PCA Prometheus Architecture & Components 3

Question 1

What is the purpose of the Write-Ahead Log (WAL) in Prometheus's TSDB?

Accepted Answer

To persist in-memory samples before they are compacted into blocks

Answer

The WAL records incoming samples so that in-memory data can be recovered after a crash before it is written to immutable TSDB blocks.

Question 2

Which Prometheus feature allows writing samples simultaneously to an external system like Thanos or Cortex?

Accepted Answer

Remote write

Answer

Remote write forwards scraped samples in real time to a remote storage endpoint, enabling long-term storage and multi-tenant scenarios.

Question 3

What is a Prometheus 'target' in the context of its architecture?

Accepted Answer

An HTTP endpoint Prometheus scrapes for metrics

Answer

A target is an HTTP endpoint (typically /metrics) that Prometheus polls at each scrape interval to collect time-series samples.

Question 4

How does Prometheus handle high cardinality when scraping a target with millions of unique label combinations?

Accepted Answer

It stores each unique label set as a separate time series, which can exhaust memory

Answer

Each unique combination of metric name and label set is a distinct time series; too many unique combinations cause memory and CPU exhaustion known as a 'cardinality explosion'.

Question 5

In Prometheus architecture, what is the function of the 'notifier' component?

Accepted Answer

It sends firing alerts from the rule evaluator to Alertmanager

Answer

The notifier queues and dispatches pending alert notifications to one or more Alertmanager instances over HTTP.

(PCA) Prometheus Certified Associate Practice Test

(PCA) Prometheus Certified Associate Practice Test

PCA Prometheus Architecture & Components 3