From 7e872566c46baff742ee5e20ca3652e6a99255bc Mon Sep 17 00:00:00 2001
From: Wilmer Paulino <wilmer.paulino@gmail.com>
Date: Tue, 14 Aug 2018 17:54:21 -0700
Subject: [PATCH] chainntnfs: query the hint cache before registering a conf
 ntfn

In this commit, we alter the different chain notifiers to query their
height hint cache before registering a confimation notification. We do
this as it's possible that the cache has a higher height hint, which
can potentially reduce the amount of blocked fetched when attempting
historical dispatches.
---
 chainntnfs/bitcoindnotify/bitcoind.go | 12 ++++++++++++
 chainntnfs/btcdnotify/btcd.go         | 12 ++++++++++++
 chainntnfs/neutrinonotify/neutrino.go | 12 ++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/chainntnfs/bitcoindnotify/bitcoind.go b/chainntnfs/bitcoindnotify/bitcoind.go
index 3fd41156..3fc60524 100644
--- a/chainntnfs/bitcoindnotify/bitcoind.go
+++ b/chainntnfs/bitcoindnotify/bitcoind.go
@@ -869,6 +869,18 @@ type confirmationNotification struct {
 func (b *BitcoindNotifier) RegisterConfirmationsNtfn(txid *chainhash.Hash,
 	_ []byte, numConfs, heightHint uint32) (*chainntnfs.ConfirmationEvent, error) {
 
+	// Before proceeding to register the notification, we'll query our
+	// height hint cache to determine whether a better one exists.
+	if hint, err := b.confirmHintCache.QueryConfirmHint(*txid); err == nil {
+		if hint > heightHint {
+			chainntnfs.Log.Debugf("Using height hint %d retrieved "+
+				"from cache for %v", hint, txid)
+			heightHint = hint
+		}
+	}
+
+	// Construct a notification request for the transaction and send it to
+	// the main event loop.
 	ntfn := &confirmationNotification{
 		ConfNtfn: chainntnfs.ConfNtfn{
 			ConfID:           atomic.AddUint64(&b.confClientCounter, 1),
diff --git a/chainntnfs/btcdnotify/btcd.go b/chainntnfs/btcdnotify/btcd.go
index 13ad76d7..d8b4c909 100644
--- a/chainntnfs/btcdnotify/btcd.go
+++ b/chainntnfs/btcdnotify/btcd.go
@@ -916,6 +916,18 @@ type confirmationNotification struct {
 func (b *BtcdNotifier) RegisterConfirmationsNtfn(txid *chainhash.Hash, _ []byte,
 	numConfs, heightHint uint32) (*chainntnfs.ConfirmationEvent, error) {
 
+	// Before proceeding to register the notification, we'll query our
+	// height hint cache to determine whether a better one exists.
+	if hint, err := b.confirmHintCache.QueryConfirmHint(*txid); err == nil {
+		if hint > heightHint {
+			chainntnfs.Log.Debugf("Using height hint %d retrieved "+
+				"from cache for %v", hint, txid)
+			heightHint = hint
+		}
+	}
+
+	// Construct a notification request for the transaction and send it to
+	// the main event loop.
 	ntfn := &confirmationNotification{
 		ConfNtfn: chainntnfs.ConfNtfn{
 			ConfID:           atomic.AddUint64(&b.confClientCounter, 1),
diff --git a/chainntnfs/neutrinonotify/neutrino.go b/chainntnfs/neutrinonotify/neutrino.go
index 7ce0934e..d3aa0d6d 100644
--- a/chainntnfs/neutrinonotify/neutrino.go
+++ b/chainntnfs/neutrinonotify/neutrino.go
@@ -869,6 +869,18 @@ func (n *NeutrinoNotifier) RegisterConfirmationsNtfn(txid *chainhash.Hash,
 	pkScript []byte,
 	numConfs, heightHint uint32) (*chainntnfs.ConfirmationEvent, error) {
 
+	// Before proceeding to register the notification, we'll query our
+	// height hint cache to determine whether a better one exists.
+	if hint, err := n.confirmHintCache.QueryConfirmHint(*txid); err == nil {
+		if hint > heightHint {
+			chainntnfs.Log.Debugf("Using height hint %d retrieved "+
+				"from cache for %v", hint, txid)
+			heightHint = hint
+		}
+	}
+
+	// Construct a notification request for the transaction and send it to
+	// the main event loop.
 	ntfn := &confirmationsNotification{
 		ConfNtfn: chainntnfs.ConfNtfn{
 			ConfID:           atomic.AddUint64(&n.confClientCounter, 1),