What metrics do you collect and monitor using Prometheus?

Prometheus is typically used to collect and monitor the following metrics:

• Application performance metrics: response time, requests per second, errors.
• System resources: CPU load, memory usage, disk I/O, network.
• Service status: availability, dependency status.
• Custom metrics: business metrics specific to the application (e.g., number of active users).

Example of a metric in Go using the Prometheus client:

var opsProcessed = prometheus.NewCounter(prometheus.CounterOpts{
    Name: "myapp_processed_ops_total",
    Help: "The total number of processed events",
})

func init() {
    prometheus.MustRegister(opsProcessed)
}

func processEvent() {
    // process event
    opsProcessed.Inc()
}

Thus, Prometheus helps monitor the state and performance of applications in real time.