// 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.
func NewProcessCollectorPIDFn(
	pidFn func() (int, error),
	namespace string,
) Collector {
	ns := ""
	if len(namespace) > 0 {
		ns = namespace + "_"
	}

	c := processCollector{
		pidFn:     pidFn,
		collectFn: func(chan<- Metric) {},

		cpuTotal: NewDesc(
			ns+"process_cpu_seconds_total",
			"Total user and system CPU time spent in seconds.",
			nil, nil,
		),
		openFDs: NewDesc(
			ns+"process_open_fds",
			"Number of open file descriptors.",
			nil, nil,
		),
		maxFDs: NewDesc(
			ns+"process_max_fds",
			"Maximum number of open file descriptors.",
			nil, nil,
		),
		vsize: NewDesc(
			ns+"process_virtual_memory_bytes",
			"Virtual memory size in bytes.",
			nil, nil,
		),
		rss: NewDesc(
			ns+"process_resident_memory_bytes",
			"Resident memory size in bytes.",
			nil, nil,
		),
		startTime: NewDesc(
			ns+"process_start_time_seconds",
			"Start time of the process since unix epoch in seconds.",
			nil, nil,
		),
	}

	// Set up process metric collection if supported by the runtime.
	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.
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.",
		}),
	}

	// Set up process metric collection if supported by the runtime.
	if _, err := procfs.NewStat(); err == nil {
		c.collectFn = c.processCollect
	}

	return &c
}
func processCollectSupported() bool {
	if _, err := procfs.NewStat(); err == nil {
		return true
	}
	return false
}