PCA Instrumentation And Exporters — 30 Questions

Question 1

Your application has a short-lived batch job that finishes before the Prometheus server can scrape it. What architectural component should be used?

Accepted Answer

Pushgateway. The Pushgateway is designed to allow ephemeral and batch jobs to expose their metrics to Prometheus.

Answer

Prometheus API

Answer

Alertmanager

Answer

node_exporter

Question 2

You need to track the number of requests received by your application. Which metric type should you choose?

Accepted Answer

Counter. A counter is a cumulative metric that represents a single monotonically increasing counter whose value can only increase or be reset to zero on restart.

Answer

Summary

Answer

Gauge

Answer

Histogram

Question 3

Which action should be avoided when creating labels for custom metrics?

Accepted Answer

Using high-cardinality labels. Adding high-cardinality data (like user IDs or unique request IDs) to labels causes an explosion in the number of time series, which can crash Prometheus.

Answer

Using static labels

Answer

Adding job labels

Answer

Adding instance labels

Question 4

When implementing a custom exporter, what format must the output follow to be correctly scraped by Prometheus?

Accepted Answer

Prometheus Text Format. Prometheus requires a text-based format where each metric is represented by lines, including name, labels, and values.

Answer

JSON

Answer

XML

Answer

Binary Protobuf

Question 5

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 6

A developer wants to expose a metric that represents the current memory usage of a process. Which type is most appropriate?

Accepted Answer

Gauge. A Gauge represents a numerical value that can arbitrarily go up and down, such as memory usage or temperature.

Answer

Counter

Answer

Summary

Answer

Histogram

Question 7

You need to monitor the duration of database queries. Which metric type is best for calculating quantiles on the server side?

Accepted Answer

Histogram. Summaries calculate configurable quantiles on the client side, while Histograms require server-side calculations.

Answer

Gauge

Answer

Counter

Answer

Summary

Question 8

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 9

What is the default port used by node_exporter?

Accepted Answer

9100. The standard Prometheus convention for node_exporter is port 9100.

Answer

9115

Answer

9090

Answer

8080

Question 10

When running node_exporter, how can you disable specific collectors like 'textfile'?

Accepted Answer

--no-collector.textfile. Collectors can be disabled using the --no-collector.<name> flag.

Answer

collector.textfile=false

Answer

exclude=textfile

Answer

--disable-textfile

Question 11

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 12

A Histogram has buckets [0.1, 0.5, 1, 5]. A request takes 0.7 seconds. Which buckets will be incremented?

Accepted Answer

1, 5. Histograms are cumulative. A value of 0.7 falls into the 1 and 5 buckets (because 0.7 <= 1 and 0.7 <= 5).

Answer

None

Answer

0.1, 0.5

Answer

Only 1

Question 13

What is the effect of using a 'Summary' metric with client-side quantiles?

Accepted Answer

It prevents cross-instance aggregation. Client-side quantiles are calculated per instance, making it impossible to aggregate them across multiple instances of an application.

Answer

It improves performance

Answer

It allows cross-instance aggregation

Answer

It doubles the scrape time

Question 14

You want to monitor the status of a specific SSL certificate via blackbox_exporter. Which module is designed for this?

Accepted Answer

http_2xx. The http_2xx module, when configured with TLS settings, can check certificate expiry via the probe_ssl_earliest_cert_expiry metric.

Answer

tcp_connect

Answer

ssl_check

Answer

cert_monitor

Question 15

When writing a custom exporter in Python, what is the most common way to expose the metrics?

Accepted Answer

Using start_http_server(). The prometheus_client library provides a start_http_server() method to expose metrics on a specified port.

Answer

Writing to a file

Answer

Using a message queue

Answer

Using a database connection

Question 16

You need to expose metrics from a legacy application that only logs to a file. What should you do?

Accepted Answer

Use the node_exporter textfile collector. The node_exporter textfile collector is designed to read metrics from a specific directory where you can drop files containing Prometheus-formatted data.

Answer

None of the above

Answer

Use a blackbox exporter

Answer

Use Pushgateway

Answer

Use a custom exporter

Question 17

What is the purpose of the 'le' label in a Histogram?

Accepted Answer

Less than or equal to. The 'le' label stands for 'less than or equal to' and defines the upper bound of the histogram bucket.

Answer

Latency estimate

Answer

Logarithmic exponent

Answer

Last entry

Question 18

When creating a custom exporter, which component is responsible for scraping the data?

Accepted Answer

The Prometheus server. The Prometheus server is responsible for initiating the scrape request to the exporter.

Answer

The Pushgateway

Answer

The exporter itself

Answer

The client library

Question 19

When using the Pushgateway, what happens if you push a metric with the same name and labels as an existing one?

Accepted Answer

It overwrites the old value. The Pushgateway overwrites the existing metric with the new value provided in the push request.

Answer

It creates a new series

Answer

It rejects the push

Answer

It adds to the existing value

Question 20

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