Merge pull request #6111 from bottlepay/cache-loading

kvdb+channeldb: speed up graph cache

channeldb/graph.go

@@ -216,15 +216,29 @@ func NewChannelGraph(db kvdb.Backend, rejectCacheSize, chanCacheSize int,
 		startTime := time.Now()
 		log.Debugf("Populating in-memory channel graph, this might " +
 			"take a while...")
+
 		err := g.ForEachNodeCacheable(
 			func(tx kvdb.RTx, node GraphCacheNode) error {
-				return g.graphCache.AddNode(tx, node)
+				g.graphCache.AddNodeFeatures(node)
+
+				return nil
 			},
 		)
 		if err != nil {
 			return nil, err
 		}
 
+		err = g.ForEachChannel(func(info *ChannelEdgeInfo,
+			policy1, policy2 *ChannelEdgePolicy) error {
+
+			g.graphCache.AddChannel(info, policy1, policy2)
+
+			return nil
+		})
+		if err != nil {
+			return nil, err
+		}
+
 		log.Debugf("Finished populating in-memory channel graph (took "+
 			"%v, %s)", time.Since(startTime), g.graphCache.Stats())
 	}
@@ -232,6 +246,71 @@ func NewChannelGraph(db kvdb.Backend, rejectCacheSize, chanCacheSize int,
 	return g, nil
 }
 
+// channelMapKey is the key structure used for storing channel edge policies.
+type channelMapKey struct {
+	nodeKey route.Vertex
+	chanID  [8]byte
+}
+
+// getChannelMap loads all channel edge policies from the database and stores
+// them in a map.
+func (c *ChannelGraph) getChannelMap(edges kvdb.RBucket) (
+	map[channelMapKey]*ChannelEdgePolicy, error) {
+
+	// Create a map to store all channel edge policies.
+	channelMap := make(map[channelMapKey]*ChannelEdgePolicy)
+
+	err := kvdb.ForAll(edges, func(k, edgeBytes []byte) error {
+		// Skip embedded buckets.
+		if bytes.Equal(k, edgeIndexBucket) ||
+			bytes.Equal(k, edgeUpdateIndexBucket) ||
+			bytes.Equal(k, zombieBucket) ||
+			bytes.Equal(k, disabledEdgePolicyBucket) ||
+			bytes.Equal(k, channelPointBucket) {
+
+			return nil
+		}
+
+		// Validate key length.
+		if len(k) != 33+8 {
+			return fmt.Errorf("invalid edge key %x encountered", k)
+		}
+
+		var key channelMapKey
+		copy(key.nodeKey[:], k[:33])
+		copy(key.chanID[:], k[33:])
+
+		// No need to deserialize unknown policy.
+		if bytes.Equal(edgeBytes, unknownPolicy) {
+			return nil
+		}
+
+		edgeReader := bytes.NewReader(edgeBytes)
+		edge, err := deserializeChanEdgePolicyRaw(
+			edgeReader,
+		)
+
+		switch {
+		// If the db policy was missing an expected optional field, we
+		// return nil as if the policy was unknown.
+		case err == ErrEdgePolicyOptionalFieldNotFound:
+			return nil
+
+		case err != nil:
+			return err
+		}
+
+		channelMap[key] = edge
+
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return channelMap, nil
+}
+
 var graphTopLevelBuckets = [][]byte{
 	nodeBucket,
 	edgeBucket,
@@ -332,50 +411,47 @@ func (c *ChannelGraph) NewPathFindTx() (kvdb.RTx, error) {
 func (c *ChannelGraph) ForEachChannel(cb func(*ChannelEdgeInfo,
 	*ChannelEdgePolicy, *ChannelEdgePolicy) error) error {
 
-	// TODO(roasbeef): ptr map to reduce # of allocs? no duplicates
-
-	return kvdb.View(c.db, func(tx kvdb.RTx) error {
-		// First, grab the node bucket. This will be used to populate
-		// the Node pointers in each edge read from disk.
-		nodes := tx.ReadBucket(nodeBucket)
-		if nodes == nil {
-			return ErrGraphNotFound
-		}
-
-		// Next, grab the edge bucket which stores the edges, and also
-		// the index itself so we can group the directed edges together
-		// logically.
+	return c.db.View(func(tx kvdb.RTx) error {
 		edges := tx.ReadBucket(edgeBucket)
 		if edges == nil {
 			return ErrGraphNoEdgesFound
 		}
+
+		// First, load all edges in memory indexed by node and channel
+		// id.
+		channelMap, err := c.getChannelMap(edges)
+		if err != nil {
+			return err
+		}
+
 		edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
 		if edgeIndex == nil {
 			return ErrGraphNoEdgesFound
 		}
 
-		// For each edge pair within the edge index, we fetch each edge
-		// itself and also the node information in order to fully
-		// populated the object.
-		return edgeIndex.ForEach(func(chanID, edgeInfoBytes []byte) error {
-			infoReader := bytes.NewReader(edgeInfoBytes)
-			edgeInfo, err := deserializeChanEdgeInfo(infoReader)
-			if err != nil {
-				return err
-			}
-			edgeInfo.db = c.db
+		// Load edge index, recombine each channel with the policies
+		// loaded above and invoke the callback.
+		return kvdb.ForAll(edgeIndex, func(k, edgeInfoBytes []byte) error {
+			var chanID [8]byte
+			copy(chanID[:], k)
 
-			edge1, edge2, err := fetchChanEdgePolicies(
-				edgeIndex, edges, nodes, chanID, c.db,
-			)
+			edgeInfoReader := bytes.NewReader(edgeInfoBytes)
+			info, err := deserializeChanEdgeInfo(edgeInfoReader)
 			if err != nil {
 				return err
 			}
 
-			// With both edges read, execute the call back. IF this
-			// function returns an error then the transaction will
-			// be aborted.
-			return cb(&edgeInfo, edge1, edge2)
+			policy1 := channelMap[channelMapKey{
+				nodeKey: info.NodeKey1Bytes,
+				chanID:  chanID,
+			}]
+
+			policy2 := channelMap[channelMapKey{
+				nodeKey: info.NodeKey2Bytes,
+				chanID:  chanID,
+			}]
+
+			return cb(&info, policy1, policy2)
 		})
 	}, func() {})
 }
@@ -628,7 +704,6 @@ func (c *ChannelGraph) ForEachNodeCacheable(cb func(kvdb.RTx,
 			return ErrGraphNotFound
 		}
 
-		cacheableNode := newGraphCacheNode(route.Vertex{}, nil)
 		return nodes.ForEach(func(pubKey, nodeBytes []byte) error {
 			// If this is the source key, then we skip this
 			// iteration as the value for this key is a pubKey
@@ -638,8 +713,8 @@ func (c *ChannelGraph) ForEachNodeCacheable(cb func(kvdb.RTx,
 			}
 
 			nodeReader := bytes.NewReader(nodeBytes)
-			err := deserializeLightningNodeCacheable(
-				nodeReader, cacheableNode,
+			cacheableNode, err := deserializeLightningNodeCacheable(
+				nodeReader,
 			)
 			if err != nil {
 				return err
@@ -2740,8 +2815,6 @@ func (c *ChannelGraph) FetchLightningNode(nodePub route.Vertex) (
 type graphCacheNode struct {
 	pubKeyBytes route.Vertex
 	features    *lnwire.FeatureVector
-
-	nodeScratch [8]byte
 }
 
 // newGraphCacheNode returns a new cache optimized node.
@@ -4090,51 +4163,60 @@ func fetchLightningNode(nodeBucket kvdb.RBucket,
 	return deserializeLightningNode(nodeReader)
 }
 
-func deserializeLightningNodeCacheable(r io.Reader, node *graphCacheNode) error {
+func deserializeLightningNodeCacheable(r io.Reader) (*graphCacheNode, error) {
 	// Always populate a feature vector, even if we don't have a node
 	// announcement and short circuit below.
-	node.features = lnwire.EmptyFeatureVector()
+	node := newGraphCacheNode(
+		route.Vertex{},
+		lnwire.EmptyFeatureVector(),
+	)
+
+	var nodeScratch [8]byte
 
 	// Skip ahead:
 	// - LastUpdate (8 bytes)
-	if _, err := r.Read(node.nodeScratch[:]); err != nil {
-		return err
+	if _, err := r.Read(nodeScratch[:]); err != nil {
+		return nil, err
 	}
 
 	if _, err := io.ReadFull(r, node.pubKeyBytes[:]); err != nil {
-		return err
+		return nil, err
 	}
 
 	// Read the node announcement flag.
-	if _, err := r.Read(node.nodeScratch[:2]); err != nil {
-		return err
+	if _, err := r.Read(nodeScratch[:2]); err != nil {
+		return nil, err
 	}
-	hasNodeAnn := byteOrder.Uint16(node.nodeScratch[:2])
+	hasNodeAnn := byteOrder.Uint16(nodeScratch[:2])
 
 	// The rest of the data is optional, and will only be there if we got a
 	// node announcement for this node.
 	if hasNodeAnn == 0 {
-		return nil
+		return node, nil
 	}
 
 	// We did get a node announcement for this node, so we'll have the rest
 	// of the data available.
 	var rgb uint8
 	if err := binary.Read(r, byteOrder, &rgb); err != nil {
-		return err
+		return nil, err
 	}
 	if err := binary.Read(r, byteOrder, &rgb); err != nil {
-		return err
+		return nil, err
 	}
 	if err := binary.Read(r, byteOrder, &rgb); err != nil {
-		return err
+		return nil, err
 	}
 
 	if _, err := wire.ReadVarString(r, 0); err != nil {
-		return err
+		return nil, err
 	}
 
-	return node.features.Decode(r)
+	if err := node.features.Decode(r); err != nil {
+		return nil, err
+	}
+
+	return node, nil
 }
 
 func deserializeLightningNode(r io.Reader) (LightningNode, error) {
@@ -4652,6 +4734,27 @@ func serializeChanEdgePolicy(w io.Writer, edge *ChannelEdgePolicy,
 func deserializeChanEdgePolicy(r io.Reader,
 	nodes kvdb.RBucket) (*ChannelEdgePolicy, error) {
 
+	// Deserialize the policy. Note that in case an optional field is not
+	// found, both an error and a populated policy object are returned.
+	edge, deserializeErr := deserializeChanEdgePolicyRaw(r)
+	if deserializeErr != nil &&
+		deserializeErr != ErrEdgePolicyOptionalFieldNotFound {
+
+		return nil, deserializeErr
+	}
+
+	// Populate full LightningNode struct.
+	pub := edge.Node.PubKeyBytes[:]
+	node, err := fetchLightningNode(nodes, pub)
+	if err != nil {
+		return nil, fmt.Errorf("unable to fetch node: %x, %v", pub, err)
+	}
+	edge.Node = &node
+
+	return edge, deserializeErr
+}
+
+func deserializeChanEdgePolicyRaw(r io.Reader) (*ChannelEdgePolicy, error) {
 	edge := &ChannelEdgePolicy{}
 
 	var err error
@@ -4701,13 +4804,9 @@ func deserializeChanEdgePolicy(r io.Reader,
 	if _, err := r.Read(pub[:]); err != nil {
 		return nil, err
 	}
-
-	node, err := fetchLightningNode(nodes, pub[:])
-	if err != nil {
-		return nil, fmt.Errorf("unable to fetch node: %x, %v",
-			pub[:], err)
+	edge.Node = &LightningNode{
+		PubKeyBytes: pub,
 	}
-	edge.Node = &node
 
 	// We'll try and see if there are any opaque bytes left, if not, then
 	// we'll ignore the EOF error and return the edge as is.

channeldb/graph_cache.go

@@ -205,9 +205,8 @@ func (c *GraphCache) Stats() string {
 		numChannels)
 }
 
-// AddNode adds a graph node, including all the (directed) channels of that
-// node.
-func (c *GraphCache) AddNode(tx kvdb.RTx, node GraphCacheNode) error {
+// AddNodeFeatures adds a graph node and its features to the cache.
+func (c *GraphCache) AddNodeFeatures(node GraphCacheNode) {
 	nodePubKey := node.PubKey()
 
 	// Only hold the lock for a short time. The `ForEachChannel()` below is
@@ -217,6 +216,12 @@ func (c *GraphCache) AddNode(tx kvdb.RTx, node GraphCacheNode) error {
 	c.mtx.Lock()
 	c.nodeFeatures[nodePubKey] = node.Features()
 	c.mtx.Unlock()
+}
+
+// AddNode adds a graph node, including all the (directed) channels of that
+// node.
+func (c *GraphCache) AddNode(tx kvdb.RTx, node GraphCacheNode) error {
+	c.AddNodeFeatures(node)
 
 	return node.ForEachChannel(
 		tx, func(tx kvdb.RTx, info *ChannelEdgeInfo,

channeldb/graph_test.go

@@ -1207,11 +1207,22 @@ func TestGraphTraversalCacheable(t *testing.T) {
 	// Iterate through all the known channels within the graph DB by
 	// iterating over each node, once again if the map is empty that
 	// indicates that all edges have properly been reached.
+	var nodes []GraphCacheNode
 	err = graph.ForEachNodeCacheable(
 		func(tx kvdb.RTx, node GraphCacheNode) error {
 			delete(nodeMap, node.PubKey())
 
-			return node.ForEachChannel(
+			nodes = append(nodes, node)
+
+			return nil
+		},
+	)
+	require.NoError(t, err)
+	require.Len(t, nodeMap, 0)
+
+	err = graph.db.View(func(tx kvdb.RTx) error {
+		for _, node := range nodes {
+			err := node.ForEachChannel(
 				tx, func(tx kvdb.RTx, info *ChannelEdgeInfo,
 					policy *ChannelEdgePolicy,
 					policy2 *ChannelEdgePolicy) error {
@@ -1220,10 +1231,15 @@ func TestGraphTraversalCacheable(t *testing.T) {
 					return nil
 				},
 			)
-		},
-	)
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}, func() {})
+
 	require.NoError(t, err)
-	require.Len(t, nodeMap, 0)
 	require.Len(t, chanIndex, 0)
 }
 
@@ -3695,9 +3711,20 @@ func BenchmarkForEachChannel(b *testing.B) {
 			totalCapacity btcutil.Amount
 			maxHTLCs      lnwire.MilliSatoshi
 		)
-		err := graph.ForEachNodeCacheable(
-			func(tx kvdb.RTx, n GraphCacheNode) error {
-				return n.ForEachChannel(
+
+		var nodes []GraphCacheNode
+		err = graph.ForEachNodeCacheable(
+			func(tx kvdb.RTx, node GraphCacheNode) error {
+				nodes = append(nodes, node)
+
+				return nil
+			},
+		)
+		require.NoError(b, err)
+
+		err = graph.db.View(func(tx kvdb.RTx) error {
+			for _, n := range nodes {
+				err := n.ForEachChannel(
 					tx, func(tx kvdb.RTx,
 						info *ChannelEdgeInfo,
 						policy *ChannelEdgePolicy,
@@ -3715,8 +3742,13 @@ func BenchmarkForEachChannel(b *testing.B) {
 						return nil
 					},
 				)
-			},
-		)
+				if err != nil {
+					return err
+				}
+			}
+
+			return nil
+		}, func() {})
 		require.NoError(b, err)
 	}
 }
@@ -3760,3 +3792,52 @@ func TestGraphCacheForEachNodeChannel(t *testing.T) {
 
 	require.Equal(t, numChans, 1)
 }
+
+// TestGraphLoading asserts that the cache is properly reconstructed after a
+// restart.
+func TestGraphLoading(t *testing.T) {
+	// First, create a temporary directory to be used for the duration of
+	// this test.
+	tempDirName, err := ioutil.TempDir("", "channelgraph")
+	require.NoError(t, err)
+	defer os.RemoveAll(tempDirName)
+
+	// Next, create the graph for the first time.
+	backend, backendCleanup, err := kvdb.GetTestBackend(tempDirName, "cgr")
+	require.NoError(t, err)
+	defer backend.Close()
+	defer backendCleanup()
+
+	opts := DefaultOptions()
+	graph, err := NewChannelGraph(
+		backend, opts.RejectCacheSize, opts.ChannelCacheSize,
+		opts.BatchCommitInterval, opts.PreAllocCacheNumNodes,
+		true, false,
+	)
+	require.NoError(t, err)
+
+	// Populate the graph with test data.
+	const numNodes = 100
+	const numChannels = 4
+	_, _ = fillTestGraph(t, graph, numNodes, numChannels)
+
+	// Recreate the graph. This should cause the graph cache to be
+	// populated.
+	graphReloaded, err := NewChannelGraph(
+		backend, opts.RejectCacheSize, opts.ChannelCacheSize,
+		opts.BatchCommitInterval, opts.PreAllocCacheNumNodes,
+		true, false,
+	)
+	require.NoError(t, err)
+
+	// Assert that the cache content is identical.
+	require.Equal(
+		t, graph.graphCache.nodeChannels,
+		graphReloaded.graphCache.nodeChannels,
+	)
+
+	require.Equal(
+		t, graph.graphCache.nodeFeatures,
+		graphReloaded.graphCache.nodeFeatures,
+	)
+}

docs/release-notes/release-notes-0.14.2.md

@@ -19,6 +19,11 @@ connection from the watch-only node.
   In other words, freshly-installed LND can now be initialized with multiple
   channels from an external (e.g. hardware) wallet *in a single transaction*.
 
+## Database
+
+* [Speed up graph cache loading on startup with
+Postgres](https://github.com/lightningnetwork/lnd/pull/6111)
+
 ## Build System
 
 * [Clean up Makefile by using go

go.mod

@@ -46,7 +46,7 @@ require (
 	github.com/lightningnetwork/lnd/cert v1.1.0
 	github.com/lightningnetwork/lnd/clock v1.1.0
 	github.com/lightningnetwork/lnd/healthcheck v1.2.0
-	github.com/lightningnetwork/lnd/kvdb v1.2.5
+	github.com/lightningnetwork/lnd/kvdb v1.3.0
 	github.com/lightningnetwork/lnd/queue v1.1.0
 	github.com/lightningnetwork/lnd/ticker v1.1.0
 	github.com/ltcsuite/ltcd v0.0.0-20190101042124-f37f8bf35796

kvdb/etcd/readwrite_bucket.go

@@ -406,3 +406,9 @@ func (b *readWriteBucket) Prefetch(paths ...[]string) {
 
 	b.tx.stm.Prefetch(flattenMap(keys), flattenMap(ranges))
 }
+
+// ForAll is an optimized version of ForEach with the limitation that no
+// additional queries can be executed within the callback.
+func (b *readWriteBucket) ForAll(cb func(k, v []byte) error) error {
+	return b.ForEach(cb)
+}

kvdb/interface.go

@@ -109,6 +109,12 @@ type ExtendedRBucket interface {
 
 	// Prefetch will attempt to prefetch all values under a path.
 	Prefetch(paths ...[]string)
+
+	// ForAll is an optimized version of ForEach.
+	//
+	// NOTE: ForAll differs from ForEach in that no additional queries can
+	// be executed within the callback.
+	ForAll(func(k, v []byte) error) error
 }
 
 // Prefetch will attempt to prefetch all values under a path from the passed
@@ -119,6 +125,16 @@ func Prefetch(b RBucket, paths ...[]string) {
 	}
 }
 
+// ForAll is an optimized version of ForEach with the limitation that no
+// additional queries can be executed within the callback.
+func ForAll(b RBucket, cb func(k, v []byte) error) error {
+	if bucket, ok := b.(ExtendedRBucket); ok {
+		return bucket.ForAll(cb)
+	}
+
+	return b.ForEach(cb)
+}
+
 // RootBucket is a wrapper to ExtendedRTx.RootBucket which does nothing if
 // the implementation doesn't have ExtendedRTx.
 func RootBucket(t RTx) RBucket {

kvdb/postgres/readwrite_bucket.go

@@ -427,3 +427,36 @@ func (b *readWriteBucket) Sequence() uint64 {
 
 	return uint64(seq)
 }
+
+// Prefetch will attempt to prefetch all values under a path from the passed
+// bucket.
+func (b *readWriteBucket) Prefetch(paths ...[]string) {}
+
+// ForAll is an optimized version of ForEach with the limitation that no
+// additional queries can be executed within the callback.
+func (b *readWriteBucket) ForAll(cb func(k, v []byte) error) error {
+	rows, cancel, err := b.tx.Query(
+		"SELECT key, value FROM " + b.table + " WHERE " +
+			parentSelector(b.id) + " ORDER BY key",
+	)
+	if err != nil {
+		return err
+	}
+	defer cancel()
+
+	for rows.Next() {
+		var key, value []byte
+
+		err := rows.Scan(&key, &value)
+		if err != nil {
+			return err
+		}
+
+		err = cb(key, value)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

kvdb/postgres/readwrite_tx.go

@@ -4,6 +4,7 @@
 package postgres
 
 import (
+	"context"
 	"database/sql"
 	"sync"
 
@@ -39,7 +40,16 @@ func newReadWriteTx(db *db, readOnly bool) (*readWriteTx, error) {
 	}
 	locker.Lock()
 
-	tx, err := db.db.Begin()
+	// Start the transaction. Don't use the timeout context because it would
+	// be applied to the transaction as a whole. If possible, mark the
+	// transaction as read-only to make sure that potential programming
+	// errors cannot cause changes to the database.
+	tx, err := db.db.BeginTx(
+		context.Background(),
+		&sql.TxOptions{
+			ReadOnly: readOnly,
+		},
+	)
 	if err != nil {
 		locker.Unlock()
 		return nil, err
@@ -165,6 +175,21 @@ func (tx *readWriteTx) QueryRow(query string, args ...interface{}) (*sql.Row,
 	return tx.tx.QueryRowContext(ctx, query, args...), cancel
 }
 
+// Query executes a multi-row query call with a timeout context.
+func (tx *readWriteTx) Query(query string, args ...interface{}) (*sql.Rows,
+	func(), error) {
+
+	ctx, cancel := tx.db.getTimeoutCtx()
+	rows, err := tx.tx.QueryContext(ctx, query, args...)
+	if err != nil {
+		cancel()
+
+		return nil, func() {}, err
+	}
+
+	return rows, cancel, nil
+}
+
 // Exec executes a Exec call with a timeout context.
 func (tx *readWriteTx) Exec(query string, args ...interface{}) (sql.Result,
 	error) {

kvdb/postgres_test.go

@@ -84,7 +84,35 @@ func TestPostgres(t *testing.T) {
 		},
 		{
 			name: "bucket for each",
-			test: testBucketForEach,
+			test: func(t *testing.T, db walletdb.DB) {
+				testBucketIterator(t, db, func(bucket walletdb.ReadWriteBucket,
+					callback func(key, val []byte) error) error {
+
+					return bucket.ForEach(callback)
+				})
+			},
+			expectedDb: m{
+				"test_kv": []m{
+					{"id": int64(1), "key": "apple", "parent_id": nil, "sequence": nil, "value": nil},
+					{"id": int64(2), "key": "banana", "parent_id": int64(1), "sequence": nil, "value": nil},
+					{"id": int64(3), "key": "key1", "parent_id": int64(1), "sequence": nil, "value": "val1"},
+					{"id": int64(4), "key": "key1", "parent_id": int64(2), "sequence": nil, "value": "val1"},
+					{"id": int64(5), "key": "key2", "parent_id": int64(1), "sequence": nil, "value": "val2"},
+					{"id": int64(6), "key": "key2", "parent_id": int64(2), "sequence": nil, "value": "val2"},
+					{"id": int64(7), "key": "key3", "parent_id": int64(1), "sequence": nil, "value": "val3"},
+					{"id": int64(8), "key": "key3", "parent_id": int64(2), "sequence": nil, "value": "val3"},
+				},
+			},
+		},
+		{
+			name: "bucket for all",
+			test: func(t *testing.T, db walletdb.DB) {
+				testBucketIterator(t, db, func(bucket walletdb.ReadWriteBucket,
+					callback func(key, val []byte) error) error {
+
+					return ForAll(bucket, callback)
+				})
+			},
 			expectedDb: m{
 				"test_kv": []m{
 					{"id": int64(1), "key": "apple", "parent_id": nil, "sequence": nil, "value": nil},

kvdb/readwrite_bucket_test.go

@@ -159,7 +159,20 @@ func testBucketDeletion(t *testing.T, db walletdb.DB) {
 	require.Nil(t, err)
 }
 
+type bucketIterator = func(walletdb.ReadWriteBucket,
+	func(key, val []byte) error) error
+
 func testBucketForEach(t *testing.T, db walletdb.DB) {
+	testBucketIterator(t, db, func(bucket walletdb.ReadWriteBucket,
+		callback func(key, val []byte) error) error {
+
+		return bucket.ForEach(callback)
+	})
+}
+
+func testBucketIterator(t *testing.T, db walletdb.DB,
+	iterator bucketIterator) {
+
 	err := Update(db, func(tx walletdb.ReadWriteTx) error {
 		// "apple"
 		apple, err := tx.CreateTopLevelBucket([]byte("apple"))
@@ -199,7 +212,7 @@ func testBucketForEach(t *testing.T, db walletdb.DB) {
 		require.Equal(t, expected, got)
 
 		got = make(map[string]string)
-		err = banana.ForEach(func(key, val []byte) error {
+		err = iterator(banana, func(key, val []byte) error {
 			got[string(key)] = string(val)
 			return nil
 		})

routing/router.go

@@ -157,11 +157,6 @@ type ChannelGraphSource interface {
 
 	// ForEachNode is used to iterate over every node in the known graph.
 	ForEachNode(func(node *channeldb.LightningNode) error) error
-
-	// ForEachChannel is used to iterate over every channel in the known
-	// graph.
-	ForEachChannel(func(chanInfo *channeldb.ChannelEdgeInfo,
-		e1, e2 *channeldb.ChannelEdgePolicy) error) error
 }
 
 // PaymentAttemptDispatcher is used by the router to send payment attempts onto
@@ -2541,16 +2536,6 @@ func (r *ChannelRouter) ForAllOutgoingChannels(cb func(kvdb.RTx,
 	})
 }
 
-// ForEachChannel is used to iterate over every known edge (channel) within our
-// view of the channel graph.
-//
-// NOTE: This method is part of the ChannelGraphSource interface.
-func (r *ChannelRouter) ForEachChannel(cb func(chanInfo *channeldb.ChannelEdgeInfo,
-	e1, e2 *channeldb.ChannelEdgePolicy) error) error {
-
-	return r.cfg.Graph.ForEachChannel(cb)
-}
-
 // AddProof updates the channel edge info with proof which is needed to
 // properly announce the edge to the rest of the network.
 //