Empty result when using offset modifier in query

[jstaffans]

I'm using promxy 0.0.73 and the following minimal configuration:

global:
  evaluation_interval: 30s
  external_labels:
    source: promxy

promxy:
  server_groups:
    - static_configs:
        - targets:
          # downstream Prometheus is version 2.29.2
          - prometheus.local
      anti_affinity: 10s

A query like count(node_exporter_build_info) works, but if you introduce the offset modifier like count(node_exporter_build_info offset 2h) the result set is empty.

Querying the Prometheus query UI directly works so the problem seems to be in Promxy.

[jstaffans]

Downgrading to 0.0.72 fixed the problem.

[jacksontj]

I am unable to reproduce the same; I am using the following config:

promxy:
  server_groups:
    - static_configs:
      - targets:
        - demo.robustperception.io:9090
      http_client:
        dial_timeout: 1s

And both the direct and the offset query work

I'm also unable to reproduce with a local build of lastest prom

Config:

promxy:
  server_groups:
    - static_configs:
        - targets:
          - localhost:9090
      labels:
        az: a

So unfortunately I don't see to be able to reproduce your issue; can you reproduce with the first demo config?

[jstaffans]

I can reproduce it with promxy 0.0.73 and a locally running prom 2.30.3 and the following config:

promxy:
  server_groups:
    - static_configs:
      - targets:
        - localhost:9090
      http_client:
        dial_timeout: 1s

Prometheus

Promxy

[jacksontj]

I was able to reproduce; this seems to be an issue specifically for VectorSelectors (meaning if you add a function like count it doesn't reproduce). I have a test and fix in #467