add tiny sleep

go/pools/smartconnpool/pool.go

@@ -396,9 +396,7 @@ func (pool *ConnPool[C]) put(conn *Pooled[C]) {
 		}
 	}
 
-	log.Error("========================== I'M TRYING TO RETURN A CONNECTION HERE")
 	if !pool.wait.tryReturnConn(conn) {
-		log.Error("============================= tryReturnConn returned false, we're in that branch")
 		connSetting := conn.Conn.Setting()
 		if connSetting == nil {
 			pool.clean.Push(conn)

go/pools/smartconnpool/waitlist.go

@@ -18,8 +18,8 @@ package smartconnpool
 
 import (
 	"context"
-	"math/rand"
 	"sync"
+	"time"
 
 	"vitess.io/vitess/go/list"
 	"vitess.io/vitess/go/vt/log"
@@ -59,14 +59,10 @@ func (wl *waitlist[C]) waitForConn(ctx context.Context, setting *Setting) (*Pool
 	wl.mu.Lock()
 	// add ourselves as a waiter at the end of the waitlist
 	wl.list.PushBackValue(elem)
-	log.Errorf("========================== THIS IS WHAT THE WAITLIST LOOKS LIKE BEFORE I START WAITING:\n%+v", wl)
 	wl.mu.Unlock()
 
 	// block on our waiter's semaphore until somebody can hand over a connection to us
-	i := rand.Int()
-	log.Errorf("======================= %d: I'M WAITING", i)
 	elem.Value.sema.wait()
-	log.Error("======================== %d: I'M DONE WAITING", i)
 
 	// we're awake -- the conn in our waiter contains the connection that was handed
 	// over to us, or nothing if we've been waken up forcefully. save the conn before
@@ -114,8 +110,12 @@ func (wl *waitlist[C]) expire(force bool) {
 func (wl *waitlist[D]) tryReturnConn(conn *Pooled[D]) bool {
 	// fast path: if there's nobody waiting there's nothing to do
 	if wl.list.Len() == 0 {
-		log.Error("======================= WE HIT THE FAST PATH, WE'RE RETURNING")
-		return false
+		// HACK: we're gonna sleep for a bit and try again, to see if there are still no waiters
+		time.Sleep(250 * time.Millisecond)
+		if wl.list.Len() == 0 {
+			log.Error("======================= WE HIT THE FAST PATH, WE'RE RETURNING")
+			return false
+		}
 	}
 	// split the slow path into a separate function to enable inlining
 	return wl.tryReturnConnSlow(conn)
@@ -153,12 +153,9 @@ func (wl *waitlist[D]) tryReturnConnSlow(conn *Pooled[D]) bool {
 	// maybe there isn't anybody to hand over the connection to, because we've
 	// raced with another client returning another connection
 	if target == nil {
-		log.Error("====================== target was nil, we couldn't find someone to give the connection to")
 		return false
 	}
 
-	log.Errorf("===================== WE'VE FOUND A TARGET: %+v", target)
-
 	// if we have a target to return the connection to, simply write the connection
 	// into the waiter and signal their semaphore. they'll wake up to pick up the
 	// connection.