ceremonyclient/go-libp2p/p2p/net/connmgr/connmgr.go

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2023-08-21 03:50:38 +00:00
package connmgr
import (
"context"
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"fmt"
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"sort"
"sync"
"sync/atomic"
"time"
"github.com/benbjohnson/clock"
"github.com/libp2p/go-libp2p/core/connmgr"
"github.com/libp2p/go-libp2p/core/network"
"github.com/libp2p/go-libp2p/core/peer"
logging "github.com/ipfs/go-log/v2"
ma "github.com/multiformats/go-multiaddr"
)
var log = logging.Logger("connmgr")
// BasicConnMgr is a ConnManager that trims connections whenever the count exceeds the
// high watermark. New connections are given a grace period before they're subject
// to trimming. Trims are automatically run on demand, only if the time from the
// previous trim is higher than 10 seconds. Furthermore, trims can be explicitly
// requested through the public interface of this struct (see TrimOpenConns).
//
// See configuration parameters in NewConnManager.
type BasicConnMgr struct {
*decayer
clock clock.Clock
cfg *config
segments segments
plk sync.RWMutex
protected map[peer.ID]map[string]struct{}
// channel-based semaphore that enforces only a single trim is in progress
trimMutex sync.Mutex
connCount atomic.Int32
// to be accessed atomically. This is mimicking the implementation of a sync.Once.
// Take care of correct alignment when modifying this struct.
trimCount uint64
lastTrimMu sync.RWMutex
lastTrim time.Time
refCount sync.WaitGroup
ctx context.Context
cancel func()
unregisterMemoryWatcher func()
}
var (
_ connmgr.ConnManager = (*BasicConnMgr)(nil)
_ connmgr.Decayer = (*BasicConnMgr)(nil)
)
type segment struct {
sync.Mutex
peers map[peer.ID]*peerInfo
}
type segments struct {
// bucketsMu is used to prevent deadlocks when concurrent processes try to
// grab multiple segment locks at once. If you need multiple segment locks
// at once, you should grab this lock first. You may release this lock once
// you have the segment locks.
bucketsMu sync.Mutex
buckets [256]*segment
}
func (ss *segments) get(p peer.ID) *segment {
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return ss.buckets[p[len(p)-1]]
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}
func (ss *segments) countPeers() (count int) {
for _, seg := range ss.buckets {
seg.Lock()
count += len(seg.peers)
seg.Unlock()
}
return count
}
func (s *segment) tagInfoFor(p peer.ID, now time.Time) *peerInfo {
pi, ok := s.peers[p]
if ok {
return pi
}
// create a temporary peer to buffer early tags before the Connected notification arrives.
pi = &peerInfo{
id: p,
firstSeen: now, // this timestamp will be updated when the first Connected notification arrives.
temp: true,
tags: make(map[string]int),
decaying: make(map[*decayingTag]*connmgr.DecayingValue),
conns: make(map[network.Conn]time.Time),
}
s.peers[p] = pi
return pi
}
// NewConnManager creates a new BasicConnMgr with the provided params:
// lo and hi are watermarks governing the number of connections that'll be maintained.
// When the peer count exceeds the 'high watermark', as many peers will be pruned (and
// their connections terminated) until 'low watermark' peers remain.
func NewConnManager(low, hi int, opts ...Option) (*BasicConnMgr, error) {
cfg := &config{
highWater: hi,
lowWater: low,
gracePeriod: time.Minute,
silencePeriod: 10 * time.Second,
clock: clock.New(),
}
for _, o := range opts {
if err := o(cfg); err != nil {
return nil, err
}
}
if cfg.decayer == nil {
// Set the default decayer config.
cfg.decayer = (&DecayerCfg{}).WithDefaults()
}
cm := &BasicConnMgr{
cfg: cfg,
clock: cfg.clock,
protected: make(map[peer.ID]map[string]struct{}, 16),
segments: segments{},
}
for i := range cm.segments.buckets {
cm.segments.buckets[i] = &segment{
peers: make(map[peer.ID]*peerInfo),
}
}
cm.ctx, cm.cancel = context.WithCancel(context.Background())
if cfg.emergencyTrim {
// When we're running low on memory, immediately trigger a trim.
cm.unregisterMemoryWatcher = registerWatchdog(cm.memoryEmergency)
}
decay, _ := NewDecayer(cfg.decayer, cm)
cm.decayer = decay
cm.refCount.Add(1)
go cm.background()
return cm, nil
}
// memoryEmergency is run when we run low on memory.
// Close connections until we right the low watermark.
// We don't pay attention to the silence period or the grace period.
// We try to not kill protected connections, but if that turns out to be necessary, not connection is safe!
func (cm *BasicConnMgr) memoryEmergency() {
connCount := int(cm.connCount.Load())
target := connCount - cm.cfg.lowWater
if target < 0 {
log.Warnw("Low on memory, but we only have a few connections", "num", connCount, "low watermark", cm.cfg.lowWater)
return
} else {
log.Warnf("Low on memory. Closing %d connections.", target)
}
cm.trimMutex.Lock()
defer atomic.AddUint64(&cm.trimCount, 1)
defer cm.trimMutex.Unlock()
// Trim connections without paying attention to the silence period.
for _, c := range cm.getConnsToCloseEmergency(target) {
log.Infow("low on memory. closing conn", "peer", c.RemotePeer())
c.Close()
}
// finally, update the last trim time.
cm.lastTrimMu.Lock()
cm.lastTrim = cm.clock.Now()
cm.lastTrimMu.Unlock()
}
func (cm *BasicConnMgr) Close() error {
cm.cancel()
if cm.unregisterMemoryWatcher != nil {
cm.unregisterMemoryWatcher()
}
if err := cm.decayer.Close(); err != nil {
return err
}
cm.refCount.Wait()
return nil
}
func (cm *BasicConnMgr) Protect(id peer.ID, tag string) {
cm.plk.Lock()
defer cm.plk.Unlock()
tags, ok := cm.protected[id]
if !ok {
tags = make(map[string]struct{}, 2)
cm.protected[id] = tags
}
tags[tag] = struct{}{}
}
func (cm *BasicConnMgr) Unprotect(id peer.ID, tag string) (protected bool) {
cm.plk.Lock()
defer cm.plk.Unlock()
tags, ok := cm.protected[id]
if !ok {
return false
}
if delete(tags, tag); len(tags) == 0 {
delete(cm.protected, id)
return false
}
return true
}
func (cm *BasicConnMgr) IsProtected(id peer.ID, tag string) (protected bool) {
cm.plk.Lock()
defer cm.plk.Unlock()
tags, ok := cm.protected[id]
if !ok {
return false
}
if tag == "" {
return true
}
_, protected = tags[tag]
return protected
}
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func (cm *BasicConnMgr) CheckLimit(systemLimit connmgr.GetConnLimiter) error {
if cm.cfg.highWater > systemLimit.GetConnLimit() {
return fmt.Errorf(
"conn manager high watermark limit: %d, exceeds the system connection limit of: %d",
cm.cfg.highWater,
systemLimit.GetConnLimit(),
)
}
return nil
}
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// peerInfo stores metadata for a given peer.
type peerInfo struct {
id peer.ID
tags map[string]int // value for each tag
decaying map[*decayingTag]*connmgr.DecayingValue // decaying tags
value int // cached sum of all tag values
temp bool // this is a temporary entry holding early tags, and awaiting connections
conns map[network.Conn]time.Time // start time of each connection
firstSeen time.Time // timestamp when we began tracking this peer.
}
type peerInfos []*peerInfo
// SortByValueAndStreams sorts peerInfos by their value and stream count. It
// will sort peers with no streams before those with streams (all else being
// equal). If `sortByMoreStreams` is true it will sort peers with more streams
// before those with fewer streams. This is useful to prioritize freeing memory.
func (p peerInfos) SortByValueAndStreams(segments *segments, sortByMoreStreams bool) {
sort.Slice(p, func(i, j int) bool {
left, right := p[i], p[j]
// Grab this lock so that we can grab both segment locks below without deadlocking.
segments.bucketsMu.Lock()
// lock this to protect from concurrent modifications from connect/disconnect events
leftSegment := segments.get(left.id)
leftSegment.Lock()
defer leftSegment.Unlock()
rightSegment := segments.get(right.id)
if leftSegment != rightSegment {
// These two peers are not in the same segment, lets get the lock
rightSegment.Lock()
defer rightSegment.Unlock()
}
segments.bucketsMu.Unlock()
// temporary peers are preferred for pruning.
if left.temp != right.temp {
return left.temp
}
// otherwise, compare by value.
if left.value != right.value {
return left.value < right.value
}
incomingAndStreams := func(m map[network.Conn]time.Time) (incoming bool, numStreams int) {
for c := range m {
stat := c.Stat()
if stat.Direction == network.DirInbound {
incoming = true
}
numStreams += stat.NumStreams
}
return
}
leftIncoming, leftStreams := incomingAndStreams(left.conns)
rightIncoming, rightStreams := incomingAndStreams(right.conns)
// prefer closing inactive connections (no streams open)
if rightStreams != leftStreams && (leftStreams == 0 || rightStreams == 0) {
return leftStreams < rightStreams
}
// incoming connections are preferred for pruning
if leftIncoming != rightIncoming {
return leftIncoming
}
if sortByMoreStreams {
// prune connections with a higher number of streams first
return rightStreams < leftStreams
} else {
return leftStreams < rightStreams
}
})
}
// TrimOpenConns closes the connections of as many peers as needed to make the peer count
// equal the low watermark. Peers are sorted in ascending order based on their total value,
// pruning those peers with the lowest scores first, as long as they are not within their
// grace period.
//
// This function blocks until a trim is completed. If a trim is underway, a new
// one won't be started, and instead it'll wait until that one is completed before
// returning.
func (cm *BasicConnMgr) TrimOpenConns(_ context.Context) {
// TODO: error return value so we can cleanly signal we are aborting because:
// (a) there's another trim in progress, or (b) the silence period is in effect.
cm.doTrim()
}
func (cm *BasicConnMgr) background() {
defer cm.refCount.Done()
interval := cm.cfg.gracePeriod / 2
if cm.cfg.silencePeriod != 0 {
interval = cm.cfg.silencePeriod
}
ticker := cm.clock.Ticker(interval)
defer ticker.Stop()
for {
select {
case <-ticker.C:
if cm.connCount.Load() < int32(cm.cfg.highWater) {
// Below high water, skip.
continue
}
case <-cm.ctx.Done():
return
}
cm.trim()
}
}
func (cm *BasicConnMgr) doTrim() {
// This logic is mimicking the implementation of sync.Once in the standard library.
count := atomic.LoadUint64(&cm.trimCount)
cm.trimMutex.Lock()
defer cm.trimMutex.Unlock()
if count == atomic.LoadUint64(&cm.trimCount) {
cm.trim()
cm.lastTrimMu.Lock()
cm.lastTrim = cm.clock.Now()
cm.lastTrimMu.Unlock()
atomic.AddUint64(&cm.trimCount, 1)
}
}
// trim starts the trim, if the last trim happened before the configured silence period.
func (cm *BasicConnMgr) trim() {
// do the actual trim.
for _, c := range cm.getConnsToClose() {
log.Debugw("closing conn", "peer", c.RemotePeer())
c.Close()
}
}
func (cm *BasicConnMgr) getConnsToCloseEmergency(target int) []network.Conn {
candidates := make(peerInfos, 0, cm.segments.countPeers())
cm.plk.RLock()
for _, s := range cm.segments.buckets {
s.Lock()
for id, inf := range s.peers {
if _, ok := cm.protected[id]; ok {
// skip over protected peer.
continue
}
candidates = append(candidates, inf)
}
s.Unlock()
}
cm.plk.RUnlock()
// Sort peers according to their value.
candidates.SortByValueAndStreams(&cm.segments, true)
selected := make([]network.Conn, 0, target+10)
for _, inf := range candidates {
if target <= 0 {
break
}
s := cm.segments.get(inf.id)
s.Lock()
for c := range inf.conns {
selected = append(selected, c)
}
target -= len(inf.conns)
s.Unlock()
}
if len(selected) >= target {
// We found enough connections that were not protected.
return selected
}
// We didn't find enough unprotected connections.
// We have no choice but to kill some protected connections.
candidates = candidates[:0]
cm.plk.RLock()
for _, s := range cm.segments.buckets {
s.Lock()
for _, inf := range s.peers {
candidates = append(candidates, inf)
}
s.Unlock()
}
cm.plk.RUnlock()
candidates.SortByValueAndStreams(&cm.segments, true)
for _, inf := range candidates {
if target <= 0 {
break
}
// lock this to protect from concurrent modifications from connect/disconnect events
s := cm.segments.get(inf.id)
s.Lock()
for c := range inf.conns {
selected = append(selected, c)
}
target -= len(inf.conns)
s.Unlock()
}
return selected
}
// getConnsToClose runs the heuristics described in TrimOpenConns and returns the
// connections to close.
func (cm *BasicConnMgr) getConnsToClose() []network.Conn {
if cm.cfg.lowWater == 0 || cm.cfg.highWater == 0 {
// disabled
return nil
}
if int(cm.connCount.Load()) <= cm.cfg.lowWater {
log.Info("open connection count below limit")
return nil
}
candidates := make(peerInfos, 0, cm.segments.countPeers())
var ncandidates int
gracePeriodStart := cm.clock.Now().Add(-cm.cfg.gracePeriod)
cm.plk.RLock()
for _, s := range cm.segments.buckets {
s.Lock()
for id, inf := range s.peers {
if _, ok := cm.protected[id]; ok {
// skip over protected peer.
continue
}
if inf.firstSeen.After(gracePeriodStart) {
// skip peers in the grace period.
continue
}
// note that we're copying the entry here,
// but since inf.conns is a map, it will still point to the original object
candidates = append(candidates, inf)
ncandidates += len(inf.conns)
}
s.Unlock()
}
cm.plk.RUnlock()
if ncandidates < cm.cfg.lowWater {
log.Info("open connection count above limit but too many are in the grace period")
// We have too many connections but fewer than lowWater
// connections out of the grace period.
//
// If we trimmed now, we'd kill potentially useful connections.
return nil
}
// Sort peers according to their value.
candidates.SortByValueAndStreams(&cm.segments, false)
target := ncandidates - cm.cfg.lowWater
// slightly overallocate because we may have more than one conns per peer
selected := make([]network.Conn, 0, target+10)
for _, inf := range candidates {
if target <= 0 {
break
}
// lock this to protect from concurrent modifications from connect/disconnect events
s := cm.segments.get(inf.id)
s.Lock()
if len(inf.conns) == 0 && inf.temp {
// handle temporary entries for early tags -- this entry has gone past the grace period
// and still holds no connections, so prune it.
delete(s.peers, inf.id)
} else {
for c := range inf.conns {
selected = append(selected, c)
}
target -= len(inf.conns)
}
s.Unlock()
}
return selected
}
// GetTagInfo is called to fetch the tag information associated with a given
// peer, nil is returned if p refers to an unknown peer.
func (cm *BasicConnMgr) GetTagInfo(p peer.ID) *connmgr.TagInfo {
s := cm.segments.get(p)
s.Lock()
defer s.Unlock()
pi, ok := s.peers[p]
if !ok {
return nil
}
out := &connmgr.TagInfo{
FirstSeen: pi.firstSeen,
Value: pi.value,
Tags: make(map[string]int),
Conns: make(map[string]time.Time),
}
for t, v := range pi.tags {
out.Tags[t] = v
}
for t, v := range pi.decaying {
out.Tags[t.name] = v.Value
}
for c, t := range pi.conns {
out.Conns[c.RemoteMultiaddr().String()] = t
}
return out
}
// TagPeer is called to associate a string and integer with a given peer.
func (cm *BasicConnMgr) TagPeer(p peer.ID, tag string, val int) {
s := cm.segments.get(p)
s.Lock()
defer s.Unlock()
pi := s.tagInfoFor(p, cm.clock.Now())
// Update the total value of the peer.
pi.value += val - pi.tags[tag]
pi.tags[tag] = val
}
// UntagPeer is called to disassociate a string and integer from a given peer.
func (cm *BasicConnMgr) UntagPeer(p peer.ID, tag string) {
s := cm.segments.get(p)
s.Lock()
defer s.Unlock()
pi, ok := s.peers[p]
if !ok {
log.Info("tried to remove tag from untracked peer: ", p)
return
}
// Update the total value of the peer.
pi.value -= pi.tags[tag]
delete(pi.tags, tag)
}
// UpsertTag is called to insert/update a peer tag
func (cm *BasicConnMgr) UpsertTag(p peer.ID, tag string, upsert func(int) int) {
s := cm.segments.get(p)
s.Lock()
defer s.Unlock()
pi := s.tagInfoFor(p, cm.clock.Now())
oldval := pi.tags[tag]
newval := upsert(oldval)
pi.value += newval - oldval
pi.tags[tag] = newval
}
// CMInfo holds the configuration for BasicConnMgr, as well as status data.
type CMInfo struct {
// The low watermark, as described in NewConnManager.
LowWater int
// The high watermark, as described in NewConnManager.
HighWater int
// The timestamp when the last trim was triggered.
LastTrim time.Time
// The configured grace period, as described in NewConnManager.
GracePeriod time.Duration
// The current connection count.
ConnCount int
}
// GetInfo returns the configuration and status data for this connection manager.
func (cm *BasicConnMgr) GetInfo() CMInfo {
cm.lastTrimMu.RLock()
lastTrim := cm.lastTrim
cm.lastTrimMu.RUnlock()
return CMInfo{
HighWater: cm.cfg.highWater,
LowWater: cm.cfg.lowWater,
LastTrim: lastTrim,
GracePeriod: cm.cfg.gracePeriod,
ConnCount: int(cm.connCount.Load()),
}
}
// Notifee returns a sink through which Notifiers can inform the BasicConnMgr when
// events occur. Currently, the notifee only reacts upon connection events
// {Connected, Disconnected}.
func (cm *BasicConnMgr) Notifee() network.Notifiee {
return (*cmNotifee)(cm)
}
type cmNotifee BasicConnMgr
func (nn *cmNotifee) cm() *BasicConnMgr {
return (*BasicConnMgr)(nn)
}
// Connected is called by notifiers to inform that a new connection has been established.
// The notifee updates the BasicConnMgr to start tracking the connection. If the new connection
// count exceeds the high watermark, a trim may be triggered.
func (nn *cmNotifee) Connected(n network.Network, c network.Conn) {
cm := nn.cm()
p := c.RemotePeer()
s := cm.segments.get(p)
s.Lock()
defer s.Unlock()
id := c.RemotePeer()
pinfo, ok := s.peers[id]
if !ok {
pinfo = &peerInfo{
id: id,
firstSeen: cm.clock.Now(),
tags: make(map[string]int),
decaying: make(map[*decayingTag]*connmgr.DecayingValue),
conns: make(map[network.Conn]time.Time),
}
s.peers[id] = pinfo
} else if pinfo.temp {
// we had created a temporary entry for this peer to buffer early tags before the
// Connected notification arrived: flip the temporary flag, and update the firstSeen
// timestamp to the real one.
pinfo.temp = false
pinfo.firstSeen = cm.clock.Now()
}
_, ok = pinfo.conns[c]
if ok {
log.Error("received connected notification for conn we are already tracking: ", p)
return
}
pinfo.conns[c] = cm.clock.Now()
cm.connCount.Add(1)
}
// Disconnected is called by notifiers to inform that an existing connection has been closed or terminated.
// The notifee updates the BasicConnMgr accordingly to stop tracking the connection, and performs housekeeping.
func (nn *cmNotifee) Disconnected(n network.Network, c network.Conn) {
cm := nn.cm()
p := c.RemotePeer()
s := cm.segments.get(p)
s.Lock()
defer s.Unlock()
cinf, ok := s.peers[p]
if !ok {
log.Error("received disconnected notification for peer we are not tracking: ", p)
return
}
_, ok = cinf.conns[c]
if !ok {
log.Error("received disconnected notification for conn we are not tracking: ", p)
return
}
delete(cinf.conns, c)
if len(cinf.conns) == 0 {
delete(s.peers, p)
}
cm.connCount.Add(-1)
}
// Listen is no-op in this implementation.
func (nn *cmNotifee) Listen(n network.Network, addr ma.Multiaddr) {}
// ListenClose is no-op in this implementation.
func (nn *cmNotifee) ListenClose(n network.Network, addr ma.Multiaddr) {}