)) != unsafe.Sizeof(p.ptr) {
  51                 panic(len(b))
  52         }
  53         ptr := unsafe.Pointer(&b[0])
  54         p.ptr = *(*uintptr)(ptr)
  55         log.Printf("%p", ptr)
  56         dst := reflect.SliceHeader{
  57                 Data: uintptr(unsafe.Pointer(&p.Peer)),
  58                 Len:  int(unsafe.Sizeof(p.Peer)),
  59                 Cap:  int(unsafe.Sizeof(p.Peer)),
  60         }
  61         copy(*(*[]byte)(unsafe.Pointer(&dst)), b)
  62         return nil
  63 }
  64
  65 type (
  66         RequestIndex   = request_strategy.RequestIndex
  67         chunkIndexType = request_strategy.ChunkIndex
  68 )
  69
  70 type desiredPeerRequests struct {
  71         requestIndexes []RequestIndex
  72         peer           *Peer
  73 }
  74
  75 func (p *desiredPeerRequests) Len() int {
  76         return len(p.requestIndexes)
  77 }
  78
  79 func (p *desiredPeerRequests) Less(i, j int) bool {
  80         leftRequest := p.requestIndexes[i]
  81         rightRequest := p.requestIndexes[j]
  82         t := p.peer.t
  83         leftPieceIndex := t.pieceIndexOfRequestIndex(leftRequest)
  84         rightPieceIndex := t.pieceIndexOfRequestIndex(rightRequest)
  85         ml := multiless.New()
  86         // Push requests that can't be served right now to the end. But we don't throw them away unless
  87         // there's a better alternative. This is for when we're using the fast extension and get choked
  88         // but our requests could still be good when we get unchoked.
  89         if p.peer.peerChoking {
  90                 ml = ml.Bool(
  91                         !p.peer.peerAllowedFast.Contains(leftPieceIndex),
  92                         !p.peer.peerAllowedFast.Contains(rightPieceIndex),
  93                 )
  94         }
  95         leftPiece := t.piece(leftPieceIndex)
  96         rightPiece := t.piece(rightPieceIndex)
  97         // Putting this first means we can steal requests from lesser-performing peers for our first few
  98         // new requests.
  99         ml = ml.Int(
 100                 // Technically we would be happy with the cached priority here, except we don't actually
 101                 // cache it anymore, and Torrent.piecePriority just does another lookup of *Piece to resolve
 102                 // the priority through Piece.purePriority, which is probably slower.
 103                 -int(leftPiece.purePriority()),
 104                 -int(rightPiece.purePriority()),
 105         )
 106         leftPeer := t.pendingRequests[leftRequest]
 107         rightPeer := t.pendingRequests[rightRequest]
 108         ml = ml.Bool(rightPeer == p.peer, leftPeer == p.peer)
 109         ml = ml.Bool(rightPeer == nil, leftPeer == nil)
 110         if ml.Ok() {
 111                 return ml.MustLess()
 112         }
 113         if leftPeer != nil {
 114                 // The right peer should also be set, or we'd have resolved the computation by now.
 115                 ml = ml.Uint64(
 116                         rightPeer.requestState.Requests.GetCardinality(),
 117                         leftPeer.requestState.Requests.GetCardinality(),
 118                 )
 119                 // Could either of the lastRequested be Zero? That's what checking an existing peer is for.
 120                 leftLast := t.lastRequested[leftRequest]
 121                 rightLast := t.lastRequested[rightRequest]
 122                 if leftLast.IsZero() || rightLast.IsZero() {
 123                         panic("expected non-zero last requested times")
 124                 }
 125                 // We want the most-recently requested on the left. Clients like Transmission serve requests
 126                 // in received order, so the most recently-requested is the one that has the longest until
 127                 // it will be served and therefore is the best candidate to cancel.
 128                 ml = ml.CmpInt64(rightLast.Sub(leftLast).Nanoseconds())
 129         }
 130         ml = ml.Int(
 131                 int(leftPiece.relativeAvailability),
 132                 int(rightPiece.relativeAvailability))
 133         return ml.Less()
 134 }
 135
 136 func (p *desiredPeerRequests) Swap(i, j int) {
 137         p.requestIndexes[i], p.requestIndexes[j] = p.requestIndexes[j], p.requestIndexes[i]
 138 }
 139
 140 func (p *desiredPeerRequests) Push(x interface{}) {
 141         p.requestIndexes = append(p.requestIndexes, x.(RequestIndex))
 142 }
 143
 144 func (p *desiredPeerRequests) Pop() interface{} {
 145         last := len(p.requestIndexes) - 1
 146         x := p.requestIndexes[last]
 147         p.requestIndexes = p.requestIndexes[:last]
 148         return x
 149 }
 150
 151 type desiredRequestState struct {
 152         Requests   desiredPeerRequests
 153         Interested bool
 154 }
 155
 156 func (p *Peer) getDesiredRequestState() (desired desiredRequestState) {
 157         if !p.t.haveInfo() {
 158                 return
 159         }
 160         if p.t.closed.IsSet() {
 161                 return
 162         }
 163         input := p.t.getRequestStrategyInput()
 164         requestHeap := desiredPeerRequests{
 165                 peer: p,
 166         }
 167         request_strategy.GetRequestablePieces(
 168                 input,
 169                 p.t.getPieceRequestOrder(),
 170                 func(ih InfoHash, pieceIndex int) {
 171                         if ih != p.t.infoHash {
 172                                 return
 173                         }
 174                         if !p.peerHasPiece(pieceIndex) {
 175                                 return
 176                         }
 177                         allowedFast := p.peerAllowedFast.Contains(pieceIndex)
 178                         p.t.piece(pieceIndex).undirtiedChunksIter.Iter(func(ci request_strategy.ChunkIndex) {
 179                                 r := p.t.pieceRequestIndexOffset(pieceIndex) + ci
 180                                 if !allowedFast {
 181                                         // We must signal interest to request this. TODO: We could set interested if the
 182                                         // peers pieces (minus the allowed fast set) overlap with our missing pieces if
 183                                         // there are any readers, or any pending pieces.
 184                                         desired.Interested = true
 185                                         // We can make or will allow sustaining a request here if we're not choked, or
 186                                         // have made the request previously (presumably while unchoked), and haven't had
 187                                         // the peer respond yet (and the request was retained because we are using the
 188                                         // fast extension).
 189                                         if p.peerChoking && !p.requestState.Requests.Contains(r) {
 190                                                 // We can't request this right now.
 191                                                 return
 192                                         }
 193                                 }
 194                                 if p.requestState.Cancelled.Contains(r) {
 195                                         // Can't re-request while awaiting acknowledgement.
 196                                         return
 197                                 }
 198                                 requestHeap.requestIndexes = append(requestHeap.requestIndexes, r)
 199                         })
 200                 },
 201         )
 202         p.t.assertPendingRequests()
 203         desired.Requests = requestHeap
 204         return
 205 }
 206
 207 func (p *Peer) maybeUpdateActualRequestState() {
 208         if p.closed.IsSet() {
 209                 return
 210         }
 211         if p.needRequestUpdate == "" {
 212                 return
 213         }
 214         if p.needRequestUpdate == peerUpdateRequestsTimerReason {
 215                 since := time.Since(p.lastRequestUpdate)
 216                 if since < updateRequestsTimerDuration {
 217                         panic(since)
 218                 }
 219         }
 220         pprof.Do(
 221                 context.Background(),
 222                 pprof.Labels("update request", p.needRequestUpdate),
 223                 func(_ context.Context) {
 224                         next := p.getDesiredRequestState()
 225                         p.applyRequestState(next)
 226                 },
 227         )
 228 }
 229
 230 // Transmit/action the request state to the peer.
 231 func (p *Peer) applyRequestState(next desiredRequestState) {
 232         current := &p.requestState
 233         if !p.setInterested(next.Interested) {
 234                 panic("insufficient write buffer")
 235         }
 236         more := true
 237         requestHeap := &next.Requests
 238         t := p.t
 239         originalRequestCount := current.Requests.GetCardinality()
 240         // We're either here on a timer, or because we ran out of requests. Both are valid reasons to
 241         // alter peakRequests.
 242         if originalRequestCount != 0 && p.needRequestUpdate != peerUpdateRequestsTimerReason {
 243                 panic(fmt.Sprintf(
 244                         "expected zero existing requests (%v) for update reason %q",
 245                         originalRequestCount, p.needRequestUpdate))
 246         }
 247         heap.Init(requestHeap)
 248         for requestHeap.Len() != 0 && maxRequests(current.Requests.GetCardinality()+current.Cancelled.GetCardinality()) < p.nominalMaxRequests() {
 249                 req := heap.Pop(requestHeap).(RequestIndex)
 250                 existing := t.requestingPeer(req)
 251                 if existing != nil && existing != p {
 252                         // Don't steal from the poor.
 253                         diff := int64(current.Requests.GetCardinality()) + 1 - (int64(existing.uncancelledRequests()) - 1)
 254                         // Steal a request that leaves us with one more request than the existing peer
 255                         // connection if the stealer more recently received a chunk.
 256                         if diff > 1 || (diff == 1 && p.lastUsefulChunkReceived.Before(existing.lastUsefulChunkReceived)) {
 257                                 continue
 258                         }
 259                         t.cancelRequest(req)
 260                 }
 261                 more = p.mustRequest(req)
 262                 if !more {
 263                         break
 264                 }
 265         }
 266         if !more {
 267                 // This might fail if we incorrectly determine that we can fit up to the maximum allowed
 268                 // requests into the available write buffer space. We don't want that to happen because it
 269                 // makes our peak requests dependent on how much was already in the buffer.
 270                 panic(fmt.Sprintf(
 271                         "couldn't fill apply entire request state [newRequests=%v]",
 272                         current.Requests.GetCardinality()-originalRequestCount))
 273         }
 274         newPeakRequests := maxRequests(current.Requests.GetCardinality() - originalRequestCount)
 275         // log.Printf(
 276         //      "requests %v->%v (peak %v->%v) reason %q (peer %v)",
 277         //      originalRequestCount, current.Requests.GetCardinality(), p.peakRequests, newPeakRequests, p.needRequestUpdate, p)
 278         p.peakRequests = newPeakRequests
 279         p.needRequestUpdate = ""
 280         p.lastRequestUpdate = time.Now()
 281         p.updateRequestsTimer.Reset(updateRequestsTimerDuration)
 282 }
 283
 284 // This could be set to 10s to match the unchoke/request update interval recommended by some
 285 // specifications. I've set it shorter to trigger it more often for testing for now.
 286 const updateRequestsTimerDuration = 3 * time.Second