core/connpool: scrub lazily on Put()

unclear if timer.Ticker would force wake up and/or prevent sleep

intra/core/connpool.go

@@ -21,10 +21,11 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-const useread = false                // always false; here for doc purposes
-const poolcapacity = 8               // default capacity
-const maxattempts = poolcapacity / 2 // max attempts to retrieve a conn from pool
-const Nobody = uintptr(0)            // nobody
+const useread = false                 // always false; here for doc purposes
+const poolcapacity = 8                // default capacity
+const maxattempts = poolcapacity / 2  // max attempts to retrieve a conn from pool
+const Nobody = uintptr(0)             // nobody
+const scrubinterval = 5 * time.Minute // interval between subsequent scrubs
 
 var errUnexpectedRead error = errors.New("pool: unexpected read")
 
@@ -34,42 +35,55 @@ type superpool[T comparable] struct {
 }
 
 type MultConnPool[T comparable] struct {
-	ctx context.Context
-	mu  sync.RWMutex
-	m   map[T]*superpool[T]
+	ctx       context.Context
+	mu        sync.RWMutex
+	m         map[T]*superpool[T]
+	scrubtime time.Time
 }
 
 func NewMultConnPool[T comparable](ctx context.Context) *MultConnPool[T] {
-	mc := &MultConnPool[T]{
+	return &MultConnPool[T]{
 		ctx: ctx,
 		m:   make(map[T]*superpool[T]),
 	}
-	every10m := time.NewTicker(10 * time.Minute)
-	go mc.scrub(ctx, every10m)
-	return mc
 }
 
-func (m *MultConnPool[T]) scrub(ctx context.Context, tick *time.Ticker) {
-	defer tick.Stop()
-	for {
-		select {
-		case <-ctx.Done():
-			return
-		case <-tick.C:
-			m.mu.Lock()
-			for id, super := range m.m {
-				if !super.pool.closed.Load() {
-					delete(m.m, id)
-				} else if super.pool.empty() {
-					super.quit()
-					delete(m.m, id)
-				} else {
-					go super.pool.scrub()
-				}
+func (m *MultConnPool[T]) scrub() {
+	now := time.Now()
+	if now.Sub(m.scrubtime) <= scrubinterval { // too soon
+		return
+	}
+	m.scrubtime = now
+
+	select {
+	case <-m.ctx.Done():
+		return
+	default:
+	}
+
+	Go("superpool.scrub", func() {
+		m.mu.Lock()
+		defer m.mu.Unlock()
+
+		var n, nclosed, nquit, nscrubbed int
+		n = len(m.m)
+		for id, super := range m.m {
+			if super.pool.closed.Load() {
+				nclosed++
+				delete(m.m, id)
+			} else if super.pool.empty() {
+				nquit++
+				super.quit()
+				delete(m.m, id)
+			} else {
+				nscrubbed++
+				Go("poo.scrub", super.pool.scrub)
 			}
-			m.mu.Unlock()
 		}
-	}
+
+		log.D("pool: scrubbed: %d, closed: %d, quit: %d, total: %d",
+			nscrubbed, nclosed, nquit, n)
+	})
 }
 
 func (m *MultConnPool[T]) Get(id T) net.Conn {
@@ -106,6 +120,7 @@ func (m *MultConnPool[T]) Put(id T, conn net.Conn) bool {
 		m.mu.Unlock()
 	}
 
+	m.scrub()
 	return super.pool.Put(conn)
 }