You are monitoring server hardware metrics using node_exporter. You observe that the metrics are not showing up in Prometheus. Which initial troubleshooting step is most effective?
You are implementing a custom exporter for a legacy database. The database provides a single value representing the number of active connections. Which metric type should you use to best represent this data?
You need to monitor the availability of a specific web endpoint from external locations using blackbox_exporter. What is the primary purpose of the 'module' configuration in blackbox_exporter?
You have a histogram metric tracking request durations. You need to calculate the 99th percentile across all instances in a cluster. Why is this difficult with standard Prometheus metrics?