autopilot: add tracking of pending channel state

This commit adds tracking of the pending channels state within the
autopilot.Agent. This fixes a class of bugs which was discovered during
the latest test net block storm wherein the Agent would attempt to
repeatedly attach to the same node due to rapid closure of other
channels.

In this commit we fix this issue by ensuring that we always factor in
the pending channel state when querying the heuristic w.r.t if we need
more channels, and if so to which nodes should be attached to.

autopilot/agent_test.go

@@ -17,21 +17,54 @@ type moreChansResp struct {
 	amt      btcutil.Amount
 }
 
+type moreChanArg struct {
+	chans   []Channel
+	balance btcutil.Amount
+}
+
 type mockHeuristic struct {
 	moreChansResps chan moreChansResp
+	moreChanArgs   chan moreChanArg
+
 	directiveResps chan []AttachmentDirective
+	directiveArgs  chan directiveArg
 }
 
 func (m *mockHeuristic) NeedMoreChans(chans []Channel,
 	balance btcutil.Amount) (btcutil.Amount, bool) {
 
+	if m.moreChanArgs != nil {
+		m.moreChanArgs <- moreChanArg{
+			chans:   chans,
+			balance: balance,
+		}
+
+	}
+
 	resp := <-m.moreChansResps
 	return resp.amt, resp.needMore
 }
 
+type directiveArg struct {
+	self  *btcec.PublicKey
+	graph ChannelGraph
+	amt   btcutil.Amount
+	skip  map[NodeID]struct{}
+}
+
 func (m *mockHeuristic) Select(self *btcec.PublicKey, graph ChannelGraph,
+
 	amtToUse btcutil.Amount, skipChans map[NodeID]struct{}) ([]AttachmentDirective, error) {
 
+	if m.directiveArgs != nil {
+		m.directiveArgs <- directiveArg{
+			self:  self,
+			graph: graph,
+			amt:   amtToUse,
+			skip:  skipChans,
+		}
+	}
+
 	resp := <-m.directiveResps
 	return resp, nil
 }
@@ -552,3 +585,179 @@ func TestAgentImmediateAttach(t *testing.T) {
 		}
 	}
 }
+
+// TestAgentPendingChannelState ensures that the agent properly factors in its
+// pending channel state when making decisions w.r.t if it needs more channels
+// or not, and if so, who is eligible to open new channels to.
+func TestAgentPendingChannelState(t *testing.T) {
+	t.Parallel()
+
+	// First, we'll create all the dependencies that we'll need in order to
+	// create the autopilot agent.
+	self, err := randKey()
+	if err != nil {
+		t.Fatalf("unable to generate key: %v", err)
+	}
+	heuristic := &mockHeuristic{
+		moreChansResps: make(chan moreChansResp),
+		directiveResps: make(chan []AttachmentDirective),
+	}
+	chanController := &mockChanController{
+		openChanSignals: make(chan openChanIntent),
+	}
+	memGraph, _, _ := newMemChanGraph()
+
+	// The wallet will start with 6 BTC available.
+	const walletBalance = btcutil.SatoshiPerBitcoin * 6
+
+	// With the dependencies we created, we can now create the initial
+	// agent itself.
+	testCfg := Config{
+		Self:           self,
+		Heuristic:      heuristic,
+		ChanController: chanController,
+		WalletBalance: func() (btcutil.Amount, error) {
+			return walletBalance, nil
+		},
+		Graph: memGraph,
+	}
+	initialChans := []Channel{}
+	agent, err := New(testCfg, initialChans)
+	if err != nil {
+		t.Fatalf("unable to create agent: %v", err)
+	}
+
+	// With the autopilot agent and all its dependencies we'll start the
+	// primary controller goroutine.
+	if err := agent.Start(); err != nil {
+		t.Fatalf("unable to start agent: %v", err)
+	}
+	defer agent.Stop()
+
+	var wg sync.WaitGroup
+
+	// Once again, we'll start by telling the agent as part of its first
+	// query, that it needs more channels and has 3 BTC available for
+	// attachment.
+	wg.Add(1)
+	go func() {
+		select {
+
+		// We'll send over a response indicating that it should
+		// establish more channels, and give it a budget of 1 BTC to do
+		// so.
+		case heuristic.moreChansResps <- moreChansResp{true, btcutil.SatoshiPerBitcoin}:
+			wg.Done()
+			return
+		case <-time.After(time.Second * 10):
+			t.Fatalf("heuristic wasn't queried in time")
+		}
+	}()
+
+	// We'll wait for the first query to be consumed. If this doesn't
+	// happen then the above goroutine will timeout, and fail the test.
+	wg.Wait()
+
+	heuristic.moreChanArgs = make(chan moreChanArg)
+
+	// Next, the agent should deliver a query to the Select method of the
+	// heuristic. We'll only return a single directive for a pre-chosen
+	// node.
+	nodeKey, err := randKey()
+	if err != nil {
+		t.Fatalf("unable to generate key: %v", err)
+	}
+	nodeID := NewNodeID(nodeKey)
+	nodeDirective := AttachmentDirective{
+		PeerKey: nodeKey,
+		ChanAmt: 0.5 * btcutil.SatoshiPerBitcoin,
+		Addrs: []net.Addr{
+			&net.TCPAddr{
+				IP: bytes.Repeat([]byte("a"), 16),
+			},
+		},
+	}
+	select {
+	case heuristic.directiveResps <- []AttachmentDirective{nodeDirective}:
+		return
+	case <-time.After(time.Second * 10):
+		t.Fatalf("heuristic wasn't queried in time")
+	}
+
+	heuristic.directiveArgs = make(chan directiveArg)
+
+	// A request to open the channel should've also been sent.
+	select {
+	case openChan := <-chanController.openChanSignals:
+		if openChan.amt != nodeDirective.ChanAmt {
+			t.Fatalf("invalid chan amt: expected %v, got %v",
+				nodeDirective.ChanAmt, openChan.amt)
+		}
+		if !openChan.target.IsEqual(nodeKey) {
+			t.Fatalf("unexpected key: expected %x, got %x",
+				nodeKey.SerializeCompressed(),
+				openChan.target.SerializeCompressed())
+		}
+		if len(openChan.addrs) != 1 {
+			t.Fatalf("should have single addr, instead have: %v",
+				len(openChan.addrs))
+		}
+	case <-time.After(time.Second * 10):
+		t.Fatalf("channel wasn't opened in time")
+	}
+
+	// Now, in order to test that the pending state was properly updated,
+	// we'll trigger a balance update in order to trigger a query to the
+	// heuristic.
+	agent.OnBalanceChange(0.4 * btcutil.SatoshiPerBitcoin)
+
+	wg = sync.WaitGroup{}
+
+	// The heuristic should be queried, and the argument for the set of
+	// channels passed in should include the pending channels that
+	// should've been created above.
+	select {
+	// The request that we get should include a pending channel for the
+	// one that we just created, otherwise the agent isn't properly
+	// updating its internal state.
+	case req := <-heuristic.moreChanArgs:
+		if len(req.chans) != 1 {
+			t.Fatalf("should include pending chan in current "+
+				"state, instead have %v chans", len(req.chans))
+		}
+		if req.chans[0].Capacity != nodeDirective.ChanAmt {
+			t.Fatalf("wrong chan capacity: expected %v, got %v",
+				req.chans[0].Capacity, nodeDirective.ChanAmt)
+		}
+		if req.chans[0].Node != nodeID {
+			t.Fatalf("wrong node ID: expected %x, got %x",
+				req.chans[0].Node[:], nodeID)
+		}
+	case <-time.After(time.Second * 10):
+		t.Fatalf("need more chans wasn't queried in time")
+	}
+
+	// We'll send across a response indicating that it *does* need more
+	// channels.
+	select {
+	case heuristic.moreChansResps <- moreChansResp{true, btcutil.SatoshiPerBitcoin}:
+	case <-time.After(time.Second * 10):
+		t.Fatalf("need more chans wasn't queried in time")
+	}
+
+	// The response above should prompt the agent to make a query to the
+	// Select method. The arguments passed should reflect the fact that the
+	// node we have a pending channel to, should be ignored.
+	select {
+	case req := <-heuristic.directiveArgs:
+		if len(req.skip) == 0 {
+			t.Fatalf("expected to skip %v nodes, instead "+
+				"skipping %v", 1, len(req.skip))
+		}
+		if _, ok := req.skip[nodeID]; !ok {
+			t.Fatalf("pending node not included in skip arguments")
+		}
+	case <-time.After(time.Second * 10):
+		t.Fatalf("select wasn't queried in time")
+	}
+}