conn: don't spam draining cleanup log messages

conn.go

@@ -622,6 +622,7 @@ func (c *Conn) close() {
 func (c *Conn) cleanup() {
 	<-c.drainReady
 	ticker := time.NewTicker(100 * time.Millisecond)
+	lastWarning := time.Now()
 	// writeLoop has exited, drain any remaining in flight messages
 	for {
 		// we're racing with readLoop which potentially has a message
@@ -635,13 +636,19 @@ func (c *Conn) cleanup() {
 			msgsInFlight = atomic.LoadInt64(&c.messagesInFlight)
 		}
 		if msgsInFlight > 0 {
-			c.log(LogLevelWarning, "draining... waiting for %d messages in flight", msgsInFlight)
+			if time.Now().Sub(lastWarning) > time.Second {
+				c.log(LogLevelWarning, "draining... waiting for %d messages in flight", msgsInFlight)
+				lastWarning = time.Now()
+			}
 			continue
 		}
 		// until the readLoop has exited we cannot be sure that there
 		// still won't be a race
 		if atomic.LoadInt32(&c.readLoopRunning) == 1 {
-			c.log(LogLevelWarning, "draining... readLoop still running")
+			if time.Now().Sub(lastWarning) > time.Second {
+				c.log(LogLevelWarning, "draining... readLoop still running")
+				lastWarning = time.Now()
+			}
 			continue
 		}
 		goto exit