neutrino: parallelized block header download.

This commit distributes header download across peers leveraging
checckpoints and the workmanager.

Signed-off-by: Maureen Ononiwu <amaka013@gmail.com>

neutrino.go

@@ -195,6 +195,31 @@ func NewServerPeer(s *ChainService, isPersistent bool) *ServerPeer {
 	}
 }
 
+// IsSyncCandidate returns whether or not the peer is a candidate to consider
+// syncing from.
+func (sp *ServerPeer) IsSyncCandidate() bool {
+	// The peer is not a candidate for sync if it's not a full node.
+	return sp.Services()&wire.SFNodeNetwork == wire.SFNodeNetwork
+}
+
+// IsPeerBehindStartHeight returns a boolean indicating if the peer's last block height
+// is behind the start height of the request. If the peer is not behind the request start
+// height false is returned, otherwise, true is.
+func (sp *ServerPeer) IsPeerBehindStartHeight(req query.ReqMessage) bool {
+	queryGetHeaders, ok := req.(*headerQuery)
+
+	if !ok {
+		log.Debugf("request is not type headerQuery")
+
+		return true
+	}
+
+	if sp.LastBlock() < queryGetHeaders.startHeight {
+		return true
+	}
+	return false
+}
+
 // newestBlock returns the current best block hash and height using the format
 // required by the configuration for the peer package.
 func (sp *ServerPeer) newestBlock() (*chainhash.Hash, int32, error) {
@@ -800,15 +825,21 @@ func NewChainService(cfg Config) (*ChainService, error) {
 	}
 
 	bm, err := newBlockManager(&blockManagerCfg{
-		ChainParams:      s.chainParams,
-		BlockHeaders:     s.BlockHeaders,
-		RegFilterHeaders: s.RegFilterHeaders,
-		TimeSource:       s.timeSource,
-		QueryDispatcher:  s.workManager,
-		BanPeer:          s.BanPeer,
-		GetBlock:         s.GetBlock,
-		firstPeerSignal:  s.firstPeerConnect,
-		queryAllPeers:    s.queryAllPeers,
+		ChainParams:             s.chainParams,
+		BlockHeaders:            s.BlockHeaders,
+		RegFilterHeaders:        s.RegFilterHeaders,
+		TimeSource:              s.timeSource,
+		cfHeaderQueryDispatcher: s.workManager,
+		BanPeer:                 s.BanPeer,
+		GetBlock:                s.GetBlock,
+		firstPeerSignal:         s.firstPeerConnect,
+		queryAllPeers:           s.queryAllPeers,
+		blkHdrCheckptQueryDispatcher: query.NewWorkManager(&query.Config{
+			ConnectedPeers:       s.ConnectedPeers,
+			NewWorker:            query.NewWorker,
+			Ranking:              query.NewPeerRanking(),
+			IsEligibleWorkerFunc: query.IsWorkerEligibleForBlkHdrFetch,
+		}),
 	})
 	if err != nil {
 		return nil, err
@@ -1610,6 +1641,9 @@ func (s *ChainService) Start() error {
 	s.addrManager.Start()
 	s.blockManager.Start()
 	s.blockSubscriptionMgr.Start()
+	if err := s.blockManager.cfg.blkHdrCheckptQueryDispatcher.Start(); err != nil {
+		return fmt.Errorf("unable to start block header work manager: %v", err)
+	}
 	if err := s.workManager.Start(); err != nil {
 		return fmt.Errorf("unable to start work manager: %v", err)
 	}

query/interface.go

@@ -224,4 +224,11 @@ type Peer interface {
 	// OnDisconnect returns a channel that will be closed when this peer is
 	// disconnected.
 	OnDisconnect() <-chan struct{}
+
+	// IsPeerBehindStartHeight returns a boolean indicating if the peer's known last height is behind
+	// the request's start Height which it receives as an argument.
+	IsPeerBehindStartHeight(req ReqMessage) bool
+
+	// IsSyncCandidate returns true if the peer is a sync candidate.
+	IsSyncCandidate() bool
 }

query/worker.go

@@ -95,7 +95,7 @@ func (w *worker) Run(results chan<- *jobResult, quit <-chan struct{}) {
 	msgChan, cancel := peer.SubscribeRecvMsg()
 	defer cancel()
 
-nexJobLoop:
+nextJobLoop:
 	for {
 		log.Tracef("Worker %v waiting for more work", peer.Addr())
 
@@ -154,7 +154,7 @@ nexJobLoop:
 				case <-quit:
 					return
 				}
-				goto nexJobLoop
+				goto nextJobLoop
 			}
 		}
 
@@ -308,6 +308,28 @@ nexJobLoop:
 	}
 }
 
+func (w *worker) IsSyncCandidate() bool {
+	return w.peer.IsSyncCandidate()
+}
+
+func (w *worker) IsPeerBehindStartHeight(req ReqMessage) bool {
+	return w.peer.IsPeerBehindStartHeight(req)
+}
+
+// IsWorkerEligibleForBlkHdrFetch is the eligibility function used for the BlockHdrWorkManager to determine workers
+// eligible to receive jobs (the job is to fetch headers). If the peer is not a sync candidate or if its last known
+// block height is behind the job query's start height, it returns false. Otherwise, it returns true.
+func IsWorkerEligibleForBlkHdrFetch(r *activeWorker, next *queryJob) bool {
+	if !r.w.IsSyncCandidate() {
+		return false
+	}
+
+	if r.w.IsPeerBehindStartHeight(next.Req) {
+		return false
+	}
+	return true
+}
+
 // NewJob returns a channel where work that is to be handled by the worker can
 // be sent. If the worker reads a queryJob from this channel, it is guaranteed
 // that a response will eventually be deliverd on the results channel (except

query/worker_test.go

@@ -10,9 +10,10 @@ import (
 )
 
 type mockQueryEncoded struct {
-	message  *wire.MsgGetData
-	encoding wire.MessageEncoding
-	index    float64
+	message     *wire.MsgGetData
+	encoding    wire.MessageEncoding
+	index       float64
+	startHeight int
 }
 
 func (m *mockQueryEncoded) Message() wire.Message {
@@ -52,6 +53,8 @@ type mockPeer struct {
 	responses     chan<- wire.Message
 	subscriptions chan chan wire.Message
 	quit          chan struct{}
+	bestHeight    int
+	fullNode      bool
 	err           error
 }
 
@@ -72,6 +75,15 @@ func (m *mockPeer) Addr() string {
 	return m.addr
 }
 
+func (m *mockPeer) IsPeerBehindStartHeight(request ReqMessage) bool {
+	r := request.(*mockQueryEncoded)
+	return m.bestHeight < r.startHeight
+}
+
+func (m *mockPeer) IsSyncCandidate() bool {
+	return m.fullNode
+}
+
 // makeJob returns a new query job that will be done when it is given the
 // finalResp message. Similarly ot will progress on being given the
 // progressResp message, while any other message will be ignored.

query/workmanager.go

@@ -46,6 +46,13 @@ type Worker interface {
 	// delivered on the results channel (except when the quit channel has
 	// been closed).
 	NewJob() chan<- *queryJob
+
+	// IsPeerBehindStartHeight returns a boolean indicating if the peer's known last height is behind
+	// the request's start Height which it receives as an argument.
+	IsPeerBehindStartHeight(req ReqMessage) bool
+
+	// IsSyncCandidate returns if the peer is a sync candidate.
+	IsSyncCandidate() bool
 }
 
 // PeerRanking is an interface that must be satisfied by the underlying module

query/workmanager_test.go

@@ -15,6 +15,14 @@ type mockWorker struct {
 	results chan *jobResult
 }
 
+func (m *mockWorker) IsPeerBehindStartHeight(req ReqMessage) bool {
+	return m.peer.IsPeerBehindStartHeight(req)
+}
+
+func (m *mockWorker) IsSyncCandidate() bool {
+	return m.peer.IsSyncCandidate()
+}
+
 var _ Worker = (*mockWorker)(nil)
 
 func (m *mockWorker) NewJob() chan<- *queryJob {
@@ -985,3 +993,105 @@ func TestWorkManagerResultUnfinished(t *testing.T) {
 		t.Fatalf("nothing received on errChan")
 	}
 }
+
+// TestIsWorkerEligibleForBlkHdrFetch tests the IsWorkerEligibleForBlkHdrFetch function.
+func TestIsWorkerEligibleForBlkHdrFetch(t *testing.T) {
+	type testArgs struct {
+		name                string
+		activeWorker        *activeWorker
+		job                 *queryJob
+		expectedEligibility bool
+	}
+
+	testCases := []testArgs{
+		{
+			name: "peer sync candidate, best height behind job start Height",
+			activeWorker: &activeWorker{
+				w: &mockWorker{
+					peer: &mockPeer{
+						bestHeight: 5,
+						fullNode:   true,
+					},
+				},
+			},
+			job: &queryJob{
+				Request: &Request{
+					Req: &mockQueryEncoded{
+						startHeight: 10,
+					},
+				},
+			},
+			expectedEligibility: false,
+		},
+
+		{
+			name: "peer sync candidate, best height ahead job start Height",
+			activeWorker: &activeWorker{
+				w: &mockWorker{
+					peer: &mockPeer{
+						bestHeight: 10,
+						fullNode:   true,
+					},
+				},
+			},
+			job: &queryJob{
+				Request: &Request{
+					Req: &mockQueryEncoded{
+						startHeight: 5,
+					},
+				},
+			},
+			expectedEligibility: true,
+		},
+
+		{
+			name: "peer not sync candidate, best height behind job start Height",
+			activeWorker: &activeWorker{
+				w: &mockWorker{
+					peer: &mockPeer{
+						bestHeight: 5,
+						fullNode:   false,
+					},
+				},
+			},
+			job: &queryJob{
+				Request: &Request{
+					Req: &mockQueryEncoded{
+						startHeight: 10,
+					},
+				},
+			},
+			expectedEligibility: false,
+		},
+
+		{
+			name: "peer not sync candidate, best height ahead job start Height",
+			activeWorker: &activeWorker{
+				w: &mockWorker{
+					peer: &mockPeer{
+						bestHeight: 10,
+						fullNode:   false,
+					},
+				},
+			},
+			job: &queryJob{
+				Request: &Request{
+					Req: &mockQueryEncoded{
+						startHeight: 5,
+					},
+				},
+			},
+			expectedEligibility: false,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			isEligible := IsWorkerEligibleForBlkHdrFetch(test.activeWorker, test.job)
+			if isEligible != test.expectedEligibility {
+				t.Fatalf("Expected '%v'for eligibility check but got"+
+					"'%v'\n", test.expectedEligibility, isEligible)
+			}
+		})
+	}
+}