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 peerRequests struct {
  71         requestIndexes []RequestIndex
  72         peer           *Peer
  73 }
  74
  75 func (p *peerRequests) Len() int {
  76         return len(p.requestIndexes)
  77 }
  78
  79 func (p *peerRequests) Less(i, j int) bool {
  80         leftRequest := p.requestIndexes[i]
  81         rightRequest := p.requestIndexes[j]
  82         t := p.peer.t
  83         leftPieceIndex := leftRequest / t.chunksPerRegularPiece()
  84         rightPieceIndex := rightRequest / t.chunksPerRegularPiece()
  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         leftPeer := t.pendingRequests[leftRequest]
  96         rightPeer := t.pendingRequests[rightRequest]
  97         ml = ml.Bool(rightPeer == p.peer, leftPeer == p.peer)
  98         ml = ml.Bool(rightPeer == nil, leftPeer == nil)
  99         if ml.Ok() {
 100                 return ml.MustLess()
 101         }
 102         if leftPeer != nil {
 103                 // The right peer should also be set, or we'd have resolved the computation by now.
 104                 ml = ml.Uint64(
 105                         rightPeer.requestState.Requests.GetCardinality(),
 106                         leftPeer.requestState.Requests.GetCardinality(),
 107                 )
 108                 // Could either of the lastRequested be Zero? That's what checking an existing peer is for.
 109                 leftLast := t.lastRequested[leftRequest]
 110                 rightLast := t.lastRequested[rightRequest]
 111                 if leftLast.IsZero() || rightLast.IsZero() {
 112                         panic("expected non-zero last requested times")
 113                 }
 114                 // We want the most-recently requested on the left. Clients like Transmission serve requests
 115                 // in received order, so the most recently-requested is the one that has the longest until
 116                 // it will be served and therefore is the best candidate to cancel.
 117                 ml = ml.CmpInt64(rightLast.Sub(leftLast).Nanoseconds())
 118         }
 119         leftPiece := t.piece(int(leftPieceIndex))
 120         rightPiece := t.piece(int(rightPieceIndex))
 121         ml = ml.Int(
 122                 // Technically we would be happy with the cached priority here, except we don't actually
 123                 // cache it anymore, and Torrent.piecePriority just does another lookup of *Piece to resolve
 124                 // the priority through Piece.purePriority, which is probably slower.
 125                 -int(leftPiece.purePriority()),
 126                 -int(rightPiece.purePriority()),
 127         )
 128         ml = ml.Int(
 129                 int(leftPiece.relativeAvailability),
 130                 int(rightPiece.relativeAvailability))
 131         return ml.Less()
 132 }
 133
 134 func (p *peerRequests) Swap(i, j int) {
 135         p.requestIndexes[i], p.requestIndexes[j] = p.requestIndexes[j], p.requestIndexes[i]
 136 }
 137
 138 func (p *peerRequests) Push(x interface{}) {
 139         p.requestIndexes = append(p.requestIndexes, x.(RequestIndex))
 140 }
 141
 142 func (p *peerRequests) Pop() interface{} {
 143         last := len(p.requestIndexes) - 1
 144         x := p.requestIndexes[last]
 145         p.requestIndexes = p.requestIndexes[:last]
 146         return x
 147 }
 148
 149 type desiredRequestState struct {
 150         Requests   peerRequests
 151         Interested bool
 152 }
 153
 154 func (p *Peer) getDesiredRequestState() (desired desiredRequestState) {
 155         if !p.t.haveInfo() {
 156                 return
 157         }
 158         if p.t.closed.IsSet() {
 159                 return
 160         }
 161         input := p.t.getRequestStrategyInput()
 162         requestHeap := peerRequests{
 163                 peer: p,
 164         }
 165         request_strategy.GetRequestablePieces(
 166                 input,
 167                 p.t.getPieceRequestOrder(),
 168                 func(ih InfoHash, pieceIndex int) {
 169                         if ih != p.t.infoHash {
 170                                 return
 171                         }
 172                         if !p.peerHasPiece(pieceIndex) {
 173                                 return
 174                         }
 175                         allowedFast := p.peerAllowedFast.ContainsInt(pieceIndex)
 176                         p.t.piece(pieceIndex).undirtiedChunksIter.Iter(func(ci request_strategy.ChunkIndex) {
 177                                 r := p.t.pieceRequestIndexOffset(pieceIndex) + ci
 178                                 if !allowedFast {
 179                                         // We must signal interest to request this. TODO: We could set interested if the
 180                                         // peers pieces (minus the allowed fast set) overlap with our missing pieces if
 181                                         // there are any readers, or any pending pieces.
 182                                         desired.Interested = true
 183                                         // We can make or will allow sustaining a request here if we're not choked, or
 184                                         // have made the request previously (presumably while unchoked), and haven't had
 185                                         // the peer respond yet (and the request was retained because we are using the
 186                                         // fast extension).
 187                                         if p.peerChoking && !p.requestState.Requests.Contains(r) {
 188                                                 // We can't request this right now.
 189                                                 return
 190                                         }
 191                                 }
 192                                 if p.requestState.Cancelled.Contains(r) {
 193                                         // Can't re-request while awaiting acknowledgement.
 194                                         return
 195                                 }
 196                                 requestHeap.requestIndexes = append(requestHeap.requestIndexes, r)
 197                         })
 198                 },
 199         )
 200         p.t.assertPendingRequests()
 201         desired.Requests = requestHeap
 202         return
 203 }
 204
 205 func (p *Peer) maybeUpdateActualRequestState() {
 206         if p.closed.IsSet() {
 207                 return
 208         }
 209         if p.needRequestUpdate == "" {
 210                 return
 211         }
 212         if p.needRequestUpdate == peerUpdateRequestsTimerReason {
 213                 since := time.Since(p.lastRequestUpdate)
 214                 if since < updateRequestsTimerDuration {
 215                         panic(since)
 216                 }
 217         }
 218         pprof.Do(
 219                 context.Background(),
 220                 pprof.Labels("update request", p.needRequestUpdate),
 221                 func(_ context.Context) {
 222                         next := p.getDesiredRequestState()
 223                         p.applyRequestState(next)
 224                 },
 225         )
 226 }
 227
 228 // Transmit/action the request state to the peer.
 229 func (p *Peer) applyRequestState(next desiredRequestState) {
 230         current := &p.requestState
 231         if !p.setInterested(next.Interested) {
 232                 panic("insufficient write buffer")
 233         }
 234         more := true
 235         requestHeap := &next.Requests
 236         t := p.t
 237         originalRequestCount := current.Requests.GetCardinality()
 238         // We're either here on a timer, or because we ran out of requests. Both are valid reasons to
 239         // alter peakRequests.
 240         if originalRequestCount != 0 && p.needRequestUpdate != peerUpdateRequestsTimerReason {
 241                 panic(fmt.Sprintf(
 242                         "expected zero existing requests (%v) for update reason %q",
 243                         originalRequestCount, p.needRequestUpdate))
 244         }
 245         heap.Init(requestHeap)
 246         for requestHeap.Len() != 0 && maxRequests(current.Requests.GetCardinality()+current.Cancelled.GetCardinality()) < p.nominalMaxRequests() {
 247                 req := heap.Pop(requestHeap).(RequestIndex)
 248                 existing := t.requestingPeer(req)
 249                 if existing != nil && existing != p {
 250                         // Don't steal from the poor.
 251                         diff := int64(current.Requests.GetCardinality()) + 1 - (int64(existing.uncancelledRequests()) - 1)
 252                         // Steal a request that leaves us with one more request than the existing peer
 253                         // connection if the stealer more recently received a chunk.
 254                         if diff > 1 || (diff == 1 && p.lastUsefulChunkReceived.Before(existing.lastUsefulChunkReceived)) {
 255                                 continue
 256                         }
 257                         t.cancelRequest(req)
 258                 }
 259                 more = p.mustRequest(req)
 260                 if !more {
 261                         break
 262                 }
 263         }
 264         if !more {
 265                 // This might fail if we incorrectly determine that we can fit up to the maximum allowed
 266                 // requests into the available write buffer space. We don't want that to happen because it
 267                 // makes our peak requests dependent on how much was already in the buffer.
 268                 panic(fmt.Sprintf(
 269                         "couldn't fill apply entire request state [newRequests=%v]",
 270                         current.Requests.GetCardinality()-originalRequestCount))
 271         }
 272         newPeakRequests := maxRequests(current.Requests.GetCardinality() - originalRequestCount)
 273         // log.Printf(
 274         //      "requests %v->%v (peak %v->%v) reason %q (peer %v)",
 275         //      originalRequestCount, current.Requests.GetCardinality(), p.peakRequests, newPeakRequests, p.needRequestUpdate, p)
 276         p.peakRequests = newPeakRequests
 277         p.needRequestUpdate = ""
 278         p.lastRequestUpdate = time.Now()
 279         p.updateRequestsTimer.Reset(updateRequestsTimerDuration)
 280 }
 281
 282 // This could be set to 10s to match the unchoke/request update interval recommended by some
 283 // specifications. I've set it shorter to trigger it more often for testing for now.
 284 const updateRequestsTimerDuration = 3 * time.Second