PCA Promql Practice Question
You are troubleshooting a query and notice that label_replace is being used. What is the primary function of label_replace(v, dst_label, replacement, src_label, regex)?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It matches a regex against a source label value and writes the result into a destination label.
The label_replace function matches the regex against the value of src_label, and if it matches, sets dst_label to the replacement string.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It renames the Prometheus server instance in federated environments.
Why it's wrong here
Federation handles instance naming differently.
- ✗
It drops all time series that do not contain the specified source label.
Why it's wrong here
It does not drop series; it modifies label sets.
- ✓
It matches a regex against a source label value and writes the result into a destination label.
Why this is correct
Correct. label_replace modifies or creates labels based on regular expression extractions.
- ✗
It replaces the metric name with a new string.
Why it's wrong here
Metric names are stored in the special label __name__, but label_replace is generally used for arbitrary labels.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official CNCF / Linux Foundation exam blueprint
This PCA practice question is part of Courseiva's free CNCF / Linux Foundation certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCA exam.