From 09baad48e3ec3a013eba2de58087c8c7d8c3a7ab Mon Sep 17 00:00:00 2001
From: Arceliar <Arceliar@users.noreply.github.com>
Date: Sat, 2 Jun 2018 14:57:06 -0500
Subject: [PATCH] retry failed iterative searches, possibly becoming parallel
 if things are just slow, and keep track of / skip nodes that were already
 visited in the search

---
 src/yggdrasil/search.go | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/src/yggdrasil/search.go b/src/yggdrasil/search.go
index f7ef3a6c..4aa6c86c 100644
--- a/src/yggdrasil/search.go
+++ b/src/yggdrasil/search.go
@@ -21,12 +21,16 @@ import "time"
 
 //import "fmt"
 
+const search_MAX_SEARCH_SIZE = 16
+const search_RETRY_TIME = time.Second
+
 type searchInfo struct {
 	dest    *NodeID
 	mask    *NodeID
 	time    time.Time
 	packet  []byte
 	toVisit []*dhtInfo
+	visited map[NodeID]bool
 }
 
 type searches struct {
@@ -73,6 +77,9 @@ func (s *searches) addToSearch(sinfo *searchInfo, res *dhtRes) {
 	// Add responses to toVisit if closer to dest than the res node
 	from := dhtInfo{key: res.key, coords: res.coords}
 	for _, info := range res.infos {
+		if sinfo.visited[*info.getNodeID()] {
+			continue
+		}
 		if dht_firstCloserThanThird(info.getNodeID(), &res.dest, from.getNodeID()) {
 			sinfo.toVisit = append(sinfo.toVisit, info)
 		}
@@ -91,14 +98,14 @@ func (s *searches) addToSearch(sinfo *searchInfo, res *dhtRes) {
 		return dht_firstCloserThanThird(sinfo.toVisit[i].getNodeID(), &res.dest, sinfo.toVisit[j].getNodeID())
 	})
 	// Truncate to some maximum size
-	if len(sinfo.toVisit) > 16 {
-		sinfo.toVisit = sinfo.toVisit[:16]
+	if len(sinfo.toVisit) > search_MAX_SEARCH_SIZE {
+		sinfo.toVisit = sinfo.toVisit[:search_MAX_SEARCH_SIZE]
 	}
 }
 
 func (s *searches) doSearchStep(sinfo *searchInfo) {
-	if len(sinfo.toVisit) == 0 || time.Since(sinfo.time) > 6*time.Second {
-		// Dead end or timeout, do cleanup
+	if len(sinfo.toVisit) == 0 {
+		// Dead end, do cleanup
 		delete(s.searches, *sinfo.dest)
 		return
 	} else {
@@ -106,20 +113,36 @@ func (s *searches) doSearchStep(sinfo *searchInfo) {
 		var next *dhtInfo
 		next, sinfo.toVisit = sinfo.toVisit[0], sinfo.toVisit[1:]
 		s.core.dht.ping(next, sinfo.dest)
+		sinfo.visited[*next.getNodeID()] = true
 	}
 }
 
 func (s *searches) continueSearch(sinfo *searchInfo) {
-	if time.Since(sinfo.time) < time.Second {
+	if time.Since(sinfo.time) < search_RETRY_TIME {
 		return
 	}
 	sinfo.time = time.Now()
 	s.doSearchStep(sinfo)
+	// In case the search dies, try to spawn another thread later
+	// Note that this will spawn multiple parallel searches as time passes
+	// Any that die aren't restarted, but a new one will start later
+	retryLater := func() {
+		newSearchInfo := s.searches[*sinfo.dest]
+		if newSearchInfo != sinfo {
+			return
+		}
+		s.continueSearch(sinfo)
+	}
+	go func() {
+		time.Sleep(search_RETRY_TIME)
+		s.core.router.admin <- retryLater
+	}()
 }
 
 func (s *searches) newIterSearch(dest *NodeID, mask *NodeID) *searchInfo {
 	sinfo := s.createSearch(dest, mask)
 	sinfo.toVisit = s.core.dht.lookup(dest, false)
+	sinfo.visited = make(map[NodeID]bool)
 	return sinfo
 }