Add processes exporter (#950)

* Add processes exporter

Signed-off-by: Pavel Kutishchev <pavel.kutishchev@olx.com>
Signed-off-by: Ben Kochie <superq@gmail.com>

collector/processes_linux.go

@@ -0,0 +1,109 @@
+// Copyright 2018 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !noprocesses
+
+package collector
+
+import (
+	"fmt"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs"
+)
+
+type processCollector struct {
+	threadAlloc *prometheus.Desc
+	threadLimit *prometheus.Desc
+	procsState  *prometheus.Desc
+	pidUsed     *prometheus.Desc
+	pidMax      *prometheus.Desc
+}
+
+func init() {
+	registerCollector("processes", defaultDisabled, NewProcessStatCollector)
+}
+
+func NewProcessStatCollector() (Collector, error) {
+	subsystem := "processes"
+	return &processCollector{
+		threadAlloc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "threads"),
+			"Allocated threads in system",
+			nil, nil,
+		),
+		threadLimit: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "max_threads"),
+			"Limit of threads in the system",
+			nil, nil,
+		),
+		procsState: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "state"),
+			"Number of processes in each state.",
+			[]string{"state"}, nil,
+		),
+		pidUsed: prometheus.NewDesc(prometheus.BuildFQName(namespace, subsystem, "pids"),
+			"Number of PIDs", nil, nil,
+		),
+		pidMax: prometheus.NewDesc(prometheus.BuildFQName(namespace, subsystem, "max_processes"),
+			"Number of max PIDs limit", nil, nil,
+		),
+	}, nil
+}
+func (t *processCollector) Update(ch chan<- prometheus.Metric) error {
+	pids, states, threads, err := getAllocatedThreads()
+	if err != nil {
+		return fmt.Errorf("Unable to retrieve number of allocated threads %v\n", err)
+	}
+
+	ch <- prometheus.MustNewConstMetric(t.threadAlloc, prometheus.GaugeValue, float64(threads))
+	maxThreads, err := readUintFromFile(procFilePath("sys/kernel/threads-max"))
+	if err != nil {
+		return fmt.Errorf("Unable to retrieve limit number of threads %v\n", err)
+	}
+	ch <- prometheus.MustNewConstMetric(t.threadLimit, prometheus.GaugeValue, float64(maxThreads))
+
+	for state := range states {
+		ch <- prometheus.MustNewConstMetric(t.procsState, prometheus.GaugeValue, float64(states[state]), state)
+	}
+
+	pidM, err := readUintFromFile(procFilePath("sys/kernel/pid_max"))
+	if err != nil {
+		return fmt.Errorf("Unable to retrieve limit number of maximum pids alloved %v\n", err)
+	}
+	ch <- prometheus.MustNewConstMetric(t.pidUsed, prometheus.GaugeValue, float64(pids))
+	ch <- prometheus.MustNewConstMetric(t.pidMax, prometheus.GaugeValue, float64(pidM))
+
+	return nil
+}
+
+func getAllocatedThreads() (int, map[string]int32, int, error) {
+	fs, err := procfs.NewFS(*procPath)
+	if err != nil {
+		return 0, nil, 0, err
+	}
+	p, err := fs.AllProcs()
+	if err != nil {
+		return 0, nil, 0, err
+	}
+	thread := 0
+	procStates := make(map[string]int32)
+	for _, pid := range p {
+		stat, err := pid.NewStat()
+		if err != nil {
+			return 0, nil, 0, err
+		}
+		procStates[stat.State] += 1
+		thread += stat.NumThreads
+	}
+	return len(p), procStates, thread, nil
+}