dbjobqueue: acquire a new connection for each listen query

This fixes a bug where the listen function would keep trying to use a
closed, unrecoverable connection to listen for a notification. This
continued failing, which essentially made the queue instance useless.

pkg/jobqueue/dbjobqueue/dbjobqueue.go

@@ -199,8 +199,33 @@ func NewWithConfig(url string, config Config) (*DBJobQueue, error) {
 }
 
 func (q *DBJobQueue) listen(ctx context.Context, ready chan<- struct{}) {
+	ready <- struct{}{}
+
+	for {
+		err := q.waitAndNotify(ctx)
+		if err != nil {
+			// shutdown the listener if the context is canceled
+			if errors.Is(err, context.Canceled) {
+				q.logger.Info("Shutting down the listener")
+				return
+			}
+
+			// otherwise, just log the error and continue, there might just
+			// be a temporary networking issue
+			q.logger.Error(err, "Error waiting for notification on jobs channel")
+
+			// backoff to avoid log spam
+			time.Sleep(time.Millisecond * 500)
+		}
+	}
+}
+
+func (q *DBJobQueue) waitAndNotify(ctx context.Context) error {
 	conn, err := q.pool.Acquire(ctx)
 	if err != nil {
+		if errors.Is(err, context.Canceled) {
+			return err
+		}
 		panic(fmt.Errorf("error connecting to database: %v", err))
 	}
 	defer func() {
@@ -214,31 +239,20 @@ func (q *DBJobQueue) listen(ctx context.Context, ready chan<- struct{}) {
 
 	_, err = conn.Exec(ctx, sqlListen)
 	if err != nil {
+		if errors.Is(err, context.Canceled) {
+			return err
+		}
 		panic(fmt.Errorf("error listening on jobs channel: %v", err))
 	}
 
-	ready <- struct{}{}
-
-	for {
-		_, err = conn.Conn().WaitForNotification(ctx)
-		if err != nil {
-			// shutdown the listener if the context is canceled
-			if errors.Is(err, context.Canceled) {
-				q.logger.Info("Shutting down the listener")
-				return
-			}
-
-			// otherwise, just log the error and continue, there might just
-			// be a temporary networking issue
-			q.logger.Error(err, "Error waiting for notification on jobs channel")
-			// backoff to avoid log spam
-			time.Sleep(time.Millisecond * 500)
-			continue
-		}
-
-		// something happened in the database, notify all dequeuers
-		q.dequeuers.notifyAll()
+	_, err = conn.Conn().WaitForNotification(ctx)
+	if err != nil {
+		return err
 	}
+
+	// something happened in the database, notify all dequeuers
+	q.dequeuers.notifyAll()
+	return nil
 }
 
 func (q *DBJobQueue) Close() {