PCA Querying & Visualization 3

Question 1

What is the difference between `sum by (job)` and `sum without (instance)` when other labels are `job` and `instance`?

Accepted Answer

`sum by (job)` keeps only the `job` label; `sum without (instance)` also keeps `job` but drops `instance` — same result here

Answer

When only `job` and `instance` labels exist, both expressions yield the same result — `by (job)` keeps job, and `without (instance)` keeps everything except instance (i.e., job).

Question 2

What does the `topk(3, http_requests_total)` expression return?

Accepted Answer

The 3 time series with the highest values at the current moment

Answer

`topk(k, expr)` returns the k time series with the largest values at the current evaluation timestamp.

Question 3

What does the binary operator `unless` do in PromQL?

Accepted Answer

Returns elements from the left-hand side that have NO matching elements on the right-hand side

Answer

`unless` returns all elements of the left-hand vector for which there are no matching elements in the right-hand vector.

Question 4

When using `group_left` in a binary operation, what does it signify?

Accepted Answer

The left-hand side has fewer unique label sets (many-to-one matching)

Answer

`group_left` indicates a many-to-one match where multiple left-side series can match a single right-side series, and optionally copies labels from the right side.

Question 5

What does `count_values("status", http_requests_total)` produce?

Accepted Answer

A new metric with a `status` label containing each unique value and a count of how many series have that value

Answer

`count_values` groups all time series by their current value, creating a new series per unique value with a label named by the first argument containing that value.

(PCA) Prometheus Certified Associate Practice Test

(PCA) Prometheus Certified Associate Practice Test

PCA Querying & Visualization 3