Store node info timestamp to cache file

Last update isn't updated often for many nodes which makes cache
useless. Instead, we now save the last info retrieval timestamp with
it. The existing cache will be invalidated due to the structure change.

cache.go

@@ -9,7 +9,6 @@ import (
 	"time"
 
 	"github.com/gofrs/flock"
-	"github.com/lightningnetwork/lnd/lnrpc"
 )
 
 func lock() *flock.Flock {
@@ -20,6 +19,14 @@ func (r *regolancer) loadNodeCache(filename string, exp int, doLock bool) error
 	if filename == "" {
 		return nil
 	}
+	defer func() {
+		err := recover()
+		if err == nil {
+			return
+		}
+		log.Printf("Loading failed, cache format might be outdated: %s", err)
+		r.nodeCache = map[string]cachedNodeInfo{}
+	}()
 	if doLock {
 		log.Printf("Loading node cache from %s", filename)
 		l := lock()
@@ -34,10 +41,13 @@ func (r *regolancer) loadNodeCache(filename string, exp int, doLock bool) error
 		return nil
 	}
 	defer f.Close()
-	gob.NewDecoder(f).Decode(&r.nodeCache)
+	err = gob.NewDecoder(f).Decode(&r.nodeCache)
+	if err != nil {
+		return err
+	}
 	for k, v := range r.nodeCache {
-		if time.Since(time.Unix(int64(v.Node.LastUpdate), 0)) >
+		since := time.Since(v.Timestamp)
-			time.Minute*time.Duration(exp) {
+		if since > time.Minute*time.Duration(exp) {
 			delete(r.nodeCache, k)
 		}
 	}
@@ -54,7 +64,7 @@ func (r *regolancer) saveNodeCache(filename string, exp int) error {
 	l.Lock()
 	defer l.Unlock()
 
-	old := regolancer{nodeCache: map[string]*lnrpc.NodeInfo{}}
+	old := regolancer{nodeCache: map[string]cachedNodeInfo{}}
 	err := old.loadNodeCache(filename, exp, false)
 
 	if err != nil {
@@ -62,7 +72,7 @@ func (r *regolancer) saveNodeCache(filename string, exp int) error {
 	}
 	for k, v := range old.nodeCache {
 		if n, ok := r.nodeCache[k]; !ok ||
-			n.Node.LastUpdate < v.Node.LastUpdate {
+			n.Timestamp.Before(v.Timestamp) {
 			r.nodeCache[k] = v
 		}
 	}
@@ -72,6 +82,6 @@ func (r *regolancer) saveNodeCache(filename string, exp int) error {
 		return fmt.Errorf("error creating node cache file: %s", err)
 	}
 	defer f.Close()
-	gob.NewEncoder(f).Encode(r.nodeCache)
+	err = gob.NewEncoder(f).Encode(r.nodeCache)
-	return nil
+	return err
 }

main.go

@@ -57,6 +57,11 @@ type failedRoute struct {
 	expiration  *time.Time
 }
 
+type cachedNodeInfo struct {
+	*lnrpc.NodeInfo
+	Timestamp time.Time
+}
+
 type regolancer struct {
 	lnClient      lnrpc.LightningClient
 	routerClient  routerrpc.RouterClient
@@ -67,7 +72,7 @@ type regolancer struct {
 	toChannels    []*lnrpc.Channel
 	toChannelId   map[uint64]struct{}
 	channelPairs  map[string][2]*lnrpc.Channel
-	nodeCache     map[string]*lnrpc.NodeInfo
+	nodeCache     map[string]cachedNodeInfo
 	chanCache     map[uint64]*lnrpc.ChannelEdge
 	failureCache  map[string]failedRoute
 	excludeIn     map[uint64]struct{}
@@ -237,7 +242,7 @@ func main() {
 		log.Fatal(err)
 	}
 	r := regolancer{
-		nodeCache:    map[string]*lnrpc.NodeInfo{},
+		nodeCache:    map[string]cachedNodeInfo{},
 		chanCache:    map[uint64]*lnrpc.ChannelEdge{},
 		channelPairs: map[string][2]*lnrpc.Channel{},
 		failureCache: map[string]failedRoute{},

routes.go

@@ -118,11 +118,14 @@ func (r *regolancer) getRoutes(ctx context.Context, from, to uint64, amtMsat int
 
 func (r *regolancer) getNodeInfo(ctx context.Context, pk string) (*lnrpc.NodeInfo, error) {
 	if nodeInfo, ok := r.nodeCache[pk]; ok {
-		return nodeInfo, nil
+		return nodeInfo.NodeInfo, nil
 	}
 	nodeInfo, err := r.lnClient.GetNodeInfo(ctx, &lnrpc.NodeInfoRequest{PubKey: pk})
 	if err == nil {
-		r.nodeCache[pk] = nodeInfo
+		r.nodeCache[pk] = cachedNodeInfo{
+			NodeInfo:  nodeInfo,
+			Timestamp: time.Now(),
+		}
 	}
 	return nodeInfo, err
 }