VOL-1868 move simulated onu from voltha-go to voltha-simonu-adapter

Sourced from voltha-go commit 251a11c0ffe60512318a644cd6ce0dc4e12f4018

Change-Id: Iab179bc2f3dd772ed7f488d1c03d1a84ba75e874
diff --git a/vendor/github.com/armon/go-metrics/statsite.go b/vendor/github.com/armon/go-metrics/statsite.go
new file mode 100644
index 0000000..6c0d284
--- /dev/null
+++ b/vendor/github.com/armon/go-metrics/statsite.go
@@ -0,0 +1,172 @@
+package metrics
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"net"
+	"net/url"
+	"strings"
+	"time"
+)
+
+const (
+	// We force flush the statsite metrics after this period of
+	// inactivity. Prevents stats from getting stuck in a buffer
+	// forever.
+	flushInterval = 100 * time.Millisecond
+)
+
+// NewStatsiteSinkFromURL creates an StatsiteSink from a URL. It is used
+// (and tested) from NewMetricSinkFromURL.
+func NewStatsiteSinkFromURL(u *url.URL) (MetricSink, error) {
+	return NewStatsiteSink(u.Host)
+}
+
+// StatsiteSink provides a MetricSink that can be used with a
+// statsite metrics server
+type StatsiteSink struct {
+	addr        string
+	metricQueue chan string
+}
+
+// NewStatsiteSink is used to create a new StatsiteSink
+func NewStatsiteSink(addr string) (*StatsiteSink, error) {
+	s := &StatsiteSink{
+		addr:        addr,
+		metricQueue: make(chan string, 4096),
+	}
+	go s.flushMetrics()
+	return s, nil
+}
+
+// Close is used to stop flushing to statsite
+func (s *StatsiteSink) Shutdown() {
+	close(s.metricQueue)
+}
+
+func (s *StatsiteSink) SetGauge(key []string, val float32) {
+	flatKey := s.flattenKey(key)
+	s.pushMetric(fmt.Sprintf("%s:%f|g\n", flatKey, val))
+}
+
+func (s *StatsiteSink) SetGaugeWithLabels(key []string, val float32, labels []Label) {
+	flatKey := s.flattenKeyLabels(key, labels)
+	s.pushMetric(fmt.Sprintf("%s:%f|g\n", flatKey, val))
+}
+
+func (s *StatsiteSink) EmitKey(key []string, val float32) {
+	flatKey := s.flattenKey(key)
+	s.pushMetric(fmt.Sprintf("%s:%f|kv\n", flatKey, val))
+}
+
+func (s *StatsiteSink) IncrCounter(key []string, val float32) {
+	flatKey := s.flattenKey(key)
+	s.pushMetric(fmt.Sprintf("%s:%f|c\n", flatKey, val))
+}
+
+func (s *StatsiteSink) IncrCounterWithLabels(key []string, val float32, labels []Label) {
+	flatKey := s.flattenKeyLabels(key, labels)
+	s.pushMetric(fmt.Sprintf("%s:%f|c\n", flatKey, val))
+}
+
+func (s *StatsiteSink) AddSample(key []string, val float32) {
+	flatKey := s.flattenKey(key)
+	s.pushMetric(fmt.Sprintf("%s:%f|ms\n", flatKey, val))
+}
+
+func (s *StatsiteSink) AddSampleWithLabels(key []string, val float32, labels []Label) {
+	flatKey := s.flattenKeyLabels(key, labels)
+	s.pushMetric(fmt.Sprintf("%s:%f|ms\n", flatKey, val))
+}
+
+// Flattens the key for formatting, removes spaces
+func (s *StatsiteSink) flattenKey(parts []string) string {
+	joined := strings.Join(parts, ".")
+	return strings.Map(func(r rune) rune {
+		switch r {
+		case ':':
+			fallthrough
+		case ' ':
+			return '_'
+		default:
+			return r
+		}
+	}, joined)
+}
+
+// Flattens the key along with labels for formatting, removes spaces
+func (s *StatsiteSink) flattenKeyLabels(parts []string, labels []Label) string {
+	for _, label := range labels {
+		parts = append(parts, label.Value)
+	}
+	return s.flattenKey(parts)
+}
+
+// Does a non-blocking push to the metrics queue
+func (s *StatsiteSink) pushMetric(m string) {
+	select {
+	case s.metricQueue <- m:
+	default:
+	}
+}
+
+// Flushes metrics
+func (s *StatsiteSink) flushMetrics() {
+	var sock net.Conn
+	var err error
+	var wait <-chan time.Time
+	var buffered *bufio.Writer
+	ticker := time.NewTicker(flushInterval)
+	defer ticker.Stop()
+
+CONNECT:
+	// Attempt to connect
+	sock, err = net.Dial("tcp", s.addr)
+	if err != nil {
+		log.Printf("[ERR] Error connecting to statsite! Err: %s", err)
+		goto WAIT
+	}
+
+	// Create a buffered writer
+	buffered = bufio.NewWriter(sock)
+
+	for {
+		select {
+		case metric, ok := <-s.metricQueue:
+			// Get a metric from the queue
+			if !ok {
+				goto QUIT
+			}
+
+			// Try to send to statsite
+			_, err := buffered.Write([]byte(metric))
+			if err != nil {
+				log.Printf("[ERR] Error writing to statsite! Err: %s", err)
+				goto WAIT
+			}
+		case <-ticker.C:
+			if err := buffered.Flush(); err != nil {
+				log.Printf("[ERR] Error flushing to statsite! Err: %s", err)
+				goto WAIT
+			}
+		}
+	}
+
+WAIT:
+	// Wait for a while
+	wait = time.After(time.Duration(5) * time.Second)
+	for {
+		select {
+		// Dequeue the messages to avoid backlog
+		case _, ok := <-s.metricQueue:
+			if !ok {
+				goto QUIT
+			}
+		case <-wait:
+			goto CONNECT
+		}
+	}
+QUIT:
+	s.metricQueue = nil
+}