PCA Practice Test 16 — 15 Questions

Question 1

You need to calculate the 99th percentile of request latency across all instances using a Prometheus histogram metric 'http_request_duration_seconds_bucket'. Which function and setup is correct?

Accepted Answer

histogram_quantile(0.99, rate(http_request_duration_seconds_bucket[5m])). The histogram_quantile() function calculates the $\phi$-quantile from the buckets of a histogram metric. It requires the bucket metric and the quantile as arguments.

Answer

histogram_quantile(http_request_duration_seconds_bucket[5m], 0.99)

Answer

quantile_over_time(0.99, http_request_duration_seconds_bucket[5m])

Answer

rate(histogram_quantile(0.99, http_request_duration_seconds_bucket[5m]))

Question 2

When performing vector matching between two vectors of different cardinalities, which THREE vector matching modifiers can be used? (Choose three)

Accepted Answer

on. PromQL vector matching modifiers include on, ignoring, group_left, and group_right.

Answer

group_by

Answer

match_any

Question 3

What is the purpose of the 'offset' modifier in a PromQL query?

Accepted Answer

To change the time range of a query to a point in the past.. The 'offset' modifier allows querying data from the past relative to the current time.

Answer

To remove specific label dimensions.

Answer

To filter out noise from the last 5 minutes.

Answer

To increase the precision of a rate calculation.

Question 4

Which THREE of the following are valid time-range units in PromQL?

Accepted Answer

m. s, m, h, d, w, y are all valid Prometheus duration units.

Answer

ns

Answer

ms

Question 5

Which THREE of the following metrics are automatically added to all scraped targets?

Accepted Answer

up. Prometheus adds specific metadata labels such as up, scrape_duration, and scrape_samples_scraped.

Answer

cpu_usage

Answer

memory_usage

Question 6

Which TWO of the following can be configured globally?

Accepted Answer

scrape_interval. Global configuration includes scrape interval and evaluation interval.

Answer

alertmanager_host

Answer

storage_path

Answer

target_labels

Question 7

Which regular expression matcher selects all time series where the status label begins with the digit 5?

Accepted Answer

http_requests_total{status=~"^5.*"}. The =~ operator combined with a regular expression starting with ^5 matches labels beginning with 5.

Answer

http_requests_total{status=@"5*"}

Answer

http_requests_total{status=^"5"}

Answer

http_requests_total{status=~"5$"}

Question 8

You need to perform a binary operation between two vectors where the left vector has labels {job="api", instance="a"} and the right vector has labels {job="api"}. You want to match them using the job label while retaining the instance label from the left side. Which modifier configuration is correct?

Accepted Answer

vector_a * on(job) group_left(instance) vector_b. To match on a subset of labels while retaining extra labels on the left side during a one-to-many or many-to-one operation, group_left must be used with the on modifier.

Answer

vector_a * on(instance) group_left(job) vector_b

Answer

vector_a * on(job) group_right(instance) vector_b

Answer

vector_a * ignoring(instance) group_left vector_b

Question 9

An operator writes the query sum(rate(http_requests_total[5m])) without any aggregation clauses. What is the output format?

Accepted Answer

An instant vector containing a single element with no labels.. Aggregations without a by or without clause aggregate all time series into a single global vector with no labels.

Answer

A range vector spanning 5 minutes.

Answer

An instant vector preserving all original metric labels.

Answer

A scalar value representing the exact floating-point result.

Question 10

When writing a PromQL query involving a vector and a scalar, such as 'node_memory_free_bytes / (1024 * 1024)', how does Prometheus handle label matching?

Accepted Answer

The scalar operation is applied to every time series value in the vector independently, preserving all labels.. Operations between an instant vector and a scalar are performed on each data point of the vector. Labels are unaffected.

Answer

The operation is only applied to the first time series returned by the vector selector.

Answer

The scalar is matched against labels of the vector using exact label equality.

Answer

The query fails because scalars cannot be combined with vectors without an explicit 'on' clause.

Question 11

Which operator has higher precedence in PromQL: exponential (^), multiplication (*), or addition (+)?

Accepted Answer

Exponentiation (^). Exponentiation has the highest precedence in PromQL, followed by multiplication/division, and then addition/subtraction.

Answer

Addition (+)

Answer

All arithmetic operators share equal precedence.

Answer

Multiplication (*)

Question 12

Which function would you use to find the maximum value of a gauge metric 'node_cpu_load' over the past 30 minutes?

Accepted Answer

max_over_time(node_cpu_load[30m]). The max_over_time() function calculates the maximum value of all data points in the specified range vector for each time series.

Answer

rate(node_cpu_load[30m])

Answer

max(node_cpu_load[30m])

Answer

topk(1, node_cpu_load[30m])

Question 13

Which THREE built-in functions in PromQL are designed specifically to analyze changes over time for gauge metrics? (Choose three)

Accepted Answer

delta(). Functions like delta(), deriv(), and predict_linear() (as well as idelta) operate on gauges over range vectors.

Answer

rate()

Answer

increase()

Question 14

Which function should be used to smooth out short-term fluctuations in a gauge metric by calculating the rolling average over a 10-minute window?

Accepted Answer

avg_over_time(node_load1[10m]). The avg_over_time() function calculates the average value of all data points in the specified range vector for each time series.

Answer

rate(node_load1[10m])

Answer

smooth(node_load1, 10m)

Answer

avg(node_load1[10m])

Question 15

Which of the following selectors matches metric names that start with 'http_'?

Accepted Answer

{__name__=~"http_.*"}. The regex matcher '=~' is used with regular expressions, and '^' anchors the match to the beginning of the string.

Answer

http_*(5m)

Answer

{metric=~"http_.*"}

Answer

{__name__="http_*"}