Prometheus lookback_delta parameter in instant and range query API

[duricanikolic]

In this commit prometheus has added the lookback_delta parameter to the instant and range query API. In order to be prometheus compatible, mimir should support this new feature too. The goal of this issue is to discuss whether this should be done, and if the decision is affirmative, implement it.

[pracucci]

I haven't checked the changes required to support it, but I think at least we should support it in the query-frontend, and then propagate it to every partial query pushed down to queriers.

[shichanglin5]

In this commit prometheus has added the lookback_delta parameter to the instant and range query API. In order to be prometheus compatible, mimir should support this new feature too. The goal of this issue is to discuss whether this should be done, and if the decision is affirmative, implement it.

There is indeed a problem with this commit. It does not pass the lookback_delta down (for example, when querying ingester), so it does not work properly.

[shichanglin5]

I haven't checked the changes required to support it, but I think at least we should support it in the query-frontend, and then propagate it to every partial query pushed down to queriers.

Why is it not supported? The data of different tenants is independent, and the interval of writing samples may be different, resulting in problems for different tenants to use the same lookback_delta.

Please reconsider this requirement.