Add split_queries to query stats

[ssncferreira]

What this PR does

Add split_queries parameter describing the number of partial queries executed in parallel to both range and instant queries.

Which issue(s) this PR fixes or relates to

Fixes #

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[pracucci]

Thanks! Overall LGTM, but look at my comment, please.

Can we also add an assertion to 1 on the existing tests to check it's actually added to the query stats?

[ssncferreira]

Can we also add an assertion to 1 on the existing tests to check it's actually added to the query stats?

@pracucci added tests for stats: 34835d5

However, I don't see any tests that assert the written log line. Let me know if I'm missing something, otherwise I can create a unit test to assert this 🙂

[ssncferreira]

Noticed that the ruler also logs query's stats: https://github.com/grafana/mimir/blob/main/pkg/ruler/compat.go#L195

Since the split by range feature also affects the ruler, maybe it is also worthwhile adding it here 🤔

[pracucci]

Noticed that the ruler also logs query's stats: https://github.com/grafana/mimir/blob/main/pkg/ruler/compat.go#L195

Since the split by range feature also affects the ruler, maybe it is also worthwhile adding it here 🤔

The ruler is not affected by the splitting. Splitting is done only by query-frontend. The ruler has two evaluations modes:

• Internal: no splitting, requests don't go through query-frontend
• Remote: requests go though query-frontend, there's splitting supported but provided by the query-frontend so it will be logged by the query-frontend middleware

[pracucci]

Can we also add an assertion to 1 on the existing tests to check it's actually added to the query stats?

@pracucci added tests for stats: 34835d5

However, I don't see any tests that assert the written log line. Let me know if I'm missing something, otherwise I can create a unit test to assert this 🙂

I actually meant to check the stats from the context, not the log line. It's not a blocker to get this PR merged tho.

[ssncferreira]

Noticed that the ruler also logs query's stats: https://github.com/grafana/mimir/blob/main/pkg/ruler/compat.go#L195
Since the split by range feature also affects the ruler, maybe it is also worthwhile adding it here 🤔

The ruler is not affected by the splitting. Splitting is done only by query-frontend. The ruler has two evaluations modes:

• Internal: no splitting, requests don't go through query-frontend
• Remote: requests go though query-frontend, there's splitting supported but provided by the query-frontend so it will be logged by the query-frontend middleware

Ah, yes I meant the ruler will receive the split requests from the query-frontend (remote point). But already understood that that will be logged in the query-frontend. Thanks for the explanation 🙂