From 1c456a51443292728155890c4e9f4eae83c17d3f Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Wed, 1 Aug 2018 12:42:38 -0700
Subject: [PATCH] htlcswitch/link: replace batch ticker with...

resumable ticker.Ticker interface
---
 htlcswitch/link.go | 64 ++++++++--------------------------------------
 1 file changed, 11 insertions(+), 53 deletions(-)

diff --git a/htlcswitch/link.go b/htlcswitch/link.go
index b75f3af5..2f09d99b 100644
--- a/htlcswitch/link.go
+++ b/htlcswitch/link.go
@@ -18,6 +18,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnpeer"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/ticker"
 )
 
 func init() {
@@ -99,41 +100,6 @@ func ExpectedFee(f ForwardingPolicy,
 	return f.BaseFee + (htlcAmt*f.FeeRate)/1000000
 }
 
-// Ticker is an interface used to wrap a time.Ticker in a struct, making
-// mocking it easier.
-type Ticker interface {
-	Start() <-chan time.Time
-
-	Stop()
-}
-
-// BatchTicker implements the Ticker interface, and wraps a time.Ticker.
-type BatchTicker struct {
-	duration time.Duration
-	ticker   *time.Ticker
-}
-
-// NewBatchTicker returns a new BatchTicker that wraps the passed time.Ticker.
-func NewBatchTicker(d time.Duration) *BatchTicker {
-	return &BatchTicker{
-		duration: d,
-	}
-}
-
-// Start returns the tick channel for the underlying time.Ticker.
-func (t *BatchTicker) Start() <-chan time.Time {
-	t.ticker = time.NewTicker(t.duration)
-	return t.ticker.C
-}
-
-// Stop stops the underlying time.Ticker.
-func (t *BatchTicker) Stop() {
-	if t.ticker != nil {
-		t.ticker.Stop()
-		t.ticker = nil
-	}
-}
-
 // ChannelLinkConfig defines the configuration for the channel link. ALL
 // elements within the configuration MUST be non-nil for channel link to carry
 // out its duties.
@@ -241,13 +207,13 @@ type ChannelLinkConfig struct {
 	// flush out. By batching updates into a single commit, we attempt to
 	// increase throughput by maximizing the number of updates coalesced
 	// into a single commit.
-	BatchTicker Ticker
+	BatchTicker ticker.Ticker
 
 	// FwdPkgGCTicker is the ticker determining the frequency at which
 	// garbage collection of forwarding packages occurs. We use a
 	// time-based approach, as opposed to block epochs, as to not hinder
 	// syncing.
-	FwdPkgGCTicker Ticker
+	FwdPkgGCTicker ticker.Ticker
 
 	// BatchSize is the max size of a batch of updates done to the link
 	// before we do a state update.
@@ -757,12 +723,12 @@ func (l *channelLink) resolveFwdPkg(fwdPkg *channeldb.FwdPkg) (bool, error) {
 func (l *channelLink) fwdPkgGarbager() {
 	defer l.wg.Done()
 
-	fwdPkgGcTick := l.cfg.FwdPkgGCTicker.Start()
+	l.cfg.FwdPkgGCTicker.Resume()
 	defer l.cfg.FwdPkgGCTicker.Stop()
 
 	for {
 		select {
-		case <-fwdPkgGcTick:
+		case <-l.cfg.FwdPkgGCTicker.Ticks():
 			fwdPkgs, err := l.channel.LoadFwdPkgs()
 			if err != nil {
 				l.warnf("unable to load fwdpkgs for gc: %v", err)
@@ -908,13 +874,6 @@ func (l *channelLink) htlcManager() {
 	l.wg.Add(1)
 	go l.fwdPkgGarbager()
 
-	// We'll only need the batch ticker if we have outgoing updates that are
-	// not covered by our last signature. This value will be nil unless a
-	// downstream packet forces the batchCounter to be positive. After the
-	// batch is cleared, it will return to nil to prevent wasteful CPU time
-	// caused by the batch ticker waking up the htlcManager needlessly.
-	var maybeBatchTick <-chan time.Time
-
 out:
 	for {
 		// We must always check if we failed at some point processing
@@ -995,13 +954,12 @@ out:
 				break out
 			}
 
-		case <-maybeBatchTick:
+		case <-l.cfg.BatchTicker.Ticks():
 			// If the current batch is empty, then we have no work
 			// here. We also disable the batch ticker from waking up
 			// the htlcManager while the batch is empty.
 			if l.batchCounter == 0 {
-				l.cfg.BatchTicker.Stop()
-				maybeBatchTick = nil
+				l.cfg.BatchTicker.Pause()
 				continue
 			}
 
@@ -1030,8 +988,8 @@ out:
 			// If the downstream packet resulted in a non-empty
 			// batch, reinstate the batch ticker so that it can be
 			// cleared.
-			if l.batchCounter > 0 && maybeBatchTick == nil {
-				maybeBatchTick = l.cfg.BatchTicker.Start()
+			if l.batchCounter > 0 {
+				l.cfg.BatchTicker.Resume()
 			}
 
 		// A message from the switch was just received. This indicates
@@ -1059,8 +1017,8 @@ out:
 			// If the downstream packet resulted in a non-empty
 			// batch, reinstate the batch ticker so that it can be
 			// cleared.
-			if l.batchCounter > 0 && maybeBatchTick == nil {
-				maybeBatchTick = l.cfg.BatchTicker.Start()
+			if l.batchCounter > 0 {
+				l.cfg.BatchTicker.Resume()
 			}
 
 		// A message from the connected peer was just received. This