Linux Foundation PCA Dumps Updated Dec 30, 2025 WIith 62 Questions
View All PCA Actual Free Exam Questions Dec 30, 2025 Updated
NEW QUESTION # 22
What function calculates the tp-quantile from a histogram?
- A. histogram()
- B. avg_over_time()
- C. histogram_quantile()
- D. predict_linear()
Answer: C
Explanation:
In Prometheus, the histogram_quantile() function is specifically designed to compute quantiles (such as tp90, tp95, or tp99) from histogram bucket data. A histogram metric records cumulative bucket counts for observed values under specific thresholds (le label).
The function works by interpolating between buckets based on the target quantile. For example, to compute the 90th percentile latency from a histogram named http_request_duration_seconds_bucket, you would use:
histogram_quantile(0.9, sum(rate(http_request_duration_seconds_bucket[5m])) by (le)) Here, 0.9 represents the tp90 quantile, and rate() converts counter increments into per-second rates.
Other options are incorrect:
histogram() is not a valid PromQL function.
predict_linear() forecasts future values of a time series.
avg_over_time() computes a simple average over a time window, not quantiles.
Reference:
Verified from Prometheus documentation - PromQL Function: histogram_quantile(), Working with Histograms, and Quantile Calculation Details.
NEW QUESTION # 23
What is a rule group?
- A. It is a set of rules that are executed sequentially.
- B. It is the set (the group) of all the rules in a file.
- C. It is a set of rules, split into groups by type.
- D. It is a set of rules that are grouped by labels.
Answer: A
Explanation:
In Prometheus, a rule group is a logical collection of recording and alerting rules that are evaluated sequentially at a specified interval. Rule groups are defined in YAML files under the groups: key, with each group containing a name, an interval, and a list of rules.
For example:
groups:
- name: example
interval: 1m
rules:
- record: job:http_inprogress_requests:sum
expr: sum(http_inprogress_requests) by (job)
All rules in a group share the same evaluation schedule and are executed one after another. This ensures deterministic order, especially when one rule depends on another's result.
Reference:
Verified from Prometheus documentation - Rule Configuration, Rule Groups and Evaluation Order, and Recording & Alerting Rules Guide.
NEW QUESTION # 24
What are Inhibition rules?
- A. Inhibition rules inspect alerts when a matching set of alerts is firing.
- B. Inhibition rules inject a new set of alerts when a matching alert is firing.
- C. Inhibition rules mute a set of alerts when another matching alert is firing.
- D. Inhibition rules repeat a set of alerts when another matching alert is firing.
Answer: C
Explanation:
Inhibition rules in Prometheus's Alertmanager are used to suppress (mute) alerts that would otherwise be redundant when a higher-priority or related alert is already active. This feature helps avoid alert noise and ensures that operators focus on the root cause rather than multiple cascading symptoms.
For example, if a "DatacenterDown" alert is firing, inhibition rules can mute all "InstanceDown" alerts that share the same datacenter label, preventing redundant notifications. Inhibition is configured in the Alertmanager configuration file under the inhibit_rules section.
Each rule defines:
A source match (the alert that triggers inhibition),
A target match (the alert to mute), and
A match condition (labels that must be equal for inhibition to apply).
Only when the source alert is active are the target alerts silenced.
Reference:
Verified from Prometheus documentation - Alertmanager Configuration - Inhibition Rules, Alert Deduplication and Grouping, and Alert Routing Best Practices.
NEW QUESTION # 25
How can you use Prometheus Node Exporter?
- A. You can use it to collect resource metrics from the application HTTP server.
- B. You can use it to probe endpoints over HTTP, HTTPS.
- C. You can use it to collect metrics for hardware and OS metrics.
- D. You can use it to instrument applications with metrics.
Answer: C
Explanation:
The Prometheus Node Exporter is a core system-level exporter that exposes hardware and operating system metrics from *nix-based hosts. It collects metrics such as CPU usage, memory, disk I/O, filesystem space, network statistics, and load averages.
It runs as a lightweight daemon on each host and exposes metrics via an HTTP endpoint (default: :9100/metrics), which Prometheus scrapes periodically.
Key clarification:
It does not instrument applications (A).
It does not collect metrics directly from application HTTP endpoints (B).
It is unrelated to HTTP probing tasks - those are handled by the Blackbox Exporter (D).
Thus, the correct use of the Node Exporter is to collect and expose hardware and OS-level metrics for Prometheus monitoring.
Reference:
Extracted and verified from Prometheus documentation - Node Exporter Overview, Host-Level Monitoring, and Exporter Usage Best Practices sections.
NEW QUESTION # 26
With the following metrics over the last 5 minutes:
up{instance="localhost"} 1 1 1 1 1
up{instance="server1"} 1 0 0 0 0
What does the following query return:
min_over_time(up[5m])
- A. {instance="localhost"} 1 {instance="server1"} 0
- B. {instance="server1"} 0
Answer: A
Explanation:
The min_over_time() function in PromQL returns the minimum sample value observed within the specified time range for each time series.
In the given data:
For up{instance="localhost"}, all samples are 1. The minimum value over 5 minutes is therefore 1.
For up{instance="server1"}, the sequence is 1 0 0 0 0. The minimum observed value is 0.
Thus, the query min_over_time(up[5m]) returns two series - one per instance:
{instance="localhost"} 1
{instance="server1"} 0
This query is commonly used to check uptime consistency. If the minimum value over the time window is 0, it indicates at least one scrape failure (target down).
Reference:
Verified from Prometheus documentation - PromQL Range Vector Functions, min_over_time() definition, and up Metric Semantics sections.
NEW QUESTION # 27
What does the increase() function do in PromQL?
- A. Calculates the derivative of a gauge over time.
- B. Returns the absolute increase in a counter over a specified range.
- C. Returns the total sum of values in a vector.
- D. Calculates the percentage increase of a counter over time.
Answer: B
Explanation:
The increase() function computes the total increase in a counter metric over a specified range vector. It accounts for counter resets and only measures the net change in the counter's value during the time window.
Example:
increase(http_requests_total[5m])
This query returns how many HTTP requests occurred in the last five minutes. Unlike rate(), which provides a per-second average rate, increase() gives the absolute number of increments.
NEW QUESTION # 28
The following is a list of metrics exposed by an application:
http_requests_total{code="500"} 10
http_requests_total{code="200"} 20
http_requests_total{code="400"} 30
http_requests_total{verb="POST"} 30
http_requests_total{verb="GET"} 30
What is the issue with the metric family?
- A. Metric names are missing a prefix to indicate which application is exposing the query.
- B. The value represents two different things across the dimensions: code and verb.
Answer: B
Explanation:
Prometheus requires that a single metric name represents one well-defined thing, and all time series in that metric share the same set of label keys so the value's meaning is consistent across dimensions. The official guidance states that metrics should not "mix different dimensions under the same name," and that a metric name should have a consistent label schema; otherwise, "the same metric name would represent different things," making queries ambiguous and aggregations error-prone. In the example, http_requests_total{code="..."} expresses per-status-code request counts, while http_requests_total{verb="..."} expresses per-HTTP-method request counts. Because some series have only code and others only verb, the value changes its meaning across label sets, violating the consistency principle for a metric family. The correct approach is to expose one metric with both labels present on every series, e.g., http_requests_total{code="200", method="GET"}, ensuring every time series has the same label keys and the value always means "count of requests," sliced by the same dimensions. A missing application prefix is optional and not the core issue here.
NEW QUESTION # 29
Which function would you use to calculate the 95th percentile latency from histogram data?
- A. topk(0.95, http_request_duration_seconds)
- B. quantile_over_time(0.95, http_request_duration_seconds[5m])
- C. histogram_quantile(0.95, sum(rate(http_request_duration_seconds_bucket[5m])) by (le))
- D. percentile(http_request_duration_seconds, 0.95)
Answer: C
Explanation:
To calculate a percentile (e.g., 95th percentile) from histogram data in Prometheus, the correct function is histogram_quantile(). It estimates quantiles based on cumulative bucket counts.
Example:
histogram_quantile(0.95, sum(rate(http_request_duration_seconds_bucket[5m])) by (le)) This computes the 95th percentile request duration across all observed instances over the last 5 minutes.
NEW QUESTION # 30
Given the following Histogram metric data, how many requests took less than or equal to 0.1 seconds?
apiserver_request_duration_seconds_bucket{job="kube-apiserver", le="+Inf"} 3 apiserver_request_duration_seconds_bucket{job="kube-apiserver", le="0.05"} 0 apiserver_request_duration_seconds_bucket{job="kube-apiserver", le="0.1"} 1 apiserver_request_duration_seconds_bucket{job="kube-apiserver", le="1"} 3 apiserver_request_duration_seconds_count{job="kube-apiserver"} 3 apiserver_request_duration_seconds_sum{job="kube-apiserver"} 0.554003785
- A. 0
- B. 1
- C. 2
- D. 0.554003785
Answer: B
Explanation:
In Prometheus, histogram metrics use cumulative buckets to record the count of observations that fall within specific duration thresholds. Each bucket has a label le ("less than or equal to"), representing the upper bound of that bucket.
In the given metric, the bucket labeled le="0.1" has a value of 1, meaning exactly one request took less than or equal to 0.1 seconds. Buckets are cumulative, so:
le="0.05" → 0 requests ≤ 0.05 seconds
le="0.1" → 1 request ≤ 0.1 seconds
le="1" → 3 requests ≤ 1 second
le="+Inf" → all 3 requests total
The _sum and _count values represent total duration and request count respectively, but the number of requests below a given threshold is read directly from the bucket's le value.
Reference:
Verified from Prometheus documentation - Understanding Histograms and Summaries, Bucket Semantics, and Histogram Query Examples sections.
NEW QUESTION # 31
Which of the following is a valid metric name?
- A. go.goroutines
- B. go_goroutines
- C. 99_goroutines
- D. go routines
Answer: B
Explanation:
According to Prometheus naming rules, metric names must match the regex [a-zA-Z_:][a-zA-Z0-9_:]*. This means metric names must begin with a letter, underscore, or colon, and can only contain letters, digits, and underscores thereafter.
The valid metric name among the options is go_goroutines, which follows all these rules. It starts with a letter (g), uses underscores to separate words, and contains only allowed characters.
By contrast:
go routines is invalid because it contains a space.
go.goroutines is invalid because it contains a dot (.), which is reserved for recording rule naming hierarchies, not metric identifiers.
99_goroutines is invalid because metric names cannot start with a number.
Following these conventions ensures compatibility with PromQL syntax and Prometheus' internal data model.
Reference:
Extracted from Prometheus documentation - Metric Naming Conventions and Data Model Rules sections.
NEW QUESTION # 32
Which of the following signals belongs to symptom-based alerting?
- A. CPU usage
- B. Disk space
- C. API latency
- D. Database availability
Answer: C
Explanation:
Symptom-based alerting focuses on detecting user-visible or service-impacting issues rather than internal resource states. Metrics like API latency, error rates, and availability directly indicate degraded user experience and are therefore the preferred triggers for alerts.
In contrast, resource-based alerts (like CPU usage or disk space) often represent underlying causes, not symptoms. Alerting on them can produce noise and distract from actual service health problems.
For example, high API latency (http_request_duration_seconds) clearly reflects that users are experiencing delays, which is actionable and business-relevant.
This concept aligns with the RED (Rate, Errors, Duration) and USE (Utilization, Saturation, Errors) monitoring models promoted in Prometheus and SRE best practices.
Reference:
Verified from Prometheus documentation - Alerting Best Practices, Symptom vs. Cause Alerting, and RED/USE Monitoring Principles.
NEW QUESTION # 33
How can you select all the up metrics whose instance label matches the regex fe-.*?
- A. up{instance~"fe-.*"}
- B. up{instance=~"fe-.*"}
- C. up{instance=regexp(fe-.*)}
- D. up{instance="fe-.*"}
Answer: B
Explanation:
PromQL supports regular expression matching for label values using the =~ operator. To select all time series whose label values match a given regex pattern, you use the syntax {label_name=~"regex"}.
In this case, to select all up metrics where the instance label begins with fe-, the correct query is:
up{instance=~"fe-.*"}
Explanation of operators:
= → exact match.
!= → not equal.
=~ → regex match.
!~ → regex not match.
Option D uses the correct =~ syntax. Options A and B use invalid PromQL syntax, and option C is almost correct but includes a misplaced extra quote style (~''), which would cause a parsing error.
Reference:
Verified from Prometheus documentation - Expression Language Data Selectors, Label Matchers, and Regular Expression Matching Rules.
NEW QUESTION # 34
How would you correctly name a metric that provides metadata information about the binary?
- A. app_build_desc
- B. app_build_info
- C. app_metadata
- D. app_build
Answer: B
Explanation:
The Prometheus naming convention for metrics that expose build or version information about an application binary uses the _info suffix. The standard pattern is:
<application>_build_info
This metric typically includes constant labels such as version, revision, branch, and goversion to describe the build environment.
For example:
app_build_info{version="1.2.3", revision="abc123", goversion="go1.22"} 1 This approach follows the official Prometheus instrumentation guidelines, where metrics ending in _info convey metadata or constant characteristics about the running process.
The other options do not conform to the Prometheus best practice of suffix-based semantic naming.
Reference:
Extracted and verified from Prometheus documentation - Metric Naming Conventions, Exposing Build Information, and Standard _info Metrics sections.
NEW QUESTION # 35
How would you add text from the instance label to the alert's description for the following alert?
alert: InstanceDown
expr: up == 0
for: 5m
labels:
severity: page
annotations:
description: "Instance INSTANCE_NAME_HERE down"
- A. Use $metric.instance instead of INSTANCE_NAME_HERE
- B. Use $expr.instance instead of INSTANCE_NAME_HERE
- C. Use $value.instance instead of INSTANCE_NAME_HERE
- D. Use $labels.instance instead of INSTANCE_NAME_HERE
Answer: D
Explanation:
In Prometheus alerting rules, you can dynamically reference label values in annotations and labels using template variables. Each alert has access to its labels via the variable $labels, which allows direct insertion of label data into alert messages or descriptions.
To include the value of the instance label dynamically in the description, replace the placeholder INSTANCE_NAME_HERE with:
description: "Instance {{$labels.instance}} down"
or equivalently:
description: "Instance $labels.instance down"
Both forms are valid - the first follows Go templating syntax and is the recommended format.
This ensures that when the alert fires, the instance label (e.g., a hostname or IP) is automatically included in the message, producing outputs like:
Instance 192.168.1.15:9100 down
Options B, C, and D are invalid because $value, $expr, and $metric are not recognized context variables in alert templates.
Reference:
Verified from Prometheus documentation - Alerting Rules Configuration, Using Template Variables in Annotations and Labels, and Prometheus Templating Guide (Go Templates and $labels usage) sections.
NEW QUESTION # 36
What popular open-source project is commonly used to visualize Prometheus data?
- A. Grafana
- B. Loki
- C. Thanos
- D. Kibana
Answer: A
Explanation:
The most widely used open-source visualization and dashboarding platform for Prometheus data is Grafana. Grafana provides native integration with Prometheus as a data source, allowing users to create real-time, interactive dashboards using PromQL queries.
Grafana supports advanced visualization panels (graphs, heatmaps, gauges, tables, etc.) and enables users to design custom dashboards to monitor infrastructure, application performance, and service-level objectives (SLOs). It also provides alerting capabilities that can complement or extend Prometheus's own alerting system.
While Kibana is part of the Elastic Stack and focuses on log analytics, Thanos extends Prometheus for long-term storage and high availability, and Loki is a log aggregation system. None of these tools serve as the primary dashboarding solution for Prometheus metrics the way Grafana does.
Grafana's seamless Prometheus integration and templating support make it the de facto standard visualization tool in the Prometheus ecosystem.
Reference:
Verified from Prometheus documentation - Visualizing Data with Grafana, and Grafana documentation - Prometheus Data Source Integration and Dashboard Creation Guide.
NEW QUESTION # 37
What is the maximum number of Alertmanagers that can be added to a Prometheus instance?
- A. 0
- B. More than 3
- C. 1
- D. 2
Answer: B
Explanation:
Prometheus supports integration with multiple Alertmanager instances for redundancy and high availability. The alerting section of the Prometheus configuration file (prometheus.yml) allows specifying a list of Alertmanager targets, enabling Prometheus to send alerts to several Alertmanager nodes simultaneously.
There is no hard-coded limit on the number of Alertmanagers that can be added. The typical best practice is to run a minimum of three Alertmanagers in a clustered setup to achieve fault tolerance and ensure reliable alert delivery, but Prometheus can be configured with more than three if desired.
Each Alertmanager node in the cluster communicates state information (active, silenced, inhibited alerts) with its peers to maintain consistency.
Reference:
Verified from Prometheus documentation - Alertmanager Integration, High Availability Setup, and Prometheus Configuration - alerting Section.
NEW QUESTION # 38
......
New PCA Exam Questions Real Linux Foundation Dumps: https://www.examsreviews.com/PCA-pass4sure-exam-review.html
Pass Authentic Linux Foundation PCA with Free Practice Tests and Exam Dumps: https://drive.google.com/open?id=1Jd70wRz1_CHh99j4rWZzpGL8Smpknext