requesting.go

   1 package torrent
   2
   3 import (
   4         "context"
   5         "encoding/gob"
   6         "fmt"
   7         "reflect"
   8         "runtime/pprof"
   9         "time"
  10         "unsafe"
  11
  12         "github.com/RoaringBitmap/roaring"
  13         g "github.com/anacrolix/generics"
  14         "github.com/anacrolix/generics/heap"
  15         "github.com/anacrolix/log"
  16         "github.com/anacrolix/multiless"
  17
  18         requestStrategy "github.com/anacrolix/torrent/request-strategy"
  19         typedRoaring "github.com/anacrolix/torrent/typed-roaring"
  20 )
  21
  22 type (
  23         // Since we have to store all the requests in memory, we can't reasonably exceed what could be
  24         // indexed with the memory space available.
  25         maxRequests = int
  26 )
  27
  28 func (t *Torrent) requestStrategyPieceOrderState(i int) requestStrategy.PieceRequestOrderState {
  29         return requestStrategy.PieceRequestOrderState{
  30                 Priority:     t.piece(i).purePriority(),
  31                 Partial:      t.piecePartiallyDownloaded(i),
  32                 Availability: t.piece(i).availability(),
  33         }
  34 }
  35
  36 func init() {
  37         gob.Register(peerId{})
  38 }
  39
  40 type peerId struct {
  41         *Peer
  42         ptr uintptr
  43 }
  44
  45 func (p peerId) Uintptr() uintptr {
  46         return p.ptr
  47 }
  48
  49 func (p peerId) GobEncode() (b []byte, _ error) {
  50         *(*reflect.SliceHeader)(unsafe.Pointer(&b)) = reflect.SliceHeader{
  51                 Data: uintptr(unsafe.Pointer(&p.ptr)),
  52                 Len:  int(unsafe.Sizeof(p.ptr)),
  53                 Cap:  int(unsafe.Sizeof(p.ptr)),
  54         }
  55         return
  56 }
  57
  58 func (p *peerId) GobDecode(b []byte) error {
  59         if uintptr(len(b)) != unsafe.Sizeof(p.ptr) {
  60                 panic(len(b))
  61         }
  62         ptr := unsafe.Pointer(&b[0])
  63         p.ptr = *(*uintptr)(ptr)
  64         log.Printf("%p", ptr)
  65         dst := reflect.SliceHeader{
  66                 Data: uintptr(unsafe.Pointer(&p.Peer)),
  67                 Len:  int(unsafe.Sizeof(p.Peer)),
  68                 Cap:  int(unsafe.Sizeof(p.Peer)),
  69         }
  70         copy(*(*[]byte)(unsafe.Pointer(&dst)), b)
  71         return nil
  72 }
  73
  74 type (
  75         RequestIndex   = requestStrategy.RequestIndex
  76         chunkIndexType = requestStrategy.ChunkIndex
  77 )
  78
  79 type desiredPeerRequests struct {
  80         requestIndexes []RequestIndex
  81         peer           *Peer
  82         pieceStates    []g.Option[requestStrategy.PieceRequestOrderState]
  83 }
  84
  85 func (p *desiredPeerRequests) lessByValue(leftRequest, rightRequest RequestIndex) bool {
  86         t := p.peer.t
  87         leftPieceIndex := t.pieceIndexOfRequestIndex(leftRequest)
  88         rightPieceIndex := t.pieceIndexOfRequestIndex(rightRequest)
  89         ml := multiless.New()
  90         // Push requests that can't be served right now to the end. But we don't throw them away unless
  91         // there's a better alternative. This is for when we're using the fast extension and get choked
  92         // but our requests could still be good when we get unchoked.
  93         if p.peer.peerChoking {
  94                 ml = ml.Bool(
  95                         !p.peer.peerAllowedFast.Contains(leftPieceIndex),
  96                         !p.peer.peerAllowedFast.Contains(rightPieceIndex),
  97                 )
  98         }
  99         leftPiece := p.pieceStates[leftPieceIndex].UnwrapPtr()
 100         rightPiece := p.pieceStates[rightPieceIndex].UnwrapPtr()
 101         // Putting this first means we can steal requests from lesser-performing peers for our first few
 102         // new requests.
 103         priority := func() PiecePriority {
 104                 // Technically we would be happy with the cached priority here, except we don't actually
 105                 // cache it anymore, and Torrent.PiecePriority just does another lookup of *Piece to resolve
 106                 // the priority through Piece.purePriority, which is probably slower.
 107                 leftPriority := leftPiece.Priority
 108                 rightPriority := rightPiece.Priority
 109                 ml = ml.Int(
 110                         -int(leftPriority),
 111                         -int(rightPriority),
 112                 )
 113                 if !ml.Ok() {
 114                         if leftPriority != rightPriority {
 115                                 panic("expected equal")
 116                         }
 117                 }
 118                 return leftPriority
 119         }()
 120         if ml.Ok() {
 121                 return ml.MustLess()
 122         }
 123         leftRequestState := t.requestState[leftRequest]
 124         rightRequestState := t.requestState[rightRequest]
 125         leftPeer := leftRequestState.peer
 126         rightPeer := rightRequestState.peer
 127         // Prefer chunks already requested from this peer.
 128         ml = ml.Bool(rightPeer == p.peer, leftPeer == p.peer)
 129         // Prefer unrequested chunks.
 130         ml = ml.Bool(rightPeer == nil, leftPeer == nil)
 131         if ml.Ok() {
 132                 return ml.MustLess()
 133         }
 134         if leftPeer != nil {
 135                 // The right peer should also be set, or we'd have resolved the computation by now.
 136                 ml = ml.Uint64(
 137                         rightPeer.requestState.Requests.GetCardinality(),
 138                         leftPeer.requestState.Requests.GetCardinality(),
 139                 )
 140                 // Could either of the lastRequested be Zero? That's what checking an existing peer is for.
 141                 leftLast := leftRequestState.when
 142                 rightLast := rightRequestState.when
 143                 if leftLast.IsZero() || rightLast.IsZero() {
 144                         panic("expected non-zero last requested times")
 145                 }
 146                 // We want the most-recently requested on the left. Clients like Transmission serve requests
 147                 // in received order, so the most recently-requested is the one that has the longest until
 148                 // it will be served and therefore is the best candidate to cancel.
 149                 ml = ml.CmpInt64(rightLast.Sub(leftLast).Nanoseconds())
 150         }
 151         ml = ml.Int(
 152                 leftPiece.Availability,
 153                 rightPiece.Availability)
 154         if priority == PiecePriorityReadahead {
 155                 // TODO: For readahead in particular, it would be even better to consider distance from the
 156                 // reader position so that reads earlier in a torrent don't starve reads later in the
 157                 // torrent. This would probably require reconsideration of how readahead priority works.
 158                 ml = ml.Int(leftPieceIndex, rightPieceIndex)
 159         } else {
 160                 ml = ml.Int(t.pieceRequestOrder[leftPieceIndex], t.pieceRequestOrder[rightPieceIndex])
 161         }
 162         return ml.Less()
 163 }
 164
 165 type desiredRequestState struct {
 166         Requests   desiredPeerRequests
 167         Interested bool
 168 }
 169
 170 func (p *Peer) getDesiredRequestState() (desired desiredRequestState) {
 171         t := p.t
 172         if !t.haveInfo() {
 173                 return
 174         }
 175         if t.closed.IsSet() {
 176                 return
 177         }
 178         if t.dataDownloadDisallowed.Bool() {
 179                 return
 180         }
 181         input := t.getRequestStrategyInput()
 182         requestHeap := desiredPeerRequests{
 183                 peer:           p,
 184                 pieceStates:    t.requestPieceStates,
 185                 requestIndexes: t.requestIndexes,
 186         }
 187         clear(requestHeap.pieceStates)
 188         // Caller-provided allocation for roaring bitmap iteration.
 189         var it typedRoaring.Iterator[RequestIndex]
 190         requestStrategy.GetRequestablePieces(
 191                 input,
 192                 t.getPieceRequestOrder(),
 193                 func(ih InfoHash, pieceIndex int, pieceExtra requestStrategy.PieceRequestOrderState) bool {
 194                         if ih != *t.canonicalShortInfohash() {
 195                                 return false
 196                         }
 197                         if !p.peerHasPiece(pieceIndex) {
 198                                 return false
 199                         }
 200                         requestHeap.pieceStates[pieceIndex].Set(pieceExtra)
 201                         allowedFast := p.peerAllowedFast.Contains(pieceIndex)
 202                         t.iterUndirtiedRequestIndexesInPiece(&it, pieceIndex, func(r requestStrategy.RequestIndex) {
 203                                 if !allowedFast {
 204                                         // We must signal interest to request this. TODO: We could set interested if the
 205                                         // peers pieces (minus the allowed fast set) overlap with our missing pieces if
 206                                         // there are any readers, or any pending pieces.
 207                                         desired.Interested = true
 208                                         // We can make or will allow sustaining a request here if we're not choked, or
 209                                         // have made the request previously (presumably while unchoked), and haven't had
 210                                         // the peer respond yet (and the request was retained because we are using the
 211                                         // fast extension).
 212                                         if p.peerChoking && !p.requestState.Requests.Contains(r) {
 213                                                 // We can't request this right now.
 214                                                 return
 215                                         }
 216                                 }
 217                                 cancelled := &p.requestState.Cancelled
 218                                 if !cancelled.IsEmpty() && cancelled.Contains(r) {
 219                                         // Can't re-request while awaiting acknowledgement.
 220                                         return
 221                                 }
 222                                 requestHeap.requestIndexes = append(requestHeap.requestIndexes, r)
 223                         })
 224                         return true
 225                 },
 226         )
 227         t.assertPendingRequests()
 228         desired.Requests = requestHeap
 229         return
 230 }
 231
 232 func (p *Peer) maybeUpdateActualRequestState() {
 233         if p.closed.IsSet() {
 234                 return
 235         }
 236         if p.needRequestUpdate == "" {
 237                 return
 238         }
 239         if p.needRequestUpdate == peerUpdateRequestsTimerReason {
 240                 since := time.Since(p.lastRequestUpdate)
 241                 if since < updateRequestsTimerDuration {
 242                         panic(since)
 243                 }
 244         }
 245         pprof.Do(
 246                 context.Background(),
 247                 pprof.Labels("update request", p.needRequestUpdate),
 248                 func(_ context.Context) {
 249                         next := p.getDesiredRequestState()
 250                         p.applyRequestState(next)
 251                         p.t.cacheNextRequestIndexesForReuse(next.Requests.requestIndexes)
 252                 },
 253         )
 254 }
 255
 256 func (t *Torrent) cacheNextRequestIndexesForReuse(slice []RequestIndex) {
 257         // The incoming slice can be smaller when getDesiredRequestState short circuits on some
 258         // conditions.
 259         if cap(slice) > cap(t.requestIndexes) {
 260                 t.requestIndexes = slice[:0]
 261         }
 262 }
 263
 264 // Whether we should allow sending not interested ("losing interest") to the peer. I noticed
 265 // qBitTorrent seems to punish us for sending not interested when we're streaming and don't
 266 // currently need anything.
 267 func (p *Peer) allowSendNotInterested() bool {
 268         // Except for caching, we're not likely to lose pieces very soon.
 269         if p.t.haveAllPieces() {
 270                 return true
 271         }
 272         all, known := p.peerHasAllPieces()
 273         if all || !known {
 274                 return false
 275         }
 276         // Allow losing interest if we have all the pieces the peer has.
 277         return roaring.AndNot(p.peerPieces(), &p.t._completedPieces).IsEmpty()
 278 }
 279
 280 // Transmit/action the request state to the peer.
 281 func (p *Peer) applyRequestState(next desiredRequestState) {
 282         current := &p.requestState
 283         // Make interest sticky
 284         if !next.Interested && p.requestState.Interested {
 285                 if !p.allowSendNotInterested() {
 286                         next.Interested = true
 287                 }
 288         }
 289         if !p.setInterested(next.Interested) {
 290                 return
 291         }
 292         more := true
 293         orig := next.Requests.requestIndexes
 294         requestHeap := heap.InterfaceForSlice(
 295                 &next.Requests.requestIndexes,
 296                 next.Requests.lessByValue,
 297         )
 298         heap.Init(requestHeap)
 299
 300         t := p.t
 301         originalRequestCount := current.Requests.GetCardinality()
 302         for {
 303                 if requestHeap.Len() == 0 {
 304                         break
 305                 }
 306                 numPending := maxRequests(current.Requests.GetCardinality() + current.Cancelled.GetCardinality())
 307                 if numPending >= p.nominalMaxRequests() {
 308                         break
 309                 }
 310                 req := heap.Pop(requestHeap)
 311                 if cap(next.Requests.requestIndexes) != cap(orig) {
 312                         panic("changed")
 313                 }
 314                 existing := t.requestingPeer(req)
 315                 if existing != nil && existing != p {
 316                         // Don't steal from the poor.
 317                         diff := int64(current.Requests.GetCardinality()) + 1 - (int64(existing.uncancelledRequests()) - 1)
 318                         // Steal a request that leaves us with one more request than the existing peer
 319                         // connection if the stealer more recently received a chunk.
 320                         if diff > 1 || (diff == 1 && p.lastUsefulChunkReceived.Before(existing.lastUsefulChunkReceived)) {
 321                                 continue
 322                         }
 323                         t.cancelRequest(req)
 324                 }
 325                 more = p.mustRequest(req)
 326                 if !more {
 327                         break
 328                 }
 329         }
 330         if !more {
 331                 // This might fail if we incorrectly determine that we can fit up to the maximum allowed
 332                 // requests into the available write buffer space. We don't want that to happen because it
 333                 // makes our peak requests dependent on how much was already in the buffer.
 334                 panic(fmt.Sprintf(
 335                         "couldn't fill apply entire request state [newRequests=%v]",
 336                         current.Requests.GetCardinality()-originalRequestCount))
 337         }
 338         newPeakRequests := maxRequests(current.Requests.GetCardinality() - originalRequestCount)
 339         // log.Printf(
 340         //      "requests %v->%v (peak %v->%v) reason %q (peer %v)",
 341         //      originalRequestCount, current.Requests.GetCardinality(), p.peakRequests, newPeakRequests, p.needRequestUpdate, p)
 342         p.peakRequests = newPeakRequests
 343         p.needRequestUpdate = ""
 344         p.lastRequestUpdate = time.Now()
 345         if enableUpdateRequestsTimer {
 346                 p.updateRequestsTimer.Reset(updateRequestsTimerDuration)
 347         }
 348 }
 349
 350 // This could be set to 10s to match the unchoke/request update interval recommended by some
 351 // specifications. I've set it shorter to trigger it more often for testing for now.
 352 const (
 353         updateRequestsTimerDuration = 3 * time.Second
 354         enableUpdateRequestsTimer   = false
 355 )