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comments and minor cleanup

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This commit is contained in:
Arceliar 2018-11-09 23:02:38 -06:00
parent a008b42f99
commit 15d5b3f82c
2 changed files with 20 additions and 35 deletions
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51
src/yggdrasil/dht.go
View File

@ -1,19 +1,9 @@
package yggdrasil package yggdrasil
// TODO signal to predecessor when we replace them? // A chord-like Distributed Hash Table (DHT).
// Sending a ping with an extra 0 at the end of our coords should be enough to reset our throttle in their table // Used to look up coords given a NodeID and bitmask (taken from an IPv6 address).
// That should encorage them to ping us again sooner, and then we can reply with new info // Keeps track of immediate successor, predecessor, and all peers.
// Maybe remember old predecessor and check this during maintenance? // Also keeps track of other nodes if they're closer in tree space than all other known nodes encountered when heading in either direction to that point, under the hypothesis that, for the kinds of networks we care about, this should probabilistically include the node needed to keep lookups to near O(logn) steps.
// TODO make sure that, if your peer is your successor or predecessor, you still bother to ping them and ask for better nodes
// Basically, don't automatically reset the dhtInfo.recv to time.Now() whenever updating them from the outside
// But *do* set it to something that won't instantly time them out or make them get pingspammed?
// Could set throttle to 0, but that's imperfect at best... pingspam
// TODO? cache all nodes we ping (from e.g. searches), not just the important ones
// But only send maintenance pings to the important ones
// TODO reoptimize search stuff (size, timeouts, etc) to play nicer with DHT churn
import ( import (
"sort" "sort"
@ -70,7 +60,7 @@ type dht struct {
imp []*dhtInfo imp []*dhtInfo
} }
// Initializes the DHT // Initializes the DHT.
func (t *dht) init(c *Core) { func (t *dht) init(c *Core) {
t.core = c t.core = c
t.nodeID = *t.core.GetNodeID() t.nodeID = *t.core.GetNodeID()
@ -78,23 +68,19 @@ func (t *dht) init(c *Core) {
t.reset() t.reset()
} }
// Resets the DHT in response to coord changes // Resets the DHT in response to coord changes.
// This empties all info from the DHT and drops outstanding requests // This empties all info from the DHT and drops outstanding requests.
func (t *dht) reset() { func (t *dht) reset() {
t.reqs = make(map[boxPubKey]map[NodeID]time.Time) t.reqs = make(map[boxPubKey]map[NodeID]time.Time)
t.table = make(map[NodeID]*dhtInfo) t.table = make(map[NodeID]*dhtInfo)
t.imp = nil t.imp = nil
} }
// Does a DHT lookup and returns up to dht_lookup_size results // Does a DHT lookup and returns up to dht_lookup_size results.
func (t *dht) lookup(nodeID *NodeID, everything bool) []*dhtInfo { func (t *dht) lookup(nodeID *NodeID, everything bool) []*dhtInfo {
results := make([]*dhtInfo, 0, len(t.table)) results := make([]*dhtInfo, 0, len(t.table))
//imp := t.getImportant()
for _, info := range t.table { for _, info := range t.table {
results = append(results, info) results = append(results, info)
//if t.isImportant(info, imp) {
// results = append(results, info)
//}
} }
sort.SliceStable(results, func(i, j int) bool { sort.SliceStable(results, func(i, j int) bool {
return dht_ordered(nodeID, results[i].getNodeID(), results[j].getNodeID()) return dht_ordered(nodeID, results[i].getNodeID(), results[j].getNodeID())
@ -105,7 +91,7 @@ func (t *dht) lookup(nodeID *NodeID, everything bool) []*dhtInfo {
return results return results
} }
// Insert into table, preserving the time we last sent a packet if the node was already in the table, otherwise setting that time to now // Insert into table, preserving the time we last sent a packet if the node was already in the table, otherwise setting that time to now.
func (t *dht) insert(info *dhtInfo) { func (t *dht) insert(info *dhtInfo) {
if *info.getNodeID() == t.nodeID { if *info.getNodeID() == t.nodeID {
// This shouldn't happen, but don't add it if it does // This shouldn't happen, but don't add it if it does
@ -133,8 +119,7 @@ func (t *dht) insert(info *dhtInfo) {
t.table[*info.getNodeID()] = info t.table[*info.getNodeID()] = info
} }
// Return true if first/second/third are (partially) ordered correctly // Return true if first/second/third are (partially) ordered correctly.
// FIXME? maybe total ordering makes more sense
func dht_ordered(first, second, third *NodeID) bool { func dht_ordered(first, second, third *NodeID) bool {
lessOrEqual := func(first, second *NodeID) bool { lessOrEqual := func(first, second *NodeID) bool {
for idx := 0; idx < NodeIDLen; idx++ { for idx := 0; idx < NodeIDLen; idx++ {
@ -182,8 +167,7 @@ func (t *dht) handleReq(req *dhtReq) {
key: req.Key, key: req.Key,
coords: req.Coords, coords: req.Coords,
} }
imp := t.getImportant() if _, isIn := t.table[*info.getNodeID()]; !isIn && t.isImportant(&info) {
if _, isIn := t.table[*info.getNodeID()]; !isIn && t.isImportant(&info, imp) {
t.insert(&info) t.insert(&info)
} }
} }
@ -222,8 +206,7 @@ func (t *dht) handleRes(res *dhtRes) {
key: res.Key, key: res.Key,
coords: res.Coords, coords: res.Coords,
} }
imp := t.getImportant() if t.isImportant(&rinfo) {
if t.isImportant(&rinfo, imp) {
t.insert(&rinfo) t.insert(&rinfo)
} }
for _, info := range res.Infos { for _, info := range res.Infos {
@ -234,11 +217,10 @@ func (t *dht) handleRes(res *dhtRes) {
// TODO? don't skip if coords are different? // TODO? don't skip if coords are different?
continue continue
} }
if t.isImportant(info, imp) { if t.isImportant(info) {
t.ping(info, nil) t.ping(info, nil)
} }
} }
// TODO add everyting else to a rumor mill for later use? (when/how?)
} }
// Sends a lookup request to the specified node. // Sends a lookup request to the specified node.
@ -267,6 +249,7 @@ func (t *dht) sendReq(req *dhtReq, dest *dhtInfo) {
reqsToDest[req.Dest] = time.Now() reqsToDest[req.Dest] = time.Now()
} }
// Sends a lookup to this info, looking for the target.
func (t *dht) ping(info *dhtInfo, target *NodeID) { func (t *dht) ping(info *dhtInfo, target *NodeID) {
// Creates a req for the node at dhtInfo, asking them about the target (if one is given) or themself (if no target is given) // Creates a req for the node at dhtInfo, asking them about the target (if one is given) or themself (if no target is given)
if target == nil { if target == nil {
@ -282,6 +265,7 @@ func (t *dht) ping(info *dhtInfo, target *NodeID) {
t.sendReq(&req, info) t.sendReq(&req, info)
} }
// Periodic maintenance work to keep important DHT nodes alive.
func (t *dht) doMaintenance() { func (t *dht) doMaintenance() {
now := time.Now() now := time.Now()
for infoID, info := range t.table { for infoID, info := range t.table {
@ -302,6 +286,7 @@ func (t *dht) doMaintenance() {
} }
} }
// Gets a list of important nodes, used by isImportant.
func (t *dht) getImportant() []*dhtInfo { func (t *dht) getImportant() []*dhtInfo {
if t.imp == nil { if t.imp == nil {
// Get a list of all known nodes // Get a list of all known nodes
@ -343,7 +328,9 @@ func (t *dht) getImportant() []*dhtInfo {
return t.imp return t.imp
} }
func (t *dht) isImportant(ninfo *dhtInfo, important []*dhtInfo) bool { // Returns true if this is a node we need to keep track of for the DHT to work.
func (t *dht) isImportant(ninfo *dhtInfo) bool {
important := t.getImportant()
// Check if ninfo is of equal or greater importance to what we already know // Check if ninfo is of equal or greater importance to what we already know
loc := t.core.switchTable.getLocator() loc := t.core.switchTable.getLocator()
ndist := uint64(loc.dist(ninfo.coords)) ndist := uint64(loc.dist(ninfo.coords))

4
src/yggdrasil/search.go
View File

@ -113,13 +113,11 @@ func (s *searches) addToSearch(sinfo *searchInfo, res *dhtRes) {
// Sort // Sort
sort.SliceStable(sinfo.toVisit, func(i, j int) bool { sort.SliceStable(sinfo.toVisit, func(i, j int) bool {
// Should return true if i is closer to the destination than j // Should return true if i is closer to the destination than j
// FIXME for some reason it works better backwards, why?!
//return dht_ordered(sinfo.toVisit[j].getNodeID(), sinfo.toVisit[i].getNodeID(), &res.Dest)
return dht_ordered(&res.Dest, sinfo.toVisit[i].getNodeID(), sinfo.toVisit[j].getNodeID()) return dht_ordered(&res.Dest, sinfo.toVisit[i].getNodeID(), sinfo.toVisit[j].getNodeID())
}) })
// Truncate to some maximum size // Truncate to some maximum size
if len(sinfo.toVisit) > search_MAX_SEARCH_SIZE { if len(sinfo.toVisit) > search_MAX_SEARCH_SIZE {
sinfo.toVisit = sinfo.toVisit[:search_MAX_SEARCH_SIZE] //FIXME debug sinfo.toVisit = sinfo.toVisit[:search_MAX_SEARCH_SIZE]
} }
} }