node_exporter/collector/arp_linux.go
Sam Kottler 6eafa51fa8 Add ARP collector for Linux (#540)
* Implement commonalities and linux support for ARP collection

* Add ARP collector to fixtures and run as part of e2e tests

* Bubble up scanner errors

* Use single return values where it makes sense

* Add missing annotation

* Move arp_common into arp_linux

* Add license header to arp_linux.go

* Address initial feedback

* Use strings.Fields instead of strings.Split

* Deal with scanner.Err() rather than throwing away errors

* Check for scan errors in-line before interacting with the entries map

* Don't interact with potentially empty text from scan

* Check for scan errors outside the scan loop

* Add comment about moving procfs parsing

* Add more direct comment

* Update initialism style to match go style guide

* Put function args on the same line

* Add TODO in front of comment about procfs extraction

* Guard against strings.Fields returning an empty slice

* Be more defensive about ARP table format and use upcase more broadly

* Enable the ARP collector by default

* Add ARP collector to the README

* Remove 'entry'
2017-04-11 17:45:19 +02:00

103 lines
2.5 KiB
Go

// Copyright 2017 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 !noarp
package collector
import (
"bufio"
"fmt"
"io"
"os"
"strings"
"github.com/prometheus/client_golang/prometheus"
)
type arpCollector struct {
entries *prometheus.Desc
}
func init() {
Factories["arp"] = NewARPCollector
}
// NewARPCollector returns a new Collector exposing ARP stats.
func NewARPCollector() (Collector, error) {
return &arpCollector{
entries: prometheus.NewDesc(
prometheus.BuildFQName(Namespace, "arp", "entries"),
"ARP entries by device",
[]string{"device"}, nil,
),
}, nil
}
func getARPEntries() (map[string]uint32, error) {
file, err := os.Open(procFilePath("net/arp"))
if err != nil {
return nil, err
}
defer file.Close()
entries, err := parseARPEntries(file)
if err != nil {
return nil, err
}
return entries, nil
}
// TODO: This should get extracted to the github.com/prometheus/procfs package
// to support more complete parsing of /proc/net/arp. Instead of adding
// more fields to this function's return values it should get moved and
// changed to support each field.
func parseARPEntries(data io.Reader) (map[string]uint32, error) {
scanner := bufio.NewScanner(data)
entries := make(map[string]uint32)
for scanner.Scan() {
columns := strings.Fields(scanner.Text())
if len(columns) < 6 {
return nil, fmt.Errorf("unexpected ARP table format")
}
if columns[0] != "IP" {
deviceIndex := len(columns) - 1
entries[columns[deviceIndex]]++
}
}
if err := scanner.Err(); err != nil {
return nil, fmt.Errorf("failed to parse ARP info: %s", err)
}
return entries, nil
}
func (c *arpCollector) Update(ch chan<- prometheus.Metric) error {
entries, err := getARPEntries()
if err != nil {
return fmt.Errorf("could not get ARP entries: %s", err)
}
for device, entryCount := range entries {
ch <- prometheus.MustNewConstMetric(
c.entries, prometheus.GaugeValue, float64(entryCount), device)
}
return nil
}