Tailer

tail.go

func (w *Watcher) Initialize() error {
	lines := make(chan (string))

	//go get lines from file
	go func(file string) {
		defer close(lines)
		//NOTE. To implement tail properly is challenging
		// here is a link with nice explanation
		// https://github.com/fstab/grok_exporter/wiki/tailer-(tail-%E2%80%90f)
		// In all cases, if custom-made tail implementation is needed
		// it should be implemented in another package and this code
		// should remain simple to read
		tl, err := tail.TailFile(file, tail.Config{Follow: true})
		if err != nil {
			panic(err)
		}
		for line := range tl.Lines {
			lines <- line.Text
		}
	}(w.logfile)

	//go read lines and build state
	go func() {
		for l := range lines {
			parts := strings.Split(l, " ")
			if len(parts) < 4 { //TODO. improve validation
				log.Printf("error parsing line [%v]", l)
				continue
			}

			ts, err := time.Parse("2006/01/02 15:04:05", parts[0]+" "+parts[1])
			if err != nil {
				log.Printf("error parsing date %v:", err)
			}

			id := strings.Trim(parts[2], "[]")
			if id == "" { //TODO. validPID(id)
				log.Printf("error parsing line")
				continue
			}

			restMsg := strings.Join(parts[3:], " ")

			v, ok := w.Connections[id]
			if !ok {
				v = &connection{}
				w.Connections[id] = v
			}
			v.Timestamps = append(v.Timestamps, ts)
			v.Msgs = append(v.Msgs, restMsg)
			v.Update(restMsg)
		}
	}()

	return nil
}