autopilot: modify interfaces to specify *exactly* how many chans to open

In this commit, we fix a regression introduced by a recent change which
would allow the agent to detect a channel as failed, and blacklist the
node, promising faster convergence with the ideal state of the
heuristic.

The source of this bug is that we would use the set of blacklisted
nodes in order to compute how many additional channels we should open.
If 10 failures happened, then we would think that we had opened up 10
channels, and stop much earlier than we actually should.

To fix this, while ensuring we don’t retry to failed peers, the
NeedMoreChans method will now return *how* anymore channels to open,
and the Select method will take in how many channels it should try to
open *exactly*.

autopilot/prefattach_test.go

@@ -38,6 +38,7 @@ func TestConstrainedPrefAttachmentNeedMoreChan(t *testing.T) {
 
 		needMore     bool
 		amtAvailable btcutil.Amount
+		numMore      uint32
 	}{
 		// Many available funds, but already have too many active open
 		// channels.
@@ -59,6 +60,7 @@ func TestConstrainedPrefAttachmentNeedMoreChan(t *testing.T) {
 			btcutil.Amount(btcutil.SatoshiPerBitcoin * 10),
 			false,
 			0,
+			0,
 		},
 
 		// Ratio of funds in channels and total funds meets the
@@ -77,13 +79,15 @@ func TestConstrainedPrefAttachmentNeedMoreChan(t *testing.T) {
 			btcutil.Amount(btcutil.SatoshiPerBitcoin * 2),
 			false,
 			0,
+			0,
 		},
 
 		// Ratio of funds in channels and total funds is below the
 		// threshold. We have 10 BTC allocated amongst channels and
 		// funds, atm. We're targeting 50%, so 5 BTC should be
 		// allocated. Only 1 BTC is atm, so 4 BTC should be
-		// recommended.
+		// recommended. We should also request 2 more channels as the
+		// limit is 3.
 		{
 			[]Channel{
 				{
@@ -94,14 +98,16 @@ func TestConstrainedPrefAttachmentNeedMoreChan(t *testing.T) {
 			btcutil.Amount(btcutil.SatoshiPerBitcoin * 9),
 			true,
 			btcutil.Amount(btcutil.SatoshiPerBitcoin * 4),
+			2,
 		},
 
 		// Ratio of funds in channels and total funds is below the
 		// threshold. We have 14 BTC total amongst the wallet's
 		// balance, and our currently opened channels. Since we're
 		// targeting a 50% allocation, we should commit 7 BTC. The
-		// current channels commit 4 BTC, so we should expected 3 bTC
-		// to be committed.
+		// current channels commit 4 BTC, so we should expected 3 BTC
+		// to be committed. We should only request a single additional
+		// channel as the limit is 3.
 		{
 			[]Channel{
 				{
@@ -116,6 +122,7 @@ func TestConstrainedPrefAttachmentNeedMoreChan(t *testing.T) {
 			btcutil.Amount(btcutil.SatoshiPerBitcoin * 10),
 			true,
 			btcutil.Amount(btcutil.SatoshiPerBitcoin * 3),
+			1,
 		},
 
 		// Ratio of funds in channels and total funds is above the
@@ -134,6 +141,7 @@ func TestConstrainedPrefAttachmentNeedMoreChan(t *testing.T) {
 			btcutil.Amount(btcutil.SatoshiPerBitcoin),
 			false,
 			0,
+			0,
 		},
 	}
 
@@ -141,8 +149,9 @@ func TestConstrainedPrefAttachmentNeedMoreChan(t *testing.T) {
 		chanLimit, threshold)
 
 	for i, testCase := range testCases {
-		amtToAllocate, needMore := prefAttach.NeedMoreChans(testCase.channels,
-			testCase.walletAmt)
+		amtToAllocate, numMore, needMore := prefAttach.NeedMoreChans(
+			testCase.channels, testCase.walletAmt,
+		)
 
 		if amtToAllocate != testCase.amtAvailable {
 			t.Fatalf("test #%v: expected %v, got %v",
@@ -152,6 +161,10 @@ func TestConstrainedPrefAttachmentNeedMoreChan(t *testing.T) {
 			t.Fatalf("test #%v: expected %v, got %v",
 				i, testCase.needMore, needMore)
 		}
+		if numMore != testCase.numMore {
+			t.Fatalf("test #%v: expected %v, got %v",
+				i, testCase.numMore, numMore)
+		}
 	}
 }
 
@@ -247,7 +260,7 @@ func TestConstrainedPrefAttachmentSelectEmptyGraph(t *testing.T) {
 			// creation given the current state of the graph.
 			const walletFunds = btcutil.SatoshiPerBitcoin
 			directives, err := prefAttach.Select(self, graph,
-				walletFunds, skipNodes)
+				walletFunds, 5, skipNodes)
 			if err != nil {
 				t1.Fatalf("unable to select attachment "+
 					"directives: %v", err)
@@ -316,7 +329,7 @@ func TestConstrainedPrefAttachmentSelectTwoVertexes(t *testing.T) {
 			// creation given the current state of the graph.
 			const walletFunds = btcutil.SatoshiPerBitcoin * 10
 			directives, err := prefAttach.Select(self, graph,
-				walletFunds, skipNodes)
+				walletFunds, 2, skipNodes)
 			if err != nil {
 				t1.Fatalf("unable to select attachment directives: %v", err)
 			}
@@ -395,7 +408,7 @@ func TestConstrainedPrefAttachmentSelectInsufficientFunds(t *testing.T) {
 			// passing zero for the amount of wallet funds. This
 			// should return an empty slice of directives.
 			directives, err := prefAttach.Select(self, graph, 0,
-				skipNodes)
+				0, skipNodes)
 			if err != nil {
 				t1.Fatalf("unable to select attachment "+
 					"directives: %v", err)
@@ -503,7 +516,7 @@ func TestConstrainedPrefAttachmentSelectGreedyAllocation(t *testing.T) {
 			// allocate funds to channels.
 			const availableBalance = btcutil.SatoshiPerBitcoin * 2.5
 			directives, err := prefAttach.Select(self, graph,
-				availableBalance, skipNodes)
+				availableBalance, 5, skipNodes)
 			if err != nil {
 				t1.Fatalf("unable to select attachment "+
 					"directives: %v", err)
@@ -594,7 +607,7 @@ func TestConstrainedPrefAttachmentSelectSkipNodes(t *testing.T) {
 			// candidates.
 			const availableBalance = btcutil.SatoshiPerBitcoin * 2.5
 			directives, err := prefAttach.Select(self, graph,
-				availableBalance, skipNodes)
+				availableBalance, 2, skipNodes)
 			if err != nil {
 				t1.Fatalf("unable to select attachment "+
 					"directives: %v", err)
@@ -618,7 +631,7 @@ func TestConstrainedPrefAttachmentSelectSkipNodes(t *testing.T) {
 			// should get no new directives as both nodes has
 			// already been attached to.
 			directives, err = prefAttach.Select(self, graph,
-				availableBalance, skipNodes)
+				availableBalance, 2, skipNodes)
 			if err != nil {
 				t1.Fatalf("unable to select attachment "+
 					"directives: %v", err)