fix(redisotel): fix buggy append in reportPoolStats

The current append twice to `conf.attrs` approach in `reportPoolStats` may result in unexpected idleAttrs,
due to `append` [can mutate](golang/go#29115 (comment)) the underlying array of the original slice,
as demonstrated at <https://go.dev/play/p/jwRMofH91eQ?v=goprev>.

Also, I replaced `metric.WithAttributes` in `reportPoolStats` with `metric.WithAttributeSet`,
since `WithAttributes` is just `WithAttributeSet` with some extra works that are not needed here,
see <https://pkg.go.dev/go.opentelemetry.io/otel/[email protected]#WithAttributes>.

Author: FAELES-DIVINA

extra/redisotel/metrics.go

@@ -83,9 +83,9 @@ func InstrumentMetrics(rdb redis.UniversalClient, opts ...MetricsOption) error {
 }
 
 func reportPoolStats(rdb *redis.Client, conf *config) error {
-	labels := conf.attrs
-	idleAttrs := append(labels, attribute.String("state", "idle"))
-	usedAttrs := append(labels, attribute.String("state", "used"))
+	poolAttrs := attribute.NewSet(conf.attrs...)
+	idleAttrs := attribute.NewSet(append(poolAttrs.ToSlice(), attribute.String("state", "idle"))...)
+	usedAttrs := attribute.NewSet(append(poolAttrs.ToSlice(), attribute.String("state", "used"))...)
 
 	idleMax, err := conf.meter.Int64ObservableUpDownCounter(
 		"db.client.connections.idle.max",
@@ -132,14 +132,14 @@ func reportPoolStats(rdb *redis.Client, conf *config) error {
 		func(ctx context.Context, o metric.Observer) error {
 			stats := rdb.PoolStats()
 
-			o.ObserveInt64(idleMax, int64(redisConf.MaxIdleConns), metric.WithAttributes(labels...))
-			o.ObserveInt64(idleMin, int64(redisConf.MinIdleConns), metric.WithAttributes(labels...))
-			o.ObserveInt64(connsMax, int64(redisConf.PoolSize), metric.WithAttributes(labels...))
+			o.ObserveInt64(idleMax, int64(redisConf.MaxIdleConns), metric.WithAttributeSet(poolAttrs))
+			o.ObserveInt64(idleMin, int64(redisConf.MinIdleConns), metric.WithAttributeSet(poolAttrs))
+			o.ObserveInt64(connsMax, int64(redisConf.PoolSize), metric.WithAttributeSet(poolAttrs))
 
-			o.ObserveInt64(usage, int64(stats.IdleConns), metric.WithAttributes(idleAttrs...))
-			o.ObserveInt64(usage, int64(stats.TotalConns-stats.IdleConns), metric.WithAttributes(usedAttrs...))
+			o.ObserveInt64(usage, int64(stats.IdleConns), metric.WithAttributeSet(idleAttrs))
+			o.ObserveInt64(usage, int64(stats.TotalConns-stats.IdleConns), metric.WithAttributeSet(usedAttrs))
 
-			o.ObserveInt64(timeouts, int64(stats.Timeouts), metric.WithAttributes(labels...))
+			o.ObserveInt64(timeouts, int64(stats.Timeouts), metric.WithAttributeSet(poolAttrs))
 			return nil
 		},
 		idleMax,