routing: separate MissionControl from MissionControlManager

This commit renames the previous MissionControl to MissionController and
the previous MissionController interface to MissionControlQuerier. This
is done because soon the (new) MissionController will back multiple
namespaced MissionControl instances.  For now, it just houses a single
MissionControl in the default namespace.

This commit also replaces the MissionControl's `now` function with a
`clock.Clock`.

routing/missioncontrol_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -40,9 +41,10 @@ var (
 )
 
 type mcTestContext struct {
-	t   *testing.T
-	mc  *MissionControl
-	now time.Time
+	t  *testing.T
+	mc *MissionControl
+
+	clock *testClock
 
 	db     kvdb.Backend
 	dbPath string
@@ -52,8 +54,8 @@ type mcTestContext struct {
 
 func createMcTestContext(t *testing.T) *mcTestContext {
 	ctx := &mcTestContext{
-		t:   t,
-		now: mcTestTime,
+		t:     t,
+		clock: newTestClock(mcTestTime),
 	}
 
 	file, err := os.CreateTemp("", "*.db")
@@ -85,7 +87,7 @@ func createMcTestContext(t *testing.T) *mcTestContext {
 // restartMc creates a new instances of mission control on the same database.
 func (ctx *mcTestContext) restartMc() {
 	// Since we don't run a timer to store results in unit tests, we store
-	// them here before fetching back everything in NewMissionControl.
+	// them here before fetching back everything in NewMissionController.
 	if ctx.mc != nil {
 		require.NoError(ctx.t, ctx.mc.store.storeResults())
 	}
@@ -99,7 +101,7 @@ func (ctx *mcTestContext) restartMc() {
 	estimator, err := NewAprioriEstimator(aCfg)
 	require.NoError(ctx.t, err)
 
-	mc, err := NewMissionControl(
+	mc, err := NewMissionController(
 		ctx.db, mcTestSelf,
 		&MissionControlConfig{Estimator: estimator},
 	)
@@ -107,8 +109,8 @@ func (ctx *mcTestContext) restartMc() {
 		ctx.t.Fatal(err)
 	}
 
-	mc.now = func() time.Time { return ctx.now }
-	ctx.mc = mc
+	mc.cfg.clock = ctx.clock
+	ctx.mc = mc.GetDefaultStore()
 }
 
 // Assert that mission control returns a probability for an edge.
@@ -150,7 +152,7 @@ func (ctx *mcTestContext) reportSuccess() {
 func TestMissionControl(t *testing.T) {
 	ctx := createMcTestContext(t)
 
-	ctx.now = testTime
+	ctx.clock.setTime(testTime)
 
 	testTime := time.Date(2018, time.January, 9, 14, 00, 00, 0, time.UTC)
 
@@ -178,7 +180,7 @@ func TestMissionControl(t *testing.T) {
 	// Edge decay started. The node probability weighted average should now
 	// have shifted from 1:1 to 1:0.5 -> 60%. The connection probability is
 	// half way through the recovery, so we expect 30% here.
-	ctx.now = testTime.Add(30 * time.Minute)
+	ctx.clock.setTime(testTime.Add(30 * time.Minute))
 	ctx.expectP(1000, 0.3)
 
 	// Edge fails again, this time without a min penalization amt. The edge
@@ -188,7 +190,7 @@ func TestMissionControl(t *testing.T) {
 	ctx.expectP(500, 0)
 
 	// Edge decay started.
-	ctx.now = testTime.Add(60 * time.Minute)
+	ctx.clock.setTime(testTime.Add(60 * time.Minute))
 	ctx.expectP(1000, 0.3)
 
 	// Restart mission control to test persistence.
@@ -230,3 +232,29 @@ func TestMissionControlChannelUpdate(t *testing.T) {
 	)
 	ctx.expectP(100, 0)
 }
+
+// testClock is an implementation of clock.Clock that lets the caller overwrite
+// the current time at any point.
+type testClock struct {
+	now time.Time
+	clock.Clock
+}
+
+// newTestClock constructs a new testClock.
+func newTestClock(startTime time.Time) *testClock {
+	return &testClock{
+		now: startTime,
+	}
+}
+
+// Now returns the underlying current time.
+//
+// NOTE: this is part of the clock.Clock interface.
+func (c *testClock) Now() time.Time {
+	return c.now
+}
+
+// setTime overwrites the current time.
+func (c *testClock) setTime(n time.Time) {
+	c.now = n
+}