Replace xrate/xincrease functions with anchored/smoothed modifiers

[sylr]

Prometheus has added modifiers to reproduced the behavior of thanos' xrate/xincrease functions.

# Thanos
xincrease(abstraction_www_http_request_total[5m])

# Prometheus
increase(abstraction_www_http_request_total[5m] anchored)

Additional context

https://prometheus.io/docs/prometheus/latest/feature_flags/#extended-range-selectors

[GiedriusS]

Do you think it would be enough to implement these functions in the PromQL engine or how do you think we should nudge our users towards these modifiers?

[sylr]

I very much think that Thanos would benefit to be 100% prometheus compliant and I would nudge users to use anchored/smoothed.

Personally I cherish to be able to run my queries (or grafana dashboards) on prometheus and Thanos in-distinctively.

I love the fact that Thanos tried to solve a problem for prometheus users and since your two projects share maintainers I was once hopeful xrate/xincrease would be backported upstream.

However, since prometheus chose a different path, I would re-align Thanos on upstream prometheus.

Cheers.