func NewProcessCollectorPIDFn(
	pidFn func() (int, error),
	namespace string,
) Collector {
	c := processCollector{
		pidFn:     pidFn,
		collectFn: func(chan<- Metric) {},
		cpuTotal: NewCounter(CounterOpts{
			Namespace: namespace,
			Name:      "process_cpu_seconds_total",
			Help:      "Total user and system CPU time spent in seconds.",
		}),
		openFDs: NewGauge(GaugeOpts{
			Namespace: namespace,
			Name:      "process_open_fds",
			Help:      "Number of open file descriptors.",
		}),
		maxFDs: NewGauge(GaugeOpts{
			Namespace: namespace,
			Name:      "process_max_fds",
			Help:      "Maximum number of open file descriptors.",
		}),
		vsize: NewGauge(GaugeOpts{
			Namespace: namespace,
			Name:      "process_virtual_memory_bytes",
			Help:      "Virtual memory size in bytes.",
		}),
		rss: NewGauge(GaugeOpts{
			Namespace: namespace,
			Name:      "process_resident_memory_bytes",
			Help:      "Resident memory size in bytes.",
		}),
		startTime: NewGauge(GaugeOpts{
			Namespace: namespace,
			Name:      "process_start_time_seconds",
			Help:      "Start time of the process since unix epoch in seconds.",
		}),
	}
	if _, err := procfs.NewStat(); err == nil {
		c.collectFn = c.processCollect
	}
	return &c
}
NewProcessCollectorPIDFn returns a collector which exports the current state
of process metrics including cpu, memory and file descriptor usage as well
as the process start time under the given namespace. The given pidFn is
called on each collect and is used to determine the process to export
metrics for.
package prometheus
import "github.com/prometheus/procfs"
type processCollector struct {
	pid             int
	collectFn       func(chan<- Metric)
	pidFn           func() (int, error)
	cpuTotal        Counter
	openFDs, maxFDs Gauge
	vsize, rss      Gauge
	startTime       Gauge
}
func NewProcessCollector(pid int, namespace string) Collector {
	return NewProcessCollectorPIDFn(
		func() (int, error) { return pid, nil },
		namespace,
	)
}