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