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fix: use accurate bucket logic
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This reverts an optimization where we fudged the closer peers when returning
responses to users when we were within a power of two to the target.
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@Stebalien
Stebalien committed Mar 27, 2020
1 parent 6f18d79 commit 08f2efa
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Showing 4 changed files with 27 additions and 101 deletions.
2 changes: 1 addition & 1 deletion go.mod
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ module github.com/libp2p/go-libp2p-kbucket

require (
github.com/ipfs/go-ipfs-util v0.0.1
github.com/ipfs/go-log v0.0.1
github.com/ipfs/go-log v1.0.2
github.com/jbenet/goprocess v0.1.3
github.com/libp2p/go-libp2p-core v0.5.0
github.com/libp2p/go-libp2p-peerstore v0.2.0
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6 changes: 6 additions & 0 deletions go.sum
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Expand Up @@ -82,7 +82,9 @@ github.com/ipfs/go-ipfs-util v0.0.1 h1:Wz9bL2wB2YBJqggkA4dD7oSmqB4cAnpNbGrlHJulv
github.com/ipfs/go-ipfs-util v0.0.1/go.mod h1:spsl5z8KUnrve+73pOhSVZND1SIxPW5RyBCNzQxlJBc=
github.com/ipfs/go-log v0.0.1 h1:9XTUN/rW64BCG1YhPK9Hoy3q8nr4gOmHHBpgFdfw6Lc=
github.com/ipfs/go-log v0.0.1/go.mod h1:kL1d2/hzSpI0thNYjiKfjanbVNU+IIGA/WnNESY9leM=
github.com/ipfs/go-log v1.0.2 h1:s19ZwJxH8rPWzypjcDpqPLIyV7BnbLqvpli3iZoqYK0=
github.com/ipfs/go-log v1.0.2/go.mod h1:1MNjMxe0u6xvJZgeqbJ8vdo2TKaGwZ1a0Bpza+sr2Sk=
github.com/ipfs/go-log/v2 v2.0.2 h1:xguurydRdfKMJjKyxNXNU8lYP0VZH1NUwJRwUorjuEw=
github.com/ipfs/go-log/v2 v2.0.2/go.mod h1:O7P1lJt27vWHhOwQmcFEvlmo49ry2VY2+JfBWFaa9+0=
github.com/jbenet/go-cienv v0.1.0/go.mod h1:TqNnHUmJgXau0nCzC7kXWeotg3J9W34CUv5Djy1+FlA=
github.com/jbenet/goprocess v0.0.0-20160826012719-b497e2f366b8/go.mod h1:Ly/wlsjFq/qrU3Rar62tu1gASgGw6chQbSh/XgIIXCY=
Expand Down Expand Up @@ -195,6 +197,7 @@ github.com/onsi/ginkgo v1.7.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+W
github.com/onsi/gomega v1.4.3/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1CpauHY=
github.com/opentracing/opentracing-go v1.0.2 h1:3jA2P6O1F9UOrWVpwrIo17pu01KWvNWg4X946/Y5Zwg=
github.com/opentracing/opentracing-go v1.0.2/go.mod h1:UkNAQd3GIcIGf0SeVgPpRdFStlNbqXla1AfSYxPUl2o=
github.com/opentracing/opentracing-go v1.1.0 h1:pWlfV3Bxv7k65HYwkikxat0+s3pV4bsqf19k25Ur8rU=
github.com/opentracing/opentracing-go v1.1.0/go.mod h1:UkNAQd3GIcIGf0SeVgPpRdFStlNbqXla1AfSYxPUl2o=
github.com/patrickmn/go-cache v2.1.0+incompatible h1:HRMgzkcYKYpi3C8ajMPV8OFXaaRUnok+kx1WdO15EQc=
github.com/patrickmn/go-cache v2.1.0+incompatible/go.mod h1:3Qf8kWWT7OJRJbdiICTKqZju1ZixQ/KpMGzzAfe6+WQ=
Expand Down Expand Up @@ -243,8 +246,11 @@ github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:
go.opencensus.io v0.22.1/go.mod h1:Ap50jQcDJrx6rB6VgeeFPtuPIf3wMRvRfrfYDO6+BmA=
go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
go.opencensus.io v0.22.3/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
go.uber.org/atomic v1.4.0 h1:cxzIVoETapQEqDhQu3QfnvXAV4AlzcvUCxkVUFw3+EU=
go.uber.org/atomic v1.4.0/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
go.uber.org/multierr v1.1.0 h1:HoEmRHQPVSqub6w2z2d2EOVs2fjyFRGyofhKuyDq0QI=
go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
go.uber.org/zap v1.10.0 h1:ORx85nbTijNz8ljznvCMR1ZBIPKFn3jQrag10X2AsuM=
go.uber.org/zap v1.10.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
golang.org/x/crypto v0.0.0-20170930174604-9419663f5a44/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
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20 changes: 10 additions & 10 deletions table.go
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Original file line number Diff line number Diff line change
Expand Up @@ -415,18 +415,18 @@ func (rt *RoutingTable) NearestPeers(id ID, count int) []peer.ID {
// Add peers from the target bucket (cpl+1 shared bits).
pds.appendPeersFromList(rt.buckets[cpl].list)

// If we're short, add peers from buckets to the right until we have
// enough. All buckets to the right share exactly cpl bits (as opposed
// to the cpl+1 bits shared by the peers in the cpl bucket).
// If we're short, add peers from all buckets to the right. All buckets
// to the right share exactly cpl bits (as opposed to the cpl+1 bits
// shared by the peers in the cpl bucket).
//
// Unfortunately, to be completely correct, we can't just take from
// buckets until we have enough peers because peers because _all_ of
// these peers will be ~2**(256-cpl) from us.
//
// However, we're going to do that anyways as it's "good enough"
// This is, unfortunately, less efficient than we'd like. We will switch
// to a trie implementation eventually which will allow us to find the
// closest N peers to any target key.

for i := cpl + 1; i < len(rt.buckets) && pds.Len() < count; i++ {
pds.appendPeersFromList(rt.buckets[i].list)
if pds.Len() < count {
for i := cpl + 1; i < len(rt.buckets); i++ {
pds.appendPeersFromList(rt.buckets[i].list)
}
}

// If we're still short, add in buckets that share _fewer_ bits. We can
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100 changes: 10 additions & 90 deletions table_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -409,124 +409,44 @@ func TestTableFindMultiple(t *testing.T) {
}
}

func assertSortedPeerIdsEqual(t *testing.T, a, b []peer.ID) {
t.Helper()
if len(a) != len(b) {
t.Fatal("slices aren't the same length")
}
for i, p := range a {
if p != b[i] {
t.Fatalf("unexpected peer %d", i)
}
}
}

func TestTableFindMultipleBuckets(t *testing.T) {
t.Parallel()

local := test.RandPeerIDFatal(t)
localID := ConvertPeerID(local)
m := pstore.NewMetrics()

rt, err := NewRoutingTable(5, localID, time.Hour, m, PeerValidationFnc(PeerAlwaysValidFnc))
require.NoError(t, err)
rt, err := NewRoutingTable(5, ConvertPeerID(local), time.Hour, m, PeerValidationFnc(PeerAlwaysValidFnc))
if err != nil {
t.Fatal(err)
}

peers := make([]peer.ID, 100)
for i := 0; i < 100; i++ {
peers[i] = test.RandPeerIDFatal(t)
rt.HandlePeerAlive(peers[i])
}

targetID := ConvertPeerID(peers[2])

closest := SortClosestPeers(rt.ListPeers(), targetID)
targetCpl := CommonPrefixLen(localID, targetID)

// split the peers into closer, same, and further from the key (than us).
var (
closer, same, further []peer.ID
)
var i int
for i = 0; i < len(closest); i++ {
cpl := CommonPrefixLen(ConvertPeerID(closest[i]), targetID)
if targetCpl >= cpl {
break
}
}
closer = closest[:i]
closest := SortClosestPeers(rt.ListPeers(), ConvertPeerID(peers[2]))

var j int
for j = len(closer); j < len(closest); j++ {
cpl := CommonPrefixLen(ConvertPeerID(closest[j]), targetID)
if targetCpl > cpl {
break
}
}
same = closest[i:j]
further = closest[j:]
t.Logf("Searching for peer: '%s'", peers[2])

// should be able to find at least 30
// ~31 (logtwo(100) * 5)
found := rt.NearestPeers(targetID, 20)
found := rt.NearestPeers(ConvertPeerID(peers[2]), 20)
if len(found) != 20 {
t.Fatalf("asked for 20 peers, got %d", len(found))
}

// We expect this list to include:
// * All peers with a common prefix length > than the CPL between our key
// and the target (peers in the target bucket).
// * Then a subset of the peers with the _same_ CPL (peers in buckets to the right).
// * Finally, other peers to the left of the target bucket.

// First, handle the peers that are _closer_ than us.
if len(found) <= len(closer) {
// All of our peers are "closer".
assertSortedPeerIdsEqual(t, found, closer[:len(found)])
return
}
assertSortedPeerIdsEqual(t, found[:len(closer)], closer)

// We've worked through closer peers, let's work through peers at the
// "same" distance.
found = found[len(closer):]

// Next, handle peers that are at the same distance as us.
if len(found) <= len(same) {
// Ok, all the remaining peers are at the same distance.
// unfortunately, that means we may be missing peers that are
// technically closer.

// Make sure all remaining peers are _somewhere_ in the "closer" set.
pset := peer.NewSet()
for _, p := range same {
pset.Add(p)
}
for _, p := range found {
if !pset.Contains(p) {
t.Fatalf("unexpected peer %s", p)
}
for i, p := range found {
if p != closest[i] {
t.Fatalf("unexpected peer %d", i)
}
return
}
assertSortedPeerIdsEqual(t, found[:len(same)], same)

// We've worked through closer peers, let's work through the further
// peers.
found = found[len(same):]

// All _further_ peers will be correctly sorted.
assertSortedPeerIdsEqual(t, found, further[:len(found)])

// Finally, test getting _all_ peers. These should be in the correct
// order.

// Ok, now let's try finding all of them.
found = rt.NearestPeers(ConvertPeerID(peers[2]), 100)
if len(found) != rt.Size() {
t.Fatalf("asked for %d peers, got %d", rt.Size(), len(found))
}

// We should get _all_ peers in sorted order.
for i, p := range found {
if p != closest[i] {
t.Fatalf("unexpected peer %d", i)
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