Prometheus remote read via Influx api - from which retention policy?

Telegraf
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1

I use the InfluxDB remote write/read api described here: Prometheus endpoints support in InfluxDB | InfluxDB OSS 1.7 Documentation to store metrics from a Kubernetes cluster provided by prometheus.

Because I get a lot of data, i use continuous queries to aggregate the metrics and store them in different retention policies.

name     duration   shardGroupDuration replicaN default resolution
----     --------   ------------------ -------- ------- ----------
autogen  120h0m0s   6h0m0s             1        true    1m
2_months 1344h0m0s  24h0m0s            1        false   15m
2_years  17472h0m0s 336h0m0s           1        false   120m

Now I want prometheus to read from all retention policies so that I can view older data in the grafana dashboards, which use prometheus as data source. The above mentioned documentation doesn’t tell from which retention policy prometheus reads.
Can someone tell me, how the InfluxDB api translates the queries and if all retention policies are queried (or how I could configure prometheus/InfluxDB to do so)?

As described in InfluxDB API reference | InfluxDB OSS 1.7 Documentation a retention policy can be chosen by adding “rp=retentionPolicyName” to the URL if using /write. If this also applies to /api/v1/prom/read, I could just set a remote-read URL for every retention policy.
Can somebody confirm?

2

I tried what happens if I send metrics to

http://influxdb:8086/api/v1/prom/write?db=prometheus&u=root&p=root&rp=test

And as expected the metrics are written to the retention policy “test”. I assume that this also works with remote read. Maybe this can be added to the documentation of the prometheus api.