PCA Practice Questions

Question 1

What is the purpose of the 'keep_firing_for' field in an alerting rule?

Accepted Answer

To prevent alert flapping. It keeps an alert in the firing state for a specified duration after the underlying expression is no longer true, which helps prevent flapping.

Answer

To delay the initial alert

Answer

To repeat the alert every X minutes

Answer

To log the alert to disk

Question 2

Which TWO of the following are necessary to successfully inhibit an alert in Alertmanager?

Accepted Answer

target_matchers. Inhibition requires a 'target_matchers' (the alert to be silenced) and 'source_matchers' (the alert that triggers the silence), plus common labels to correlate the two.

Answer

repeat_interval

Answer

group_wait

Answer

group_interval

Question 3

You are monitoring a Linux server and need to track CPU usage. Which exporter is the standard choice for exposing hardware and OS metrics?

Accepted Answer

node_exporter. node_exporter is the standard Prometheus exporter for hardware and OS metrics exposed by *NIX kernels.

Answer

mysqld_exporter

Answer

blackbox_exporter

Answer

pushgateway

Question 4

Which THREE are true regarding the Prometheus TSDB?

Accepted Answer

It uses an inverted index for fast searching.. It uses blocks, WAL, and index files, and it is optimized for time-series data.

Answer

It uses a B-tree for all queries.

Answer

It is a relational database.

Question 5

An application is emitting logs that contain '5xx' status codes when a service is unavailable. If you want to create an alert that triggers based on the rate of these errors, what is the best practice for observability?

Accepted Answer

Expose a metric incrementing on every 5xx error and alert on the rate of that metric.. Logs are useful for root cause analysis, but for alerting on rates, you should convert the error occurrence into a metric increment, as metrics are more efficient for long-term calculation and alerting.

Answer

Alert directly on the log stream using a log aggregator.

Answer

Use Prometheus to scrape the log file directly.

Answer

Increase log verbosity to trace the request until the error is resolved.

Question 6

You are using the blackbox_exporter to monitor an HTTP endpoint. Which module configuration is required to check the HTTP status code?

Accepted Answer

http_2xx. The http_2xx module is the standard configuration for checking that an endpoint returns a successful HTTP status code.

Answer

dns_query

Answer

tcp_connect

Answer

icmp_ping

Question 7

You are instrumenting a Go application. What is the standard way to register a metric?

Accepted Answer

prometheus.MustRegister(). The prometheus.MustRegister() function is the standard way to register custom metrics with the default registry.

Answer

prometheus.Enable()

Answer

prometheus.Set()

Answer

prometheus.Add()

Question 8

What is the impact of naming a metric starting with an underscore?

Accepted Answer

Reserved for internal use. Metric names starting with underscores are reserved for internal use by Prometheus and should be avoided for user-defined metrics.

Answer

Automatic aggregation

Answer

Performance loss

Answer

Syntax error

Question 9

If you are using a Histogram, what is the purpose of the '_sum' metric?

Accepted Answer

To store the sum of observations. The _sum metric provides the sum of all observed values, which allows calculating the average when combined with the _count metric.

Answer

To store the median

Answer

To store the maximum value

Answer

To store the total count

Question 10

Which TWO of the following are true about the Blackbox exporter?

Accepted Answer

It supports HTTP, TCP, and DNS. It is used for active probing and supports multiple modules for different protocols.

Answer

It is the only exporter for databases

Answer

It automatically instruments application code

Answer

It is a passive metric collector

Question 11

Which THREE of the following are valid components within a Prometheus Alerting Rule file?

Accepted Answer

expr. Prometheus alerting rules contain a 'groups' array, which contains individual 'rules' (alerts or recordings), and each alert rule must have an 'alert' name and 'expr'.

Answer

receiver

Answer

routing_tree

Question 12

What is the purpose of the 'labels' field in an alerting rule?

Accepted Answer

To add metadata for routing and filtering. Labels allow you to attach metadata to the alert, which can then be used in Alertmanager for routing and grouping.

Answer

To define the alert message body

Answer

To select the target server

Answer

To set the alert severity level

Question 13

A legacy batch job runs once per day and finishes in seconds. Why is a standard Prometheus pull model inadequate here?

Accepted Answer

The job is too fast for HTTP polling.. Prometheus pull intervals are typically set to seconds or minutes; a job that finishes quickly might never be 'up' when Prometheus scrapes it.

Answer

The data is too large for memory.

Answer

Pull model is insecure.

Answer

Prometheus cannot scrape batch jobs.

Question 14

Which monitoring philosophy is core to the Prometheus architecture?

Accepted Answer

Centralized pull-based scraping.. Prometheus favors the pull model, where the server controls the scrape rate and frequency, providing better control over the load on the monitoring system.

Answer

Agent-less log aggregation.

Answer

Push-based data ingestion.

Answer

Event-driven architecture.

Question 15

You are seeing 'NaN' values in your gauge metrics. What does this indicate?

Accepted Answer

An undefined gauge state. NaN (Not a Number) is a valid value for gauges in Prometheus, often indicating that a value is currently undefined or not applicable.

Answer

A scrape error

Answer

Metric type mismatch

Answer

Label collision

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