PCA Practice Test 22 — 15 Questions

Question 1

Which THREE of the following are valid metric types in Prometheus?

Accepted Answer

Gauge. The four main metric types supported by Prometheus are Counter, Gauge, Histogram, and Summary.

Answer

Set

Answer

Queue

Question 2

Which THREE components are typically involved in the standard Prometheus instrumentation and scraping process?

Accepted Answer

Client library. The process involves the application (instrumented via client library), the exporter (or the application itself), and the Prometheus server (the scraper).

Answer

Grafana

Answer

Alertmanager

Question 3

A developer wants to track the total number of requests received by a web service. Which metric type is most appropriate for this requirement?

Accepted Answer

Counter. Counters are cumulative metrics that represent a single monotonically increasing counter whose value can only increase or be reset to zero on restart. This is ideal for request counts.

Answer

Summary

Answer

Histogram

Answer

Gauge

Question 4

Which TWO of the following are valid ways to modify or add labels to time series in PromQL? (Choose two)

Accepted Answer

label_replace(). PromQL provides label_replace and label_join to modify and construct labels dynamically.

Answer

label_update()

Answer

label_drop()

Answer

label_add()

Question 5

What is the result of applying a range selector like [5m] to a gauge metric?

Accepted Answer

A range vector containing all data points from the last 5 minutes.. A range selector converts an instant vector into a range vector, containing all samples in that window.

Answer

A scalar value representing the sum.

Answer

An instant vector of the average over 5 minutes.

Answer

An error, because gauges are not time-series.

Question 6

What is the purpose of the instant vector selector syntax http_requests_total{job="api-server"}?

Accepted Answer

It selects current values of time series matching the metric name and label filter.. It selects the current value of all time series for the metric http_requests_total that have the label job set to api-server.

Answer

It aggregates all API server requests into a single sum.

Answer

It triggers an alert if the job is down.

Answer

It selects historical data points spanning the last hour for the matching series.

Question 7

An operator writes a query to calculate error percentage: sum(rate(errors[5m])) / sum(rate(total[5m])) * 100. What happens if the denominator evaluates to zero or has no matching time series?

Accepted Answer

The query returns an empty vector (no data points).. Division by zero or division by an empty vector in PromQL results in an empty vector output.

Answer

Prometheus throws a fatal query evaluation runtime exception.

Answer

The query returns NaN for all series.

Answer

The query automatically returns infinity.

Question 8

What is the behavior of the clamp_max() function when applied to an instant vector?

Accepted Answer

It restricts all values in the vector so that none exceed the specified maximum.. clamp_max clamps the values of all time series in the vector to a specified maximum upper limit.

Answer

It drops any time series whose value exceeds the specified maximum.

Answer

It generates an alert if any time series exceeds the maximum.

Answer

It sets values exceeding the maximum to NaN.

Question 9

You are troubleshooting a query and notice that label_replace is being used. What is the primary function of label_replace(v, dst_label, replacement, src_label, regex)?

Accepted Answer

It matches a regex against a source label value and writes the result into a destination label.. The label_replace function matches the regex against the value of src_label, and if it matches, sets dst_label to the replacement string.

Answer

It renames the Prometheus server instance in federated environments.

Answer

It drops all time series that do not contain the specified source label.

Answer

It replaces the metric name with a new string.

Question 10

You want to find the maximum value of a gauge metric across all instances over a 1-hour sliding window. Which function accomplishes this?

Accepted Answer

max_over_time(node_memory_usage_bytes[1h]). The max_over_time() function evaluates the maximum value of all data points in a specified range vector for each time series.

Answer

max(node_memory_usage_bytes[1h])

Answer

topk(1, node_memory_usage_bytes[1h])

Answer

max_with_range(node_memory_usage_bytes, 1h)

Question 11

When evaluating a rule with offset, such as http_requests_total offset 1h, what exact time does Prometheus query?

Accepted Answer

It evaluates the query at the evaluation timestamp minus 1 hour.. The offset modifier shifts the evaluation time backward by the specified duration relative to the evaluation timestamp.

Answer

It fetches data starting 1 hour in the future.

Answer

It calculates the moving average over the past 1 hour.

Answer

It delays rule evaluation by 1 hour to wait for late-arriving data.

Question 12

If you perform 'A / B' where A and B have different sets of labels, what happens?

Accepted Answer

It returns an empty result.. Binary operations require matching labels unless modifiers are used; otherwise, the result is empty.

Answer

It automatically ignores the extra labels.

Answer

It returns the result of the division for all series.

Answer

It returns an error in the UI.

Question 13

Which TWO of the following are valid metric types natively supported by Prometheus? (Choose TWO)

Accepted Answer

Gauge. Prometheus natively supports four core metric types: Counter, Gauge, Histogram, and Summary.

Answer

Matrix

Answer

Vector

Answer

Scalar

Question 14

You need to calculate the ratio of successful HTTP requests (status 200) to total HTTP requests. Both metrics are counters named 'http_requests_total'. How do you construct this query to ensure proper label matching between status='200' and total requests?

Accepted Answer

http_requests_total{status="200"} / ignoring(status) http_requests_total. To divide two vectors with different label sets (e.g., status='200' vs all statuses), you must use binary matching modifiers like 'ignoring(status)' or 'on'.

Answer

rate(http_requests_total{status="200"}[5m]) / rate(http_requests_total[5m]) ignoring(status)

Answer

sum(http_requests_total{status="200"}) / sum(http_requests_total)

Answer

http_requests_total{status="200"} / http_requests_total

Question 15

Which TWO of the following statements regarding PromQL subqueries are correct? (Choose two)

Accepted Answer

Subqueries allow instant vector queries to be passed as range vector inputs to functions like max_over_time().. Subqueries allow running an instant vector query over a historical time range with a specified resolution and lookback delta.

Answer

Subqueries execute faster than standard instant queries because they bypass the storage engine.

Answer

Subqueries can only be executed against range vectors, never instant vectors.

Answer

The resolution parameter in a subquery is mandatory.