Add file input plugin and grok parser (#4332)

plugins/inputs/file/file.go

@@ -0,0 +1,102 @@
+package file
+
+import (
+	"fmt"
+	"io/ioutil"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal/globpath"
+	"github.com/influxdata/telegraf/plugins/inputs"
+	"github.com/influxdata/telegraf/plugins/parsers"
+)
+
+type File struct {
+	Files         []string `toml:"files"`
+	FromBeginning bool
+	parser        parsers.Parser
+
+	filenames []string
+}
+
+const sampleConfig = `
+  ## Files to parse each interval.
+  ## These accept standard unix glob matching rules, but with the addition of
+  ## ** as a "super asterisk". ie:
+  ##   /var/log/**.log     -> recursively find all .log files in /var/log
+  ##   /var/log/*/*.log    -> find all .log files with a parent dir in /var/log
+  ##   /var/log/apache.log -> only tail the apache log file
+  files = ["/var/log/apache/access.log"]
+
+  ## The dataformat to be read from files
+  ## Each data format has its own unique set of configuration options, read
+  ## more about them here:
+  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
+  data_format = "influx"
+`
+
+// SampleConfig returns the default configuration of the Input
+func (f *File) SampleConfig() string {
+	return sampleConfig
+}
+
+func (f *File) Description() string {
+	return "reload and gather from file[s] on telegraf's interval"
+}
+
+func (f *File) Gather(acc telegraf.Accumulator) error {
+	err := f.refreshFilePaths()
+	if err != nil {
+		return err
+	}
+	for _, k := range f.filenames {
+		metrics, err := f.readMetric(k)
+		if err != nil {
+			return err
+		}
+
+		for _, m := range metrics {
+			acc.AddFields(m.Name(), m.Fields(), m.Tags(), m.Time())
+		}
+	}
+	return nil
+}
+
+func (f *File) SetParser(p parsers.Parser) {
+	f.parser = p
+}
+
+func (f *File) refreshFilePaths() error {
+	var allFiles []string
+	for _, file := range f.Files {
+		g, err := globpath.Compile(file)
+		if err != nil {
+			return fmt.Errorf("could not compile glob %v: %v", file, err)
+		}
+		files := g.Match()
+		if len(files) <= 0 {
+			return fmt.Errorf("could not find file: %v", file)
+		}
+
+		for k := range files {
+			allFiles = append(allFiles, k)
+		}
+	}
+
+	f.filenames = allFiles
+	return nil
+}
+
+func (f *File) readMetric(filename string) ([]telegraf.Metric, error) {
+	fileContents, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, fmt.Errorf("E! Error file: %v could not be read, %s", filename, err)
+	}
+	return f.parser.Parse(fileContents)
+
+}
+
+func init() {
+	inputs.Add("file", func() telegraf.Input {
+		return &File{}
+	})
+}