introduce a lightweight tracking mode for connectors and update confirmation manager to cope with it

internal/blocklistener/blocklistener.go

@@ -24,7 +24,7 @@ import (
 )
 
 type NewBlockHashConsumer interface {
-	NewBlockHashes() chan<- *ffcapi.BlockHashEvent
+	GetReceiveChannel() chan<- *ffcapi.BlockHashEvent
 }
 
 // BufferChannel ensures it always pulls blocks from the channel passed to the connector
@@ -49,7 +49,7 @@ func BufferChannel(ctx context.Context, target NewBlockHashConsumer) (buffered c
 					// Have to discard this
 					blockedUpdate.GapPotential = true // there is a gap for sure at this point
 					log.L(ctx).Debugf("Blocked event stream missed new block event: %v", blockUpdate.BlockHashes)
-				case target.NewBlockHashes() <- blockedUpdate:
+				case target.GetReceiveChannel() <- blockedUpdate:
 					// We're not blocked any more
 					log.L(ctx).Infof("Event stream block-listener unblocked")
 					blockedUpdate = nil
@@ -64,7 +64,7 @@ func BufferChannel(ctx context.Context, target NewBlockHashConsumer) (buffered c
 					// Nothing to do unless we have confirmations turned on
 					if target != nil {
 						select {
-						case target.NewBlockHashes() <- update:
+						case target.GetReceiveChannel() <- update:
 							// all good, we passed it on
 						default:
 							// we can't deliver it immediately, we switch to blocked mode

internal/blocklistener/blocklistener_test.go

@@ -28,7 +28,7 @@ type testBlockConsumer struct {
 	c chan *ffcapi.BlockHashEvent
 }
 
-func (tbc *testBlockConsumer) NewBlockHashes() chan<- *ffcapi.BlockHashEvent {
+func (tbc *testBlockConsumer) GetReceiveChannel() chan<- *ffcapi.BlockHashEvent {
 	return tbc.c
 }
 

internal/confirmations/confirmations.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"fmt"
 	"sort"
+	"strings"
 	"sync"
 	"time"
 
@@ -43,7 +44,7 @@ type Manager interface {
 	Notify(n *Notification) error
 	Start()
 	Stop()
-	NewBlockHashes() chan<- *ffcapi.BlockHashEvent
+	GetReceiveChannel() chan<- *ffcapi.BlockHashEvent
 	CheckInFlight(listenerID *fftypes.UUID) bool
 	StartConfirmedBlockListener(ctx context.Context, id *fftypes.UUID, fromBlock string, checkpoint *ffcapi.BlockListenerCheckpoint, eventStream chan<- *ffcapi.ListenerEvent) error
 	StopConfirmedBlockListener(ctx context.Context, id *fftypes.UUID) error
@@ -89,14 +90,16 @@ type blockConfirmationManager struct {
 	baseContext           context.Context
 	ctx                   context.Context
 	cancelFunc            func()
-	newBlockHashes        chan *ffcapi.BlockHashEvent
+	newBlockHashEvents    chan *ffcapi.BlockHashEvent
 	connector             ffcapi.API
 	blockListenerStale    bool
 	metricsEmitter        metrics.ConfirmationMetricsEmitter
-	requiredConfirmations int
+	requiredConfirmations uint64
+	chainTrackingMode     ffcapi.ChainTrackingMode
 	staleReceiptTimeout   time.Duration
 	bcmNotifications      chan *Notification
 	highestBlockSeen      uint64
+	headBlockNumber       uint64 // used for confirmation when the connector is running in light mode
 	pending               map[string]*pendingItem
 	pendingMux            sync.Mutex
 	receiptChecker        *receiptChecker
@@ -114,11 +117,12 @@ func NewBlockConfirmationManager(baseContext context.Context, connector ffcapi.A
 		connector:             connector,
 		cbls:                  make(map[fftypes.UUID]*confirmedBlockListener),
 		blockListenerStale:    true,
-		requiredConfirmations: config.GetInt(tmconfig.ConfirmationsRequired),
+		requiredConfirmations: config.GetUint64(tmconfig.ConfirmationsRequired),
+		chainTrackingMode:     connector.GetChainTrackingMode(baseContext),
 		staleReceiptTimeout:   config.GetDuration(tmconfig.ConfirmationsStaleReceiptTimeout),
 		bcmNotifications:      make(chan *Notification, config.GetInt(tmconfig.ConfirmationsNotificationQueueLength)),
 		pending:               make(map[string]*pendingItem),
-		newBlockHashes:        make(chan *ffcapi.BlockHashEvent, config.GetInt(tmconfig.ConfirmationsBlockQueueLength)),
+		newBlockHashEvents:    make(chan *ffcapi.BlockHashEvent, config.GetInt(tmconfig.ConfirmationsBlockQueueLength)),
 		metricsEmitter:        cme,
 		retry: &retry.Retry{
 			InitialDelay: config.GetDuration(tmconfig.ConfirmationsRetryInitDelay),
@@ -143,22 +147,23 @@ const (
 // pendingItem could be a specific event that has been detected, but not confirmed yet.
 // Or it could be a transaction
 type pendingItem struct {
-	pType                 pendingType
-	added                 time.Time
-	notifiedConfirmations []*apitypes.Confirmation
-	confirmations         []*apitypes.Confirmation
-	scheduledAtLeastOnce  bool
-	confirmed             bool
-	queuedStale           *list.Element // protected by receiptChecker mux
-	lastReceiptCheck      time.Time     // protected by receiptChecker mux
-	receiptCallback       func(ctx context.Context, receipt *ffcapi.TransactionReceiptResponse)
-	confirmationsCallback func(ctx context.Context, notification *apitypes.ConfirmationsNotification)
-	transactionHash       string
-	blockHash             string        // can be notified of changes to this for receipts
-	blockNumber           uint64        // known at creation time for event logs
-	transactionIndex      uint64        // known at creation time for event logs
-	logIndex              uint64        // events only
-	listenerID            *fftypes.UUID // events only
+	pType                     pendingType
+	added                     time.Time
+	notifiedConfirmations     []*apitypes.Confirmation
+	confirmations             []*apitypes.Confirmation
+	scheduledAtLeastOnce      bool
+	confirmed                 bool
+	previousConfirmationCount *uint64       // headBlockNumber mode: last dispatched CurrentConfirmationCount
+	queuedStale               *list.Element // protected by receiptChecker mux
+	lastReceiptCheck          time.Time     // protected by receiptChecker mux
+	receiptCallback           func(ctx context.Context, receipt *ffcapi.TransactionReceiptResponse)
+	confirmationsCallback     func(ctx context.Context, notification *apitypes.ConfirmationsNotification)
+	transactionHash           string
+	blockHash                 string        // can be notified of changes to this for receipts
+	blockNumber               uint64        // known at creation time for event logs
+	transactionIndex          uint64        // known at creation time for event logs
+	logIndex                  uint64        // events only
+	listenerID                *fftypes.UUID // events only
 }
 
 func pendingKeyForTX(txHash string) string {
@@ -243,8 +248,8 @@ func (bcm *blockConfirmationManager) Stop() {
 	}
 }
 
-func (bcm *blockConfirmationManager) NewBlockHashes() chan<- *ffcapi.BlockHashEvent {
-	return bcm.newBlockHashes
+func (bcm *blockConfirmationManager) GetReceiveChannel() chan<- *ffcapi.BlockHashEvent {
+	return bcm.newBlockHashEvents
 }
 
 // Notify is used to notify the confirmation manager of detection of a new logEntry addition or removal
@@ -365,12 +370,12 @@ func (bcm *blockConfirmationManager) confirmationsListener() {
 	receivedFirstBlock := false
 	for {
 		select {
-		case bhe := <-bcm.newBlockHashes:
+		case bhe := <-bcm.newBlockHashEvents:
 			if bhe.GapPotential {
 				bcm.blockListenerStale = true
 			}
 			blockHashes = append(blockHashes, bhe.BlockHashes...)
-
+			bcm.headBlockNumber = bhe.HeadBlockNumber // always update the head block number, NOTE: the number can decrease during a re-org
 			// Need to also pass this event to any confirmed block listeners
 			// (they promise to always be efficient in handling these, having a go-routine
 			// dedicated to spinning fast just processing those separate to dispatching them)
@@ -406,9 +411,12 @@ func (bcm *blockConfirmationManager) confirmationsListener() {
 		blocks := bcm.newBlockState()
 
 		if bcm.blockListenerStale {
-			if err := bcm.walkChain(blocks); err != nil {
-				log.L(bcm.ctx).Errorf("Failed to walk chain after restoring blockListener: %s", err)
-				continue
+			if bcm.chainTrackingMode == ffcapi.ChainTrackingModeFull {
+				// only need to build the in memory partial chain when the block details are available
+				if err := bcm.walkChain(blocks); err != nil {
+					log.L(bcm.ctx).Errorf("Failed to walk chain after restoring blockListener: %s", err)
+					continue
+				}
 			}
 			bcm.blockListenerStale = false
 		}
@@ -548,6 +556,11 @@ func (bcm *blockConfirmationManager) removeItem(pending *pendingItem, stale bool
 }
 
 func (bcm *blockConfirmationManager) processBlockHashes(blockHashes []string) {
+	if bcm.chainTrackingMode == ffcapi.ChainTrackingModeLight {
+		// for light chain tracking mode, no block details are available, only need to calculate the number of confirmations using head block number
+		bcm.checkAndDispatchConfirmationsUsingBlockHeight()
+		return
+	}
 	batchSize := len(blockHashes)
 	if batchSize > 0 {
 		log.L(bcm.ctx).Debugf("New block notifications %v", blockHashes)
@@ -599,7 +612,6 @@ func (bcm *blockConfirmationManager) processBlock(block *apitypes.BlockInfo) {
 	var notifications pendingItems
 	for pendingKey, pending := range bcm.pending {
 		if pending.blockHash != "" {
-
 			// The block might appear at any point in the confirmation list
 			newConfirmations := false
 			expectedParentHash := pending.blockHash
@@ -622,7 +634,7 @@ func (bcm *blockConfirmationManager) processBlock(block *apitypes.BlockInfo) {
 				}
 				expectedBlockNumber++
 			}
-			if len(pending.confirmations) >= bcm.requiredConfirmations {
+			if uint64(len(pending.confirmations)) >= bcm.requiredConfirmations {
 				pending.confirmed = true
 			}
 			if bcm.requiredConfirmations > 0 && (pending.confirmed || newConfirmations) {
@@ -666,14 +678,21 @@ func (bcm *blockConfirmationManager) dispatchConfirmations(item *pendingItem) {
 		}
 	}
 
+	confirmationCount := uint64(len(item.confirmations))
+	if confirmationCount > bcm.requiredConfirmations {
+		confirmationCount = bcm.requiredConfirmations
+	}
+
 	// Possible for us to re-dispatch the same confirmations, if we are notified about a block later after
 	// after we previously did a crawl for blocks.
 	// So we protect here against dispatching an empty array
 	if len(notificationConfirmations) > 0 || item.confirmed {
 		notification := &apitypes.ConfirmationsNotification{
-			Confirmed:     item.confirmed,
-			NewFork:       newFork,
-			Confirmations: notificationConfirmations,
+			Confirmed:                item.confirmed,
+			CurrentConfirmationCount: confirmationCount,
+			TargetConfirmationCount:  bcm.requiredConfirmations,
+			NewFork:                  newFork,
+			Confirmations:            notificationConfirmations,
 		}
 		// Take a copy of the notification confirmations so we know what we have previously notified next time round
 		// (not safe to keep a reference, in case it's modified by the callback).
@@ -768,6 +787,10 @@ func (bcm *blockConfirmationManager) walkChainForItem(pending *pendingItem, bloc
 		return nil
 	}
 
+	if bcm.chainTrackingMode == ffcapi.ChainTrackingModeLight {
+		return bcm.confirmationCheckUsingHeadBlockNumber(pending)
+	}
+
 	pendingKey := pending.getKey()
 
 	blockNumber := pending.blockNumber + 1
@@ -796,7 +819,7 @@ func (bcm *blockConfirmationManager) walkChainForItem(pending *pendingItem, bloc
 				break
 			}
 			pending.confirmations = append(pending.confirmations, apitypes.ConfirmationFromBlock(block))
-			if len(pending.confirmations) >= bcm.requiredConfirmations {
+			if uint64(len(pending.confirmations)) >= bcm.requiredConfirmations {
 				pending.confirmed = true
 				break
 			}
@@ -811,3 +834,91 @@ func (bcm *blockConfirmationManager) walkChainForItem(pending *pendingItem, bloc
 	return nil
 
 }
+
+func (bcm *blockConfirmationManager) checkAndDispatchConfirmationsUsingBlockHeight() {
+	bcm.pendingMux.Lock()
+	items := make([]*pendingItem, 0, len(bcm.pending))
+	for _, p := range bcm.pending {
+		items = append(items, p)
+	}
+	bcm.pendingMux.Unlock()
+	for _, p := range items {
+		if err := bcm.confirmationCheckUsingHeadBlockNumber(p); err != nil {
+			log.L(bcm.ctx).Errorf("Block height confirmation refresh failed for %s: %s", p.getKey(), err)
+		}
+	}
+}
+
+func (bcm *blockConfirmationManager) confirmationCheckUsingHeadBlockNumber(pending *pendingItem) error {
+	if pending.blockHash == "" {
+		// no receipt yet, so no confirmation check
+		return nil
+	}
+
+	currentConfirmationCount := uint64(0)
+	if bcm.headBlockNumber > pending.blockNumber {
+		currentConfirmationCount = bcm.headBlockNumber - pending.blockNumber
+	}
+
+	return bcm.dispatchBlockHeightConfirmations(pending, currentConfirmationCount)
+
+}
+
+func (bcm *blockConfirmationManager) dispatchBlockHeightConfirmations(pending *pendingItem, count uint64) error {
+	if pending.previousConfirmationCount != nil && count == *pending.previousConfirmationCount {
+		// no ops as there isn't any changes detected
+		return nil
+	}
+
+	confirmationCount := count
+	if confirmationCount > bcm.requiredConfirmations {
+		confirmationCount = bcm.requiredConfirmations
+	}
+
+	confirmed := confirmationCount == bcm.requiredConfirmations
+	if confirmed {
+		// do confirmation check here to ensure the transaction receipt is still valid
+		res, reason, err := bcm.connector.TransactionReceipt(bcm.ctx, &ffcapi.TransactionReceiptRequest{
+			TransactionHash: pending.transactionHash,
+		})
+		if err != nil {
+			if reason == ffcapi.ErrorReasonNotFound {
+				// need to schedule the receipt check again as the receipt is no longer valid
+				pending.blockHash = ""
+				pending.blockNumber = 0
+				pending.previousConfirmationCount = nil
+				bcm.receiptChecker.schedule(pending, true)
+			}
+			return err
+		}
+		if res == nil || res.BlockHash == "" {
+			return i18n.NewError(bcm.ctx, tmmsgs.MsgTransactionReceiptMissingBlockHash)
+		}
+		if !strings.EqualFold(strings.ToLower(res.BlockHash), strings.ToLower(pending.blockHash)) {
+			// set the new block hash and number and requeue for confirmation check
+			pending.blockHash = res.BlockHash
+			pending.blockNumber = res.BlockNumber.Uint64()
+			pending.previousConfirmationCount = nil
+			return i18n.NewError(bcm.ctx, tmmsgs.MsgTransactionReceiptBlockHashMismatch, pending.blockHash, res.BlockHash)
+		}
+	}
+	// when not confirmed, we assume the receipt is still valid and return the actual confirmation count
+
+	notification := &apitypes.ConfirmationsNotification{
+		Confirmed:                confirmed,
+		NewFork:                  pending.previousConfirmationCount != nil && count < *pending.previousConfirmationCount, // the only fork situation we can detect is a reduction in confirmation count
+		CurrentConfirmationCount: confirmationCount,                                                                      // NOTE: we returns the actual confirmation count, which can be higher than the required confirmation count
+		TargetConfirmationCount:  bcm.requiredConfirmations,
+	}
+	pending.previousConfirmationCount = &count
+
+	log.L(bcm.ctx).Infof("Block height confirmation notification item=%s confirmed=%t count=%d/%d newFork=%t",
+		pending.getKey(), notification.Confirmed, notification.CurrentConfirmationCount, notification.TargetConfirmationCount, notification.NewFork)
+	pending.confirmationsCallback(bcm.ctx, notification)
+	bcm.metricsEmitter.RecordConfirmationMetrics(bcm.ctx, time.Since(pending.added).Seconds())
+
+	if confirmed {
+		bcm.removeItem(pending, false)
+	}
+	return nil
+}