From 6e3fd9a9e5fa594dbd2c4312cce11a2ca1e55e4e Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Wed, 7 May 2025 10:20:05 +1000
Subject: [PATCH] Remove extra Torrent closed context goroutine for trackers

---
 client.go                     |  4 +++-
 internal/testutil/greeting.go |  3 ++-
 internal/testutil/spec.go     | 10 ++++++----
 torrent.go                    |  9 +++++++--
 torrent_test.go               | 15 ++++-----------
 tracker_scraper.go            | 13 +------------
 6 files changed, 23 insertions(+), 31 deletions(-)

diff --git a/client.go b/client.go
index 62f6aadf..121bab21 100644
--- a/client.go
+++ b/client.go
@@ -1346,7 +1346,8 @@ func (cl *Client) newTorrent(ih metainfo.Hash, specStorage storage.ClientImpl) (
 	})
 }
 
-// Return a Torrent ready for insertion into a Client.
+// Return a Torrent ready for insertion into a Client. This is also the method to call to create
+// Torrents for testing.
 func (cl *Client) newTorrentOpt(opts AddTorrentOpts) (t *Torrent) {
 	var v1InfoHash g.Option[infohash.T]
 	if !opts.InfoHash.IsZero() {
@@ -1383,6 +1384,7 @@ func (cl *Client) newTorrentOpt(opts AddTorrentOpts) (t *Torrent) {
 		webSeeds:     make(map[string]*Peer),
 		gotMetainfoC: make(chan struct{}),
 	}
+	t.closedCtx, t.closedCtxCancel = context.WithCancel(context.Background())
 	var salt [8]byte
 	rand.Read(salt[:])
 	t.smartBanCache.Hash = func(b []byte) uint64 {
diff --git a/internal/testutil/greeting.go b/internal/testutil/greeting.go
index 6544483c..dbdab554 100644
--- a/internal/testutil/greeting.go
+++ b/internal/testutil/greeting.go
@@ -33,7 +33,8 @@ func CreateDummyTorrentData(dirName string) string {
 }
 
 func GreetingMetaInfo() *metainfo.MetaInfo {
-	return Greeting.Metainfo(5)
+	mi, _ := Greeting.Generate(5)
+	return &mi
 }
 
 // Gives a temporary directory containing the completed "greeting" torrent,
diff --git a/internal/testutil/spec.go b/internal/testutil/spec.go
index ad0e4074..c8727aa1 100644
--- a/internal/testutil/spec.go
+++ b/internal/testutil/spec.go
@@ -15,6 +15,7 @@ type File struct {
 	Data string
 }
 
+// High-level description of a torrent for testing purposes.
 type Torrent struct {
 	Files []File
 	Name  string
@@ -58,10 +59,11 @@ func (t *Torrent) Info(pieceLength int64) metainfo.Info {
 	return info
 }
 
-func (t *Torrent) Metainfo(pieceLength int64) *metainfo.MetaInfo {
-	mi := metainfo.MetaInfo{}
+// Create an info and metainfo with bytes set for the torrent with the provided piece length.
+func (t *Torrent) Generate(pieceLength int64) (mi metainfo.MetaInfo, info metainfo.Info) {
 	var err error
-	mi.InfoBytes, err = bencode.Marshal(t.Info(pieceLength))
+	info = t.Info(pieceLength)
+	mi.InfoBytes, err = bencode.Marshal(info)
 	expect.Nil(err)
-	return &mi
+	return
 }
diff --git a/torrent.go b/torrent.go
index 93e5b868..b8ac0248 100644
--- a/torrent.go
+++ b/torrent.go
@@ -72,8 +72,12 @@ type Torrent struct {
 	dataUploadDisallowed   bool
 	userOnWriteChunkErr    func(error)
 
-	closed  chansync.SetOnce
-	onClose []func()
+	closed chansync.SetOnce
+	// A background Context cancelled when the Torrent is closed. Added to minimize extra goroutines
+	// in tracker handlers.
+	closedCtx       context.Context
+	closedCtxCancel func()
+	onClose         []func()
 
 	infoHash   g.Option[metainfo.Hash]
 	infoHashV2 g.Option[infohash_v2.T]
@@ -1031,6 +1035,7 @@ func (t *Torrent) close(wg *sync.WaitGroup) (err error) {
 		err = errors.New("already closed")
 		return
 	}
+	t.closedCtxCancel()
 	for _, f := range t.onClose {
 		f()
 	}
diff --git a/torrent_test.go b/torrent_test.go
index 663716df..2b3a087d 100644
--- a/torrent_test.go
+++ b/torrent_test.go
@@ -11,7 +11,6 @@ import (
 	"testing"
 
 	g "github.com/anacrolix/generics"
-	"github.com/anacrolix/log"
 	"github.com/anacrolix/missinggo/v2"
 	"github.com/anacrolix/missinggo/v2/bitmap"
 	qt "github.com/frankban/quicktest"
@@ -226,25 +225,19 @@ func TestTorrentMetainfoIncompleteMetadata(t *testing.T) {
 func TestRelativeAvailabilityHaveNone(t *testing.T) {
 	c := qt.New(t)
 	var err error
-	cl := Client{
-		config: TestingConfig(t),
-	}
-	tt := Torrent{
-		cl:           &cl,
-		logger:       log.Default,
-		gotMetainfoC: make(chan struct{}),
-	}
+	cl := newTestingClient(t)
+	mi, info := testutil.Greeting.Generate(5)
+	tt := cl.newTorrentOpt(AddTorrentOpts{InfoHash: mi.HashInfoBytes()})
 	tt.setChunkSize(2)
 	g.MakeMapIfNil(&tt.conns)
 	pc := PeerConn{}
-	pc.t = &tt
+	pc.t = tt
 	pc.legacyPeerImpl = &pc
 	pc.initRequestState()
 	g.InitNew(&pc.callbacks)
 	tt.conns[&pc] = struct{}{}
 	err = pc.peerSentHave(0)
 	c.Assert(err, qt.IsNil)
-	info := testutil.Greeting.Info(5)
 	err = tt.setInfo(&info)
 	c.Assert(err, qt.IsNil)
 	tt.onSetInfo()
diff --git a/tracker_scraper.go b/tracker_scraper.go
index 10fc87b2..b8d72e98 100644
--- a/tracker_scraper.go
+++ b/tracker_scraper.go
@@ -219,22 +219,11 @@ func (me *trackerScraper) Stop() {
 func (me *trackerScraper) Run() {
 	defer me.announceStopped()
 
-	ctx, cancel := context.WithCancel(context.Background())
-	defer cancel()
-	// TODO: Get rid of the need for this.
-	go func() {
-		defer cancel()
-		select {
-		case <-ctx.Done():
-		case <-me.t.Closed():
-		}
-	}()
-
 	// make sure first announce is a "started"
 	e := tracker.Started
 
 	for {
-		ar := me.announce(ctx, e)
+		ar := me.announce(me.t.closedCtx, e)
 		// after first announce, get back to regular "none"
 		e = tracker.None
 		me.t.cl.lock()
-- 
2.51.0