PCA (Prometheus Certified Associate) sample exam question with answer 36

Question:
Which of the following is the correct syntax for defining a custom label in an alerting rule?

1. ...
   alert: HighCPUUsage
   expr: 100 * (1 - rate(node_cpu{mode="idle"}[5m])) > 80
   labels:
     severity: warning
   ...

2. ...
   alert: HighCPUUsage
   expr: 100 * (1 - rate(node_cpu{mode="idle"}[5m])) > 80
   annotations:
     severity: warning
   ...

3. ...
   alert: HighCPUUsage
   expr: 100 * (1 - rate(node_cpu{mode="idle"}[5m])) > 80
   label:
     severity: warning
   ...

4. ...
   alert: HighCPUUsage
   expr: 100 * (1 - rate(node_cpu{mode="idle"}[5m])) > 80
   annotation:
     severity: warning
   ...

Answer:
A - Labels are used to attach metadata to alerts in Prometheus.
The correct syntax for defining a custom label in an alerting rule is to include the labels keyword followed by a list of key-value pairs.
Option B uses the annotations keyword instead of labels.
Options C and D have typos in the keywords (label instead of labels and annotation instead of annotations)