Prometheusremotewrite exporter handling of empty metrics

[jjcollinge]

I have a custom receiver that is very similar to the dockerstats receiver. When there are no containers the scrape method returns a zero Metrics result (returned by pmetric.NewMetrics()) - this is exactly the same as the dockerstats receiver. However, I am also using the prometheusremotewrite exporter to push these metrics to a Cortex backend. The prometheusremotewrite exporter errors on empty metrics:

2022-04-26T05:47:01.878Z	info	exporterhelper/queued_retry.go:215	Exporting failed. Will retry the request after interval.	{"kind": "exporter", "name": "prometheusremotewrite", "error": "invalid tsMap: cannot be empty map", "interval": "188.256732ms"}

By default the send of this empty metrics set is retried several times until it is finally dropped. This was causing none empty metrics received by different receivers to not get through to Cortex consistently (presumably because there were so many retries of this empty batch blocking the pipe). Disabling retry_on_failure on the promtheusremotewrite exporter is the only way I've been able to consistently get the metrics from the other receivers through to Cortex.

Is there something I should be doing in my custom receiver to drop empty metrics sets rather than having them passed through to the exporter? If this is not possible, how should I avoid the prometheusremotewrite exporter erroring (in a non permanent way) for each empty metrics set?

I'm very new to the Otel collector so I may have missed something obvious, so would appreciate some guidance on this.