/
sessionwants.go
193 lines (165 loc) · 5.09 KB
/
sessionwants.go
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package session
import (
"fmt"
"math/rand"
"time"
cid "github.com/ipfs/go-cid"
)
// liveWantsOrder and liveWants will get out of sync as blocks are received.
// This constant is the maximum amount to allow them to be out of sync before
// cleaning up the ordering array.
const liveWantsOrderGCLimit = 32
// sessionWants keeps track of which cids are waiting to be sent out, and which
// peers are "live" - ie, we've sent a request but haven't received a block yet
type sessionWants struct {
// The wants that have not yet been sent out
toFetch *cidQueue
// Wants that have been sent but have not received a response
liveWants map[cid.Cid]time.Time
// The order in which wants were requested
liveWantsOrder []cid.Cid
// The maximum number of want-haves to send in a broadcast
broadcastLimit int
}
func newSessionWants(broadcastLimit int) sessionWants {
return sessionWants{
toFetch: newCidQueue(),
liveWants: make(map[cid.Cid]time.Time),
broadcastLimit: broadcastLimit,
}
}
func (sw *sessionWants) String() string {
return fmt.Sprintf("%d pending / %d live", sw.toFetch.Len(), len(sw.liveWants))
}
// BlocksRequested is called when the client makes a request for blocks
func (sw *sessionWants) BlocksRequested(newWants []cid.Cid) {
for _, k := range newWants {
sw.toFetch.Push(k)
}
}
// GetNextWants is called when the session has not yet discovered peers with
// the blocks that it wants. It moves as many CIDs from the fetch queue to
// the live wants queue as possible (given the broadcast limit).
// Returns the newly live wants.
func (sw *sessionWants) GetNextWants() []cid.Cid {
now := time.Now()
// Move CIDs from fetch queue to the live wants queue (up to the broadcast
// limit)
currentLiveCount := len(sw.liveWants)
toAdd := sw.broadcastLimit - currentLiveCount
var live []cid.Cid
for ; toAdd > 0 && sw.toFetch.Len() > 0; toAdd-- {
c := sw.toFetch.Pop()
live = append(live, c)
sw.liveWantsOrder = append(sw.liveWantsOrder, c)
sw.liveWants[c] = now
}
return live
}
// WantsSent is called when wants are sent to a peer
func (sw *sessionWants) WantsSent(ks []cid.Cid) {
now := time.Now()
for _, c := range ks {
if _, ok := sw.liveWants[c]; !ok && sw.toFetch.Has(c) {
sw.toFetch.Remove(c)
sw.liveWantsOrder = append(sw.liveWantsOrder, c)
sw.liveWants[c] = now
}
}
}
// BlocksReceived removes received block CIDs from the live wants list and
// measures latency. It returns the CIDs of blocks that were actually
// wanted (as opposed to duplicates) and the total latency for all incoming blocks.
func (sw *sessionWants) BlocksReceived(ks []cid.Cid) ([]cid.Cid, time.Duration) {
wanted := make([]cid.Cid, 0, len(ks))
totalLatency := time.Duration(0)
if len(ks) == 0 {
return wanted, totalLatency
}
// Filter for blocks that were actually wanted (as opposed to duplicates)
now := time.Now()
for _, c := range ks {
if sw.isWanted(c) {
wanted = append(wanted, c)
// Measure latency
sentAt, ok := sw.liveWants[c]
if ok && !sentAt.IsZero() {
totalLatency += now.Sub(sentAt)
}
// Remove the CID from the live wants / toFetch queue
delete(sw.liveWants, c)
sw.toFetch.Remove(c)
}
}
// If the live wants ordering array is a long way out of sync with the
// live wants map, clean up the ordering array
if len(sw.liveWantsOrder)-len(sw.liveWants) > liveWantsOrderGCLimit {
cleaned := sw.liveWantsOrder[:0]
for _, c := range sw.liveWantsOrder {
if _, ok := sw.liveWants[c]; ok {
cleaned = append(cleaned, c)
}
}
sw.liveWantsOrder = cleaned
}
return wanted, totalLatency
}
// PrepareBroadcast saves the current time for each live want and returns the
// live want CIDs up to the broadcast limit.
func (sw *sessionWants) PrepareBroadcast() []cid.Cid {
now := time.Now()
live := make([]cid.Cid, 0, len(sw.liveWants))
for _, c := range sw.liveWantsOrder {
if _, ok := sw.liveWants[c]; ok {
// No response was received for the want, so reset the sent time
// to now as we're about to broadcast
sw.liveWants[c] = now
live = append(live, c)
if len(live) == sw.broadcastLimit {
break
}
}
}
return live
}
// CancelPending removes the given CIDs from the fetch queue.
func (sw *sessionWants) CancelPending(keys []cid.Cid) {
for _, k := range keys {
sw.toFetch.Remove(k)
}
}
// LiveWants returns a list of live wants
func (sw *sessionWants) LiveWants() []cid.Cid {
live := make([]cid.Cid, 0, len(sw.liveWants))
for c := range sw.liveWants {
live = append(live, c)
}
return live
}
// RandomLiveWant returns a randomly selected live want
func (sw *sessionWants) RandomLiveWant() cid.Cid {
if len(sw.liveWants) == 0 {
return cid.Cid{}
}
// picking a random live want
i := rand.Intn(len(sw.liveWants))
for k := range sw.liveWants {
if i == 0 {
return k
}
i--
}
return cid.Cid{}
}
// Has live wants indicates if there are any live wants
func (sw *sessionWants) HasLiveWants() bool {
return len(sw.liveWants) > 0
}
// Indicates whether the want is in either of the fetch or live queues
func (sw *sessionWants) isWanted(c cid.Cid) bool {
_, ok := sw.liveWants[c]
if !ok {
ok = sw.toFetch.Has(c)
}
return ok
}