Document and add support to input plugins for logging alias (#6357)

plugins/inputs/filestat/README.md

@@ -11,6 +11,7 @@ The filestat plugin gathers metrics about file existence, size, and other stats.
   ## These accept standard unix glob matching rules, but with the addition of
   ## ** as a "super asterisk". See https://github.com/gobwas/glob.
   files = ["/etc/telegraf/telegraf.conf", "/var/log/**.log"]
+
   ## If true, read the entire file and calculate an md5 checksum.
   md5 = false
 ```

plugins/inputs/filestat/filestat.go

@@ -4,7 +4,6 @@ import (
 	"crypto/md5"
 	"fmt"
 	"io"
-	"log"
 	"os"
 
 	"github.com/influxdata/telegraf"
@@ -23,6 +22,7 @@ const sampleConfig = `
   ## See https://github.com/gobwas/glob for more examples
   ##
   files = ["/var/log/**.log"]
+
   ## If true, read the entire file and calculate an md5 checksum.
   md5 = false
 `
@@ -31,6 +31,8 @@ type FileStat struct {
 	Md5   bool
 	Files []string
 
+	Log telegraf.Logger
+
 	// maps full file paths to globmatch obj
 	globs map[string]*globpath.GlobPath
 }
@@ -41,11 +43,11 @@ func NewFileStat() *FileStat {
 	}
 }
 
-func (_ *FileStat) Description() string {
+func (*FileStat) Description() string {
 	return "Read stats about given file(s)"
 }
 
-func (_ *FileStat) SampleConfig() string { return sampleConfig }
+func (*FileStat) SampleConfig() string { return sampleConfig }
 
 func (f *FileStat) Gather(acc telegraf.Accumulator) error {
 	var err error
@@ -86,7 +88,7 @@ func (f *FileStat) Gather(acc telegraf.Accumulator) error {
 			}
 
 			if fileInfo == nil {
-				log.Printf("E! Unable to get info for file [%s], possible permissions issue",
+				f.Log.Errorf("Unable to get info for file %q, possible permissions issue",
 					fileName)
 			} else {
 				fields["size_bytes"] = fileInfo.Size()

plugins/inputs/filestat/filestat_test.go

@@ -14,6 +14,7 @@ import (
 func TestGatherNoMd5(t *testing.T) {
 	dir := getTestdataDir()
 	fs := NewFileStat()
+	fs.Log = testutil.Logger{}
 	fs.Files = []string{
 		dir + "log1.log",
 		dir + "log2.log",
@@ -44,6 +45,7 @@ func TestGatherNoMd5(t *testing.T) {
 func TestGatherExplicitFiles(t *testing.T) {
 	dir := getTestdataDir()
 	fs := NewFileStat()
+	fs.Log = testutil.Logger{}
 	fs.Md5 = true
 	fs.Files = []string{
 		dir + "log1.log",
@@ -77,6 +79,7 @@ func TestGatherExplicitFiles(t *testing.T) {
 func TestGatherGlob(t *testing.T) {
 	dir := getTestdataDir()
 	fs := NewFileStat()
+	fs.Log = testutil.Logger{}
 	fs.Md5 = true
 	fs.Files = []string{
 		dir + "*.log",
@@ -103,6 +106,7 @@ func TestGatherGlob(t *testing.T) {
 func TestGatherSuperAsterisk(t *testing.T) {
 	dir := getTestdataDir()
 	fs := NewFileStat()
+	fs.Log = testutil.Logger{}
 	fs.Md5 = true
 	fs.Files = []string{
 		dir + "**",
@@ -136,6 +140,7 @@ func TestGatherSuperAsterisk(t *testing.T) {
 func TestModificationTime(t *testing.T) {
 	dir := getTestdataDir()
 	fs := NewFileStat()
+	fs.Log = testutil.Logger{}
 	fs.Files = []string{
 		dir + "log1.log",
 	}
@@ -153,6 +158,7 @@ func TestModificationTime(t *testing.T) {
 
 func TestNoModificationTime(t *testing.T) {
 	fs := NewFileStat()
+	fs.Log = testutil.Logger{}
 	fs.Files = []string{
 		"/non/existant/file",
 	}