fix: bitswap performance issue (#692)

- Fix exhausted wants problem resulting in possible performance issue
- Minor improvements for GC.
- RWLock not justified for time reading
- replace unneeded RWMutex with Mutex
- build strings with strings.Builder

CHANGELOG.md

@@ -26,6 +26,7 @@ The following emojis are used to highlight certain changes:
 
 - `routing/http/client`: optional address and protocol filter parameters from [IPIP-484](https://github.com/ipfs/specs/pull/484) use human-readable `,` instead of `%2C`. [#688](https://github.com/ipfs/boxo/pull/688)
 - `bitswap/client` Cleanup live wants when wants are canceled. This prevents live wants from continuing to get rebroadcasted even after the wants are canceled. [#690](https://github.com/ipfs/boxo/pull/690)
+- Fix problem adding invalid CID to exhausted wants list resulting in possible performance issue. [#692](https://github.com/ipfs/boxo/pull/692)
 
 ### Security
 

bitswap/client/internal/messagequeue/messagequeue.go

@@ -93,7 +93,7 @@ type MessageQueue struct {
 
 	// Dont touch any of these variables outside of run loop
 	sender                bsnet.MessageSender
-	rebroadcastIntervalLk sync.RWMutex
+	rebroadcastIntervalLk sync.Mutex
 	rebroadcastInterval   time.Duration
 	rebroadcastTimer      *clock.Timer
 	// For performance reasons we just clear out the fields of the message
@@ -389,9 +389,9 @@ func (mq *MessageQueue) SetRebroadcastInterval(delay time.Duration) {
 
 // Startup starts the processing of messages and rebroadcasting.
 func (mq *MessageQueue) Startup() {
-	mq.rebroadcastIntervalLk.RLock()
+	mq.rebroadcastIntervalLk.Lock()
 	mq.rebroadcastTimer = mq.clock.Timer(mq.rebroadcastInterval)
-	mq.rebroadcastIntervalLk.RUnlock()
+	mq.rebroadcastIntervalLk.Unlock()
 	go mq.runQueue()
 }
 
@@ -422,7 +422,7 @@ func (mq *MessageQueue) runQueue() {
 	}
 
 	var workScheduled time.Time
-	for mq.ctx.Err() == nil {
+	for {
 		select {
 		case <-mq.rebroadcastTimer.C:
 			mq.rebroadcastWantlist()
@@ -471,9 +471,9 @@ func (mq *MessageQueue) runQueue() {
 
 // Periodically resend the list of wants to the peer
 func (mq *MessageQueue) rebroadcastWantlist() {
-	mq.rebroadcastIntervalLk.RLock()
+	mq.rebroadcastIntervalLk.Lock()
 	mq.rebroadcastTimer.Reset(mq.rebroadcastInterval)
-	mq.rebroadcastIntervalLk.RUnlock()
+	mq.rebroadcastIntervalLk.Unlock()
 
 	// If some wants were transferred from the rebroadcast list
 	if mq.transferRebroadcastWants() {

bitswap/client/internal/notifications/notifications.go

@@ -69,12 +69,13 @@ func (ps *impl) Shutdown() {
 // corresponding to |keys|.
 func (ps *impl) Subscribe(ctx context.Context, keys ...cid.Cid) <-chan blocks.Block {
 	blocksCh := make(chan blocks.Block, len(keys))
-	valuesCh := make(chan interface{}, len(keys)) // provide our own channel to control buffer, prevent blocking
 	if len(keys) == 0 {
 		close(blocksCh)
 		return blocksCh
 	}
 
+	valuesCh := make(chan interface{}, len(keys)) // provide our own channel to control buffer, prevent blocking
+
 	// prevent shutdown
 	ps.lk.RLock()
 	defer ps.lk.RUnlock()

bitswap/client/internal/peermanager/peermanager.go

@@ -42,7 +42,7 @@ type PeerManager struct {
 	createPeerQueue PeerQueueFactory
 	ctx             context.Context
 
-	psLk         sync.RWMutex
+	psLk         sync.Mutex
 	sessions     map[uint64]Session
 	peerSessions map[peer.ID]map[uint64]struct{}
 

bitswap/client/internal/peermanager/peerwantmanager.go

@@ -1,8 +1,8 @@
 package peermanager
 
 import (
-	"bytes"
 	"fmt"
+	"strings"
 
 	cid "github.com/ipfs/go-cid"
 	peer "github.com/libp2p/go-libp2p/core/peer"
@@ -158,8 +158,6 @@ func (pwm *peerWantManager) broadcastWantHaves(wantHaves []cid.Cid) {
 // sendWants only sends the peer the want-blocks and want-haves that have not
 // already been sent to it.
 func (pwm *peerWantManager) sendWants(p peer.ID, wantBlocks []cid.Cid, wantHaves []cid.Cid) {
-	fltWantBlks := make([]cid.Cid, 0, len(wantBlocks))
-	fltWantHvs := make([]cid.Cid, 0, len(wantHaves))
 
 	// Get the existing want-blocks and want-haves for the peer
 	pws, ok := pwm.peerWants[p]
@@ -169,6 +167,8 @@ func (pwm *peerWantManager) sendWants(p peer.ID, wantBlocks []cid.Cid, wantHaves
 		return
 	}
 
+	fltWantBlks := make([]cid.Cid, 0, len(wantBlocks))
+
 	// Iterate over the requested want-blocks
 	for _, c := range wantBlocks {
 		// If the want-block hasn't been sent to the peer
@@ -198,6 +198,8 @@ func (pwm *peerWantManager) sendWants(p peer.ID, wantBlocks []cid.Cid, wantHaves
 		pwm.reverseIndexAdd(c, p)
 	}
 
+	fltWantHvs := make([]cid.Cid, 0, len(wantHaves))
+
 	// Iterate over the requested want-haves
 	for _, c := range wantHaves {
 		// If we've already broadcasted this want, don't bother with a
@@ -450,7 +452,7 @@ func (pwm *peerWantManager) getWants() []cid.Cid {
 }
 
 func (pwm *peerWantManager) String() string {
-	var b bytes.Buffer
+	var b strings.Builder
 	for p, ws := range pwm.peerWants {
 		b.WriteString(fmt.Sprintf("Peer %s: %d want-have / %d want-block:\n", p, ws.wantHaves.Len(), ws.wantBlocks.Len()))
 		for _, c := range ws.wantHaves.Keys() {

bitswap/client/internal/session/peerresponsetracker.go

@@ -31,8 +31,6 @@ func (prt *peerResponseTracker) choose(peers []peer.ID) peer.ID {
 		return ""
 	}
 
-	rnd := rand.Float64()
-
 	// Find the total received blocks for all candidate peers
 	total := 0
 	for _, p := range peers {
@@ -41,6 +39,7 @@ func (prt *peerResponseTracker) choose(peers []peer.ID) peer.ID {
 
 	// Choose one of the peers with a chance proportional to the number
 	// of blocks received from that peer
+	rnd := rand.Float64()
 	counted := 0.0
 	for _, p := range peers {
 		counted += float64(prt.getPeerCount(p)) / float64(total)
@@ -52,8 +51,7 @@ func (prt *peerResponseTracker) choose(peers []peer.ID) peer.ID {
 	// We shouldn't get here unless there is some weirdness with floating point
 	// math that doesn't quite cover the whole range of peers in the for loop
 	// so just choose the last peer.
-	index := len(peers) - 1
-	return peers[index]
+	return peers[len(peers)-1]
 }
 
 // getPeerCount returns the number of times the peer was first to send us a

bitswap/client/internal/session/sessionwants.go

@@ -56,8 +56,12 @@ func (sw *sessionWants) GetNextWants() []cid.Cid {
 	// limit)
 	currentLiveCount := len(sw.liveWants)
 	toAdd := sw.broadcastLimit - currentLiveCount
+	liveSize := min(toAdd, sw.toFetch.Len())
+	if liveSize == 0 {
+		return nil
+	}
 
-	var live []cid.Cid
+	live := make([]cid.Cid, 0, liveSize)
 	for ; toAdd > 0 && sw.toFetch.Len() > 0; toAdd-- {
 		c := sw.toFetch.Pop()
 		live = append(live, c)
@@ -117,6 +121,7 @@ func (sw *sessionWants) BlocksReceived(ks []cid.Cid) ([]cid.Cid, time.Duration)
 				cleaned = append(cleaned, c)
 			}
 		}
+		clear(sw.liveWantsOrder[len(cleaned):]) // GC cleared items
 		sw.liveWantsOrder = cleaned
 	}
 
@@ -127,7 +132,7 @@ func (sw *sessionWants) BlocksReceived(ks []cid.Cid) ([]cid.Cid, time.Duration)
 // live want CIDs up to the broadcast limit.
 func (sw *sessionWants) PrepareBroadcast() []cid.Cid {
 	now := time.Now()
-	live := make([]cid.Cid, 0, len(sw.liveWants))
+	live := make([]cid.Cid, 0, min(len(sw.liveWants), sw.broadcastLimit))
 	for _, c := range sw.liveWantsOrder {
 		if _, ok := sw.liveWants[c]; ok {
 			// No response was received for the want, so reset the sent time

bitswap/client/internal/session/sessionwantsender.go

@@ -161,8 +161,7 @@ func (sws *sessionWantSender) Cancel(ks []cid.Cid) {
 // Update is called when the session receives a message with incoming blocks
 // or HAVE / DONT_HAVE
 func (sws *sessionWantSender) Update(from peer.ID, ks []cid.Cid, haves []cid.Cid, dontHaves []cid.Cid) {
-	hasUpdate := len(ks) > 0 || len(haves) > 0 || len(dontHaves) > 0
-	if !hasUpdate {
+	if len(ks) == 0 && len(haves) == 0 && len(dontHaves) == 0 {
 		return
 	}
 
@@ -349,8 +348,7 @@ func (sws *sessionWantSender) trackWant(c cid.Cid) {
 	}
 
 	// Create the want info
-	wi := newWantInfo(sws.peerRspTrkr)
-	sws.wants[c] = wi
+	sws.wants[c] = newWantInfo(sws.peerRspTrkr)
 
 	// For each available peer, register any information we know about
 	// whether the peer has the block
@@ -481,7 +479,7 @@ func (sws *sessionWantSender) checkForExhaustedWants(dontHaves []cid.Cid, newlyU
 	// (because it may be the last peer who hadn't sent a DONT_HAVE for a CID)
 	if len(newlyUnavailable) > 0 {
 		// Collect all pending wants
-		wants = make([]cid.Cid, len(sws.wants))
+		wants = make([]cid.Cid, 0, len(sws.wants))
 		for c := range sws.wants {
 			wants = append(wants, c)
 		}

bitswap/client/internal/sessionmanager/sessionmanager.go

@@ -57,7 +57,7 @@ type SessionManager struct {
 	notif                  notifications.PubSub
 
 	// Sessions
-	sessLk   sync.RWMutex
+	sessLk   sync.Mutex
 	sessions map[uint64]Session
 
 	// Session Index
@@ -159,13 +159,13 @@ func (sm *SessionManager) ReceiveFrom(ctx context.Context, p peer.ID, blks []cid
 
 	// Notify each session that is interested in the blocks / HAVEs / DONT_HAVEs
 	for _, id := range sm.sessionInterestManager.InterestedSessions(blks, haves, dontHaves) {
-		sm.sessLk.RLock()
+		sm.sessLk.Lock()
 		if sm.sessions == nil { // check if SessionManager was shutdown
-			sm.sessLk.RUnlock()
+			sm.sessLk.Unlock()
 			return
 		}
 		sess, ok := sm.sessions[id]
-		sm.sessLk.RUnlock()
+		sm.sessLk.Unlock()
 
 		if ok {
 			sess.ReceiveFrom(p, blks, haves, dontHaves)