Add softnet collector (#1576)

Signed-off-by: Peter Nicholson <petergoods@hotmail.com>

collector/softnet_linux.go

@@ -0,0 +1,99 @@
+// Copyright 2019 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 !nosoftnet
+
+package collector
+
+import (
+	"fmt"
+	"strconv"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs"
+)
+
+type softnetCollector struct {
+	fs           procfs.FS
+	processed    *prometheus.Desc
+	dropped      *prometheus.Desc
+	timeSqueezed *prometheus.Desc
+}
+
+const (
+	softnetSubsystem = "softnet"
+)
+
+func init() {
+	registerCollector("softnet", defaultEnabled, NewSoftnetCollector)
+}
+
+// NewSoftnetCollector returns a new Collector exposing softnet metrics.
+func NewSoftnetCollector() (Collector, error) {
+	fs, err := procfs.NewFS(*procPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open procfs: %w", err)
+	}
+
+	return &softnetCollector{
+		fs: fs,
+		processed: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, softnetSubsystem, "processed_total"),
+			"Number of processed packets",
+			[]string{"cpu"}, nil,
+		),
+		dropped: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, softnetSubsystem, "dropped_total"),
+			"Number of dropped packets",
+			[]string{"cpu"}, nil,
+		),
+		timeSqueezed: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, softnetSubsystem, "times_squeezed_total"),
+			"Number of times processing packets ran out of quota",
+			[]string{"cpu"}, nil,
+		),
+	}, nil
+}
+
+// Update gets parsed softnet statistics using procfs.
+func (c *softnetCollector) Update(ch chan<- prometheus.Metric) error {
+	stats, err := c.fs.GatherSoftnetStats()
+	if err != nil {
+		return fmt.Errorf("could not get softnet statistics: %s", err)
+	}
+
+	for cpuNumber, cpuStats := range stats {
+		cpu := strconv.Itoa(cpuNumber)
+
+		ch <- prometheus.MustNewConstMetric(
+			c.processed,
+			prometheus.CounterValue,
+			float64(cpuStats.Processed),
+			cpu,
+		)
+		ch <- prometheus.MustNewConstMetric(
+			c.dropped,
+			prometheus.CounterValue,
+			float64(cpuStats.Dropped),
+			cpu,
+		)
+		ch <- prometheus.MustNewConstMetric(
+			c.timeSqueezed,
+			prometheus.CounterValue,
+			float64(cpuStats.TimeSqueezed),
+			cpu,
+		)
+	}
+
+	return nil
+}