Add fallback piece ordering for non-readahead priorities

diff --git a/requesting.go b/requesting.go
index f1831346e816cc2508d96e8e3b79ff055ac31cbd..b781316d0bf75b6b16d8f7b61b4172cd616b3890 100644 (file)
--- a/requesting.go
+++ b/requesting.go
@@ -156,9 +156,7 @@ func (p *desiredPeerRequests) lessByValue(leftRequest, rightRequest RequestIndex
                // torrent. This would probably require reconsideration of how readahead priority works.
                ml = ml.Int(leftPieceIndex, rightPieceIndex)
        } else {
-               // TODO: To prevent unnecessarily requesting from disparate pieces, and to ensure pieces are
-               // selected randomly when availability is even, there should be some fixed ordering of
-               // pieces.
+               ml = ml.Int(t.pieceRequestOrder[leftPieceIndex], t.pieceRequestOrder[rightPieceIndex])
        }
        return ml.Less()
 }

diff --git a/torrent.go b/torrent.go
index dbfbea18ef2a5d8998bd283605724e5eefd325e6..55ba2230fe6eea449d9d0c62c1df55f95b41145d 100644 (file)
--- a/torrent.go
+++ b/torrent.go
@@ -8,6 +8,7 @@ import (
        "errors"
        "fmt"
        "io"
+       "math/rand"
        "net/netip"
        "net/url"
        "sort"
@@ -62,6 +63,9 @@ type Torrent struct {
        closed   chansync.SetOnce
        infoHash metainfo.Hash
        pieces   []Piece
+
+       // The order pieces are requested if there's no stronger reason like availability or priority.
+       pieceRequestOrder []int
        // Values are the piece indices that changed.
        pieceStateChanges pubsub.PubSub[PieceStateChange]
        // The size of chunks to request from peers over the wire. This is
@@ -459,6 +463,7 @@ func (t *Torrent) pieceRequestOrderKey(i int) request_strategy.PieceRequestOrder
 
 // This seems to be all the follow-up tasks after info is set, that can't fail.
 func (t *Torrent) onSetInfo() {
+       t.pieceRequestOrder = rand.Perm(t.numPieces())
        t.initPieceRequestOrder()
        MakeSliceWithLength(&t.requestState, t.numChunks())
        MakeSliceWithLength(&t.requestPieceStates, t.numPieces())
@@ -849,7 +854,7 @@ func (t *Torrent) usualPieceSize() int {
 }
 
 func (t *Torrent) numPieces() pieceIndex {
-       return pieceIndex(t.info.NumPieces())
+       return t.info.NumPieces()
 }
 
 func (t *Torrent) numPiecesCompleted() (num pieceIndex) {