Add polling method to logparser and tail inputs (#3213)

plugins/inputs/tail/tail.go

@@ -15,10 +15,15 @@ import (
 	"github.com/influxdata/telegraf/plugins/parsers"
 )
 
+const (
+	defaultWatchMethod = "inotify"
+)
+
 type Tail struct {
 	Files         []string
 	FromBeginning bool
 	Pipe          bool
+	WatchMethod   string
 
 	tailers []*tail.Tail
 	parser  parsers.Parser
@@ -50,6 +55,9 @@ const sampleConfig = `
   ## Whether file is a named pipe
   pipe = false
 
+  ## Method used to watch for file updates.  Can be either "inotify" or "poll".
+  # watch_method = "inotify"
+
   ## Data format to consume.
   ## Each data format has its own unique set of configuration options, read
   ## more about them here:
@@ -83,6 +91,11 @@ func (t *Tail) Start(acc telegraf.Accumulator) error {
 		}
 	}
 
+	var poll bool
+	if t.WatchMethod == "poll" {
+		poll = true
+	}
+
 	// Create a "tailer" for each file
 	for _, filepath := range t.Files {
 		g, err := globpath.Compile(filepath)
@@ -96,6 +109,7 @@ func (t *Tail) Start(acc telegraf.Accumulator) error {
 					Follow:    true,
 					Location:  seek,
 					MustExist: true,
+					Poll:      poll,
 					Pipe:      t.Pipe,
 					Logger:    tail.DiscardingLogger,
 				})