implement decaying tags. (#61)

p2p/net/connmgr/connmgr.go

@@ -27,27 +27,30 @@ var log = logging.Logger("connmgr")
 //
 // See configuration parameters in NewConnManager.
 type BasicConnMgr struct {
-	highWater   int
-	lowWater    int
-	connCount   int32
-	gracePeriod time.Duration
-	segments    segments
+	*decayer
+
+	cfg      *BasicConnManagerConfig
+	segments segments
 
 	plk       sync.RWMutex
 	protected map[peer.ID]map[string]struct{}
 
-	trimTrigger chan chan<- struct{}
+	// channel-based semaphore that enforces only a single trim is in progress
+	trimRunningCh chan struct{}
+	trimTrigger   chan chan<- struct{}
+	connCount     int32
 
 	lastTrimMu sync.RWMutex
 	lastTrim   time.Time
 
-	silencePeriod time.Duration
-
 	ctx    context.Context
 	cancel func()
 }
 
-var _ connmgr.ConnManager = (*BasicConnMgr)(nil)
+var (
+	_ connmgr.ConnManager = (*BasicConnMgr)(nil)
+	_ connmgr.Decayer     = (*BasicConnMgr)(nil)
+)
 
 type segment struct {
 	sync.Mutex
@@ -80,6 +83,7 @@ func (s *segment) tagInfoFor(p peer.ID) *peerInfo {
 		firstSeen: time.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
@@ -92,15 +96,32 @@ func (s *segment) tagInfoFor(p peer.ID) *peerInfo {
 //   their connections terminated) until 'low watermark' peers remain.
 // * grace is the amount of time a newly opened connection is given before it becomes
 //   subject to pruning.
-func NewConnManager(low, hi int, grace time.Duration) *BasicConnMgr {
+func NewConnManager(low, hi int, grace time.Duration, opts ...Option) *BasicConnMgr {
 	ctx, cancel := context.WithCancel(context.Background())
-	cm := &BasicConnMgr{
+
+	cfg := &BasicConnManagerConfig{
 		highWater:     hi,
 		lowWater:      low,
 		gracePeriod:   grace,
+		silencePeriod: SilencePeriod,
+	}
+
+	for _, o := range opts {
+		// TODO we're ignoring errors from options because we have no way to
+		// return them, or otherwise act on them.
+		_ = o(cfg)
+	}
+
+	if cfg.decayer == nil {
+		// Set the default decayer config.
+		cfg.decayer = (&DecayerCfg{}).WithDefaults()
+	}
+
+	cm := &BasicConnMgr{
+		cfg:           cfg,
+		trimRunningCh: make(chan struct{}, 1),
 		trimTrigger:   make(chan chan<- struct{}),
 		protected:     make(map[peer.ID]map[string]struct{}, 16),
-		silencePeriod: SilencePeriod,
 		ctx:           ctx,
 		cancel:        cancel,
 		segments: func() (ret segments) {
@@ -113,11 +134,17 @@ func NewConnManager(low, hi int, grace time.Duration) *BasicConnMgr {
 		}(),
 	}
 
+	decay, _ := NewDecayer(cfg.decayer, cm)
+	cm.decayer = decay
+
 	go cm.background()
 	return cm
 }
 
 func (cm *BasicConnMgr) Close() error {
+	if err := cm.decayer.Close(); err != nil {
+		return err
+	}
 	cm.cancel()
 	return nil
 }
@@ -151,10 +178,12 @@ func (cm *BasicConnMgr) Unprotect(id peer.ID, tag string) (protected bool) {
 
 // peerInfo stores metadata for a given peer.
 type peerInfo struct {
-	id    peer.ID
-	tags  map[string]int // value for each tag
-	value int            // cached sum of all tag values
-	temp  bool           // this is a temporary entry holding early tags, and awaiting connections
+	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
 
@@ -199,7 +228,7 @@ func (cm *BasicConnMgr) background() {
 		var waiting chan<- struct{}
 		select {
 		case <-ticker.C:
-			if atomic.LoadInt32(&cm.connCount) < int32(cm.highWater) {
+			if atomic.LoadInt32(&cm.connCount) < int32(cm.cfg.highWater) {
 				// Below high water, skip.
 				continue
 			}
@@ -235,7 +264,7 @@ func (cm *BasicConnMgr) trim() {
 	cm.lastTrimMu.RUnlock()
 
 	// skip this attempt to trim if the last one just took place.
-	if time.Since(lastTrim) < cm.silencePeriod {
+	if time.Since(lastTrim) < cm.cfg.silencePeriod {
 		return
 	}
 
@@ -256,21 +285,21 @@ func (cm *BasicConnMgr) trim() {
 // getConnsToClose runs the heuristics described in TrimOpenConns and returns the
 // connections to close.
 func (cm *BasicConnMgr) getConnsToClose() []network.Conn {
-	if cm.lowWater == 0 || cm.highWater == 0 {
+	if cm.cfg.lowWater == 0 || cm.cfg.highWater == 0 {
 		// disabled
 		return nil
 	}
 
 	nconns := int(atomic.LoadInt32(&cm.connCount))
-	if nconns <= cm.lowWater {
+	if nconns <= cm.cfg.lowWater {
 		log.Info("open connection count below limit")
 		return nil
 	}
 
 	npeers := cm.segments.countPeers()
 	candidates := make([]*peerInfo, 0, npeers)
 	ncandidates := 0
-	gracePeriodStart := time.Now().Add(-cm.gracePeriod)
+	gracePeriodStart := time.Now().Add(-cm.cfg.gracePeriod)
 
 	cm.plk.RLock()
 	for _, s := range cm.segments {
@@ -291,7 +320,7 @@ func (cm *BasicConnMgr) getConnsToClose() []network.Conn {
 	}
 	cm.plk.RUnlock()
 
-	if ncandidates < cm.lowWater {
+	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.
@@ -311,7 +340,7 @@ func (cm *BasicConnMgr) getConnsToClose() []network.Conn {
 		return left.value < right.value
 	})
 
-	target := ncandidates - cm.lowWater
+	target := ncandidates - cm.cfg.lowWater
 
 	// slightly overallocate because we may have more than one conns per peer
 	selected := make([]network.Conn, 0, target+10)
@@ -363,6 +392,9 @@ func (cm *BasicConnMgr) GetTagInfo(p peer.ID) *connmgr.TagInfo {
 	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
 	}
@@ -439,10 +471,10 @@ func (cm *BasicConnMgr) GetInfo() CMInfo {
 	cm.lastTrimMu.RUnlock()
 
 	return CMInfo{
-		HighWater:   cm.highWater,
-		LowWater:    cm.lowWater,
+		HighWater:   cm.cfg.highWater,
+		LowWater:    cm.cfg.lowWater,
 		LastTrim:    lastTrim,
-		GracePeriod: cm.gracePeriod,
+		GracePeriod: cm.cfg.gracePeriod,
 		ConnCount:   int(atomic.LoadInt32(&cm.connCount)),
 	}
 }
@@ -478,6 +510,7 @@ func (nn *cmNotifee) Connected(n network.Network, c network.Conn) {
 			id:        id,
 			firstSeen: time.Now(),
 			tags:      make(map[string]int),
+			decaying:  make(map[*decayingTag]*connmgr.DecayingValue),
 			conns:     make(map[network.Conn]time.Time),
 		}
 		s.peers[id] = pinfo