scrape/scrape.go
func appender(app storage.Appender, limit int) storage.Appender {
	app = &timeLimitAppender{
		Appender: app,
		maxTime:  timestamp.FromTime(time.Now().Add(maxAheadTime)),
	}

	// The limit is applied after metrics are potentially dropped via relabeling.
	if limit > 0 {
		app = &limitAppender{
			Appender: app,
			limit:    limit,
		}
	}
	return app
}
func appender(app storage.Appender, limit int) storage.Appender {
	app = &timeLimitAppender{
		Appender: app,
		maxTime:  timestamp.FromTime(time.Now().Add(maxAheadTime)),
	}

	// The limit is applied after metrics are potentially dropped via relabeling.
	if limit > 0 {
		app = &limitAppender{
			Appender: app,
			limit:    limit,
		}
	}
	return app
}
// appender returns an appender for ingested samples from the target.