PCA Prometheus Fundamentals — 20 Questions

Question 1

How can you view the current configuration of a running Prometheus server?

Accepted Answer

Visit /config in the UI. The /config endpoint displays the currently loaded configuration.

Answer

Check the /metrics endpoint

Answer

View /status/config

Answer

Run a PromQL query

Answer

Look at the PID file

Question 2

How does Prometheus handle metrics with the same name and identical label sets?

Accepted Answer

It returns a scrape error. Prometheus considers a series unique by its name and label set; duplicate series are not allowed in the same scrape.

Answer

It keeps the first one received

Answer

It averages them

Answer

It keeps both values

Question 3

Where can you see a list of all currently active targets?

Accepted Answer

/targets. The /targets page in the Prometheus UI shows the status of all configured targets.

Answer

/alerts

Answer

/status/targets

Answer

/graph

Question 4

You need to add a static label to all metrics from a specific job. Where do you configure this?

Accepted Answer

scrape_configs.labels. The 'labels' block within a 'scrape_config' adds constant labels to every metric scraped from those targets.

Answer

global.labels

Answer

remote_write.labels

Answer

relabel_configs

Question 5

What is the standard interval for Alertmanager to send notification retries?

Accepted Answer

4h. Alertmanager doesn't have a simple retry interval; it uses the 'repeat_interval' to decide when to re-notify.

Answer

1m

Answer

1s

Answer

24h

Question 6

When configuring Alertmanager to send notifications to Slack, which block defines the routing tree?

Accepted Answer

route. The 'route' block defines the top-level tree for incoming alerts.

Answer

receivers

Answer

inhibit_rules

Answer

global

Question 7

Which file format does Prometheus use for its main configuration?

Accepted Answer

YAML. Prometheus configuration is strictly defined in YAML format.

Answer

XML

Answer

JSON

Answer

TOML

Question 8

In the Prometheus data model, what is a 'sample'?

Accepted Answer

A value and a timestamp. A sample is a value-timestamp pair associated with a specific series.

Answer

The metric name

Answer

A label key-value pair

Answer

An alert rule

Question 9

You are deploying Prometheus in a Kubernetes cluster and need to ensure it discovers pods labeled 'app=frontend'. Which configuration block is required?

Accepted Answer

kubernetes_sd_configs. kubernetes_sd_configs is the standard mechanism to discover pods dynamically.

Answer

dns_sd_configs

Answer

static_configs

Answer

file_sd_configs

Question 10

You observe data gaps in your Prometheus graph after increasing the scrape interval. What is the most likely cause?

Accepted Answer

The scrape_timeout is shorter than the time taken to fetch metrics. If the scrape interval is too long, the 'scrape_duration' may exceed the interval or cause stale data handling issues.

Answer

TSDB block corruption

Answer

Stale markers not being processed

Answer

Too many labels on the metric

Question 11

A batch job runs for only 30 seconds every hour. How should you expose these metrics to Prometheus?

Accepted Answer

Use the Pushgateway. The Pushgateway is designed specifically for short-lived jobs that cannot be scraped directly.

Answer

Use an exporter sidecar

Answer

Increase scrape interval to 1 hour

Answer

Add a scrape_config for the batch job

Question 12

Which component is responsible for receiving alerts from Prometheus and managing notification delivery?

Accepted Answer

Alertmanager. Alertmanager is the dedicated component for deduplicating, grouping, and routing alerts.

Answer

Prometheus Server

Answer

Exporter

Answer

Pushgateway

Question 13

Your Prometheus server is hitting high memory usage due to high cardinality. Which action is most effective at reducing memory pressure?

Accepted Answer

Drop high-cardinality labels using relabel_configs. Reducing label cardinality (e.g., removing unique user IDs) is the primary way to reduce TSDB index size and memory usage.

Answer

Increase scrape_interval

Answer

Use more exporters

Answer

Enable remote write

Question 14

What is the default port that Prometheus listens on?

Accepted Answer

9090. 9090 is the well-known default port for the Prometheus server web interface.

Answer

9100

Answer

9093

Answer

8080

Question 15

You are performing a 'label_replace' operation. What is the correct syntax for a regex capture group?

Accepted Answer

$1. Prometheus uses standard RE2 regex syntax, where capture groups are accessed via $1, $2, etc.

Answer

\1

Answer

{1}

Answer

%1

Question 16

Which TSDB component is responsible for ensuring data durability if the server crashes?

Accepted Answer

WAL (Write-Ahead Log). The Write-Ahead Log (WAL) records incoming samples before they are committed to blocks.

Answer

Tombstone file

Answer

Head block

Answer

Index file

Question 17

You want to rename a metric during the scrape process. Which configuration block is appropriate?

Accepted Answer

metric_relabel_configs. relabel_configs is the correct way to modify metric labels (including __name__) before they are ingested.

Answer

scrape_configs

Answer

remote_write

Answer

target_relabel_configs

Question 18

Which mechanism allows Prometheus to discover targets by reading a list from a file?

Accepted Answer

file_sd_configs. file_sd_configs is designed to read target lists from JSON or YAML files.

Answer

dns_sd_configs

Answer

static_configs

Answer

consul_sd_configs

Question 19

What is the primary language used to query Prometheus data?

Accepted Answer

PromQL. PromQL (Prometheus Query Language) is the functional query language for Prometheus.

Answer

Regex

Answer

GraphQL

Answer

SQL

Question 20

When using the 'scrape_timeout', what happens if the timeout is reached?

Accepted Answer

The scrape is marked as failed. If the timeout is reached, the scrape is aborted, and a 'up{job=...} == 0' metric is recorded.

Answer

It automatically retries once

Answer

The previous value is kept indefinitely

Answer

The scrape continues silently