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p2p/discover: avoid dropping unverified nodes when table is almost empty (#21396)

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This change improves discovery behavior in small networks. Very small
networks would often fail to bootstrap because all member nodes were
dropping table content due to findnode failure. The check is now changed
to avoid dropping nodes on findnode failure when their bucket is almost
empty. It also relaxes the liveness check requirement for FINDNODE/v4
response nodes, returning unverified nodes as results when there aren't
any verified nodes yet.

The "findnode failed" log now reports whether the node was dropped
instead of the number of results. The value of the "results" was
always zero by definition.

Co-authored-by: Felix Lange <fjl@twurst.com>
This commit is contained in:
timcooijmans
2020-08-24 14:42:39 +02:00
committed by GitHub
parent bdde616f23
commit 7b5107b73f
5 changed files with 140 additions and 25 deletions
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13
p2p/discover/lookup.go
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@ -104,9 +104,7 @@ func (it *lookup) startQueries() bool {
// The first query returns nodes from the local table.
if it.queries == -1 {
it.tab.mutex.Lock()
closest := it.tab.closest(it.result.target, bucketSize, false)
it.tab.mutex.Unlock()
closest := it.tab.findnodeByID(it.result.target, bucketSize, false)
// Avoid finishing the lookup too quickly if table is empty. It'd be better to wait
// for the table to fill in this case, but there is no good mechanism for that
// yet.
@ -150,11 +148,14 @@ func (it *lookup) query(n *node, reply chan<- []*node) {
} else if len(r) == 0 {
fails++
it.tab.db.UpdateFindFails(n.ID(), n.IP(), fails)
it.tab.log.Trace("Findnode failed", "id", n.ID(), "failcount", fails, "results", len(r), "err", err)
if fails >= maxFindnodeFailures {
it.tab.log.Trace("Too many findnode failures, dropping", "id", n.ID(), "failcount", fails)
// Remove the node from the local table if it fails to return anything useful too
// many times, but only if there are enough other nodes in the bucket.
dropped := false
if fails >= maxFindnodeFailures && it.tab.bucketLen(n.ID()) >= bucketSize/2 {
dropped = true
it.tab.delete(n)
}
it.tab.log.Trace("FINDNODE failed", "id", n.ID(), "failcount", fails, "dropped", dropped, "err", err)
} else if fails > 0 {
// Reset failure counter because it counts _consecutive_ failures.
it.tab.db.UpdateFindFails(n.ID(), n.IP(), 0)