Multiple queries per chart

Problem to solve

We had built support for multiple queries per chart (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15201), however with the importing of metrics into the database we lost support for it (https://gitlab.com/gitlab-org/gitlab-ee/issues/6948).

Multiple queries per chart are important, since sometimes you need to have a different query to generate a related time series. For example if you want to display on the same chart, both the maximum value as well as the average value. Or for example the p99 and p95.

Target audience

Further details

Proposal

We need to re-implement this feature:

  1. Update the internal database schema to support multiple queries (our YML format already does)
  2. Update the importer of library metrics to support multiple queries
  3. Update the library metrics (primarily cAdvisor CPU/Memory) to merge the queries back into one chart

What does success look like, and how can we measure that?

Links / references

/label ~feature

Edited by silv