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pool.go
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pool.go
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package peers
import (
"context"
"sync"
"time"
"github.com/libp2p/go-libp2p/core/peer"
)
const defaultCleanupThreshold = 2
// pool stores peers and provides methods for simple round-robin access.
type pool struct {
m sync.RWMutex
peersList []peer.ID
statuses map[peer.ID]status
cooldown *timedQueue
activeCount int
nextIdx int
hasPeer bool
hasPeerCh chan struct{}
cleanupThreshold int
}
type status int
const (
active status = iota
cooldown
removed
)
// newPool returns new empty pool.
func newPool(peerCooldownTime time.Duration) *pool {
p := &pool{
peersList: make([]peer.ID, 0),
statuses: make(map[peer.ID]status),
hasPeerCh: make(chan struct{}),
cleanupThreshold: defaultCleanupThreshold,
}
p.cooldown = newTimedQueue(peerCooldownTime, p.afterCooldown)
return p
}
// tryGet returns peer along with bool flag indicating success of operation.
func (p *pool) tryGet() (peer.ID, bool) {
p.m.Lock()
defer p.m.Unlock()
if p.activeCount == 0 {
return "", false
}
// if pointer is out of range, point to first element
if p.nextIdx > len(p.peersList)-1 {
p.nextIdx = 0
}
start := p.nextIdx
for {
peerID := p.peersList[p.nextIdx]
p.nextIdx++
if p.nextIdx == len(p.peersList) {
p.nextIdx = 0
}
if p.statuses[peerID] == active {
return peerID, true
}
// full circle passed
if p.nextIdx == start {
return "", false
}
}
}
// next sends a peer to the returned channel when it becomes available.
func (p *pool) next(ctx context.Context) <-chan peer.ID {
peerCh := make(chan peer.ID, 1)
go func() {
for {
if peerID, ok := p.tryGet(); ok {
peerCh <- peerID
return
}
p.m.RLock()
hasPeerCh := p.hasPeerCh
p.m.RUnlock()
select {
case <-hasPeerCh:
case <-ctx.Done():
return
}
}
}()
return peerCh
}
func (p *pool) add(peers ...peer.ID) {
p.m.Lock()
defer p.m.Unlock()
for _, peerID := range peers {
status, ok := p.statuses[peerID]
if ok && status != removed {
continue
}
if !ok {
p.peersList = append(p.peersList, peerID)
}
p.statuses[peerID] = active
p.activeCount++
}
p.checkHasPeers()
}
func (p *pool) remove(peers ...peer.ID) {
p.m.Lock()
defer p.m.Unlock()
for _, peerID := range peers {
if status, ok := p.statuses[peerID]; ok && status != removed {
p.statuses[peerID] = removed
if status == active {
p.activeCount--
}
}
}
// do cleanup if too much garbage
if len(p.peersList) >= p.activeCount+p.cleanupThreshold {
p.cleanup()
}
p.checkHasPeers()
}
func (p *pool) has(peer peer.ID) bool {
p.m.RLock()
defer p.m.RUnlock()
status, ok := p.statuses[peer]
return ok && status != removed
}
func (p *pool) peers() []peer.ID {
p.m.RLock()
defer p.m.RUnlock()
peers := make([]peer.ID, 0, len(p.peersList))
for peer, status := range p.statuses {
if status != removed {
peers = append(peers, peer)
}
}
return peers
}
// cleanup will reduce memory footprint of pool.
func (p *pool) cleanup() {
newList := make([]peer.ID, 0, p.activeCount)
for _, peerID := range p.peersList {
status := p.statuses[peerID]
switch status {
case active, cooldown:
newList = append(newList, peerID)
case removed:
delete(p.statuses, peerID)
}
}
p.peersList = newList
}
func (p *pool) putOnCooldown(peerID peer.ID) {
p.m.Lock()
defer p.m.Unlock()
if status, ok := p.statuses[peerID]; ok && status == active {
p.cooldown.push(peerID)
p.statuses[peerID] = cooldown
p.activeCount--
p.checkHasPeers()
}
}
func (p *pool) afterCooldown(peerID peer.ID) {
p.m.Lock()
defer p.m.Unlock()
// item could have been already removed by the time afterCooldown is called
if status, ok := p.statuses[peerID]; !ok || status != cooldown {
return
}
p.statuses[peerID] = active
p.activeCount++
p.checkHasPeers()
}
// checkHasPeers will check and indicate if there are peers in the pool.
func (p *pool) checkHasPeers() {
if p.activeCount > 0 && !p.hasPeer {
p.hasPeer = true
close(p.hasPeerCh)
return
}
if p.activeCount == 0 && p.hasPeer {
p.hasPeerCh = make(chan struct{})
p.hasPeer = false
}
}
func (p *pool) len() int {
p.m.RLock()
defer p.m.RUnlock()
return p.activeCount
}