Linux Foundation PCA Exam Dumps

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.

Extracted from Prometheus documentation -- Metric Naming Conventions and Data Model Rules sections.

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.

Verified from Prometheus documentation -- Expression Language Data Selectors, Label Matchers, and Regular Expression Matching Rules.

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.

Verified from Prometheus documentation -- Alerting Rules Configuration, Using Template Variables in Annotations and Labels, and Prometheus Templating Guide (Go Templates and $labels usage) sections.

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.

Extracted and verified from Prometheus documentation -- Node Exporter Overview, Host-Level Monitoring, and Exporter Usage Best Practices sections.

In Prometheus, the part before the curly braces {} represents the metric name. Therefore, in the metric api_http_requests_total{method='POST', handler='/messages'}, the term api_http_requests_total is the metric name. Metric names describe the specific quantity being measured --- in this example, the total number of HTTP requests received by an API.

The portion within the braces defines labels, which provide additional dimensions to the metric. Here, method='POST' and handler='/messages' are labels describing request attributes. The metric name should follow Prometheus conventions: lowercase letters, numbers, and underscores only, and ending in _total for counters.

This naming scheme ensures clarity and standardization across instrumented applications. The metric type (e.g., counter, gauge) is declared separately in the exposition format, not within the metric name itself.

Verified from Prometheus documentation -- Metric and Label Naming, Data Model, and Instrumentation Best Practices sections.