Add instance name option to varnish plugin (#3398)

This change add a new configuration option to allow probing of
namespaced varnish instances, usually reached using the '-n' switch on
the varnish cli.

plugins/inputs/varnish/varnish.go

@@ -17,13 +17,14 @@ import (
 	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
-type runner func(cmdName string, UseSudo bool) (*bytes.Buffer, error)
+type runner func(cmdName string, UseSudo bool, InstanceName string) (*bytes.Buffer, error)
 
 // Varnish is used to store configuration values
 type Varnish struct {
-	Stats   []string
+	Stats        []string
-	Binary  string
+	Binary       string
-	UseSudo bool
+	UseSudo      bool
+	InstanceName string
 
 	filter filter.Filter
 	run    runner
@@ -44,6 +45,10 @@ var sampleConfig = `
   ## Glob matching can be used, ie, stats = ["MAIN.*"]
   ## stats may also be set to ["*"], which will collect all stats
   stats = ["MAIN.cache_hit", "MAIN.cache_miss", "MAIN.uptime"]
+
+  ## Optional name for the varnish instance (or working directory) to query
+  ## Usually appened after -n in varnish cli
+  #name = instanceName
 `
 
 func (s *Varnish) Description() string {
@@ -56,8 +61,13 @@ func (s *Varnish) SampleConfig() string {
 }
 
 // Shell out to varnish_stat and return the output
-func varnishRunner(cmdName string, UseSudo bool) (*bytes.Buffer, error) {
+func varnishRunner(cmdName string, UseSudo bool, InstanceName string) (*bytes.Buffer, error) {
 	cmdArgs := []string{"-1"}
+
+	if InstanceName != "" {
+		cmdArgs = append(cmdArgs, []string{"-n", InstanceName}...)
+	}
+
 	cmd := exec.Command(cmdName, cmdArgs...)
 
 	if UseSudo {
@@ -99,7 +109,7 @@ func (s *Varnish) Gather(acc telegraf.Accumulator) error {
 		}
 	}
 
-	out, err := s.run(s.Binary, s.UseSudo)
+	out, err := s.run(s.Binary, s.UseSudo, s.InstanceName)
 	if err != nil {
 		return fmt.Errorf("error gathering metrics: %s", err)
 	}
@@ -155,10 +165,11 @@ func (s *Varnish) Gather(acc telegraf.Accumulator) error {
 func init() {
 	inputs.Add("varnish", func() telegraf.Input {
 		return &Varnish{
-			run:     varnishRunner,
+			run:          varnishRunner,
-			Stats:   defaultStats,
+			Stats:        defaultStats,
-			Binary:  defaultBinary,
+			Binary:       defaultBinary,
-			UseSudo: false,
+			UseSudo:      false,
+			InstanceName: "",
 		}
 	})
 }

plugins/inputs/varnish/varnish_test.go

@@ -5,14 +5,15 @@ package varnish
 import (
 	"bytes"
 	"fmt"
-	"github.com/influxdata/telegraf/testutil"
-	"github.com/stretchr/testify/assert"
 	"strings"
 	"testing"
+
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/assert"
 )
 
-func fakeVarnishStat(output string, useSudo bool) func(string, bool) (*bytes.Buffer, error) {
+func fakeVarnishStat(output string, useSudo bool, InstanceName string) func(string, bool, string) (*bytes.Buffer, error) {
-	return func(string, bool) (*bytes.Buffer, error) {
+	return func(string, bool, string) (*bytes.Buffer, error) {
 		return bytes.NewBuffer([]byte(output)), nil
 	}
 }
@@ -20,7 +21,7 @@ func fakeVarnishStat(output string, useSudo bool) func(string, bool) (*bytes.Buf
 func TestGather(t *testing.T) {
 	acc := &testutil.Accumulator{}
 	v := &Varnish{
-		run:   fakeVarnishStat(smOutput, false),
+		run:   fakeVarnishStat(smOutput, false, ""),
 		Stats: []string{"*"},
 	}
 	v.Gather(acc)
@@ -36,7 +37,7 @@ func TestGather(t *testing.T) {
 func TestParseFullOutput(t *testing.T) {
 	acc := &testutil.Accumulator{}
 	v := &Varnish{
-		run:   fakeVarnishStat(fullOutput, true),
+		run:   fakeVarnishStat(fullOutput, true, ""),
 		Stats: []string{"*"},
 	}
 	err := v.Gather(acc)
@@ -51,7 +52,7 @@ func TestParseFullOutput(t *testing.T) {
 func TestFilterSomeStats(t *testing.T) {
 	acc := &testutil.Accumulator{}
 	v := &Varnish{
-		run:   fakeVarnishStat(fullOutput, false),
+		run:   fakeVarnishStat(fullOutput, false, ""),
 		Stats: []string{"MGT.*", "VBE.*"},
 	}
 	err := v.Gather(acc)
@@ -74,7 +75,7 @@ func TestFieldConfig(t *testing.T) {
 	for fieldCfg, expected := range expect {
 		acc := &testutil.Accumulator{}
 		v := &Varnish{
-			run:   fakeVarnishStat(fullOutput, true),
+			run:   fakeVarnishStat(fullOutput, true, ""),
 			Stats: strings.Split(fieldCfg, ","),
 		}
 		err := v.Gather(acc)