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/anacrolix/log"
  13         "github.com/anacrolix/multiless"
  14         "github.com/lispad/go-generics-tools/binheap"
  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         return p.lessByValue(p.requestIndexes[i], p.requestIndexes[j])
  81 }
  82
  83 func (p *desiredPeerRequests) lessByValue(leftRequest, rightRequest RequestIndex) bool {
  84         t := p.peer.t
  85         leftPieceIndex := t.pieceIndexOfRequestIndex(leftRequest)
  86         rightPieceIndex := t.pieceIndexOfRequestIndex(rightRequest)
  87         ml := multiless.New()
  88         // Push requests that can't be served right now to the end. But we don't throw them away unless
  89         // there's a better alternative. This is for when we're using the fast extension and get choked
  90         // but our requests could still be good when we get unchoked.
  91         if p.peer.peerChoking {
  92                 ml = ml.Bool(
  93                         !p.peer.peerAllowedFast.Contains(leftPieceIndex),
  94                         !p.peer.peerAllowedFast.Contains(rightPieceIndex),
  95                 )
  96         }
  97         leftPiece := t.piece(leftPieceIndex)
  98         rightPiece := t.piece(rightPieceIndex)
  99         // Putting this first means we can steal requests from lesser-performing peers for our first few
 100         // new requests.
 101         priority := func() piecePriority {
 102                 // Technically we would be happy with the cached priority here, except we don't actually
 103                 // cache it anymore, and Torrent.piecePriority just does another lookup of *Piece to resolve
 104                 // the priority through Piece.purePriority, which is probably slower.
 105                 leftPriority := leftPiece.purePriority()
 106                 rightPriority := rightPiece.purePriority()
 107                 ml = ml.Int(
 108                         -int(leftPriority),
 109                         -int(rightPriority),
 110                 )
 111                 if !ml.Ok() {
 112                         if leftPriority != rightPriority {
 113                                 panic("expected equal")
 114                         }
 115                 }
 116                 return leftPriority
 117         }()
 118         if ml.Ok() {
 119                 return ml.MustLess()
 120         }
 121         leftRequestState := t.requestState[leftRequest]
 122         rightRequestState := t.requestState[rightRequest]
 123         leftPeer := leftRequestState.peer
 124         rightPeer := rightRequestState.peer
 125         // Prefer chunks already requested from this peer.
 126         ml = ml.Bool(rightPeer == p.peer, leftPeer == p.peer)
 127         // Prefer unrequested chunks.
 128         ml = ml.Bool(rightPeer == nil, leftPeer == nil)
 129         if ml.Ok() {
 130                 return ml.MustLess()
 131         }
 132         if leftPeer != nil {
 133                 // The right peer should also be set, or we'd have resolved the computation by now.
 134                 ml = ml.Uint64(
 135                         rightPeer.requestState.Requests.GetCardinality(),
 136                         leftPeer.requestState.Requests.GetCardinality(),
 137                 )
 138                 // Could either of the lastRequested be Zero? That's what checking an existing peer is for.
 139                 leftLast := leftRequestState.when
 140                 rightLast := rightRequestState.when
 141                 if leftLast.IsZero() || rightLast.IsZero() {
 142                         panic("expected non-zero last requested times")
 143                 }
 144                 // We want the most-recently requested on the left. Clients like Transmission serve requests
 145                 // in received order, so the most recently-requested is the one that has the longest until
 146                 // it will be served and therefore is the best candidate to cancel.
 147                 ml = ml.CmpInt64(rightLast.Sub(leftLast).Nanoseconds())
 148         }
 149         ml = ml.Int(
 150                 leftPiece.relativeAvailability,
 151                 rightPiece.relativeAvailability)
 152         if priority == PiecePriorityReadahead {
 153                 // TODO: For readahead in particular, it would be even better to consider distance from the
 154                 // reader position so that reads earlier in a torrent don't starve reads later in the
 155                 // torrent. This would probably require reconsideration of how readahead priority works.
 156                 ml = ml.Int(leftPieceIndex, rightPieceIndex)
 157         } else {
 158                 // TODO: To prevent unnecessarily requesting from disparate pieces, and to ensure pieces are
 159                 // selected randomly when availability is even, there should be some fixed ordering of
 160                 // pieces.
 161         }
 162         return ml.Less()
 163 }
 164
 165 func (p *desiredPeerRequests) Swap(i, j int) {
 166         p.requestIndexes[i], p.requestIndexes[j] = p.requestIndexes[j], p.requestIndexes[i]
 167 }
 168
 169 func (p *desiredPeerRequests) Push(x interface{}) {
 170         p.requestIndexes = append(p.requestIndexes, x.(RequestIndex))
 171 }
 172
 173 func (p *desiredPeerRequests) Pop() interface{} {
 174         last := len(p.requestIndexes) - 1
 175         x := p.requestIndexes[last]
 176         p.requestIndexes = p.requestIndexes[:last]
 177         return x
 178 }
 179
 180 type desiredRequestState struct {
 181         Requests   desiredPeerRequests
 182         Interested bool
 183 }
 184
 185 func (p *Peer) getDesiredRequestState() (desired desiredRequestState) {
 186         if !p.t.haveInfo() {
 187                 return
 188         }
 189         if p.t.closed.IsSet() {
 190                 return
 191         }
 192         input := p.t.getRequestStrategyInput()
 193         requestHeap := desiredPeerRequests{
 194                 peer: p,
 195         }
 196         request_strategy.GetRequestablePieces(
 197                 input,
 198                 p.t.getPieceRequestOrder(),
 199                 func(ih InfoHash, pieceIndex int) {
 200                         if ih != p.t.infoHash {
 201                                 return
 202                         }
 203                         if !p.peerHasPiece(pieceIndex) {
 204                                 return
 205                         }
 206                         allowedFast := p.peerAllowedFast.Contains(pieceIndex)
 207                         p.t.piece(pieceIndex).undirtiedChunksIter.Iter(func(ci request_strategy.ChunkIndex) {
 208                                 r := p.t.pieceRequestIndexOffset(pieceIndex) + ci
 209                                 if !allowedFast {
 210                                         // We must signal interest to request this. TODO: We could set interested if the
 211                                         // peers pieces (minus the allowed fast set) overlap with our missing pieces if
 212                                         // there are any readers, or any pending pieces.
 213                                         desired.Interested = true
 214                                         // We can make or will allow sustaining a request here if we're not choked, or
 215                                         // have made the request previously (presumably while unchoked), and haven't had
 216                                         // the peer respond yet (and the request was retained because we are using the
 217                                         // fast extension).
 218                                         if p.peerChoking && !p.requestState.Requests.Contains(r) {
 219                                                 // We can't request this right now.
 220                                                 return
 221                                         }
 222                                 }
 223                                 if p.requestState.Cancelled.Contains(r) {
 224                                         // Can't re-request while awaiting acknowledgement.
 225                                         return
 226                                 }
 227                                 requestHeap.requestIndexes = append(requestHeap.requestIndexes, r)
 228                         })
 229                 },
 230         )
 231         p.t.assertPendingRequests()
 232         desired.Requests = requestHeap
 233         return
 234 }
 235
 236 func (p *Peer) maybeUpdateActualRequestState() {
 237         if p.closed.IsSet() {
 238                 return
 239         }
 240         if p.needRequestUpdate == "" {
 241                 return
 242         }
 243         if p.needRequestUpdate == peerUpdateRequestsTimerReason {
 244                 since := time.Since(p.lastRequestUpdate)
 245                 if since < updateRequestsTimerDuration {
 246                         panic(since)
 247                 }
 248         }
 249         pprof.Do(
 250                 context.Background(),
 251                 pprof.Labels("update request", p.needRequestUpdate),
 252                 func(_ context.Context) {
 253                         next := p.getDesiredRequestState()
 254                         p.applyRequestState(next)
 255                 },
 256         )
 257 }
 258
 259 // Transmit/action the request state to the peer.
 260 func (p *Peer) applyRequestState(next desiredRequestState) {
 261         current := &p.requestState
 262         if !p.setInterested(next.Interested) {
 263                 panic("insufficient write buffer")
 264         }
 265         more := true
 266         requestHeap := binheap.FromSlice(next.Requests.requestIndexes, next.Requests.lessByValue)
 267         t := p.t
 268         originalRequestCount := current.Requests.GetCardinality()
 269         // We're either here on a timer, or because we ran out of requests. Both are valid reasons to
 270         // alter peakRequests.
 271         if originalRequestCount != 0 && p.needRequestUpdate != peerUpdateRequestsTimerReason {
 272                 panic(fmt.Sprintf(
 273                         "expected zero existing requests (%v) for update reason %q",
 274                         originalRequestCount, p.needRequestUpdate))
 275         }
 276         for requestHeap.Len() != 0 && maxRequests(current.Requests.GetCardinality()+current.Cancelled.GetCardinality()) < p.nominalMaxRequests() {
 277                 req := requestHeap.Pop()
 278                 existing := t.requestingPeer(req)
 279                 if existing != nil && existing != p {
 280                         // Don't steal from the poor.
 281                         diff := int64(current.Requests.GetCardinality()) + 1 - (int64(existing.uncancelledRequests()) - 1)
 282                         // Steal a request that leaves us with one more request than the existing peer
 283                         // connection if the stealer more recently received a chunk.
 284                         if diff > 1 || (diff == 1 && p.lastUsefulChunkReceived.Before(existing.lastUsefulChunkReceived)) {
 285                                 continue
 286                         }
 287                         t.cancelRequest(req)
 288                 }
 289                 more = p.mustRequest(req)
 290                 if !more {
 291                         break
 292                 }
 293         }
 294         if !more {
 295                 // This might fail if we incorrectly determine that we can fit up to the maximum allowed
 296                 // requests into the available write buffer space. We don't want that to happen because it
 297                 // makes our peak requests dependent on how much was already in the buffer.
 298                 panic(fmt.Sprintf(
 299                         "couldn't fill apply entire request state [newRequests=%v]",
 300                         current.Requests.GetCardinality()-originalRequestCount))
 301         }
 302         newPeakRequests := maxRequests(current.Requests.GetCardinality() - originalRequestCount)
 303         // log.Printf(
 304         //      "requests %v->%v (peak %v->%v) reason %q (peer %v)",
 305         //      originalRequestCount, current.Requests.GetCardinality(), p.peakRequests, newPeakRequests, p.needRequestUpdate, p)
 306         p.peakRequests = newPeakRequests
 307         p.needRequestUpdate = ""
 308         p.lastRequestUpdate = time.Now()
 309         p.updateRequestsTimer.Reset(updateRequestsTimerDuration)
 310 }
 311
 312 // This could be set to 10s to match the unchoke/request update interval recommended by some
 313 // specifications. I've set it shorter to trigger it more often for testing for now.
 314 const updateRequestsTimerDuration = 3 * time.Second