func (t *processor004) ProcessSingle(i io.Reader, out Ingester, o *ProcessOptions) error {
	var parser text.Parser
	metricFamilies, err := parser.TextToMetricFamilies(i)
	if err != nil {
		return err
	}
	for _, metricFamily := range metricFamilies {
		if err := extractMetricFamily(out, o, metricFamily); err != nil {
			return err
		}
	}
	return nil
}

func fetchMetricFamilies(url string, ch chan<- *dto.MetricFamily) {
	defer close(ch)
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		log.Fatalf("creating GET request for URL %q failed: %s", url, err)
	}
	req.Header.Add("Accept", acceptHeader)
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		log.Fatalf("executing GET request for URL %q failed: %s", url, err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		log.Fatalf("GET request for URL %q returned HTTP status %s", url, resp.Status)
	}

	mediatype, params, err := mime.ParseMediaType(resp.Header.Get("Content-Type"))
	if err == nil && mediatype == "application/vnd.google.protobuf" &&
		params["encoding"] == "delimited" &&
		params["proto"] == "io.prometheus.client.MetricFamily" {
		for {
			mf := &dto.MetricFamily{}
			if _, err = pbutil.ReadDelimited(resp.Body, mf); err != nil {
				if err == io.EOF {
					break
				}
				log.Fatalln("reading metric family protocol buffer failed:", err)
			}
			ch <- mf
		}
	} else {
		// We could do further content-type checks here, but the
		// fallback for now will anyway be the text format
		// version 0.0.4, so just go for it and see if it works.
		var parser text.Parser
		metricFamilies, err := parser.TextToMetricFamilies(resp.Body)
		if err != nil {
			log.Fatalln("reading text format failed:", err)
		}
		for _, mf := range metricFamilies {
			ch <- mf
		}
	}
}

// Push returns an http.Handler which accepts samples over HTTP and stores them
// in the MetricStore. If replace is true, all metrics for the job and instance
// given by the request are deleted before new ones are stored.
//
// The returned handler is already instrumented for Prometheus.
func Push(
	ms storage.MetricStore, replace bool,
) func(http.ResponseWriter, *http.Request, httprouter.Params) {
	var ps httprouter.Params
	var mtx sync.Mutex // Protects ps.

	instrumentedHandlerFunc := prometheus.InstrumentHandlerFunc(
		"push",
		func(w http.ResponseWriter, r *http.Request) {
			job := ps.ByName("job")
			labelsString := ps.ByName("labels")
			mtx.Unlock()

			labels, err := splitLabels(labelsString)
			if err != nil {
				http.Error(w, err.Error(), http.StatusBadRequest)
				return
			}
			if job == "" {
				http.Error(w, "job name is required", http.StatusBadRequest)
				return
			}
			labels["job"] = job

			if replace {
				ms.SubmitWriteRequest(storage.WriteRequest{
					Labels:    labels,
					Timestamp: time.Now(),
				})
			}

			var metricFamilies map[string]*dto.MetricFamily
			ctMediatype, ctParams, ctErr := mime.ParseMediaType(r.Header.Get("Content-Type"))
			if ctErr == nil && ctMediatype == "application/vnd.google.protobuf" &&
				ctParams["encoding"] == "delimited" &&
				ctParams["proto"] == "io.prometheus.client.MetricFamily" {
				metricFamilies = map[string]*dto.MetricFamily{}
				for {
					mf := &dto.MetricFamily{}
					if _, err = pbutil.ReadDelimited(r.Body, mf); err != nil {
						if err == io.EOF {
							err = nil
						}
						break
					}
					metricFamilies[mf.GetName()] = mf
				}
			} else {
				// We could do further content-type checks here, but the
				// fallback for now will anyway be the text format
				// version 0.0.4, so just go for it and see if it works.
				var parser text.Parser
				metricFamilies, err = parser.TextToMetricFamilies(r.Body)
			}
			if err != nil {
				http.Error(w, err.Error(), http.StatusInternalServerError)
				return
			}
			sanitizeLabels(metricFamilies, labels)
			ms.SubmitWriteRequest(storage.WriteRequest{
				Labels:         labels,
				Timestamp:      time.Now(),
				MetricFamilies: metricFamilies,
			})
			w.WriteHeader(http.StatusAccepted)
		},
	)

	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
		mtx.Lock()
		ps = params
		instrumentedHandlerFunc(w, r)
	}
}

func parseTextFiles() []*dto.MetricFamily {
	var parser text.Parser
	error := 0.0
	metricFamilies := make([]*dto.MetricFamily, 0)
	mtimes := map[string]time.Time{}

	// Iterate over files and accumulate their metrics.
	files, _ := ioutil.ReadDir(*textFileDirectory)
	for _, f := range files {
		if !strings.HasSuffix(f.Name(), ".prom") {
			continue
		}
		path := filepath.Join(*textFileDirectory, f.Name())
		file, err := os.Open(path)
		if err != nil {
			log.Errorf("Error opening %s: %v", path, err)
			error = 1.0
			continue
		}
		parsedFamilies, err := parser.TextToMetricFamilies(file)
		if err != nil {
			log.Errorf("Error parsing %s: %v", path, err)
			error = 1.0
			continue
		}
		// Only set this once it has been parsed, so that
		// a failure does not appear fresh.
		mtimes[f.Name()] = f.ModTime()
		for _, mf := range parsedFamilies {
			if mf.Help == nil {
				help := fmt.Sprintf("Metric read from %s", path)
				mf.Help = &help
			}
			metricFamilies = append(metricFamilies, mf)
		}
	}

	// Export the mtimes of the successful files.
	if len(mtimes) > 0 {
		mtimeMetricFamily := dto.MetricFamily{
			Name:   proto.String("node_textfile_mtime"),
			Help:   proto.String("Unixtime mtime of textfiles successfully read."),
			Type:   dto.MetricType_GAUGE.Enum(),
			Metric: []*dto.Metric{},
		}
		for name, mtime := range mtimes {
			mtimeMetricFamily.Metric = append(mtimeMetricFamily.Metric,
				&dto.Metric{
					Label: []*dto.LabelPair{
						&dto.LabelPair{
							Name:  proto.String("file"),
							Value: &name,
						},
					},
					Gauge: &dto.Gauge{Value: proto.Float64(float64(mtime.UnixNano()) / 1e9)},
				},
			)
		}
		metricFamilies = append(metricFamilies, &mtimeMetricFamily)
	}
	// Export if there were errors.
	metricFamilies = append(metricFamilies, &dto.MetricFamily{
		Name: proto.String("node_textfile_scrape_error"),
		Help: proto.String("1 if there was an error opening or reading a file, 0 otherwise"),
		Type: dto.MetricType_GAUGE.Enum(),
		Metric: []*dto.Metric{
			&dto.Metric{
				Gauge: &dto.Gauge{Value: &error},
			},
		},
	})

	return metricFamilies
}